Phosphine Ligand Selection Guide: How to Simultaneously Lower the Ar–Cl Activation Barrier, Improve Catalyst Longevity, and Stabilize the Impurity Profile in Pd-Catalyzed Cross-Coupling (Tables 1–4 Included)
1.Real-world pain point: why “aryl chloride + low Pd + scale-up” is most prone to instability
1. In cross-coupling (especially Pd-catalyzed C–N/C–C bond formation), researchers often set multiple goals at once: more challenging substrates (Ar–Cl/heteroaryl chlorides), less metal (low Pd loading), larger scale (scale-up), and tighter control of outcomes (stable impurity profile and batch-to-batch reproducibility). Instability typically shows up as three observable signals: slow initiation, rate drop-off at the later stage, and drift in selectivity/impurity profile.
2. A key reason aryl chlorides trigger these problems more readily is that C–Cl bonds are harder to activate at the metal center, making oxidative addition more likely to become rate-controlling. When Pd loading is reduced, the system becomes more “sensitive” to ionic environment and impurities: the same halide salts/alkali-metal salts, water/oxygen, strongly coordinating substrates, or byproducts can exert a magnified inhibitory effect per active site. Scale-up further amplifies risks of aggregation/deactivation and selectivity drift through changes in mass transfer, local concentration gradients, and phase behavior.
Table 1. Instability signals and first checks (identify whether the issue is “initiation / longevity / selectivity”)
Observable signal | Most likely bottleneck in the catalytic cycle | First checks (prioritize 1–2 items) |
Very long induction period; conversion fails to take off | Initiation barrier (often oxidative addition / insufficient activation) | Substrate is Ar–Cl/heteroaryl chloride; ligand is not electron-donating enough or binds in an unfavorable way; slow formation of the catalytically active species |
Runs well initially, then clearly slows down or even stops | Longevity / deactivation (progressive loss of active species) | Metal aggregation/“blackening”; ligand is consumed or sequestered by salts/substrate via strong coordination; scale-up–induced mass-transfer/phase changes amplify deactivation |
Impurity profile/selectivity drifts with time or between batches | Shift in pathway competition (side pathways become amplified) | Sluggish reductive elimination allows side pathways to accumulate; sterics/geometry mismatch causes key intermediates to persist too long; changes in substrate/base/salt environment alter relative rates |
2.What “phosphine ligands” means
1. In IUPAC terminology, phosphines are a class of compounds derived from PH₃ by substitution with hydrocarbyl groups (RPH₂, R₂PH, R₃P). In inorganic coordination entities, a ligand refers to an atom or group bound to a central atom. A “phosphine ligand” can thus be understood as a ligand family—most commonly tertiary phosphines (R₃P)—that donates electron density to, coordinates to, and modulates the reactivity of a metal center.
2. Their value in “making a reaction robust” does not come from a single structure, but from their ability to systematically tune three key variables: electronic donation, steric bulk, and the geometric constraints introduced by monodentate versus chelating binding.
3.The three-step catalytic cycle: oxidative addition → transmetalation → reductive elimination; how phosphines “speed up / stabilize / control selectivity”
Using Pd-catalyzed cross-coupling as an example, a widely used minimal framework has three steps:
Oxidative addition (initiation) → exchange/transmetalation (mid-cycle) → reductive elimination (bond formation and finish).
When the target is Ar–Cl substrates under low Pd loading, the most common instability comes from pressure at both ends: initiation barrier + longevity.
Table 2. Three gates × three knobs (electronics / sterics / geometry): mapping to “initiation / longevity / selectivity”
Catalytic gate | Main risk | Key phosphine “knob” | Typical direction of effect |
Initiation: oxidative addition / activation (more sensitive for Ar–Cl) | Slow initiation; long induction period | Stronger electron donation + appropriate sterics | Stronger donation often improves activation of difficult substrates; for Ar–Cl, it is commonly used to overcome the initiation barrier |
Mid-cycle: intermediate exchange and equilibria | Rate depends strongly on salts/base/substrate; scale-up prone to drift | Coordination stability vs. lability (monodentate vs. chelating; coupled tuning of electronics and sterics) | Must stabilize productive active species while avoiding “locking” the metal in unproductive complexes; this balance is more sensitive at low Pd loading |
Finish: reductive elimination and competition with side reactions | Late-stage slowdown; poorer selectivity; impurity-profile drift | Steric organization + geometric constraints (bulky monodentate ligands or chelate bite angle) | Proper sterics/geometry often more directly promote faster reductive elimination and a cleaner finish, suppressing side pathways (e.g., cascade side reactions/rearrangements enabled by overly persistent intermediates). Electronic effects on reductive elimination are system-dependent; confirm the dominant factor via controls. |
Note: This is why “switching phosphine ligands” can often improve initiation, longevity, and selectivity simultaneously—it is not a minor tweak, but a reshuffling of the relative difficulty of the three gates.
4.Three classification dimensions
4.1 Monodentate vs. bidentate phosphines (chelating or not)
Chelation refers to binding of a single ligand to the same metal center through two or more donor sites; such ligands are termed bidentate/polydentate accordingly.
1. Monodentate phosphines are often used for “rapid tuning of electronics and sterics,” and they show high-activity operating windows in many Pd couplings.
2. Bidentate phosphines stabilize certain conformations and intermediates through geometric constraints, making them better suited when one needs to “lock in selectivity and pathway control.”
Note: Bidentate chelation is not always “more active.” In some Ar–Cl / low-temperature systems, overly strong chelation more readily forms relatively “saturated” L₂Pd coordination states, raising the barrier to accessing an “open site” on the active species. A common practical approach is therefore: monodentate phosphines are prioritized for the “initiation/high-activity” window, while bidentate phosphines are more often used for “selectivity/longevity” optimization.
4.2 How to quantify electron-donating strength: the Tolman electronic parameter as a unified “scale”
1. The electronic donation from phosphine ligands can be indirectly characterized using metrics such as the Tolman electronic parameter (TEP), which uses the CO stretching frequency in a defined metal carbonyl complex as a probe to reflect changes in overall donor ability.
2. For problems such as “slow Ar–Cl initiation,” more strongly donating phosphines are commonly used to improve activation and shorten the induction period.
4.3 Sterics and geometry: from “cone angle” to “bite angle”
1. Sterics (steric volume) is another core variable by which phosphines influence catalysis. Tolman’s work systematically discusses steric parameters of phosphine ligands (e.g., cone angle) and their significance in homogeneous catalysis.
2. Bite angle is one of the key geometric descriptors for bidentate phosphines; its impact on selectivity and reaction pathways has been examined through systematic reviews and classic experimental evidence across many homogeneous catalytic systems.
Table 3. Mapping classification dimensions to “which pain point they address”
Classification dimension | What it controls (tunable variable) | Targeted pain point | Why it works (mechanistic level) |
Monodentate phosphines | Flexible tuning of electronics/sterics | Initiation barrier; rate enhancement | Stronger donation plus better-matched sterics shifts the relative rates of oxidative addition and reductive elimination |
Bidentate phosphines (chelating) | Conformation and intermediate stability | Selectivity; longevity (in some systems) | Geometric constraint makes key intermediates more “organized,” lowering the probability of pathway drift |
Electronic parameter (TEP) | Comparable measure of donor strength | Slow initiation / difficult substrates | Donor strength changes electron density at the metal center and activation ability; often used to rationalize “why certain phosphines can ignite Ar–Cl” |
Sterics / cone angle | Spatial shielding and pathway selection | Late-stage slowdown; side reactions | Sterics can suppress unproductive aggregation/side pathways and promote faster completion of bond-forming steps |
Bite angle (bidentate) | P–M–P geometry (“bite-angle” geometry of diphosphines) | Selectivity and pathway locking | Changes transition-state geometry and relative barriers, systematically influencing product distribution |
5.Choosing ligands by initiation / longevity / selectivity: decision order and key control experiments
5.1 Selection sequence
1. First, classify the problem qualitatively: is it an initiation barrier, longevity/deactivation, or selectivity/impurity-profile drift issue?
2. Then choose the “main knob” of your ligand strategy:
①Initiation barrier first: prioritize a monodentate phosphine strategy built around stronger electron donation + appropriate sterics. This is a typical approach for coupling of aryl halides, especially aryl chlorides.
②Longevity/deactivation first: use steric organization + exchangeable coordination to reduce aggregation and unproductive complexation, so the reaction can retain activity in the later stage.
③Selectivity drift first: use bidentate phosphine geometric constraints / bite-angle effects, or a specific monodentate steric pattern, to suppress side pathways.
3. Finally, incorporate process constraints: air sensitivity, workup requirements (metal residues / phosphine-related impurities), and compatibility with the solvent and base system.
Table 4. Process-constraint checklist: the “operability” requirements a phosphine ligand must meet
Process constraint (operational constraint) | Core information | Selection guidance |
Air / moisture sensitivity | Trialkylphosphines oxidize more readily in air; triarylphosphines (e.g., PPh₃) are relatively more air-stable. Oxidation converts active phosphine into phosphine oxide, causing drift in the “effective ligand concentration.” | For low Pd + scalable reproducibility, prioritize more stable, better-controlled supply formats: stable ligands, precatalysts, or ligand solutions to reduce batch variation. |
Solubility and dosing mode | Typical solvents for Buchwald-type monophosphines include toluene and 1,4-dioxane; THF, 2-MeTHF, DME, etc. are also common. At scale, whether the system is homogeneous and can be dosed reliably is critical. | Don’t look only at activity: confirm stable solubility and uniform dosing at the target solvent and concentration. In scale-up, “soluble and feedable” often matters more than “theoretically strongest.” |
Compatibility with the base system | Once the ligand/system is mature, many reactions can run under relatively mild inorganic bases such as carbonates / phosphates / hydroxides; strong bases more readily amplify side reactions and operational burden at scale. | If late-stage slowdown or impurity drift appears, first assess “base choice and salt burden.” Systems that run stably under carbonates/phosphates are generally more scale- and workup-friendly. |
Workup: metal residues and phosphorus-related impurities | Scale-up usually requires control of Pd residues and residual phosphine/phosphine oxide. Common removal strategies include adsorption (e.g., activated carbon) and scavengers (resins/silica, etc.). | Consider “finishing” and “cleaning” together: prioritize systems that remain stable at low ligand loadings, and plan metal/phosphorus-impurity control steps (adsorption / washing / crystallization). |
5.2 Key control experiments
Table 5. Key validation / controls
Objective: confirm which bottleneck dominates | Key control setup | What to look for | How the conclusion guides the next step |
Initiation barrier (especially Ar–Cl) | Run parallel comparisons between a phosphine system with stronger donation / better-matched sterics and a baseline control system | Induction period clearly shortens; early-stage rate increases | If confirmed, prioritize fine-tuning along stronger donation + steric organization, rather than immediately making major changes to base/solvent |
Longevity / deactivation dominates | At the same initial rate, compare a system with stronger steric organization / more stable coordination to a control system | Late-stage rate persists longer; conversion profile becomes smoother; batch-to-batch fluctuation decreases | If confirmed, subsequent optimization should focus on minimizing aggregation and unproductive binding (ligand strategy + salt-environment management) |
Selectivity / impurity-profile drift | Compare a monodentate strategy against a bidentate geometric-constraint (bite-angle) strategy | Main-product selectivity stays stable; time-dependent drift of impurity profile decreases | If confirmed, focus on locking pathways via geometry/steric patterns, rather than continuing to increase catalyst loading |
6.Application landscape: why phosphine ligands are “indispensable”
Phosphine ligands are not confined to cross-coupling. Across homogeneous catalysis, they frequently serve to turn a reaction from merely feasible into controllable:
1. In industrial homogeneous processes such as hydroformylation, ligands influence not only rate but also directly determine regioselectivity (linear vs. branched). In Rh–diphosphine systems, systematic studies and practical rules link the geometry of bidentate phosphines—especially the natural bite angle—together with sterics, to linear-aldehyde selectivity. In many substrate classes, wider bite-angle diphosphines often correlate with higher linear selectivity, making “bite angle / sterics” a key handle for designing process selectivity.
2. In asymmetric catalysis, chiral diphosphines (e.g., the BINAP family and derivatives) are classic “chiral-environment building blocks.” They underpin systematic methodologies and industrial application pathways in areas such as asymmetric hydrogenation. Their value likewise is not that “one structure is universally the strongest,” but that they provide a transferable stereochemical environment and a reproducible framework for selectivity control.
7.Product Navigation Table | Phosphine Ligand Selection in Cross-Coupling: Locate the Right Product Table by Research Task (Tables 1–4)
Research / experimental need | Which table to consult first | Why start there | Representative products in that table |
“Aryl chloride / heteroaryl chloride (Ar–Cl) + low Pd loading + scalable reproducibility”: slow start, need stronger activation | Table 1 Buchwald / biaryl monophosphines and next-generation high-activity monophosphines | The core tension is a high oxidative-addition barrier and higher deactivation risk under low Pd; typically start with biaryl/next-gen monophosphines featuring strong donation + large steric bulk to lower the initiation barrier, while sterics suppress Pd aggregation | AlPhos; 2-(di-tert-butylphosphino)biphenyl; 2-di-tert-butylphosphino-2′,4′,6′-triisopropylbiphenyl; 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl |
C–N amination (especially aryl/heteroaryl chloride amination): higher initiation barrier, more ligand-sensitive | Table 1 (and consult Table 2 in parallel if needed for baseline controls) | Amination often depends more strongly on electron-rich monophosphines to accelerate oxidative addition and maintain late-stage rate; biaryl monophosphines bearing amino/alkoxy substitution are often easier to stabilize in terms of activity–robustness–solubility; then use Table 2 baseline phosphines to verify whether a stronger ligand is truly required | 2-dicyclohexylphosphino-2′-(N,N-dimethylamino)biphenyl; 2-dicyclohexylphosphino-2′,6′-bis(dimethylamino)biphenyl; 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl |
Reaction starts but shows “late-stage slowdown / batch fluctuation”: suspect Pd black, insufficient ligand, or easier deactivation | Table 1 + Table 3 achiral bidentate diphosphines (robust chelation / linker-length series) | Late-stage durability often comes from two routes: (1) use bulky monophosphines in Table 1 to suppress aggregation/deactivation; (2) use bidentate diphosphines in Table 3 to stabilize productive species via chelation and improve lifetime/impurity profile. These map to “steric anti-deactivation” vs “chelation-stabilized steady state.” | Table 1: DTB/iPr biaryl monophosphines; Table 3: DPPF, 1,1′-bis(di-tert-butylphosphino)ferrocene, DPPE/DPPP/DPPB |
Need a “clean selectivity / impurity profile”: many side reactions, sluggish reductive elimination, or unwanted side coupling | Table 3 (and consult Table 2 in parallel if needed for electronic/steric controls) | Selectivity and impurity profile often depend on bite angle/geometry and coordination dynamics; Table 3 diphosphines (varying linker length/rigidity) are better for systematically screening “which geometry slows side pathways.” Table 2 helps verify whether the issue is simply “insufficient donation/sterics.” | Table 3: dppm/DPPE/DPPP/DPPB, biphenyl-framework diphosphines, xanthene-based diphosphines; Table 2: tris(4-fluorophenyl)phosphine vs tris(4-methoxyphenyl)phosphine control |
Asymmetric cross-coupling / need ee or enantioselective control: require a chiral environment and reproducible selectivity direction | Table 4 chiral diphosphines | If the target is ee/enantioselectivity, start from chiral diphosphine libraries; Table 4 covers “classic benchmarks + bulky derivatives + electronically/sterically asymmetric platforms,” allowing you to first establish reproducible direction and ee, then return to Tables 1/3 to reinforce activity and longevity | BINAP (R/S/±), SEGPHOS, (S)-DTBM-SEGPHOS, Josiphos, DuPhos, DIOP, DIPAMP |
Need “configuration inversion / direction check”: confirm which enantiomer gives the opposite selectivity | Table 4 | Most ligands in Table 4 come as enantiomeric pairs (or racemates), ideal for building “same-scaffold controls” to confirm direction; avoid comparing different scaffolds, which makes conclusions less robust | (R)-BINAP / (S)-BINAP / (±)-BINAP; DIOP enantiomers; DuPhos enantiomers; (1R,2R)-type DIPAMP |
“Aqueous / biphasic cross-coupling” or desire easy catalyst separation and recycling | Table 2 monophosphine baseline/control library (water-soluble…) | In aqueous/biphasic systems, the ligand must be water-soluble and phase behavior must be controllable; TPPTS/TPPMS are the most direct entry points to water-soluble phosphines for building the system and validating recycling routes | Trisodium tris(m-sulfonatophenyl)phosphine (TPPTS); sodium 3-(diphenylphosphino)benzenesulfonate (TPPMS) |
Systematic “electronic effect / steric effect” controls: quickly decide whether the bottleneck is initiation or the late stage | Table 2 (then revisit Tables 1/3 if needed) | Table 2 provides a graded control series from “weaker donation (4-F) → baseline (PPh₃) → stronger donation (4-OMe) → strongly donating alkyl phosphines (PCy₃/TBP/TEP) → extreme sterics (PAd₃),” ideal for rapid bottleneck localization | Tris(4-fluorophenyl)phosphine; triphenylphosphine; tris(4-methoxyphenyl)phosphine; PCy₃; TBP; PAd₃; PMe₃ (model reference) |
Suspect “ligand oxidation / air exposure–driven deactivation”: sudden loss of activity, large batch-to-batch differences | Table 2 | Using phosphine oxides as “deactivation markers/controls” is the most direct approach: it separates “catalyst failure” from “ligand state changed,” and supports strengthening inert handling, solvent deoxygenation, and dosing order/process controls | 5,5′-bis(diphenylphosphoryl)-… (phosphine oxide control) |
Start from easy substrates (Ar–Br/Ar–I) to map conditions, then progressively upgrade to difficult substrates | Table 2 → Table 1 | Use Table 2 baseline phosphines first to establish base/solvent/temperature/halide type; once upgrading to Ar–Cl or low Pd/scale introduces a barrier, switch to Table 1 high-activity monophosphines to solve initiation and longevity | Table 2: PPh₃, tri-p-tolylphosphine; Table 1: biaryl monophosphines, AlPhos |
Table 1 | Buchwald / Biaryl Monophosphines and Next-Generation High-Activity Monophosphines (targeting “hard initiation / low Pd / scale-up”)
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Product features or applications |
Buchwald-type biaryl monophosphine (strong donation / large sterics; promotes Ar–Cl initiation) | 1160861-53-9 | D396850 | Di-tert-butyl(2′,4′,6′-triisopropyl-3,6-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine | 98% | A typical monophosphine combining strong σ donation + large steric bulk: often used to accelerate oxidative addition of aryl/heteroaryl chlorides under Pd catalysis and to enable low-Pd operation; sterics help suppress Pd-black formation, improving scale-up durability and batch reproducibility. |
Buchwald-type biaryl monophosphine (strong donation / large sterics; promotes Ar–Cl initiation) | 224311-51-7 | 2-(Di-tert-butylphosphino)biphenyl | ≥99% | A bulky, strongly donating biaryl monophosphine: increases oxidative-addition rate and lowers the initiation barrier; commonly used in difficult-substrate windows for amination/etherification/C–C coupling, and helps suppress deactivation under low Pd. | |
Buchwald-type biaryl monophosphine (extreme sterics / strong donation: difficult-substrate window) | 857356-94-6 | 2-di-tert-butylphosphino-3,4,5,6-tetramethyl-2′,4′,6′-triisopropyl-1,1′-biphenyl | ≥98% | An extremely sterically congested biaryl monophosphine for high-barrier scenarios (aryl/heteroaryl chlorides, low Pd, scalable reproducibility); improves late-stage durability and selectivity by accelerating oxidative addition and suppressing deactivation. | |
Buchwald-type biaryl monophosphine (amino substituent assists tuning; common in amination) | 213697-53-1 | 2-dicyclohexylphosphino-2′-(N,N-dimethylamino)biphenyl | ≥98% | Biaryl monophosphines bearing dimethylamino substitution are frequently used in C–N coupling (amination): they provide a strongly donating phosphine while the substituent tunes solubility/coordination environment, lowering initiation barriers and improving process robustness. | |
Buchwald-type biaryl monophosphine (alkoxy substitution: solubility / durability optimization) | 787618-22-8 | 2-dicyclohexylphosphino-2′,6′-diisopropoxybiphenyl | ≥98% | A biaryl monophosphine with diisopropoxy substitution: often used when better solubility and a broader operating window are needed; improves durability and reduces batch fluctuation under low Pd and complex substrates. | |
Buchwald-type biaryl monophosphine (OMe substitution: solubility / durability / difficult substrates) | 657408-07-6 | 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl | ≥98% | Biaryl monophosphine with 2′,6′-OMe substitution often expands the conditions window in Pd couplings; balances initiation and durability under low Pd and difficult substrates, and can improve solubility/ligand availability. | |
Buchwald-type biaryl monophosphine (strongly donating amino substitution: strong for initiation / amination) | 1160556-64-8 | 2-dicyclohexylphosphino-2′,6′-bis(dimethylamino)-1,1′-biphenyl | ≥98% | 2′,6′-dimethylamino groups significantly strengthen electronic effects: commonly used in C–N coupling (amination) and difficult-initiation systems to lower oxidative-addition barriers and improve low-Pd durability and scale-up reproducibility. | |
Buchwald-type biaryl monophosphine (large sterics / strong donation: difficult substrates, low Pd) | 564483-19-8 | 2-(Di-tert-butylphosphino)-2′,4′,6′-triisopropylbiphenyl | ≥97% | A representative high-steric biaryl monophosphine: enables fast initiation for difficult substrates (aryl/heteroaryl chlorides); sterics suppress deactivation, suitable for low Pd and stable scale-up. | |
Buchwald-type biaryl monophosphine (OMe substitution: stronger activation / broader window) | 1070663-78-3 | 2-(Dicyclohexylphosphino)-3,6-dimethoxy-2′,4′,6′-triisopropyl-1,1′-biphenyl | ≥97% | Combining a strongly donating phosphine with methoxy tuning, this ligand is often used in more difficult-initiation scenarios; offers a favorable balance among initiation rate, durability, and selectivity, improving robustness on scale. | |
Buchwald-type biaryl monophosphine (Cy₂P + large sterics: promotes initiation / resists deactivation) | 564483-18-7 | 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl | ≥97% | Cy₂P provides strong donation and 2′,4′,6′-iPr provides steric bulk: commonly used for low-Pd cross-coupling to lower initiation barriers and suppress Pd aggregation/deactivation, improving batch reproducibility. | |
Next-generation monophosphine (high activity / difficult substrates / low Pd: industry-friendly) | 1805783-60-1 | AlPhos | ≥98% | A newer high-performance monophosphine for high-barrier tasks (aryl/heteroaryl chlorides, low Pd loading, scale-up reproducibility); typically improves robustness and selectivity via fast initiation + deactivation resistance. |
Table 2 | Monophosphine Baseline / Control Library (water-soluble / triaryl / alkyl / ultra-bulky) + Phosphine Oxide Controls
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Product features or applications |
Oxidized phosphine / phosphine oxide (oxidation control / deactivation-factor monitoring) | 244261-66-3 | 5,5′-Bis(diphenylphosphoryl)-4,4′-di-1,3-biphenyl | ≥99% (HPLC) | A common oxidized form of phosphine ligands (P=O): typically not an effective ligand in the main cross-coupling cycle, but ideal as an oxidation/deactivation control and for assessing sensitivity to oxygen/air exposure during scale-up. | |
Monophosphine (general triarylphosphine / baseline control) | 603-35-0 | Triphenylphosphine | ≥99% (GC) | Classic baseline ligand for controls and initial screening (especially for easier substrates such as Ar–Br/Ar–I). Under low Pd or Ar–Cl conditions, stronger-donating and/or bulkier phosphines are often required to lower initiation barriers. | |
Monophosphine (electron-rich heteroaryl triarylphosphine; promotes initiation / useful control) | 5518-52-5 | Tris(2-furyl)phosphine | ≥99% | More electron-rich and more tunable than PPh₃ in some contexts: can improve initiation efficiency or serve as a comparative ligand control; also useful as a “air-stability boundary” check if oxidation sensitivity is a concern. | |
Monophosphine (sterically enhanced triarylphosphine; control / rate tuning) | 6163-58-2 | Tris(2-tolyl)phosphine | ≥99% | Larger sterics and slightly stronger donation than PPh₃: often used to suppress side reactions, improve selectivity, or serve as a “sterics-enhanced” control; in some systems may slow Pd aggregation and improve longevity. | |
Monophosphine (triarylphosphine: steric/electronic control) | 1038-95-5 | Tri-p-tolylphosphine | ≥98% | Slightly more electron-rich and more hydrophobic than PPh₃: commonly used as a control ligand or for modest initiation-rate improvement; useful as an “electronic-effect” comparator when moving from easy to more difficult substrates. | |
Monophosphine (triarylphosphine: electronic-effect / selectivity control) | 18437-78-0 | Tris(4-fluorophenyl)phosphine | ≥98% | 4-F substitution makes the triarylphosphine more electron-withdrawing: serves as a “weaker donation” control to test whether stronger donors are needed to overcome oxidative-addition barriers or sustain late-stage rate. | |
Monophosphine (triarylphosphine: OMe substituted, stronger donation / control) | 855-38-9 | Tris(4-methoxyphenyl)phosphine | ≥95% | 4-OMe increases donor strength: commonly compared against PPh₃/tri-p-tolylphosphine to diagnose donation-limited systems; can improve initiation or reduce side reactions for certain substrates. | |
Alkyl monophosphine (strong donation: PCy₃; promotes initiation / resists deactivation) | 2622-14-2 | Tricyclohexylphosphine (PCy₃) | ≥98% | Strong σ donor with large steric bulk: can markedly increase Pd activation ability and lower initiation barriers; sterics also suppress aggregation/deactivation—useful for difficult windows in C–N/C–O/C–C couplings. | |
Small-molecule phosphine source (PMe₃: very strong donation; model / specific systems) | 594-09-2 | T101175 | Trimethylphosphine | ≥97% | Extremely strong σ donor with small size: often used in mechanistic/model studies or specific coordination chemistry; practical coupling use requires attention to volatility and handling safety, but it is valuable as an “extremely strong donor” reference. |
Ultra-bulky monophosphine (PAd₃: suppresses deactivation / difficult substrates) | 897665-73-5 | Tris(1-adamantyl)phosphine | ≥97% | Extremely bulky and strongly donating: helps suppress metal aggregation and side reactions; useful for certain difficult substrates or where stronger anti-deactivation capacity is needed; often included as a “steric-limit” screening point. | |
Alkyl monophosphine (TBP: strong donation / readily oxidized; promotes initiation) | 998-40-3 | T102760 | Tributylphosphine (TBP) | ≥95% | Strongly donating alkyl phosphine that can promote initiation; more prone to oxidation and requires management of odor/handling. Useful for “alkyl vs triaryl phosphine” comparisons and operating-window exploration. |
Alkyl monophosphine (TEP: moderately strong donation / common control) | 554-70-1 | Triethylphosphine | ≥90% | A common alkyl-phosphine control: provides stronger donation to help overcome initiation barriers; also air/oxidation sensitive, making it a good “donation-enhanced” control point. | |
Water-soluble phosphine (TPPTS: aqueous/biphasic coupling and recycling) | 63995-70-0 | Trisodium tris(m-sulfonatophenyl)phosphine | ≥90% | A classic water-soluble phosphine for aqueous or water/organic biphasic cross-coupling and catalyst phase-separation/recycling; can also aid mass transfer and scale-up operations (workup tends to be water-phase centered). | |
Water-soluble phosphine (TPPMS: aqueous/biphasic ligand module) | 63995-75-5 | Sodium 3-(diphenylphosphino)benzenesulfonate | ≥90% | A water-soluble monophosphine module used to tune aqueous/biphasic Pd systems; together with TPPTS forms a practical “water-soluble phosphine set” for process exploration with reduced organic solvent and easier workup. |
Table 3 | Achiral Bidentate Diphosphines (Robust Chelation / Bite-Angle / Linker-Length Series: Tuning Longevity and Selectivity)
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Product features or applications |
Ferrocene-based diphosphine (robust / durable) | 12150-46-8 | 1,1′-Bis(diphenylphosphino)ferrocene (DPPF) | ≥99% | Classic robust diphosphine: the ferrocene scaffold often delivers good thermal stability and resistance to deactivation; in Suzuki/Negishi and related couplings it can extend catalyst lifetime and, for some substrates, give a cleaner impurity profile. | |
Ferrocene-based diphosphine (high sterics / anti-deactivation: DTBPF-type) | 84680-95-5 | 1,1′-Bis(di-tert-butylphosphino)ferrocene | ≥98% | A highly sterically demanding, strongly donating ferrocene diphosphine: supports fast initiation and resistance to Pd aggregation/deactivation; suitable for improving lifetime and stability under low Pd loading, scale-up, and difficult-substrate windows. | |
Alkyl diphosphine (strong donation / base-tolerant / robust: DCPE-type) | 23743-26-2 | 1,2-Bis(dicyclohexylphosphino)ethane | ≥98% | Alkyl diphosphines tend to be stronger donors: they increase electron density at Pd and promote oxidative addition; often used when stronger activation and higher durability are required, and can improve selectivity/suppress side reactions in certain systems. | |
Alkyl diphosphine (strong donation: DEPE-type, rate tuning / control) | 6411-21-8 | 1,2-Bis(diethylphosphino)ethane | ≥98% | A relatively more electron-rich alkyl diphosphine: useful as an “electron-enhanced” control to probe whether the reaction is limited by oxidative addition or reductive elimination; also applicable for screening coupling systems where faster initiation is desired. | |
Alkyl diphosphine (strong donation: DMPE-type, promotes initiation) | 23936-60-9 | 1,2-Bis(dimethylphosphino)ethane | ≥97% | A small yet strongly donating alkyl diphosphine: increases electron density at the metal center and promotes oxidative addition; also commonly used as an “electronic-limit” control to diagnose the rate-determining step. | |
Classic bidentate diphosphine (DPPE: bite-angle / chelation stability) | 1663-45-2 | 1,2-Bis(diphenylphosphino)ethane (DPPE) | ≥98% | A classic bidentate phosphine: chelation stabilizes Pd species and it is often used as a “stability / bite-angle effect” control; in some systems it improves selectivity and impurity profile, but its ability to initiate Ar–Cl is usually weaker than that of strongly donating, bulky monophosphines. | |
Bidentate diphosphine (short linker: dppm, geometry / pathway control) | 2071-20-7 | Bis(diphenylphosphino)methane (dppm) | ≥98% | The shortest bridge length and most constrained geometry: commonly used to compare how “bite angle / chelation strength” affects key coupling steps; in some systems it shifts the balance between reductive elimination and side reactions, thereby influencing selectivity. | |
Bidentate diphosphine (DPPP: linker length / bite-angle tuning) | 6737-42-4 | 1,3-Bis(diphenylphosphino)propane (DPPP) | ≥97% | Longer bridge than DPPE: bite-angle changes can affect reductive elimination and side reactions; used to optimize selectivity and suppress pathways such as β-H elimination / side coupling (depending on substrate/conditions). | |
Bidentate diphosphine (DPPB: longer linker, tuning selectivity / durability) | 7688-25-7 | 1,4-Bis(diphenylphosphino)butane (DPPB) | ≥96% | Longer, more flexible linker: can tune Pd coordination geometry and dynamics; in some systems it helps improve selectivity or durability, and is frequently used in “linker-length series” control screening. | |
Olefin-backbone diphosphine (cis-dppe derivative: geometry / bite-angle control) | 983-80-2 | cis-1,2-Bis(diphenylphosphino)ethylene | ≥97% | The cis-olefin backbone locks the conformation: used to control for the impact of “fixed ligand geometry” on the catalytic cycle; may shift the balance between reductive elimination and side-reaction pathways, affecting selectivity and stability. | |
Biphenyl-backbone bidentate diphosphine (BIPHEP-type: bite-angle tuning / robust) | 84783-64-2 | 2,2′-Bis(diphenylphosphino)biphenyl | ≥98% | Biphenyl-backbone diphosphines are often used to tune reductive elimination and side reactions via bite angle/rigidity; a “robust chelating diphosphine” option in cross-coupling for durability and selectivity optimization. | |
Rigid heterocycle-backbone bidentate diphosphine (bite-angle / steric-environment tuning) | 161265-03-8 | 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene | ≥98% | The rigid xanthene backbone provides constrained geometry: used to control key Pd steps (reductive elimination / side-pathway competition) through bite angle and spatial organization, helping improve selectivity and stability. | |
Ether-bridged biaryl bidentate diphosphine (BIPHEP/DBF-oriented: rigidity / spatial organization) | 166330-10-5 | Bis[(2-diphenylphosphino)phenyl] ether | ≥98% | The ether bridge provides rigidity and a defined orientation: used to stabilize Pd intermediates via spatial organization and to tune reductive elimination vs side reactions; suitable for “structure–performance” screening and controls. |
Table 4 | Chiral Diphosphines (Asymmetric / Selectivity First: SEGPHOS / BINAP / Josiphos / DuPhos / DIOP / CHIRAPHOS / DIPAMP)
Category | CAS No. | Aladdin Cat. No. | Name | Specification / Purity | Product features or applications |
SEGPHOS-series chiral diphosphine (rigid scaffold / chiral screening) | 210169-54-3 | (S)-(-)-5,5′-Bis(diphenylphosphino)-4,4′-bi-1,3-benzodioxole | ≥99% (HPLC) | A chiral diphosphine scaffold for ligand screening in asymmetric cross-coupling/allylic substitution; rigidity and a defined chiral environment aid selectivity control, and it serves as a benchmark ligand in many chiral workflows. | |
SEGPHOS-derived bulky chiral diphosphine (low Pd / durability / difficult substrates) | 210169-40-7 | (S)-DTBM-SEGPHOS | ≥98% | DTBM substitution delivers stronger sterics and higher stability: often used in Pd reactions requiring higher durability and stronger selectivity; helps suppress deactivation and stabilize the catalytic cycle under low Pd and complex substrate environments. | |
BINAP-series chiral diphosphine (classic benchmark) | 76189-55-4 | (R)-(+)-2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl | ≥98% | A classic benchmark chiral diphosphine: a common starting point for asymmetric cross-coupling/allylic substitution; frequently used in “selectivity-first” routes as a first-round screening ligand. | |
BINAP-series chiral diphosphine (classic benchmark) | 76189-56-5 | (S)-(-)-2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl | ≥98% | Paired with (R)-BINAP for configuration-inversion checks; also convenient for establishing reproducible “chiral ligand–substrate–selectivity” control sets. | |
BINAP series (racemic / control) | 98327-87-8 | (±)-2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl | ≥98% | Racemic BINAP: useful as an achiral control (testing whether a chiral environment is required) or for parameter tuning in systems where ee is not emphasized; same scaffold enables direct comparison to R/S forms. | |
Chiral alkane-backbone diphosphine (C2-symmetric; stereoselectivity screening) | 96183-46-9 | (2R,4R)-2,4-Bis(diphenylphosphino)pentane | ≥99% | Chiral diphosphine for screening asymmetric Pd reactions (e.g., asymmetric coupling/allylic substitution); bidentate chelation stabilizes active species and can steer reductive-elimination pathways, improving selectivity. | |
Chiral alkane-backbone diphosphine (C2-symmetric; stereoselectivity screening) | 77876-39-2 | (2S,4S)-2,4-Bis(diphenylphosphino)pentane | ≥98% | Used as the enantiomeric counterpart to (2R,4R): suitable for asymmetric Pd reactions and enantioselectivity verification; bidentate chelation can also enhance active-species stability. | |
Small bite-angle chiral diphosphine (DuPhos-type; stereocontrol / selectivity tuning) | 136735-95-0 | (+)-1,2-Bis[(2S,5S)-2,5-dimethylphospholano]benzene | ≥98% | DuPhos-type diphosphines often influence key-step selectivity through small bite angle and rigidity; used for screening asymmetric Pd reactions or coupling systems sensitive to reductive elimination / stereocontrol. | |
Small bite-angle chiral diphosphine (DuPhos-type; enantioselectivity) | 147253-67-6 | (-)-1,2-Bis[(2R,5R)-2,5-dimethylphospholano]benzene | ≥97% | DuPhos-type ligand for asymmetric Pd reactions; small bite angle/rigidity can improve ee by altering transition-state geometry, and may also improve activity and late-stage durability in some systems. | |
DIOP-type chiral diphosphine (ligand screening / mechanistic control) | 32305-98-9 | (2R,3R)-(-)-1,4-Bis(diphenylphosphino)-2,3-O-isopropylidene-2,3-butanediol | ≥98% | DIOP-type chiral diphosphine: commonly used for chiral-environment construction and as a control; in Pd systems it serves as a screening point and a mechanistic comparator for “chelation/bite-angle effects on pathways.” | |
DIOP-type chiral diphosphine (ligand screening / mechanistic control) | 37002-48-5 | (2S,3S)-(+)-1,4-Bis(diphenylphosphino)-2,3-O-isopropylidene-2,3-butanediol | ≥98% | Enantiomeric counterpart: used to verify configuration inversion/selectivity direction in asymmetric reactions; also useful for comparing effects on catalytic-cycle rate and side reactions. | |
Chiral diphosphine (DIPAMP-type: selectivity screening) | 63589-61-7 | 1,2-Bis[(2-methoxyphenyl)phenylphosphino]ethane | ≥98% | DIPAMP-type chiral diphosphine: suitable for screening Pd systems requiring stereoselectivity or high sensitivity to ligand electronics/sterics; methoxy substitution can also influence solubility and coordination environment, affecting selectivity. | |
Chiral diphosphine (DIPAMP-type: selectivity screening) | 55739-58-7 | (1R,2R)-Bis[(2-methoxyphenyl)phenylphosphino]ethane | ≥97% | DIPAMP-type ligand for enantioselectivity screening and configuration-inversion controls; methoxy substitution may improve solubility and fine-tune electronics, influencing the selectivity/rate balance. | |
Josiphos-type (high selectivity and difficult substrates: ferrocene chiral platform) | 292638-88-1 | (R)-(-)-1-{(S)-2-[Bis(3,5-bis(trifluoromethyl)phenyl)phosphino]ferrocenyl}ethyl dicyclohexylphosphine | ≥97% | A representative design combining a ferrocene chiral platform with asymmetric electronics/sterics: often used for demanding asymmetric Pd reactions; helps increase selectivity while maintaining activity and controllability under complex substrates and low Pd loading. |
Note: The above are representative Aladdin products. For additional specifications, please refer to the product list at the end of the article, or search the Aladdin website using the “product name / CAS / catalog number.”
Aladdin: https://www.aladdinsci.com/
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