Chiral Platinum Duphos Terminal Phosphido Complexes:  Synthesis, Structure, Phosphido Transfer, and Ligand Behavior

Abstract

Treatment of Pt halide precursors with the secondary phosphine PHMe(Is) in the presence of the base NaOSiMe3 gave the terminal phosphido complexes Pt(Duphos)(Ph)(PMeIs) (Is = 2,4,6-(i-Pr)3C6H2, Duphos = (R,R)-Me-Duphos (1), (R,R)-i-Pr-Duphos (2)), Pt((R,R)-Me-Duphos)(X)(PMeIs) (X = I (3), Cl (4)), and Pt((R,R)-Me-Duphos)(PMeIs)2 (5). Low-barrier pyramidal inversion in the phosphido complexes was investigated by 31P NMR spectroscopy. Protonation of 1−5 with HBF4 gave the secondary phosphine complexes [Pt(Duphos)(Ph)(PHMeIs)][BF4] (Duphos = (R,R)-Me-Duphos (6), (R,R)-i-Pr-Duphos) (7)), [Pt((R,R)-Me-Duphos)(X)(PHMeIs)][BF4] (X = I (8), Cl (9)), and [Pt((R,R)-Me-Duphos)(PHMeIs)2][BF4]2 (10); cations 6, 9, and 10 were prepared independently from Pt chloride precursors using Ag(I) salts and PHMe(Is) and then deprotonated to yield phosphido complexes 1−5. Oxidation of the phosphido ligands in 4 and 5 with H2O2 gave Pt((R,R)-Me-Duphos)(Cl)(P(O)MeIs) (11) and Pt((R,R)-Me-Duphos)(P(O)MeIs)2 (12), respectively. Complexes 1−6, 9, and 11 were structurally characterized by X-ray crystallography; structural and 31P NMR results suggest the trans influence order P(O)MeIs > PMeIs > PHMe(Is). Reaction of 1 with [Pd(allyl)Cl]2, followed by treatment with dppe, gave Pt((R,R)-Me-Duphos)(Ph)(Cl), PMeIs(allyl) (13), and Pd(dppe)2. Treatment of 1 with Pd(P(o-Tol)3)2 gave an equilibrium mixture containing the two-coordinate palladium complex Pd(P(o-Tol)3)(μ-PMeIs)Pt((R,R)-Me-Duphos)(Ph) (14), Pd(P(o-Tol)3)2, P(o-Tol)3, and 1.

1,3,2‐Diselenaphospholanes with an Anellated Dicarba‐closo‐dodecaborane(12) Unit

“…atom has been described [22] with all 31 P NMR data, and the trend of these data agrees reasonably well with that observed here for 9. Typical are the small magnitudes of 2 J( 31 P, 31 P) cis and the large magnitude of 2 J( 31 P, 31 P) trans .…”

Asymmetric Electrophilic Reactions in Phosphorus Chemistry

“…Asymmetric alkylation or arylation of racemic secondary phosphines, catalyzed by chiral Lewis acids, in many cases led to the formation of enantiomerically enriched tertiary phosphines [106][107][108][109][110][111][112][113]. For example, the chiral platinum complex Pt(Me-Duphos)(Ph)(Br) catalyzed the asymmetric alkylation of secondary phosphines with benzyl halides to form tertiary phosphines (or their boranes) in good yields and with 50-93% ee (Equation (77)) [108].…”

“…Addition of Pd((S,S)-Chiraphos)(o-An) to enantiomerically enriched secondary phosphine in the presence of NaOSiMe3 led to the formation of a stable complex, which, when heated in excess diphenylacetylene, was converted to the tertiary (RP)-phosphine borane in 70-98% yields (Equation (79)). (79) Enantioselective alkylation of secondary phosphines with benzyl halides catalyzed by [RuH(i-Pr-PHOX)2] + complexes produced bisphosphines with high enantiomeric excesses [109,110]. The alkylation of 1,2-bis((2R,5R)-2,5-dimethylphospholano)ethane afforded (R,R)-Me-BPE) analogues with high diastereoselectivity [110].…”

“…(79) Enantioselective alkylation of secondary phosphines with benzyl halides catalyzed by [RuH(i-Pr-PHOX)2] + complexes produced bisphosphines with high enantiomeric excesses [109,110]. The alkylation of 1,2-bis((2R,5R)-2,5-dimethylphospholano)ethane afforded (R,R)-Me-BPE) analogues with high diastereoselectivity [110]. Catalytic asymmetric alkylation of bis(secondary phosphines) with benzyl bromide using NaOSiMe3 base and Pt((R,R)-Me-Duphos)(Ph)(Cl) led to the formation of The reaction of chiral secondary phosphine boranes with anisyl iodide, catalyzed by chiral Pd complex with (S,S)-Chiraphos ligand, proceeded with retention of configuration at the phosphorus atom [112].…”

“…Catalytic alkylation of bis-phosphines with 2-(bromomethyl) naphthalene using 10 mol% of the Pt((R,R)-Me-DuPhos)(Ph)(Cl) catalyst and NaOSiMe3 allowed to obtain diastereomerically pure bis(tertiary)-phosphines as shown in Equations (80) and 81 Alkylation of secondary diphosphines with o-trifluoromethylbenzyl bromide using NaOSiMe3 as a base and platinum catalysts [Pt((R,R)-Me-DuPhos)(Ph)(Cl), Pt((R,R)-Me-BPE)(Ph)(Cl)] gave tertiary diphosphines, which were isolated as optically pure boranes (Equation (82)) [73,118,119]. (82) Arylation of secondary phosphines by aryl halides, catalyzed by chiral copper complexes [97], platinum [107,111,116,118], ruthenium [109,110], palladium [73,106,113,[119][120][121] in many cases proceeded with good enantioselectivity and is a convenient method for the synthesis of tertiary phosphines. For example, the reaction of aryl iodides with secondary arylphosphines, catalyzed by chiral complex Pd((R,R)-Me-Duphos)(trans-stilbene), gives tertiary phosphines with enantioselectivity up to 88% ee [111,120] (Equation (83)).…”