Synthesis and Structure of Metal Complexes of P-Stereogenic Chiral Phosphiranes: An EDA-NOCV Analysis of the Donor–Acceptor Properties of Phosphirane Ligands

Abstract

Reaction of the enantiomerically enriched P-stereogenic phosphiranes syn-(R P ,S C )-Mes*PCH 2 CH(Ph) (syn-1) and anti-(S P ,S C )-Mes*PCH 2 CH(Ph) (anti-2, Mes* = 2,4,6-(t-Bu) 3 C 6 H 2 ) with metal complex precursors gave Au(L)(Cl) (L = 1 (3); L = 2 (4)), trans-ML 2 Cl 2 (L = 1, M = Pd (5), Pt ( 6)), Pd(η 3 -C 3 H 5 )(L)(Cl) (L = 1 (7)), and trans-RhL 2 (CO)(Cl) (L = 1 (8); L = 2 (9)); 3, 4, 7, and 9 were crystallographically characterized. Phosphirane coordination resulted in shortening of the P−C bonds and increased bond angles at P, consistent with rehybridization at phosphorus. A comparison of complexes of phenylphosphirane and phenyldimethylphosphine using IR spectra, coupled with DFT studies using electronic decomposition analysis (EDA) and natural orbitals for chemical valence (NOCV), indicated that phosphiranes are slightly poorer σ-donors than the analogous phosphines and that the π-acceptor properties of these ligands are similar. Pauli repulsion, dispersion, and electrostatic attraction are also important factors in determining the strength of these metal−ligand interactions.

Transition Metal-Induced Cyclization of 1-Phosphabutadienes: Selective Formation of 1-Phosphet-2-ene or P═C-Substituted Phosphacyclohexene Ligands

“…All four isomers are shown in Chart . This type of isomerism for Pd-allyl complexes bearing chiral substituents is well-established …”

Asymmetric 1,3-dipolar cycloaddition reaction of chiral 1-alkyl-1,2-diphospholes with diphenyldiazomethane

“…26,41,42 Phosphiranes are 3-membered cyclic phosphines with unique stereoelectronic properties, (smaller cone angles and higher inversion barriers compared with their acyclic analogues) and are thought to be poorer s donors and better p acceptors, 40 but their use as ligands in metal-catalyzed reactions is rare. 43 Chiral phosphiranes are especially rare; [44][45][46][47] therefore, the convenient asymmetric cycloaddition reaction reported here is potentially useful for expanding their limited applications in asymmetric catalysis. [48][49][50] In conclusion, we have shown that a diastereoselective 1,3dipolar cycloaddition reaction of 1-alkyl-1,2-diphospholes 1 and 4 with a chiral substituent at phosphorus with diphenyldiazomethane is a new way for the selective synthesis of P-chiral bicyclic phosphiranes from cheap and readily available starting materials.…”

Displacement of P-Stereogenic Phosphiranes from Rhodium by CO in Hydroformylation Catalysis

“…12 The CO stretching frequency of 1968 cm −1 for both 3−4 was in between the values for complexes where L is the powerful donor PAd 3 (Ad = 1-adamantyl, 1948 cm −1 ) 13 or the acceptor P(NC 4 H 4 ) 3 (2012 cm −1 ), 14 and similar to the PPhMe 2 complex (1971 cm −1 ), 14 consistent with intermediate donor−acceptor properties of the phosphiranes. 7 The crystal structure of syn-phosphirane complex 3 (Figure 1 and the Supporting Information) showed the expected square planar coordination at rhodium. The Rh−O1 distance trans to CO (2.041(2) Å) was shorter than the Rh−O2 bond length trans to the phosphirane (2.057(2) Å) and the analogous distance in Rh(acac)(CO)(PPh 3 ) (2.087(4) Å), consistent with the trans influence order CO < synphosphirane 1 < PPh 3 .…”

“…4 The P−N bond in BABAR-Phos and its bicyclic structure are unusual in phosphiranes, 5 so we wanted to test the simpler P-stereogenic phosphiranes syn-and anti-Mes*PCH 2 CHPh (1−2) 6 , which formed stable Vaska-type rhodium complexes trans-RhL 2 (CO)(Cl) (Mes* = 2,4,6-(t-Bu) 3 C 6 H 2 , Chart 1). 7 Experimental and computational evidence suggests that phosphiranes are slightly poorer σ-donors than the analogous phosphines, and, in contrast to the earlier hypothesis, their πacceptor properties are similar. 7,8 These unusual ligands might therefore behave like "normal" phosphines in catalysis, but the three-membered ring causes significant differences, which may limit their applications.…”