Chiral Bisphosphinite Metalloligands Derived from a P-Chiral Secondary Phosphine Oxide

Interaction of PdCl2(MeCN)2 with 2 equiv of (SP)-tBuPhP(O)H (1H) followed by treatment with Et3N gave [Pd{(1)2H}]2(μ-Cl)2 (2). Reaction of 2 with Na[S2CNEt2] or K[N(PPh2S)2] afforded Pd[(1)2H](S2CNEt2) (3) or Pd[(1)2H)[N(PPh2S)2] (4), respectively. Treatment of 3 with V(O)(acac)2 (acac = acetylacetonate) and CuSO4 in the presence of Et3N afforded bimetallic complexes V(O)[Pd(1)2(S2CNEt2)]2 (5) or Cu[Pd(1)2(S2CNEt2)]2 (6), respectively. X-ray crystallography established the SP configuration for the phosphinous acid ligands in 3 and 6, indicating that 1H binds to Pd(II) with retention of configuration at phosphorus. The geometry around Cu in 6 is approximately square planar with the average Cu−O distance of 1.915(3) A. Treatment of 2 with HBF4 gave the BF2-capped compound [Pd{(1)2BF2}]2(μ-Cl)2 (7). The solid-state structure of 7 containing a PdP2O2B metallacycle has been determined. Chloride abstraction of 7 with AgBF4 in acetone/water afforded the aqua compound [Pd{(1)2BF2}(H2O)2][BF4] (8) that reacted wit...