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) Å. 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 with [NH4]2[WS4] to give [Pd{(1)2BF2}2]2[μ-WS4] (9). The average Pd−S and W−S distances in 9 are
2.385(3) and 2.189(3) Å, respectively. Treatment of [(η6-p-cymene)RuCl2]2 with 1H afforded the phosphinous acid
adduct (η6-p-cymene)RuCl2(1H) (10). Reduction of [Cp*RuCl2]x (Cp* = η5-C5Me5) with Zn followed by treatment
with 1H resulted in the formation of the Zn(II) phosphinate complex [{Cp*Ru(η6-C6H5)}tBuPO2}]2(ZnCl2)2 (11) that
contains a Zn2O4P2 eight-membered ring.