Synthesis, Crystal Structures, and Reactivity of Osmium(II) and -(IV) Complexes Containing a Dithioimidodiphosphinate Ligand

Reduction of trans-[OsL2(O)2] (1) (L- = [N(i-Pr2PS)2]-) with hydrazine hydrate afforded a dinitrogen complex 2,
possibly “[OsL2(N2)(solv)]” (solv = H2O or THF), which reacted with RCN, R‘NC, and SO2 to give trans-[OsL2(RCN)2] (R = Ph (3), 4-tolyl (4), 4-t-BuC6H4 (5)), trans-[OsL2(R‘NC)2] (R‘ = 2,6-Me2C6H3 (xyl) (6), t-Bu (7)), and
[Os(L)2(SO2)(H2O)] (8) complexes, respectively. Protonation of compounds 2, 3, and 6 with HBF4 led to formation
of dicationic trans-[Os(LH)2(N2)(H2O)][BF4]2 (9), trans-[Os(LH)2(PhCN)2][BF4]2 (10), and trans-[Os(LH)2(xylNC)2][BF4]2
(11), respectively. Treatment of 1 with phenylhydrazine and SnCl2 afforded trans-[OsL2(N2Ph)2] (12) and trans-[OsL2Cl2] (13), respectively. Air oxidation of compound 2 in hexane/MeOH gave the dimethoxy complex trans-[OsL2(OMe)2] (14), which in CH2Cl2 solution was readily air oxidized to 1. Compound 1 is capable of catalyzing
aerobic oxidation of PPh3, possibly via an Os(IV) intermediate. The formal potentials for the Os−L complexes have
been determined by cyclic voltammetry. The solid-state structures of compounds 4, 6, cis-8, 13, and 14 have been
established by X-ray crystallography.