Synthesis, Characterization, and Electrochemical Properties of Bisosmabenzenes Bridged by Diisocyanides

Treatment of osmabenzene [Os(CHC(PPh3)CHC(PPh3)CH)Cl-2(PPh3)(2)]OH (3) with various diisocyanides in the presence of NH4PF6 afforded a series of diisocyanide-bridged bisosmabenzenes [(mu-CN-R-NC){Os(CHC(PPh3)CHC(PPh3)CH)Cl-2(PPh3)}(2)][PF6](2) (R = 4,4'-C6H4-C6H4 (5a), 4,4'-C6H4CH2C6H4 (5b), 4,4'-C6H4OC6H4 (5c), 1,4-C6H4 (5d)) in good yields through ligand substitution reactions. Similarly, reaction of osmafuran [Os(CHC(PPh3)C(OEt)O)Cl-2(PPh3)(2)] (6) with 1,4-phenylenediisocyanide produced the diisocynide-bridged bisosmafuran [mu-(1,4-phenylenediisocyanide){Os(CHC(PPh3)C(OEt)O)Cl(PPh3)(2)}(2))Cl-2 (7). Bisosmabenzenes containing a chloro and a phosphonium substituent on each metallacycle [(mu-CN-R-NC){Os(CHC(PPh3)CHCCICH)Cl(PPh3)(2)}(2)]Cl-2 (R = 4,4'-C6H4-C6H4 (9a), 4,4'-C6H4CH2C6H4 (9b), 4,4'-C6H4OC6H4 (9c), 1,4-C6H4 (9d)) could be obtained in modest yields from the reactions of the osmacycle [Os(CH=C(PPh3)CH(OH)-eta(2)-C CH)Cl-2(PPh3)(2)] (8) with corresponding diisocyanides in the presence of NH4PF6 and NaCl via nucleophilic addition reactions. All of these complexes have been fully characterized by H-1, P-31{H-1}, and C-13{H-1} NMR spectrometry, IR spectrometry, and elemental analyses. Moreover, the structure of 9d has been established by X-ray crystallography. The electrochemical properties of stable bisosmabenzenes 9a-d have been investigated, which revealed that the two metal centers in 9c and 9d can interact with each other through a diisocyanide bridge.