Reaction of an Osmium(VI) Nitrido Complex with Cyanide: Formation and Reactivity of an Osmium(III) Hydrogen Cyanamide Complex

Reaction of [Os-VI(N)(L-1)(Cl)(OH2)](1) with CN- under various conditions affords (PPh4)[Os-VI(N)(L-1)(CN)(Cl)] (2), (PPh4)(2)[Os-VI(N)(L-2)(CN)(2)] (3), and a novel hydrogen cyanamido complex, (PPh4)(2)[Os-III{N(H)CN}(L-3)(CN)(3)] (4). Compound 4 reacts readily with both electrophiles and nucleophiles. Protonation and methylation of 4 produce (PPh4)[Os-III(NCNH2)(L-3)(CN)(3)] (5) and (PPh4)[Os-III(NCNMe2)(L-3)(CN)(3)] (6), respectively. Nucleophilic addition of NH3, ethylamine, and diethylamine readily occur at the C atom of the hydrogen cyanamide ligand of 4 to produce osmium guanidine complexes with the general formula [Os-III{N(H)C-(NH2)(NRR2)-R-1}(L-3)(CN)(3)](-), which have been isolated as PPh4 salts (R-1 = R-2 = H (7); R-1 = H, R-2 = CH2CH3 (8); R-1 = R-2 = CH2CH3 (9)). The molecular structures of 1-5 and 7 and 8 have been determined by X-ray crystallography.