Reaction of an osmium(VI) nitrido complex with cyanide: Formation and reactivity of an osmium(III) hydrogen cyanamide complex

Reaction of [Os^VI(N)(L¹)(Cl)(OH₂)] (1) with CN^- under various conditions affords (PPh₄)[Os ^VI(N)(L¹)(CN)(Cl)] (2), (PPh₄) ₂[Os^VI(N)(L²)(CN)₂] (3), and a novel hydrogen cyanamido complex, (PPh₄)₂[Os ^III{N(H)CN}(L³)(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)(L³)(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)NR¹R²}(L ³)(CN)₃]^-, which have been isolated as PPh ₄ salts (R¹=R²=H (7); R¹=H, R ²=CH₂CH₃ (8); R¹=R ²=CH₂CH₃ (9)). The molecular structures of 1-5 and 7 and 8 have been determined by X-ray crystallography. Wizards of osmium: The reaction of an osmium(VI) nitrido complex that bears a tridentate Schiff base ligand with CN^- generates an osmium(III) hydrogen cyanamido complex (see scheme). This complex reacts readily with amines to produce a series of osmium(III) guanidine complexes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.