Reactivity study of cyclopentadienyl osmium(II) bisphosphine azido complexes with activated alkynes and nitriles: Isolation of osmium triazolato and tetrazolato complexes by 1,3-dipolar addition

The cyclopentadienyl osmium(II) complexes (η⁵-C₅H₅)Os(PPh₃)₂X] X = Br (1), CH₃CN (2)] reacts with sodium azide (NaN₃) to yield the corresponding azido complex (η⁵-C₅H₅)Os(PPh₃)₂N₃] (3). This undergoes 3+2] dipolar cycloaddition reaction with activated alkynes like dimethyl and diethyl acetylenedicarboxylate to yield triazolato complexes (η⁵-C₅H₅)Os(PPh₃)₂{N₃C₂(CO₂R)₂}] R = –CH₂CH₃ (4) and –CH₃ (5)]. The complex 3 also reacts with nitriles such as tetracyanoethylene (TCE), fumaronitrile and p-nitrobenzonitrile to yield complexes of the type (η⁵-C₅H₅)Os(PPh₃)₂{N₄C₂(CN)C(CN)₂}] (6), (η⁵-C₅H₅)Os(PPh₃)₂{N₃C₂HCN}] (7) and (η⁵-C₅H₅)Os(PPh₃)₂{N₄C(C₆H₄–p-NO₂)}] (8). These complexes were fully characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. The molecular structure of the representative complex (η⁵-C₅H₅)Os(PPh₃)₂{N₃C₂(CO₂CH₂CH₃)₂}] (4) was determined by single crystal X-ray analysis.