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.

The azido complex [(η5-C5H5)Os(PPh3)2N3] undergo 1,3-cycloaddition reactions with activated alkynes and nitriles to yield corresponding triazolato and tetrazolato complexes. Where as similar reactions with ruthenium analogues [(η5-C5H5)Ru(PPh3)2N3] and [(η5-indenyl)Ru(PPh3)2N3] were not yielded such complexes.Figure optionsDownload as PowerPoint slide