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

Abstract

The cyclopentadienyl osmium(II) complexes [(η 5-C 5H 5)Os(PPh 3) 2X] [X = Br ( 1), CH 3CN ( 2)] reacts with sodium azide (NaN 3) to yield the corresponding azido complex [(η 5-C 5H 5)Os(PPh 3) 2N 3] ( 3). This undergoes [3+2] dipolar cycloaddition reaction with activated alkynes like dimethyl and diethyl acetylenedicarboxylate to yield triazolato complexes [(η 5-C 5H 5)Os(PPh 3) 2{N 3C 2(CO 2R) 2}] [R = –CH 2CH 3 ( 4) and –CH 3 ( 5)]. The complex 3 also reacts with nitriles such as tetracyanoethylene (TCE), fumaronitrile and p-nitrobenzonitrile to yield complexes of the type [(η 5-C 5H 5)Os(PPh 3) 2{N 4C 2(CN) C(CN) 2}] ( 6), [(η 5-C 5H 5)Os(PPh 3) 2{N 3C 2HCN}] ( 7) and [(η 5-C 5H 5)Os(PPh 3) 2{N 4C(C 6H 4– p-NO 2)}] ( 8). These complexes were fully characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. The molecular structure of the representative complex [(η 5-C 5H 5)Os(PPh 3) 2{N 3C 2(CO 2CH 2CH 3) 2}] ( 4) was determined by single crystal X-ray analysis.