Molecular geometry of M(NO)2 complexes: single crystal X-ray structure of Co(NO)2(C5H5N)2+BF4−, lability of the pyridine ligands of Co(NO)2(C5H5N)2+, and its relevance to the formation of the Co2(NO)3+ bimetallic core

The BPh 4 − and BF 4 − derivatives of Co(NO) 2 (Py) 2 + 3 (Py = pyridine) have been prepared. In solution, whereas Co(NO) 2 (L) 2 + BPh 4 − (L = phosphane) and 3-BF 4 − are inert, 3-BPh 4 − decomposes rapidly in the absence of an excess of Py. Complex 3-BF 4 − crystallizes in the monoclinic system with two independent molecules, A and B, in the asymmetric unit, space group P2 1 /a, a = 14.7633(6) Å, b = 13.9739(5) Å, c = 15.1667(6) Å, β = 109.334(4)°, 2225 reflections, R = 0.054, Rw = 0.023. The cobalt coordination polyhedron is a distorted tetrahedron. The comparison of the (O)N—Co—N(O) angles of 115.6(3)° (molecule A) and 115.9(3)° (molecule B) with those of other [Formula: see text] pseudotetrahedral dinitrosyl complexes suggests that the lability of the Py ligands of cation 3 reflects the compression experienced by the Co(NO) 2 + molecular portion.