Ortho-metallation reactions of 2-substituted pyridines, 1,2-, 1,3-, and 1,4-diazines, and 2,2′-bipyridyl with triosmium clusters. Crystal and molecular structure of nonacarbonyl-µ-(2,2′-bipyridyl-6-yl)-µ-hydrido-triangulo-triosmium(3Os–Os)

Abstract

2-Methyl- or 2-benzyl-pyridine, and 1,2-, 1,3-, and 1,4-diazines all react like pyridine itself with [Os₃(CO)₁₀-(C₈H₁₄)₂](C₈H₁₄= cycle-octene) to give complexes of the type [Os₃H(CO)₁₀(µ-L)] where Lisa 2-metallated heterocycle. The ¹H n.m.r.spectrum of the 2-benzylpyridine complex shows that µ-L is in a locked configuration on the n.m.r. time-scale and does not alternate its bonding between the two Os atoms it bridges. 2,2′-Bipyridyl reacts with [Os₃(CO)₁₂] to give the related red complex [Os₃H(CO)₉(C₁₀H₇N₂)] which contains the chelating bridging 6-metallated bipy ligand as established by a single-crystal X-ray structure determination. The crystals are monoclinic, space group P2₁/c, with a= 9.113(2), b= 13.157(2), c= 18.209(2)Å, β= 91.59(2)°, and Z= 4. The structure was refined to R= 0.0427 for 3 550 observed reflections. The structure of [Os₃H(CO)₉-(C₁₀H₇N₂)] is rather like those of compounds [Os₃H(CO)₁₀,X] and in particular where X = 2-pyridyl except that in the nonacarbonyl complex described here the ortho-metallated pyridine ring is part of a 2,2′-bipyridyl chelating ligand.