2-Methyl-or 2-benzyl-pyridine, and 1,2-, 1,3-, and 1,4-diazines all react like pyridine itself with [Os,(CO),,-(C8H14)2] (CBH14 = cyclo-octene) to give complexes of the type [0s3H(CO),,(p-L)] where L is a 2-metallated heterocycle. The H n.m.r. spectrum of the 2-benzylpyridine complex shows that p-L is in a locked configuration on the n.m.r. time-scale and does not alternate its bonding between the two 0 s atoms it bridges. 2,2'-Bipyridyl reacts with [OS~(CO)~ 2] 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 P2,/c, with a = 9.113( 2), b = 13.157(2), c = 18.209(2) A, p = 91.59(2)", and Z = 4. The structure was refined to R = 0.0427 for 3 550 observed reflections. The structure of [Os,H(CO)?-(C10H7N2)] is rather like those of compounds [OS,H(CO)~~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.

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The complexes [M3H(CO)9(p3-C-CCPh20H)] (M = Ru or 0s) were prepared by reaction of [M3(C0)&J with HOCPh2C-CCPh20H in saturated hydrocarbon at 130 "C for M = 0 s or in refluxing cyclohexane from M = Ru. In the latter case the yield of cluster is low and there is some 1 ,I ,4,4-tetraphenylbutadiene formed. Treatment of the trinuclear clusters in chloroform with trifluoroacetic acid leads to isomerisation with migration of the OH group from carbon to metal atoms. This was confirmed by an X-ray structure determination for the osmium productThe crystals are monoclinic, space group P2,, a = 10.569( 1), b = 20.259(3), c = 12.287(2) A, p = 95.66(1)", and 2 = 4. The structure was refined to R = 0.0621 for 4 11 2 observed reflections. There are two independent molecules (A and B) in the'unit cell with very closely similar structures. Spectroscopically, an OH group was identified and another hydrogen bound to osmium but neither hydrogen atom was located by X-ray diffraction. The OH group bridges two non-bonded osmium atoms separated by 3.374(5) A in molecule A [3.372(5) A in B], while the p-H was deduced to be across the longer 0s-0s bond [2.905(5) versus 2.861 (5) A for molecule A and 2.902(5) versus 2.869( 5) A for molecule B]. The 3,3-diphenylallene-I ,1 -diyl ligand is bonded through two 0s-C CT bonds and a 1,2-q2-co-ordination to the other osmium atom and is bent about the central atom [145(3)" for molecule A and 144(3)' for B]. The orientation of the phenyl substituents at the non-co-ordinated allene carbon atom agrees with this interpretation of the bonding.We have been interested in introducing hydroxy-or aminosubstituted alkynes into triruthenium and triosmium clusters

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