Vinylidene complexes molecular structure

Obviously, the first intermediates in the syntheses with terminal alkynols are the vinylidene complexes [Ru(bdmpza)Cl(=C= CH(CH2) +iOH)(PPhg)] (n = 1, 2), which then react further via an intramolecular addition of the alcohol functionality to the a-carbon (Scheme 22), although in none of our experiments we were able to observe or isolate any intermediate vinylidene complexes. The subsequent intramolecular ring closure provides the cyclic carbene complexes with a five-membered ring in case of the reaction with but-3-yn-l-ol and with a six-membered ring in case of pent-4-yn-l-ol. For both products type A and type B isomers 35a-I/35a-II and 35b-I/ 35b-II are observed (Scheme 22, Fig. 22). The molecular structure shows a type A isomer 35b-I with the carbene ligand and the triphenylphosphine ligand in the two trans positions to the pyrazoles and was obtained from an X-ray structure determination (Fig. 25). 

Fig. 7. Molecular structures of (a) the vinylidene complex 587 (hydrogen atoms omitted) and (b) the iridabenzene 587 (Tp hydrogen atoms omitted).

The first Mo-vinylidene complexes have been prepared by the unusual carbyne to carbene conversions illustrated in Scheme 18. The nature of (8) was confirmed by a crystal and molecular structure determination. ... 

Ab initio molecular orbital calculations on the alkyne complexes [MX4(C2H2)] (M = Mo, W X = F, Cl) and their vinylidene isomer [MX4(CCH2)1 and the anionic complexes [MX5(C2H2)] have been reported S and their electronic structure and geometry optimisation explored in detail. 

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