Titanocene benzyne complex

Many stable metal complexes of arynes are known but in most of their reactions of synthetic interest, the yields are poor. For example, thermolysis of titanocene (Cp2TiPh2) at 80-100 C gives rise to a tita-nium-benzyne complex which reacts with molecular nitrogen to afford aniline with low efficiency.29 However, procedures are available for in situ generation of zirconium complexes (14) and for their coupling reactions to synthesize functionalized aromatic compounds in preparatively useful yields (Scheme I).30 Whether such complexes should be regarded as ir-bonded benzynes or o-bonded o-phenylenes, remains a debatable point.31... 

Prior to the development of the cyclization reactions discussed earlier, some three-membered metalla-cycles containing Group IV metals were known. In 1968, the thermal reaction of Ph2TiCp2 with PhCHCPh producing (36 equation 34) was reported. One of the presumed intermediates was (37). No experimental support was presented, and the mechanistic interpretation was probably erroneous in the light of what is now known. The same compound was later prepared by another method, and benzyne-titanocene complex (38 equation 35) was suggested as an intermediate. ... 

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