Ruthenium from carbyne complexes

The reluctance of the carbyne carbon to react with nucleophiles is revealed by the reaction with LiEt3BH (see Scheme 6). Here the most electrophilic site is not the carbyne carbon but the ipara position of the aryl ring in the carbyne substituent Both ruthenium and osmium five coordinate, cationic, carbyne complexes undergo this reaction. The structure of a representative example, the osmium compound derived from the p-tolyl carbyne complex, has been determined by X-ray crystallography [16]. The unusual vinylidene complex reacts with HCl to produce a substituted benzyl derivative. The reaction may proceed through the intermediate a-vinyl complex depicted in Scheme 6 although there is also the possibility that the vinylidene compound is in equilibrium with the carbene tautomer as shown below. 

Support from the N.Z. Universities Grants Committee and the University of Auckland Research Committee is gratefully acknowledged. The author thanks all his coworkers named in the references but particularly Drs. James Wright and Tony Wright who were principally responsible for developing the carbyne complex chemistry of ruthenium and osmium. 

Shaffer EA, Chen C-L, Beatty AM, Valente EJ, Schanz H-J. Synthesis of ruthenium phenylindenylidene, carbyne, aUenyHdene and vinylmethylidene complexes from (PPh3)3 4RuCl2 A mechanistic and stmctural investigation. J Organomet Chem. 2007 692(23) 5221-5233. 

P. Gonzalez-Herrero, B. Weberndorfer, K. Ilg, J. Wolf, and H. Werner, The Sensitive Balance Between Five-Coordinate Carbene Ruthenium Complexes and Six-Coordinate Carbyne Ruthenium Complexes Formed from Ruthenium Vinylidene Precursors, Organometallics 20, 3672-3685 (2001). 

A similar procedure for the two-step synthesis of the first-generation ruthenium indenylidene catalysts has been patented by Umicore (Scheme 14.11) [38]. The main differences from the previously reported route lie in the utilization of diox-ane as the reaction solvent at 90 C in the first step, followed by the addition of HCl for the acid-promoted formation ofthe indenylidene ligand via the alkenyl carbyne [19]. The preparation of the tricyclohexylphosphine complex was carried out in one pot without isolating the intermediate triphenylphosphine complex 5 [38]. 

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