Carbyne complexes reactivity patterns

BONDING MODELS AND REACTIVITY PATTERNS FOR TRANSITION METAL CARBENE AND CARBYNE COMPLEXES... 

The wealth of empirical information collected for transition metal carbene and carbyne complexes may be best interpreted within the framework of sound theoretical models for these compounds. Perhaps the most significant contribution made by the theoretical studies of carbene and carbyne complexes concerns an understanding of the reactivity patterns they display. In this section the relationship between bonding and reactivity is examined, with particular emphasis being given to the ways in which studies of Ru, Os, and Ir compounds have helped unify the bonding models applied to seemingly diverse types of carbene and carbyne complexes. 

In view of the similarities between the bonding models for carbene and carbyne complexes it is not surprising that similar patterns of reactivity should be observed for these compounds. Thus nucleophilic and electrophilic additions to the metal-carbon triple bond are anticipated under appropriate circumstances, and both orbital and electrostatic considerations will be expected to play a role. 

A related reactivity pattern is observed when the complexes 4c or 4d are protonated with HBF4 Et20, using the donor molecule NCMe as a solvent (29). In this instance, a dication results as the carbyne ligand is transformed into an rj1-acyl group in a stepwise process such as described earlier (Scheme 4). The coordination sphere of the metal is filled by two NCMe molecules, yielding the salts [ W (CO)( NCMe)2( 2-COCH2RXf7-... 

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