Coupling Reactions of Terminal Two‐Faced π Ligands and Related Cleavage Reactions

Terminal Mo Carbide and Carbyne Reactivity: H2 Cleavage, B–C Bond Activation, and C–C Coupling

“…Although the reaction proceeds in low yield (<5%), the ketenyl product 7 is notable as a rare example of a metal-coordinated “CHCO” fragment, according to a Cambridge Crystallographic Database search. In addition to 7 , only one other crystallographically characterized example has been reported in which the “WCHCO” fragment is bound by AlCl 3 at the oxygen; all other examples bear non-H substitution at the terminal ketenyl C. ,, In the W example, coupling between the [W]CH and CO fragments was induced through addition of AlCl 3 , in contrast with the present example, in which coupling occurred spontaneously. Complex 7 with H substitution is of relevance to selective C 1 conversion to C 2 products, as the organic C 2 product, ketene, can formally be released through addition of H – .…”

“…Improved understanding can lead to rationally tuned catalysts, greater selectivity toward desired products, and, importantly, reduced cost . Toward this end, discrete organometallic model systems have been investigated as a means of parsing the elementary steps of C–O bond cleavage, C–C coupling, and hydrogenation. − Of these, complexes with multiply bonded ligands including terminal carbides, alkylidynes, and alkylidenes remain of interest, as these have been invoked as intermediates of hydrogenation and oligomerization to catenated products. , While the C–C coupling of alkylidyne and alkylidene complexes has been extensively studied, ,− the reactivity of carbides remains much more poorly understood, likely owing to the rarity of these structures, particularly the more reactive terminal examples. − Still, terminal carbides have strong potential for the development of new catalytic methodologies owing to their steric accessibility and reactivity.…”