Alkylidyne ligand molybdenum complex

An efficient method for the formal abstraction of oxide from acyl ligands was developed in our laboratory 44). Oxalyl halides react directly with the pentacarbonylmetal acyl complexes of chromium, molybdenum, and tungsten to form the fra ,s-alkylidyne(halo)tetracarbonyl complexes [Eq. (5)]. Other suitable Lewis acids are COCI2, CI3COCI, CI3COCOCI, and... 

Metal alkylidyne complexes undergo a variety of oxidation and reduction reactions as well as redox-induced transformations of the alkylidyne ligands. A method for the direct transformation of Fischer-type carbyne complexes into Schrock-type alkylidyne complexes was developed in our laboratory. Bromine oxidation of the /ra/7, -carbyne bromo tetracarbonyl complexes 49 of molybdenum and tungsten in the presence of dimethox-yethane affords the dme-stabilized alkylidyne tribromo metal complexes 50 [Eq. (42)] (81). For alkyl-substituted complexes (R = Me, CH2CMe3)... 

The alkylidyne ligands in the molybdenum complexes 179 were modified by deprotonation at the y -carbon with strong bases and subsequent addition of electrophiles [Eq. (146)]. Complexes 180 were desilylated by treatment with fluoride [Eq. (147)] (48). 

Treatment of the molybdenum alkylidyne complex 191 with 300 atm CO affords a mixture of three products the products of substitution of one and two phosphite ligands and complex 192 [Eq. (154)] (91). The methox-ycarbonyl group in 192 may have arisen from the reaction of an intermediate ketenyl ligand with methanol (derived from hydrolysis of trimethyl-phosphite). Reaction of the compounds 193 with xylylisocyanide was shown to give complexes 194 [Eq. (155)] (91). The products contain the... 

Scheme 6 Formation of molybdenum complexes bearing ditbiocarboxylato ligands by sulfurization of tbe alkylidyne complexes...

Protonation of vinylidene and acetylide ligands was also found to be useful for the synthesis of high-oxidation state molybdenum alkylidyne complexes. Green and co-workers demonstrated protonation of the vinylidene complex 20 as shown in Eq. (21) (64). Selegue and co-workers... 

The metal-alkylidyne complex TpW( = CMe)(CO)2 reacts with Cp2Mo2(CO)4 or Mo(CO)3(NCMe)3 to afford the trimetal complexes Cp2TpMo2W(/t3-CMe)(CO)6 and Tp2MoW2(ia-CMe)2(ia-CO)2(CO)4, respectively (Scheme 75)." In the latter complex, one of the terminal carbonyl ligands of each tungsten centre is f/ -bound to the central molybdenum atom. 

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