Vinylidene ligand substitution

Various modes of reactivity of vinylidene complexes are illustrated in Scheme 1. The first four modes of reactivity shown in Scheme 1 are (1) simple substitution of the ligands bound to the metal [6] (2) oxidation of the metal [7] (3) modification or exchange of a vinylidene substituent [8] and (4) transfer of the vinylidene ligand [9]. The last two modes... 

When trans-halo-tetracarbonylcarbyne complexes of molybdenum and tungsten, X(CO)4M=CR, are treated with sodium cyclopentadienyl, not only the displacement of the halide, but an additional elimination of two carbonyl ligands is observed, affording dicarbonyl(rj -cyclopenta-dienyl)carbyne complexes [2,3]. A different synthetic approach converts vinylidene ligands into carbyne ligands to yield comparable bisdimethylphosphite substituted complexes of molybdenum [4]. 

Ru3(CO)i2 reacts with 4-/-butyM-methyl-l-(phenylthio)cyclobutene to give Ru6(/t4-S) /t4-CCHCH=C(Me)Bu1-(CO)i6 275 in trace amounts. The bridged square-pyramidal cluster contains the sulfido ligand capping the square face and a /i4-substituted vinylidene ligand. ... 

Acetylene-vinylidene rearrangements of silylacetylene-iron carbonyl complexes have been observed,537 while iron-acetylide hydride complexes of the type [Fe(H)(C=CR)(dmpe)2], where dmpe=l,2-bis(dimethylphosphino)ethane, have been found to react with anions to afford substituted alkenyl complexes. It has been proposed538 that a likely reaction course for this latter rearrangement involves initial protonation of the cr-bound acetylide ligand at the carbon (I to the metal centre to form a vinylidene complex. Metal-to-carbon hydride migration in this vinylidene complex with attack by the anion would then lead to the neutral complex (see Scheme 106). A detailed mechanistic investigation has been carried out539 on the novel metathetical... 

Alkenes and alkynes can substitute for carbonyl ligands on Os3(CO)i2. Carbon monoxide slowly dissociates from Os3(CO)ii(j7 -PhC=CPh) and a cluster with a bridging alkyne ligand forms, Os3(CO)io(/n-PhC=CPh). The addition of ethene to the cluster gives a bridging vinylidene complex, Os3(CO)9(/u-H)2(/u-C=CH2). The oxidative addition of terminal alkynes to Os3(CO)i2 gives Os3(CO)9(/u.-H)(/u,3-CCR). Nucleophiles add to the bridging alkyne unit. 

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