Synthesis and characterization of new transition metal diynyl complexes

The reaction of (η5-C5H5)Mo(CO)(dppe)Cl with LiCCCCSiMe3 yielded (η5-C5H5)(CO)(dppe)MoCCCCSiMe3 (1b) and, as a by-product (η5-C5H5)Mo(CO)(dppe)Br (1a). Treatment of 1b with 0.2 equivalents of tetrabutylammonium fluoride or (η5-C5H5)Mo(CO)(dppe)Cl with HCCCCH gave the terminal butadiyne complex (η5-C5H5)(CO)(dppe)MoCCCCH (2). Complex 2 was deprotonated with sec-BuLi or lithium diisopropylamide, and the resulting anion (η5-C5H5)(CO)(dppe)MoCCCCLi (3) was trapped with Me3SiCl to regenerate 1b. The synthesis of Co2(CO)4L2(μ-η2-Me3SiC2CCSiMe3) (L2=dppa 4, 2PPh2Me 5) compounds can be achieved by two methods: from Co2(CO)6(μ-dppa) by reaction with Me3SiCCCCSiMe3 in 1:1 ratio to yield 4, or from Co2(CO)6(μ-η2-Me3SiC2CCSiMe3) by reaction with dppa (1:1 ratio) and PPh2Me (1:2 ratio) to yield 4 and 5, respectively. When the Co2(CO)4(μ-dppa)(μ-η2-Me3SiC2CCSiMe3) complex was treated with more Co2(CO)6(μ-dppa) the green di-substituted complex [Co2(CO)4(μ-dppa)]2(μ-η2:μ-η2-Me3SiC2C2SiMe3) (6) was obtained. Desilylation of 4 with Bu4NF gave Co2(CO)4(μ-dppa)(μ-η2-Me3SiC2CCH) (7). All compounds synthesized have been characterized by analytical and spectroscopic data (IR, 1H-, 31P-, 13C-NMR, MS). In addition, compounds 1a and 4 were characterized by X-ray structure analysis.