OXYGEN TRIPOD LIGAND SUPPORTED MOLYBDENUM AND TUNGSTEN CARBYNE COMPLEXES - CARBON-CARBON BOND FORMATION REACTIONS - CRYSTAL-STRUCTURES OF [L(CO)2W=CC6H4-P-CH3] AND [L(CO)MO(MU-CO)PD(I)C(C6H4-P-CH3)C6H4-O-CH2N(CH3)2], L-=[(C5H5)CO(P(O)(OCH3)2)3]-

Several carbyne complexes of the type [LR(CO)2MCC6H4-p-CH3] (1) (where LR- is the tris-chelating oxygen ligand: [(C5H5)Co{P(O)R2}3]-, R = OMe, OEt, O-i-Pr; M = Mo, W) have been synthesized. One of these, [LOMe(CO)2WCC6H4-p-CH3] (1a) was fully characterized by a crystal structure determination. Complex 1a adds one mole of trimethylphosphine to afford high yields of a tungstacyclopropenone derivative, [LOMe(CO){P(CH3)3}W(η2-C(O)CC6H4-p-CH3)] (2), which is formed via formal migration of CO to the MC bond. On the other hand, the molybdenum complexes 1c-e [R = OMe (1c), OEt (1d), O-i-Pr (1e)] react with trimethylphosphine exclusively by CO displacement to afford [LR(CO){P(CH3)3}MoCC6H4-p-CH3] (3a-c). The reaction requires several days at room temperature to reach completion, and no intermediates (e.g. of type 2) are detected. When the carbyne complexes 1a and 1c react with di-μ-iodo-bis(N,N-dimethylaminomethylphenyl-2C,N)dipalladium, [{(dmba)PdI}2], insertion of the MC bond into the PdC bond takes place. Only one regioisomer, namely the carbon-carbon coupling product, {A figure is presented}[M = W (4a), Mo (4b)] was observed. The crystal structure of 4b was determined. The carbyne carbon atom of 1c is σ-bonded to the ortho carbon of the dmba moiety and the palladium atom interacts strongly with this carbon atom, the molybdenum center, and a CO group. The new organometallic ligand can be regarded as a unprecedented metalla-allyl unit η3-bonded to palladium. The 1H and 31P NMR spectra of the compounds have been analyzed. © 1990.