Synthesis and characterization of trimetallic complexes containing M-Pd-M arrays (M = Mo, W) and their relevance in palladium-catalyzed metal-carbon bond formation

Article abstract of DOI:10.1021/om020043j

The heterobimetallic complexes [MPd(PPh₃)(C≡C-Ph)(CO)₃(η⁵-C₅ -C₅H₂Ph₂(PPh₂)] (5a, M = Mo; 5b, M = W) convert under chromatography to diastereomeric mixtures of the new trimetallic clusters [Pd{M(CO)₃(η⁵-C₅H₂Ph₂ (PPh₂)}₂] (M = Mo, 9a; W, 9b), which contain a linear M-Pd-M array clamped between two (diphenyl)cyclopentadienyl-diphenylphosphino ligands. Diastereomeric pure forms of both trimetallic clusters 9a,b were obtained by fractional crystallization procedures, and the molecular structures of rac-9a and rac-9b were determined by single-crystal X-ray diffraction analyses. The trimetallic complexes 9a,b have been found to be intermediates in coupling reactions between M-I moieties and Bu₃Sn-C≡C-Ph, to form metallacetylides M-C≡C-Ph. Independent high-yield synthetic routes to 9a,b have been developed.