Chemistry of di-and tri-metal complexes with bridging carbene or carbyne ligands. Part 36. Reactions of the dimetal compounds [ReM(CC6H4Me-4)(CO)9](M = Cr, Mo, or W) with octacarbonyldicobalt; crystal structures of [Co2WRe(µ3-CC6H4Me-4)(CO)15] and [Co2Re(µ3-CC6H4Me-4)(CO)10]

Abstract

Treatment of the compounds [ReM(CC₆H₄Me-4)(CO)₉](M = Cr, MO, or W) with [Co₂(CO)₈] in light petroleum at room temperature afforded the tetranuclear metal complexes [Co₂MRe(µ₃-CC₆H₄Me-4)(CO)₁₅]. The structure of the tungsten-containing species has been established by X-ray diffraction. Crystals are monoclinic (space group P2₁), with two crystallographically independent molecules in the asymmetric unit. The two cobalt atoms and the tungsten form a triangle [mean Co–W 2.72(1), mean Co–Co 2.482(3)Å], to which the rhenium atom is attached via the tungsten [mean Re–W 3.13(2)Å]. The Co₂W triangle is capped by the tolylmethylidyne ligand [mean µ-C–W 2.08(2), mean µ-C–Co 1.94(2)Å]. The carbonyl ligands are all terminally bound; five to the rhenium, four to the tungsten, and three to each cobalt. When toluene solutions of the tetranuclear metal compounds are heated to ca. 100 °C, they are converted into a dicobaltrhenium complex [Co₂Re(µ₃-CC₆H₄Me-4)(CO)₁₀], with concomitant formation of the hexacarbonyls [M(CO)₆]. An X-ray crystallographic study established the structure of the dicobaltrhenium species. Crystals are monoclinic (space group P2₁/c). The metal-atom triangle [Co–Co 2.535(1), mean Co–Re 2.70(2)Å] is asymmetrically triply bridged by the tolylmethylidyne group [µ₃-C–Re 2.189(6), mean µ₃-C–Co 1.89(1)Å]. The carbonyl ligands are terminally bound to the metal atoms; four to the rhenium, and three to each cobalt. Spectroscopic data (i.r. and n.m.r.) for the new compounds are reported and discussed.