Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 92. Synthesis of alkynylmethylidyne-molybdenum and -tungsten complexes and their reactions with [Co₂(CO)₈] and [Mo₂(CO)₆(η-C₅H₅)₂]

Abstract

The mononuclear metal-alkylidyne compounds [M(≡C-C≡But)(O2CCF3)(CO) 2L2][L2 = tmen (N,N,N′,N′-tetramethylethylenediamine), M = Mo (1a) or W (1b); L2 = bipy (2,2′-bipyridine), M = Mo (1c); L2 = 2 × py (py = pyridine), M = W (1d)] have been prepared by treating the complexes [M(CO)6] in thf (tetrahydrofuran) successively with Li(C≡CBut), (CF3CO)2O, and L2. The species (1a), (1c), and (1d) have been used as precursors for the synthesis of the compounds [M(≡C-C≡CBut)(CO)2L] {L = η-C5H5, M = Mo (2a) or W (2b); L = HB(pz)3 [hydrotris(pyrazol-1-yl) borate], M = Mo (2c) or W (2d); L = HB(dmpz)3 [tris(3,5-dimethylpyrazol-1-yl)hydroborate], M = MO (2e). Treatment of the complexes (2a) and (2b), respectively, with [Co2(CO)8] in light petroleum gives the trimetallatetrahedrane clusters [MCo2(μ3-C-C≡CBut)(CO) 8(η-C5H5)] (M = Mo or W) in quantitative yield. In contrast, (2d) and (2e) with [Co2(CO)8] afford, respectively, the μ-alkyne trimetal compounds [Co2{μ-ButC2C≡M(CO) 2L}(CO)6][M = W, L = HB(pz)3; M = Mo, L = HB(dmpz)3]. Similarly, whereas (2b) reacts with [Mo2(CO)6(η-C5H5)2] to yield a trimetallatetrahedrane cluster [Mo2W(μ3-C-C≡CBut)(CO) 6(η-C5H5)3], complex (2d) with the dimolybdenum reagent gives the μ-alkyne trimetal compound [Mo2{μ-ButC2C≡W(CO) 2[HB(pz)3]}(CO)4(η-C5H 5)2]. The n.m.r. data for the new compounds are reported and discussed. Show more