Photochemical synthesis and structural characterization of (η5-C5Me5)3Mo3(CO)42-H)(μ3-O): an unprecedented 46-electron trimolybdenum cluster containing a localized monoprotonated MoMo double bond

Charles P. Gibson, A. David Rae, Diana R. Tomchick, Lawrence F. Dahl

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Irradiation of the 30-electron Mo25-C5Me5)2(CO)4 and Re2(CO)10 in toluene solution (containing H2O) afforded (in 1-2% yields) a novel triangular metal cluster, (η5-C5Me5)3Mo3(CO)42-H)(η3-O) (1), which was characterized by a single-crystal X-ray diffraction study. Compound 1, of pseudo Cs-m symmetry, has a triangulo-Mo33-O) core with composite MoHMo and MoMo electron-pair bonds along one unusually short edge (2.660(1) Å) and Mo electron-pair bonds along the other two edges (2.916(1) and 2.917(1) Å). The edge-bridged hydride ligand, which displays a characteristic high-field proton NMR resonance at δ -17.79 ppm, was not found from the crystallographic determination but was located via a quantitative potential-energy-minimization method. This procedure unambiguously established that the optimized hydrogen position, which corresponds to a distinct coordination site with identical MoH distances of 1.85 Å, is the only one that can be sterically occupied by a metal-bound hydride ligand. This 46-electron species is the first electron-deficient trimolybdenum cluster containing a monoprotonated MoMo double bond; its existence is attributed to ligand overcrowding due to the bulky pentamethylcyclopentadienyl rings. Black (η5- C5Me5)3Mo3(CO)42-H)(η3-O) · 1/2THF crystallizes with two formula species in a triclinic unit cell of P1 symmetry with a 8.603(4), b 11.115(4), c 19.412(11) Å, α 80.69(4)°, β 101.10(4)°, and γ 98.88(3)° at -40° C. Least-squares refinement (RAELS with 221 variables) of one independent Mo3 molecule and a centrosymmetrically-disordered THF molecule converged at R1(F) 5.62%, R2(F 6.88% for 8460 independent diffractometry data (I0 ρ 3σ(I0 collected at -40° C with Mo-Kα radiation.

Original languageEnglish (US)
Pages (from-to)C23-C30
JournalJournal of Organometallic Chemistry
Issue number3
StatePublished - Feb 23 1988


ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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