Synthesis, Characterization, and Oxygen Atom Transfer Reactions of {HB(Me2C3N2H)3}MoO{S2P(OR)2} and {HB(Me2C3N2H)3}MoO21-S2P(OEt)2}

Sue A. Roberts, Charles G. Young, W. E. Cleland, Richard B. Ortega, John H. Enemark

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Abstract

The compounds {HB(Me2pz)3}MoO{S2P(OEt)2} (1a) and {HB(Me2pz)3}MoO2{S2P(OEt)2} (2) containing bidentate and monodentate S2P(OEt)2- ligands, respectively, have been prepared by the reaction of Mo2O3{S2P(OEt)2}4 with K{HB(Me2pz)3}. {HB(Me2pz)3}MoO{S2P(OEt)2} and its analogue {HB(Me2pz)3}MoO{S2P(OMe)2} have also been prepared in higher yield by the reaction of Mo2O3{S2P(OEt)2}4 with Ph3P followed by reaction with K{HB(Me2pz)3}. Both 1a and 2 have been structurally characterized by X-ray crystallography. The blue Mo(lV) compound 1a crystallizes in the monoclinic space group P21/c with a = 17.987 (3) Å, b = 8.219 (3) Å, c = 18.681 (7) Å, β = 104.88 (2)°, and Z = 4. The molybdenum atom is six-coordinate and facially coordinated by the tridentate HB(Me2pz)3- ligand, by one terminal oxo ligand (Mo═O = 1.644 (6) Å) and by the bidentate S2P(OEt)2- ligand. The gold-colored Mo(VI) complex 2 crystallizes as the toluene hemisolvate in the triclinic space group PI with a = 8.421 (1) Å, b = 12.654 (6) Å, c = 15.240 (5) Å, α = 87.77 (3)°, β = 81.36 (2)°, γ = 74.37 (3)°, and Z = 2. The molybdenum atom is six-coordinate with a tridentate HB(Me2pz)3- ligand, two terminal oxo ligands (Mo═O = 1.690 (2) and 1.697 (2) Å), and a monodentate S2P(OEt)2- ligand. The S2P(OEt)2- ligand adopts an extended geometry, and the uncoordinated sulfur atom is 5.42 Å from the molybdenum atom. Compound 1a reduces Me2SO to Me2S. The kinetic data can be fit to a second-order rate law with k = 5.46 (6) × 10-5 (M s)-1 in toluene at 40 °C. Activation parameters determined from plots of In (k/T) vs 1/T are ΔH* = 15.3 (2) kcal mol-1 and ΔS* = -29 (2) cal (mol K)-1. The large negative entropy of activation indicates that an associative mechanism is operative. Compound 2 oxidizes Ph3P to Ph3PO. Again, a second-order rate law is followed; k = 3.4 (1) × 10-3 (M s)-1 in toluene at 25 °C. Both complexes catalyze the oxidation of Ph3P by Me2SO.

Original languageEnglish (US)
Pages (from-to)3044-3051
Number of pages8
JournalInorganic Chemistry
Volume27
Issue number17
DOIs
StatePublished - Aug 1 1988

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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