Four-Coordinate Molybdenum Chalcogenide Complexes Relevant to Nitrous Oxide N−N Bond Cleavage by Three-Coordinate Molybdenum(III): Synthesis, Characterization, Reactivity, and Thermochemistry

Abstract

The terminal chalcogenide complexes Mo(E)(N[R]Ar)3 (R = C(CD3)2CH3, Ar = 3,5-C6H3Me2), where E = O, S, Se, and Te, were prepared by reaction of the three-coordinate complex Mo(N[R]Ar)3 with ONC5H5, S8 or SC2H4, Se, and Te/PEt3 in respective yields of 72, 63, 80, and 73%. The Mo(E)(N[R]Ar)3 complexes were studied by EPR, SQUID, cyclic voltammetry, 2H NMR spectroscopy, and single-crystal X-ray diffraction. Thermolysis of each Mo(E)(N[R]Ar)3 complex resulted in (formal) tert-butyl radical elimination giving molybdenum(VI) chalcogenide complexes Mo(E)(NAr)(N[R]Ar)2 in yields of 85 (E = O), 84 (E = S), 64 (E = Se) and 40% (E = Te). tert-Butyl elimination kinetics were monitored (2H NMR) over a 62−104 °C temperature range for Mo(O)(N[R]Ar)3, and from 66 to 93 °C for Mo(S)(N[R]Ar)3; in both cases, a first-order decay was observed. Treatment of Mo(O)(N[R]Ar)3 with iodine (0.5 equiv) provided [Mo(O)(N[R]Ar)3][I] in 88% yield. The triflate salt [Mo(O)(N[R]Ar)3][O3SCF3] was prepared similarly (71% yield) upon treatm...