MOLYBDENUM OXO NITROSYL COMPLEXES .2. MO-95 NMR-STUDIES OF DEFECT AND COMPLETE LINDQVIST-TYPE DERIVATIVES - CRYSTAL AND MOLECULAR-STRUCTURE OF (N-BU4N)2[MO6O17(OCH3)(NO)]

Reaction of (n-Bu4N)3[Mo6O18(NO)] (1) with dimethyl sulfate in methanol gives (n-Bu4N)2[SMo12O40] and (n-Bu4N)2[Mo6O17(OCH3)(NO)] (2). Compound 2 has been characterized by X-ray diffraction. Crystal data for 2: monoclinic space group P2(1)/c, a = 9.514(3) angstrom, b = 18.066(5) angstrom, c = 15.418(4) angstrom, beta = 105.25(2)degrees, Z = 2; 2451 reflections, R = 0.037. The anion [Mo6O17(OCH3)(NO)]2- is structurally related to [Mo6O18(NO)]3- and to [Mo6O19]2-; however, due to its location on an inversion center, structural parameters for only a disorder-averaged anion were obtained. Compounds 1, 2, and (n-Bu4N)2[Mo5O13(OCH3)4(NO){Na(CH3OH)}.3MeOH (3) have been studied by Mo-95 solution NMR spectroscopy. For all species, the expected numbers of Mo signals were observed although much effort was required to reveal the Mo(II)(NO) signal. The very high deshielding of the Mo(II) resonances has been ascribed to paramagnetic shifts for the most part. The possible activation of [Mo6O19]2- upon nitrosylation has been discussed on the basis of O-17 NMR data; the charge distribution on the surface oxygen atoms in the anions of 1 and 2 appears to result from the electron-withdrawing effect of the nitrosyl ligand, which is opposed to the overall increase in charge of the polyanion.