Preparation and Characterization of 1,2-Dialkyl Compounds of Dimolybdenum an Ditungsten of Formula M2R2(NMe2)4 M-Triple bond-M

摘要

1,2-M2Cl2 (NMe2)4 compounds, where M = Mo and W, and alkyllithium reagents react in hydrocarbon solvents to give 1,2-M2R2 (NMe2)4 compounds (M-triple bond M), where R = CH2CH3, -Ch2CD3, -CD2CH3, -CH2CH2CH2CH3, -CH(CH3)2, -CH-(CH3)(C2H5), -CH2C(CH3)3, -CH2Si(CH3)3 and -C(CH3)3. These new compounds have been characterized by a combination of physicochemical studies, which include elemental analyses, mass spectroscopy, infrared spectroscopy and nmr spectroscopy. The molybdenum compounds where R = CH2CH3 and -CH(CH3)2 have been examined by single-crystal X-ray diffraction studies. The characterization data establishes that all compounds have a staggered ethane-like M2N4C2 core. In solution, nmr studies reveal the existence of a mixture of anti and gauche rotamers: as the bulkiness of the alkyl group increases, the gauche rotamer becomes increasingly favored. In the crystalline state, a gauche Mo2(C2H5)2(NMe2)4 molecule has been fully characterized by X-ray studies. The molecule has a virtual C2 axis of symmetry with the following important structural parameters: Mo-Mo = 2.203(1) A, Mo-N = 1.96(1) A (average), M-C = 2.16(1) A (average), Mo-Mo-N angle = 104(1) (average) and Mo-Mo-C = 100.57 (average).