Reactions of molybdenum(II) azides Mo(η3-C3H5)(CO)2(L2)(N3) (L2 = en, dppe) toward dipolarophiles

The reactions of molybdenum(II) azides Mo(η3-C3H5)(CO)2(L2)(N3) (L2 = en, dppe) with various unsaturated dipolarophiles were investigated. The isolated [3 + 2] cycloaddition products were tetrazolate complexes Mo(η3-C3H5)(CO)2(en)(N4CR) (R = C(CN)C(CN)2 (1), C6H4NO2 (2), CHCH2 (3)) and Mo(η3-C3H5)(CO)2(dppe){N4C(C(CN)C(CN)2) (5), and triazolate complexes Mo(η3-C3H5)(CO)2(en){N3C2(CO2C2H5)2} (4) and Mo(η3-C3H5)(CO)2(dppe){N3C2(CO2C2H5)2} (6). Elevated temperature is required for the preparations of the en containing complexes 2 and 3. In the reactions of Mo(η3-C3H5)(CO)2(L2)(N3) (L2 = en, dppe) with carbon disulfide, the isothiocyanate complexes Mo(η3-C3H5)(CO)2(L2)(NCS) (L2 = en (7), L2 = dppe (8)) were isolated. These complexes are fluxional in solution, from which broad unsolved NMR signals were observed for the en containing complexes, and average NMR signals were observed for the dppe containing complexes at room temperature. The solution structures of 1–8 were studied by low temperature NMR spectroscopy, except for 5, asymmetric conformation was found in each complex. A static solution structure of 5 cannot be reached even at −90 °C. The single-crystal X-ray diffraction analyses revealed the asymmetric endo-conformation of 1–8 and the heterocycle ligand in complexes 1–6 to be N(2) bound to the metal.