Syntheses and crystal structures of the nitrido complexes [MoNCl3(MeCN)](4) and (MoNCl2(bipy)](4)

[MoNCl3(MeCN)](4) (1) is obtained by the reaction of MoCl4(MeCN)(2) with Me 3SiN3 in CH2Cl2 as a sparingly soluble and water sensitive red compound. It crystallizes as 1 . 3 CH2Cl2 in the triclinic space group P (1) over bar w ith a = 889.7(1), b = 1004.8(1), c = 1270.4(2) pm; alpha = 71.69(1)degrees; beta = 73.63(1)degrees; gamma = 86.32(1)degrees, and Z = 1. It forms centr osymmetric tetranuclear complexes, in which the Mo atoms are connected by a symmetric and linear nitrido bridges with distances Mo-N of 167.5 and 214.3 pm. The acetonitrile molecules are coordinated with a long bond length Mo- N of 241 pm in trans position to the Mo-N triple bond. The reaction of 1 wi th 2,2'-bipyridine in CH2Cl2/THF yields the tetranuclear molybdenum(V) comp lex [MoNCl2(bipy)](4) (2) as main product. It crystallizes in the tetragona l space group P4(2)/n with a = 1637.5(2), c = 1018.3(2)pm, and Z = 2. In th e tetranuclear complexes with the symmetry S-4 linear and asymmetric nitrid o bridges connect the Mo atoms to form an almost planar eight membered Mo-N ring with distances Mo-N of 173 and 203 pm. The bipyridine molecules coord inate as chelates in cis and trans position to the Mo-N triple bond. In thi s case the trans influence causes different Mo-N distances of 219 and 232 p m.