Mixed dinitrogen-organocyanamide complexes of molybdenum(0) and their protic conversion into hydrazide and amidoazavinylidene derivatives

Organocyanamides, NdropCNR(2) (R = Me or Et), react with trans-[Mo(N-2)(2)(dppe)(2)] (1, dppe = Ph2PCH2CH2PPh2), in THF, to give the first mixed molybdenum dinitrogen-cyanamide complexes trans-[Mo(N-2) (NCNR2)(dppe)(2)] (R = Me 2a or Et 2b) which are selectively protonated at N-2 by HBF4 to yield the hydrazide(2-) complexes trans[Mo(NNH2)(NCNR2)(dppe)(2)][BF4](2) (R = Me, 3a, or Et, 3b). On treatment with Ag[BF4], oxidation and metal fluorination occur, and the ligating cyanamide undergoes an unprecedented beta-protonation at the unsaturated C atom to form trans-[MoF(NCHNR2)(dppe)(2)][BF4](2) (R = Me, 4a, or Et, 4b) compounds which present the novel amidoazavinylidene (or amidomethyleneamide) ligands. Complexes 4 are also formed from the corresponding compounds 3, with liberation of ammonia and hydrazine. The crystal structure of 2b was determined by single-crystal X-ray diffraction analysis which indicates that the N atom of the amide group has a trigonal planar geometry.