Mixed Dinitrogen−Organocyanamide Complexes of Molybdenum(0) and Their Protic Conversion into Hydrazide and Amidoazavinylidene Derivatives

Organocyanamides, N⋮CNR2 (R = Me or Et), react with trans-[Mo(N2)2(dppe)2] (1, dppe = Ph2PCH2CH2PPh2),
in THF, to give the first mixed molybdenum dinitrogen−cyanamide complexes trans-[Mo(N2)(NCNR2)(dppe)2] (R =
Me 2a or Et 2b) which are selectively protonated at N2 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 β-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.