Vinylidene complexes [Ru(eta(5)-C5H5){=C=C(H)R}(PPh3)L]BPh4 (1, 2) [L = P(OMe)(3), P(OEt)(3); R = Ph, p-tolyl, Bu-t, H] react with hydrazine R1NHNH(2) (R1 = H, Me, Ph) to afford nitrile derivatives [Ru(eta(5)-C5H5)( N=CCH2R)(PPh3)L]BPh4 (3, 4) and amine R1NH(2). Hydroxylamine NH2OH also reacts with vinylidenes 1, 2 to yield nitrile derivatives 3, 4 and H2O. Studies with N-15-labeled hydrazine and DFT calculations allowed a reaction path to be proposed. The complexes were characterized by spectroscopy (IR, H-1, P-31, C-13 and N-15 NMR) and by X-ray crystal structure determination of [Ru(mu(5)-C5H5)(N=CCH2Ph)(PPh3){P(OEt)(3)}] BPh4 (4a).