HYDRAZINOCARBENE METAL-COMPLEXES - SYNTHESIS FROM ALLENYLIDENE COMPLEXES AND HYDRAZINES, REARRANGEMENT AND CYCLIZATION

The diarylallenylidene pentacarbonyl complexes (CO)(5)M=C=C=C(C(6)H(4)NMe(2)-p), (M = W (1), Cr (2)) add I,2-disubstituted hydrazines RNH-HNR to form alkenyl hydrazino carbene complexes (CO)(5)M=C(C(H)=C(C(6)H(4)NMe(2)-p)(2))NR-N(H)R (M = W, R = Bn (3b), Pr-i (3c), (c)Hex (3d); M = Cr, R = Me (4a), Pr-i (4b)) in good yield. 3e and 4b are formed selectively as E-conformers (E arrangement of N(beta)HR and (CO)(5)M with respect to the C(carbene)-N-alpha bond). In contrast, all other derivatives of 3 and 4 are obtained as a mixture of E/Z-isomers. On heating, E-3a and E-3b rearrange to give the acrylamidine complexes (C0)(5)W-NR=C(NHR>C(H)=C(C(6)H(4)NMe(2)-p)(2) (R = Me (5a), Bn (5b)). The structure of complex 5b was established by X-ray analysis. Acid-catalyzed, the alkenyl hydrazino carbene complexes E-3a, E-3b and 3e are transformed by intramolecular cyclization into the pyrazolidinylidene complexes (CO)(5)W=C-NR-NR-C(C(6)H(4)NMe(2)-p)(2) R = Me (6a), Bn (6b), Pr-i (6c)).