Amidine and guanidine complexes of manganese and molybdenum. Crystal structures of (η-cyclopentadienyl)(N,N′-diphenylguanidino)- and (η-cyclopentadienyl)(N,N′,N″-triphenylguanidino)-dicarbonylmolybdenum(II)

Abstract

Reactions of N,N′-diphenyl- and N,N′,N″-triphenylguanidine with [MnBr(CO)₅] gave cis-[MnBr{PhNC(NHR)NHPh}(CO)₄], fac-[MnBr{PhNC(NHR)NHPh}₂(CO)₃] and [Mn{PhNC(NHR)NPh}(CO)₄] (R = H or Ph), the last complex being formed at higher temperatures with an excess of ligand. In reactions of these guanidines with [MoCl(η-C₅H₅)(CO)₃], HCl was eliminated and [Mo(η-C₅H₅){PhNC(NHR)NPh}(CO)₂] complexes (R = H or Ph) formed. Crystal structures of these molybdenum complexes have been determined, revealing symmetrically chelating co-ordination of the guanidino ligands (in close semblance of corresponding amidino-complexes) with the four-membered metallacycle planar for R = Ph but unusually (by 21°) folded for R = H due to hydrogen bonding of an uncommon type. Reaction of lithio-N,N′-di-p-tolylbenzamidine with [Mo(η-C₇H₇)(CO)₃]BF₄ yielded [Mo{η-C₇H₇N(p-MeC₆H₄)C(Ph)NC₆H₄Me-p}(CO)₃], consistent with nucleophilic attack at the ring, followed by nitrogen co-ordination at the metal by a pendant amidine group.