Ruthenium(II) pentamethylcyclopentadienyl half-sandwich carbene complexes with polypyridyl ligands

Polypyridyl complexes [RuCl(η5-C5Me5)(N–N)] (1–4) [N–N [dbnd] 2,2′-bipyridine (bpy) (1), 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me2bpy) (2), 1,10-phenanthroline (phen) (3) and 4,7-dimethyl-1,10-phenanthroline (4,7-Me2phen) (4)] were prepared by reacting [RuCl2(η5-C5Me5)]2 with Zn dust in the presence of polypyridyl ligands. Unlike the related [RuCl(η5-C5Me5)(L1)(L2)]+ [L1, L2 = P(OR)3, PPh3] derivatives with P-donor ligands, treatment of chloro compounds 1–4 with diazoalkanes Ar1Ar2CN2 afforded polypyridyl carbene complexes [Ru(η5-C5Me5)([dbnd]CAr1Ar2)(N–N)]BPh4 (5–8) [Ar1 = Ar2 = Ph (a), Ar1 = Ph, Ar2 = p-tolyl (b)]. Comparative DFT studies of the formation of metallacarbenes from aromatic diazoalkanes are reported. Phosphite complex [Ru(η5-C5Me5)(bpy)P(OEt)3]BPh4 (9) and acetylide derivatives [Ru(η5-C5Me5)(C[tbnd]CAr)(bpy)] (10, 11) [Ar = Ph (10), p-tolyl (11)] were also obtained by substitution of the carbene in 5–8. Unstable vinylidene cations [Ru(η5-C5Me5)[dbnd]C[dbnd]C(H)Ar](bpy)]+ (12, 13) were formed by protonation with HBF4•Et2O of acetylide species 10, 11. The complexes were characterized spectroscopically (IR and 1H, 13C, 31P NMR) and by X-ray crystal structure determination of [Ru(η5-C5Me5)[dbnd]C(Ph)(p-tolyl)(bpy)]BPh4 (5b).