A series of bimetallic titanium-ruthenium complexes of general formula [(η(5)-C(5)H(5))(μ-η(5):κ(1)-C(5)H(4)(CR(2))(n)PR'R'')TiCl(2)](η(6)-p-cymene)RuCl(2) (n = 0, 1, 2 or 4; R = H or Me; R' = H, Ph, or Cy; R'' = Ph or Cy) have been synthesized, including two novel compounds as well as two cationic derivatives of formula [(η(5)-C(5)H(5))(μ-η(5):κ(1)-C(5)H(4)(CH(2))(n)PPh(2))TiCl(2)] [(η(6)-p-cymene)RuCl](BF(4)) (n = 0 or 2). The solid state structure of two of these compounds was also established by X-ray crystallography. The complexes showed a cytotoxic effect on human ovarian cancer cells and were markedly more active than their Ti or Ru monometallic analogues titanocene dichloride and RAPTA-C, respectively. Studies of cathepsin B inhibition, an enzyme involved in cancer progression, showed that enzyme inhibition by the bimetallic complexes is influenced by the length of the alkyl chain in between the metal centers. Complementary ESI-MS studies provided evidence for binding of a Ru(II) fragment to proteins.

A series of three-coordinate N-heterocyclic carbene bis­(trimethylsilyl)­amide complexes of cobalt, [Co­{N­(SiMe3)2}2(NHC)] (NHC = N,N′-diarylimidazolin-2-ylidene, aryl = 2,6-diisopropylphenyl, SIPr (1), aryl = mesityl, SIMes (2); κ1-N,N′-diphosphanylimidazol-2-ylidene, PCP (5); κ1-N-phosphanyl-N′-2,6-diisopropylphenylimidazol-2-ylidene, PC (6); cyclic alkyl amino carbene :C­(Cy)­CH2CMe2N-2,6-Pri 2C6H3, cAACCy (7)) were prepared by the reaction of [Co­{N­(SiMe3)2}2] with the corresponding NHCs. The complexes exhibited interesting transamination reactivity in reactions with bulky 2,6-diisopropylaniline (NH2(DiPP)), where adjustment of the stoichiometry and reaction conditions resulted in the substitution of one or two N­(SiMe3)2 ligands by the anilido ligand NH­(DiPP), giving [Co­{N­(SiMe3)2}­{NH­(DiPP)}­(NHC)] (NHC = N,N′-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene, IPr (8)) and [Co­{NH­(DiPP)}2(NHC)] (NHC = SIPr (9); IPr (10); PCP (11)). X-ray crystallography revealed trigonal-planar coordination geometry at Co for all of the new complexes and long Co–CNHC bond lengths; in the cases of 5, 8, 9, 10, and 11, intramolecular Co···H and/or H···P interactions may provide further stabilization of specific conformations. Magnetic and electron paramagnetic resonance studies showed that the three-coordinate Co­(II) centers in 1–7 behave as S = 3/2 spins with strong anisotropy arising from the low symmetry of the coordination site (C 2v ). The anisotropy results in large values of the zero-field splitting parameter D.