Group 9 and 10 complexes with the bidentate di(1H-indazol-1-yl)methane and di(2H-indazol-2-yl)methane ligands: synthesis and structural characterization

Abstract

Novel [MX₂(L)₂], [MX₂(L)], [M(L)₂]X₂ and [MX(H₂O)₃(L)]X derivatives were obtained by interaction of MX₂ (M = Co(II), X = Cl; M = Ni(II), X = Cl; M = Pd(II), X = Cl or CH₃COO) with chelating L ligands (L in general, in detail L¹ = bis(1H-indazol-1-yl)methane, L² = bis(2H-indazol-2-yl)methane). With PdCl₂ as an acceptor the more hindered L² ligand affords an ionic complex of composition [Pd(L²)₂]Cl₂, while a neutral species of composition [PdCl₂(L¹)] has been isolated with L¹. Whereas, by using Pd(OOCCH₃)₂ as an acceptor, neutral complexes of general formula [Pd(OAc)₂(L)] have been isolated with both L¹ and L² ligands. All the palladium complexes adopt a slightly distorted square planar geometry, as confirmed by three X-ray structures. Additional hydrated species, one of Co(II) and the other of Pd(II), were isolated from attempts of crystallization carried out in the air, and that of cobalt displays an interesting metal environment where a L¹ and a Cl are replaced by three water molecules giving rise to an ionic species, where intermolecular electrostatic interactions, intermolecular hydrogen bonds and the intermolecular aromatic interactions between the indazole groups in neigbouring L¹ ligand assemble the cobalt species into a three-dimensional network.