Synthesis of chelating bidentate isocyano and cyano ligands and their metal complexes

Article abstract of DOI:10.1021/ic00136a009

Three air-stable, odorless, solid, bidentate isocyano and cyano ligands of the following structure have been prepared: (Chemical Equation Presented) Molecular models indicate that they should chelate to metals with the donor groups at 90° with respect to each other. From reactions of the diisocyano ligand DiNC, the following complexes with chelating DiNC ligands have been isolated: Cr(CO)₄(DiNC), Mo(CO)₄(DiNC), W(CO)₄(DiNC), Mn(CO)₃(DiNC)Br, CpFe(CO)(DiNC)⁺, and CpFe(CS)(DiNC)⁺. The characterization of these complexes demonstrates that DiNC can function as a chelating ligand despite its formation of a 13-member chelate ring. The t-BuDiNC ligand, which is much more soluble in organic solvents than DiNC, also gives complexes Cr(CO)₄(t-BuDiNC), Mo(CO)₄(t-BuDiNC), and CpFe(CS)(t-BuDiNC)⁺, which are more soluble than their DiNC analogues. When only one ligand in a reacting complex such as Cr(CO)₅[(CH₃)₂CO], W(CO)₅[(CH₃)₂CO], or W(CO)₄(piperidine)₂ is substitution labile, DiNC reacts to give complexes in which the isocyano donors are coordinated to separate metal atoms; the resulting bridging DiNC complexes [Cr(CO)₅]₂(u-DiNC), [W(CO)₅]₂(μ-DiNC), and [cis-W(CO)₄(pip)]₂(μ-DiNC) have been isolated. The dicyano ligand DiCN reacts to form the following complexes: Mn-(CO)₃(DiCN)Br, CpFe(CS)(DiCN)⁺, and PtCl₂(DiCN). These are the first examples of complexes containing a bidentate cyano ligand that chelates to a metal through the nitrogen lone pairs. The formation of PtCl₂(DiCN) from equimolar PtCl₂(NCPh)₂ and DiCN indicates that the chelating DiCN binds more favorably to the metal than do the monodentate benzonitrile ligands. The ligands and complexes described above have been characterized by their IR, ¹H and ¹³C NMR, and mass spectra.