Crowded bis ligand complexes of Ttz super(Ph,Me) with first row transition metals rearrange due to ligand field effects: structural and electronic characterization (Ttz super(Ph,Me) = tris(3-phenyl-5-methyl-1,2,4-triazolyl)borate)

The tris(3-phenyl-5-methyl-1,2,4-triazolyl)borate (Ttz super(Ph,Me)) ligand provides intermediate steric bulk and forms predominantly bis(ligand) complexes of the form M(Ttz super(Ph,Me)) sub(2) with first row divalent transition metals (1 sub(M), M = Zn, Cu, Ni, Co, Fe, Mn). Due to ligand field effects that are greatest with Ni and Cu, ligand rearrangement is favored with these metals and Cu(Ttz super(Ph,Me)*) sub(2) (1 sub(Cu)* ) and (Ttz super(Ph,Me)*)Ni(Ttz super(Ph,Me)) (1 sub(Ni)* ) were isolated by selective recrystallization and fully characterized (* indicates a rearranged Ttz ligand with Ph and Me in swapped positions in one triazole ring). For comparison with Co(Ttz super(Ph,Me)) sub(2), the less bulky analogs (Ttz super(H,H)) sub(2)Co (4) and (Ttz super(Me,Me)) sub(2)Co (5) were studied by NMR and EPR spectroscopy, and 5 was crystallographically characterized. These complexes allow for a study of how slight changes in structure and electron donor properties (for Ni and Cu), as well as dramatic changes in steric bulk (for Co), influence the physical properties; specifically there are significant changes in the UV-Vis, EPR and NMR spectra. Bis(ligand) complexes predominate with all metals, but (Ttz super(Ph,Me))Ni(OH sub(2)) Cl (2) and (Ttz super(Ph,Me))ZnBr (3) were also isolated and these show that Ttz super(Ph,Me) is coordinatively flexible.