Study on the pseudotetrahedral and tetrahedral cobalt(II) complexes.

Pseudotetrahedral zwitterionic complexes of stoichiometry CoX3 (L+)(X = Cl, Br and I) and CoX2Y(L+) (X = Cl and Y = Br and I; X = Br and Y = I), where L represents the cationic ligand, were prepared and tetrahedral complexes of stoichiometry CoX4[L(+2)], where X = Cl, Br and I and L represents the cationic ligand. In the pseudotetrahedral zwitterionic complexes, the electronic spectra may be assigned assuming an effective C3v symmetry and the low symmetry ligand field is proposed to be less important than the spin-orbit coupling effects, vibronic coupling and Jahn–Teller distortions. The i.r. spectra of the zwitterionic complexes suggest a lack of influence of the cationic site on the ligand properties of the donor atom. The magnetic properties and electronic spectra of the CoX4[L(2+)] complexes were correlated and the ligand field strength (10Dq), the Racah parameters (B') and the spin-orbit coupling constants (λ') were calculated. From B' and λ' we obtained evidence that appreciable overlap of metal and ligand orbitals occurs in these complexes. In addition the far i.r. spectra and tentative assignments of Co–X and Co–N absorption are also discussed.