Electron spin resonance behaviour of the [Fe3Pt3(CO)15]– carbonyl cluster anion
The e.s.r. spectra of the paramagnetic [Fe3Pt3(CO)15]– monoanion have been recorded in solution and in the solid state at variable concentration and temperature. A comparison of e.s.r. and electronic diffuse-reflectance spectra with X-ray structural data of [Fe3Pt3(CO)15]n–(n= 1 or 2) clusters suggests that the unpaired electron is mainly located in a non-degenerate molecular orbital of the triplatinum system which, under an idealized D3h symmetry, may primarily be the a2′* combination of three dxz platinum orbitals. The stability of the paramagnetic cluster probably derives from the unpaired electron being localised mostly on the platinum atoms, and from the steric properties of the µ-Fe(CO)4 groups which hinder spin-pairing by dimerization.