Nuclear spin–spin coupling to 89Y. A model to investigate the question of covalent bonding in lanthanoid dithiophosphinate complexes

Abstract

The observation of spin–spin coupling between ⁸⁹Y and ³¹P nuclei in the complex [Y(S₂PR₂)₄]^–, R = OEt, is interpreted as evidence for covalent bonding. The magnitude of the reduced coupling constant ²K_Y–P is of the same order as ²K_Rh–P and ²K_Pt–P in [Rh(S₂PR₂)₃] and [Pt(S₂PR₂)₂] indicating similarity in the covalent contribution to their bonds. This result is extrapolated to the chemically similar lanthanoid complexes. The mechanism of hyperfine coupling in paramagnetic lanthanoid complexes, the nephelauxetic effect and the intensities of observed f–f transitions are discussed with respect to the above model.