Electron transfer in tetramethylbiphosphinine complexes of Cp*2Yb and Cp*2Sm†
This article reports the synthesis and the characterization of two Cp*2Ln (Ln = Sm and Yb) fragments containing the tetramethylbiphosphinine (tmbp) ligand in equatorial position. The solid-state data indicate the reduction of the tmbp ligand with the decamethylsamarocene fragment along with the oxidation of the metal center, while the metrical parameters highlight a more dubious electronic structure for the tmbp adduct of the decamethylytterbocene fragment. 1H and 31P NMR have been recorded for both complexes and show the unambiguous oxidation of the samarium complex. On the other hand, the NMR data for Cp*2Yb(tmpb) exhibit weakly shifted paramagnetic resonances along with a weak effective moment in solution; a situation that is neither in agreement with a divalent metal center and a neutral ligand, nor with an oxidized ytterbium ion and a radical tmbp ligand. In addition to these experimental data, theoretical calculations were performed on both complexes. DFT calculations highlight a large orbital contribution and an f occupation of 5.4 for the samarium complex, which is to compare to an f occupation of 13.8 and less orbital interactions in the ytterbium complex.