Ytterbium(II) phosphinidene complexes

Abstract

The first trivalent rare-earth metal phosphinidene complex was reported in 2008, but the divalent rare-earth metal phosphinidene complex is still absent up to date. Herein, we report the synthesis and structural characterization of divalent ytterbium alkyl/phosphido/phosphinidene, phosphido/phosphinidene, and phosphinidene complexes. These three complexes were obtained through a stepwise synthesis using a divalent ytterbium dialkyl complex as the starting material. The alkyl/phosphido/phosphinidene, phosphido/phosphinidene, and phosphinidene complexes are all polymetallic, and the number of ytterbium centers in the complexes increases from 4 to 5 to 6. DFT calculations indicate the presence of Yb-P single bonds in the complexes, with additional π delocalization evidenced by the presence of ring critical points in the Yb-P-Yb-P diamond cores at the Quantum Theory of Atoms in Molecules level. The phosphido/phosphinidene complex reacts with one equivalent of 1-isocyanoadamantane (AdNC) to afford a divalent ytterbium complex through selective insertion of AdNC into one Yb-P(phosphinidene) bond. In contrast, treatment with an excess of AdNC leads to complete insertion into all Yb-P(phosphinidene) bonds and redox reactions at the Yb(II) centers, yielding a structurally intriguing mixed-valence Yb(II)/Yb(III) complex.