Ytterbium(ii) phosphinidene complexes

Abstract

The first trivalent rare-earth metal phosphinidene complex was reported in 2008, but a divalent rare-earth metal phosphinidene complex has not been reported 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.