The case of a μ 2 -P aromatic phosphinine as a 4-electron donor forming σ- and π-three-center-two-electron bonds

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 53; no. 12; pp. 5608 - 5615
• Main Authors: Zhang, Jie, Hou, Yuanfeng, Liu, Shihua, Lin, Jieli, Li, Zhongshu
• Format: Journal Article
• Language: English
• Published: England 19.03.2024
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/D4DT00228H

Profound insight into the electronic structures of occasionally observed μ -P bridging phosphinines remains limited. In this work, we present the isolation and X-ray crystallographic characterization of a dimeric Rh(I) phosphinine complex exhibiting both η -P and μ -P phosphinine coordination modes. Variable temperature NMR analyses and DOSY spectrum measurement confirmed the presence of two types of fluxional phenomena in solution: η -P phosphinine bonding and dissociation, and η -P and μ -P equilibrium. DFT calculations in conjunction with single crystal X-ray diffraction studies suggest that the μ -P phosphinines donate four electrons a σ-lone pair and a high-lying π-type electron pair, instead of two σ-lone pairs, forming σ- and π-three-center-two-electron bonds. The stronger π-type interactions lead to longer P-C bonds and larger negative coordination chemical shifts for μ -P phosphinines. However, the binding interactions of μ -P are thermodynamically weaker than those of η -P. Reactivity studies further confirm the labile nature of the μ -P phosphinine bonds, which could be easily converted to an η -P phosphinine.