3<i>H</i>-Benzophosphepine Complexes:  Versatile Phosphinidene Precursors Mark L. G. Borst Rosa E. Bulo Danièle J. Gibney Yonathan Alem Frans J. J. de Kanter Andreas W. Ehlers Marius Schakel Martin Lutz Anthony L. Spek Koop Lammertsma 10.1021/ja054885w.s002 https://acs.figshare.com/articles/journal_contribution/3_i_H_i_Benzophosphepine_Complexes_Versatile_Phosphinidene_Precursors/3253207 The synthesis of a variety of benzophosphepine complexes [R = Ph, <i>t-</i>Bu, Me; ML<i><sub>n </sub></i>= W(CO)<sub>5</sub>, Mo(CO)<sub>5</sub>, Cr(CO)<sub>5</sub>, Mn(CO)<sub>2</sub>Cp] by two successive hydrophosphinations of 1,2-diethynylbenzene is discussed in detail. The first hydrophosphination step proceeds at ambient temperature without additional promoters, and subsequent addition of base allows full conversion to benzophosphepines. Novel benzeno-1,4-diphosphinanes were isolated as side products. The benzophosphepine complexes themselves serve as convenient phosphinidene precursors at elevated, substituent-dependent temperatures (>55 °C). Kinetic and computational analyses support the proposal that the phosphepine−phosphanorcaradiene isomerization is the rate-determining step. In the absence of substrate, addition of the transient phosphinidene to another benzophosphepine molecule is observed, and addition to 1,2-diethynylbenzene furnishes a delicate bidentate diphosphirene complex. 2005-12-07 00:00:00 benzophosphepine complexes phosphinidene hydrophosphination step proceeds ML diethynylbenzene