3H-benzophosphepine complexes: versatile phosphinidene precursors.
The synthesis of a variety of benzophosphepine complexes [R = Ph, t-Bu, Me; ML(n )()= W(CO)(5), Mo(CO)(5), Cr(CO)(5), Mn(CO)(2)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 degrees 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.
Borst
Mark L G
ML
Department of Chemistry, Faculty of Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
Bulo
Rosa E
RE
Gibney
Danièle J
DJ
Alem
Yonathan
Y
de Kanter
Frans J J
FJ
Ehlers
Andreas W
AW
Schakel
Marius
M
Lutz
Martin
M
Spek
Anthony L
AL
Lammertsma
Koop
K