Trapping Highly Electrophilic Metalladiphosphanylcarbenes

Imidazoline‐Functionalized Diphosphines: Models for N‐Heterocyclic Carbene–Diphosphinocarbene Coupling

“…Obviously, in the ylidic form the negative charge of the diphosphinomethanide fragment is stabilized by charge delocalization through the metallacycle, whereas the positive one is stabilized by π‐donation from the nitrogen lone‐pairs. If we consider complexes 2 a and 2 b as models for carbene–carbene coupling, the structural data described here are in agreement with the well‐known nucleophilic character of N‐heterocyclic carbenes10 and the electrophilic character of transient metalladiphosphinocarbenes,11 whose coupling should lead to a net charge‐transfer from the former to the latter, thus justifying the contribution of structure b in Figure 4. The IR spectra of 2 a and 2 b in the ν CO region (see the Experimental Section), which show absorptions at values intermediate between those of diphosphine complexes and diphosphinomethanide derivatives,12 support the above interpretation and indicate that the new diphosphines are strongly basic.…”

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

“…[141] Previously other groups had reported some metal complexes with phosphorus-stabilized carbene centers. [142] The free P-heterocyclic carbene could, however, not be isolated. It was Bertrand et al who recently prepared the first stable PHC 60, [143] where a pyramidalization of the phosphorus atoms [144] was prevented by the use of sterically demanding substituents.…”

A Bis(thiophosphinoyl)methanediide Palladium Complex: Coordinated Dianion or Nucleophilic Carbene Complex?

“…In this perspective, phosphorus-substituted methane derivatives have attracted the attention of many groups as potential precursors. [3,4] Besides the particular electronic properties of phosphorus, which markedly differ from that of their nitrogen counterparts, the interest of such derivatives also resides in the possibility of using phosphorus as an anchor for other heteroatoms through oxidation of its lone pair. This approach was elegantly demonstrated by Cavell and co-workers who successfully developed the chemistry of bis(iminophosphorano)methanediide complexes.…”