Carbenes phosphinidene complex

The cyclopolyphosphines that were used to prepare the carbene-phosphinidene complexes described earlier were formed by the reduction of higher oxidation state phosphorus compounds, typically di-chlorophosphines, RPC12 (47-49). However, in some cases a separate reduction step is not necessary and it is possible to prepare the car-bene-phosphinidene complex (74) directly by reaction of a stable nucleophilic carbene with RPC12 (44). 

Mathey et al. have described an unusual [5C+1S] process involving the reaction of a transient terminal phosphinidene complex [PhP=W(CO)5] with a bu-tadienyl carbene complex yielding a 1-phenyl-1,2-dihydrophosphine P-W(CO)5 complex [112]. 

Phosphinidenes differ from carbenes because of the additional lone pair. This lone pair enables interactions with, e.g., a transition metal group for increased stability, while maintaining carbene-hke behavior. These terminal /] -complexed phosphinidenes differ from the p2-> fi3-> and p4-complexes, which are not part of this survey. Phosphinidenes that are stabilized by a transition metal group also relate to carbene complexes. A distinction in Fischer and Schrock-type complexes has been advanced to distinguish phosphinidene complexes with nucleophilic properties from those that are electrophiHc [ 13 ]. In this survey we address this topic in more detail. 

Electrophilic and nucleophilic phosphinidene complexes have been related to the corresponding carbene complexes of which the Fischer-type is usually considered as a singlet-singlet combination and the Schrock-type as a triplet-triplet combination. However, both the strongly preferred triplet state of R-P and the M=P bond analysis suggest this schematic interpretation to be less appropriate for transition metal complexed phosphinidenes. 

More than 35 years ago, it was reported that the reaction of tri-methylphosphine with the cyclotetraphosphine (CF3P)4 affords the phosphine-phosphinidene complex, Me3P —> PCF3 (43). More recently, it has been demonstrated that stable carbenes are sufficiently nucleophilic to effect the depolymerization of cyclopolyphosphines and cyclopolyarsines to produce carbene-pnictinidene complexes 66-70, the first examples of p-block pnictinidenes (44, 45). Two extreme canonical forms, 71 and 72, can be written for such species. Structure 71... 

Carbene-like reactions, applications, and mechanistic insights of phosphinidene complexes (particularly, formation of P-heterocycles) 02EJO1127. 

It should be emphasized that the difference between silylenes and carbenes on the one hand and the phosphinidene complexes on the other hand is due to the nucleophilic or electrophilic, respectively, natures of these species. The former attack the carbon atom of a P/C double bond in the 1,3,5-triphosphinine, whereas the latter should preferentially attack the phosphorus atom. 

Interest has again continued in studies of the generation and reactivity of phosphinidene species (RP ), phosphorus analogues of carbenes, and this area has been reviewed. A review has also appeared of the use of terminal phosphinidene complexes in the formation of phosphorus-element bonds. Further studies of phosphanylidene-a -phosphoranes, RP = PR3, (regarded as phosphine-complexed phosphinidenes, i.e., ArP -PRs), have shown that the species Me3P=PAr (Ar = Mes or 2,6-Mes2C6H3) are good vehicles for the delivery of the terminal phosphinidene moiety ArP to zirconium and vanadium sites. Terminal phosphinidene complexes of cobalt, ruthenium, rhodium and osmium, and iridium, have also been... 

Sc-P bonds of a four-coordinate scandium phosphinidene complex has been determined (13JA14784). Reactions of electrophilic carbenes with white phosphorus in benzene afforded Pg clusters supported by four carbenes or a carbene—P4 adduct (13CC4486). A mechanistic insight into CO capture by amidophosphoranes which contain a highly reactive P—N bond within a four-membered ring, has been published (13CAJ3147). 

The following chapter concerns another kind of low-valent organophosphorus compounds, namely phosphinidenes. Little is known about free phos-phinidenes in contrast to the corresponding transition metal complexes. Many new reagents have been generated exhibiting either electrophilic or nucleophilic properties. The reactivity of these carbene-like reagents is evaluated (K. hammer tsma). 

Phosphinidenes (recommended IUPAC name phosphanylidenes) are unstable species and analogous to the carbenes. The parent compound H-P is a six-electron species that is still unknown, but its organic derivatives can give rise to seven different types of complexes, as listed in Table 15.5.2. 

Phosphinidenes (R-P), short-lived, reactive intermediates that are isoelec-tronic with nitrenes and carbenes, are accessible by fragmentation of phos-phiranes, phosphol-3-enes, triazaphospholenes, and oxazaphospholenes and can be characterized by trapping reactions. The metal-complexed species [R-P-M, e.g., M = W(CO)5] are more stable (but also not isolable) and react more selectively. As a model example we describe the transformation of (3,4-dimethyl-l-phenylphosphole)(pentacarbonyl)tungsten 4 with dimethyl acetylenedicarboxylate to the 7-phosphanorbomadiene derivative 5.11 The (phosphinidene)(pentacarbonyl)tungsten complex 6 is generated from the latter by a [4+ 1]-cycloreversion and trapped with diphenylacetylene via a [2+1]-cycloaddition to furnish the triphenyl-2-phosphirene complex 7 (Scheme l).12... 

An aminophosphinidene complex Cp Os(CO)2 PCl(N-Tr2) was prepared by reaction of [Cp Os(CO)2] with Tr2NPCl2. As with Fischer carbenes (see Fischer-type Carbene Complexes), the nitrogen group stabilizes the electron-deficient phosphorus atom of the phosphinidene ligand. Based on a crystal structure of the ruthenium analog, there is likely... 

Phosphinidenes RP (with a sextet of electrons at the P-atom) are isolobal with carbenes R2C, and their dimers (RP)2, with a P=P double bond, are the counterparts of the carbene dimers, the olefins R2C=CR2. The coordination chemistry of the two phosphorus species is far less developed, but the number of stable complexes is growing rapidly, as summarized in review articles. ... 

Phosphinidene carbene (6.472) and phosphorane carbene (6.473) complexes are known [8,9]. 

Geminally dimetallated gold-copper complexes derived from carbodi-phosphoranes and phosphinidene-carbene adducts have been prepared... 

The complexes with a double bond M=0 and M=NR, i.e. metal-oxo and metal-imido are isoelectronic to metal-carbene complexes and show, as the latter, a rich chemistry, all the more so as the binary complexes M(=0)n and M(=NR)n are well known. - - The phosphinidenes M=PR and the nitrido complexes M=N, isoelectronic to metal carbynes, are also known. All these ligands can bridge two or three metals, in which case there is no multiple bond. 

Marinetti et Mathey have shown that the complexes of electrophilic phosphinidene, although they are not isolable, have a rich chemistry resembling that of carbenes ... 

This area continues to generate interest across the range of p -bonded phosphorus compounds. Whereas long-established topics such as the chemistry of diphosphenes and phosphaall nes have again received comparatively little study, the chemistry of phosphaalkenes (and related P=C=X compounds), and the less-developed groups of low coordination number phosphorus compounds, in particular phosphenium ions, phosphinidenes, and their complexes with carbenes and metal ions, has again dominated the area. 

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