Phosphinidene metal complexes

Terminal phosphinidene-metal complexes, L TM=PR, readily add to double bonds (equation 17). Both metal-stabilized and phosphine-stabilized phosphinidenes, R P= PR3, can act as phospha-Wittig reagents, which undergo metathesis reactions with carbonyl-containing compounds to generate carbon phosphorus double bonds (equations 18 and 19). Pnictinidenes and their complexes have been extensively reviewed in terms of both their syntheses and reactivities. ... 

The chemistry of phosphiranes and phosphirenes and their derivatives comprehends theoretical questions, for example, antiaromaticity of phosphirenes, a -aromaticity, reaction behavior like ring opening of vinylphosphiranes, complex building ability, and synthesis strategies. The cycloaddition reactions of transient phosphinidene metal complexes play an outstanding role. 

Keywords 1,2-silyl migration, double bond formation, phosphinidene metal complexes... 

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. 

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 (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... 

Early transition metal complexes that contain doubly bonded ligands have been developed in view to synthetical applications. Imido, phosphinidene, and chalcogenido... 

Stable 77 -l//-phosphirane and -l//.pho5phifgf,g metal complexes are known, especially carbonyl complexes of Cr, W, and Fe. Most of them are obtained by reaction of phosphinidenes stabilized by the corresponding metal fragment with alkenes (— phosphirane complexes) or alkynes phosphirene complexes) see discussion in Section 1.08.4.1. In general,... 

Interest continues in the development of the chemistry of phosphinidenes and phosphenium salts, and also that of their metal complexes. A molecular orbital study of the... 

Phosphinidenes appear to form various types of metal complexes whose reactions have aroused much interest in recent years (Chapter 8.17). 

Phosphinidenes, RP, although not radicals (Table 13.12), can be identified as species formed on thermolysis or photolysis of polyphosphines such as (PPh)5 (Chapter 6.17). They also form metal complexes (Chapter 8). The first phosphinidene, which was observed in 1994 by Caspar et al. using ESR spectroscopy, was (13.146a) [18-20]. 

A metal-complexed phosphinidene has been postulated in the formation of phos-phacyclobutadiene by thermolysis of benzophosphiepines. ... 

Activity in this area has remained at a similar level to that reported for 2007. Well-established topics such as the chemistry of diphosphenes, phos-phaalkenes and phosphaalkynes have continued to attract attention, as also has work on the less-developed classes of low coordination number phosphorus compounds, in particular phosphenium ions and phosphinidenes, and their metal complexes. Recent work on kinetically-stabilised doubly bonded systems involving two of the heavier Group 15 elements has been... 

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