Terminal phosphinidenes

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]. 

Table 4. M=P bond distances, M=P-R bond angles, and P NMR chemical shifts of stable cationic terminal phosphinidene complexes ...

As an illustration of the phosphorus-carbon analogy, consider the result of replacing a carbon fragment (CR2) by a phosphorus moiety (PR) in each of the common low-coordinate organic compounds (1C-4C) shown in Fig. 1. For example, the replacement of a single carbon in an alkene (1C) results in a phos-phaalkene (IP). Similarly, the phosphaalkynes (2P) are isolobal relatives of the alkynes (2C), and terminal phosphinidene complexes (3P) can be related to the... 

Note also that a related complex 98 has been synthesized by reacting a carbyne complex with a transient terminal phosphinidene complex.90... 

Phosphorus compounds having coordination number 1 2.1 Phosphinidenes (IUPAC phosphanylidenes) and terminal phosphinidene complexes9,10... 

The transient electrophilic terminal phosphinidene 188, which is readily accessible by thermolysis of 7-phospha-norbornadiene complex 187 (Scheme 59), is a powerful precursor to phospholenes. For example, it reacts with ethoxyacetylene to give phosphole 189, which upon hydrolysis affords the 2-phospholene complex 190 (Scheme 59)... 

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. ... 

An example for the above-mentioned insertion reactions for enlargement of three-membered phosphorus heterocyles is the intercalation of terminal phosphinidene complexes in the conjunctively destabilized P-C(2) bond of 2-alkinylphosphirene complexes (Equation 22) <1997OM4501, 19990M796>. An intramolecular version of the same reaction which does not required the destabilizing alkynyl substituent has also been described <1999JOM(582)53>. 

The phosphirene complex 26, as generated from a terminal phosphinidene complex and 4-phenylbut-3-yn-l-ol, reacts with a second molecule of the phosphinidine complex giving an intermediate phosphirene 27 with additional secondary alkoxyphosphine functionality. An intramolecular hydrophosphination yields then the complex 28 as a mixture of two diastereomers (Scheme 7) <20050M696>. 

Table 3 Phosphirane and phosphirene complexes by cycloaddition reactions of terminal phosphinidene complexes with either alkenes or alkynes...

X -systems, and other low coordination phosphorus species, in particular phosphenium ions, R2P , and phosphinidenes, RP . The reactions of phosphenium ions with isocyanides, 1,3-dienes and o-quinones, and amidines, have been investigated. The coordination chemistry of phosphenium ions also continues to stimulate interest.The thermal decomposition of phosphirene and phosphirane P-complexes provides a new approach for the synthesis of terminal phosphinidene complexes, e.g., (180), which can be trapped with a variety of reagents. Evidence of the formation of surface phosphinidene intermediates has been adduced in the heterogeneous dechlorination of alkyldi-chlorophosphines by magnesium metal at 600K. ... 

A new approach to the phosphole ring system is provided by the reaction of terminal phosphinidene complexes with electron rich... 

As we discovered that bulky electrophilic terminal phosphinidene tungsten complexes with CsMes or CH(SiMe3)2 at the phosphoms do not dimerize in the absence of trapping reagents [16, 17], we became interested in their fate. 

Transition metal phosphinidene complexes were originally prepared in order to access what was expected to be a rich chemistry of phosphorus(I)T However, terminal phosphinidenes have been found to be difficult to prepare, partly because they tend to either catenate or bridge. This is a manifestation of the double-bond rule for the main group elements. However, breakthroughs in syntheses of these complexes came about through the use of devious synthetic techniques in combination with sterically encumbered ligands. 

Past attempts to prepare terminal phosphinidenes indicate that these species are inherently electrophilic. To compensate, phosphinidenes were prepared that possessed intramolecular base stabilization, e.g., by means of a pyrazolyl borate derivative. The precursor, [HB(pz )3]PCl2, is combined with a metal anion to form the complex in 70% yield ... 

So far, much of the discussion has focussed on the bonding of phosphinidene units to aluminum, gallium, or indium. However, we are also interested in the coordination of phosphinidenes to transition metals - particularly in cases where the phosphinidene unit coordinates in a terminal fashion. As indicated below, terminal phosphinidene complexes, like imido complexes, can exist in angular or linear forms. 

Much elegant work has been done with terminal phosphinidenes as... 

Further progress has been reported in the area of terminal phosphinidene complexes. A range of tungsten phosphinidene... 

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