Metal-phosphinidene intermediates

Keywords. Phosphinidene, P chemistry. Transition metal. Reactive intermediate, Fischer,... 

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. ... 

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... 

The relevance of new P-Cl phosphinidenes as intermediates for the preparation of more elaborated products, like P-heterocycles or C-H activation molecules, led Sterenberg ° to explore new synthetic routes for dichlorophosphido complexes (Scheme 4). The treatment of dichloro-phosphido complex 12 with AICI3 led to the exclusive formation of the chlorinated diphosphorus metal complex 13 involving a Lewis acid assisted nucleophilic mechanism. The large P-P coupling constant indicated a direct P-P bond between two chemically non-equivalent phosphorus atoms. 

Formation of this complex may occur via an initial formation of a low-valent tantalum intermediate which oxidatively adds one terminal P-Cph bond to the metal centre resulting in transfer of the phenyl ligand to the metal and formation of complex 42. The P NMR spectrum of the reaction mixture showed formation of a mixture of cyclooligophosphanes, the phosphinidene-bridged complex [ Ta( -C5Me5)Cl( U-PPh) 2] as well as numerous low-intensity multiplets which could not... 

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