Reactions of Coordinated Phosphorus Compounds

A combination of kinetic and labeling studies established a mechanism involving attack by copper-bound hydroxide, followed by PO bond cleavage. Further details of the mechanisms of these reactions has come from a detailed study of the hydrolysis of ci5-[Ir(en)2(0H) 0P(=0)(0R)2 ] (36) complexes (R = ethyl or 4-nitrophenyl). The reaction involves intramolecular attack by coordinated hydroxide, and rate enhancements of 10 are found. The products of the reactions are not the chelated phosphate esters (37) expected from a knowledge of cobalt(III) chemistry, but monodentate phosphate monoesters (38). This is assigned to relative differences in the sizes of the metal ions and the basicity of the coordinated 

A similar transformation of P—-O bonded compounds at a metal center is seen in the reaction of [PtCl2(dppm)] with aqueous sodium hydroxide to yield [(Ph2MeP) Ph2P(=0) Pt(/Li-0H)2Pt(Ph2MeP) Ph2P(=0) ]. The key step in the reaction is thought to involve nucleophilic attack by hydroxide with cleavage of a P—C bond as shown in Eq. (6). 

Metal-directed cycloaddition reactions of vinylphosphines have recently been reported. Upon heating [NiBr2L2] (L = diphenylvinylphosphine) in butanol, a retro-Michael reaction occurs see Eq. (7), loss of acetylene is followed by an intramolecular addition to yield [NiBr2(dppe)]. °  

Very closely related processes are observed in the cycloaddition of diphenylvinylphosphine to nickel, platinum or palladium coordinated phospholes to yield complexes of the type (40) as in Eq. (8). 

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