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Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



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Paper

J. Chem. Soc., Dalton Trans., 1993, 269 - 274, DOI: 10.1039/DT9930000269

Hydrophosphination of formaldehyde catalysed by tris-(hydroxymethyl)phosphine complexes of platinum, palladium or nickel

Peter A. T. Hoye, Paul G. Pringle, Martin B. Smith and Kerry Worboys

The addition of PH3 to formaldehyde to give P(CH2OH)3 is catalysed by a range of platinum-(IV), -(II) and -(0) compounds including Na2[PtCl6], K2[PtCl4], [PtCl2{P(CH2OH)3}2]2 and [Pt{P(CH2OH)3}4]·H2O 3. A large ratio of P(CH2OH)3 to Pt is present under the conditions in which the catalysis is operated and the hypothesis that a common platinum–P(CH2OH)3 complex is present under these conditions has been tested. It is shown that Na2[PtCl6] is reduced by 3 equivalents of P(CH2OH)3 to give [PtCl2{P(CH2OH)3}2]2, the same species that is formed upon addition of 2 equivalents of P(CH2OH)3 to K2[PtCl4]. Addition of 1 equivalent of P(CH2OH)3 to 2 gives [PtCl{P(CH2OH)3}]3Cl 4a while addition of 2 equivalents of P(CH2OH)3 to 2 gives an unstable species, tentatively assigned the five-co-ordinate structure [PtCl{P(CH2OH)3}4]Cl 5a. In the presence of further P(CH2OH)3, 5a decomposes smoothly to give a mixture of [PtH{P(CH2OH)3}4]Cl 3b, [P(CH2OH)4]Cl and the unusual bis(chelate) salts trans- and cis-[Pt{(HOCH2)2PCH2OP(CH2OH)2}2]Cl26a and 6b. A mechanism rationalising this reaction is presented. The pH of the reaction medium during the catalysis is ca. 9–10 and it is therefore concluded that [Pt{P(CH2OH)3}4]3a is the main platinum-containing species present during all the platinum catalysed reactions. It is shown that [Ni{P(CH2OH)3}4]18 and [Pd{P(CH2OH)3}4]19 are also catalysts for the hydrophosphination of formaldehyde and a general mechanism is suggested.