Johannes A. van Doorn

‘Capped’ tri-ruthenium carbonyl cluster: X-ray crystal structure of [Ru3(CO)9{MeSi(PBu2)3}]

The tridentate tertiary-phosphine ligand MeSi(PBu2)3 reacts with Ru3(CO)12 in refluxing benzene to give the symmetrical complex [Ru3(CO)9{MeSi(PBu2)3}], containing three bridging carbonyl ligands and one phosphorus centre co-ordinated to each of the ruthenium atoms as shown by X-ray crystallography.

Addition of acetic formic anhydride to trans-[ IrCl(CO)(PMe2Ph)2]; anion-, including hydrido-, transfer reactions

Addition of acetic formic anhydride to trans-[ IrCl(CO)(PMe2Ph)2] leads, via a series of intermolecular anion (hydrido, formato and chloro) ligand exchange reactions, to the formation of the cis-dihydrido, trans-tertiary-phosphino complex [ IrClH2(CO)(PMe2Ph)2].

Formation and reactions of bis(phosphino)succinic anhydrides

A route to 2,3-bis(phosphino)succinic anhydrides and related compounds is described. The compounds are formed by reaction of a secondary phosphine with maleic anhydrides which bear a leaving group at the alkenic carbon atom. The reaction of bromomaleic anhydride with diphenylphosphine proceeds via diphenylphosphinomaleic anhydride. An acid-catalysed Michael addition leads to cis-2,3-bis(diphenylphosphino)succinic anhydride, which in turn rearranges to the trans isomer by an acid-catalysed process. The trans isomer was isolated as a hydrobromide. The formation of diphosphines from the corresponding maleic acids and esters has also been observed. A primary phosphine does not lead to a phosphinosuccinic anhydride.Addition of a base to the bis(phosphino)succinic anhydride generally leads to the elimination of the phosphine moiety. However, the anhydride ring can be opened with sodium methoxide and a diphosphine, with both a carboxylic acid and a carboxylate ester moiety, is formed in moderate yield. Two conformers or isomers of this compound are obtained, both of which decarboxylate readily to give methyl 2,3-bis(diphenylphosphino)propanoate.Co-ordination of the diphosphine system to PtII prevents both the elimination of secondary phosphine and the decarboxylation of carboxylic groups.

Thermal stability of phosphinoacetic acids

Phosphinoacetic acids decarboxylate smoothly in toluene solution at 99 °C and the corresponding alkylphosphine is formed in quantitative yields. Electron-withdrawing substituents at the α position of the carboxylic acid lead to a large increase in the reaction rate. In contrast, electron-withdrawing substituents at the phosphorus atom lead to a small decrease in the rate. We have concluded from the substituent effects, solvent effects, and the influence of bases and acids that both the lone pair of the phosphorus atom and the carboxylate hydrogen atom play a crucial role in the reaction. A mechanism is proposed that proceeds via an ylide. Sodium phosphinocarboxylates do not decarboxylate in an aqueous solution at 95 °C. Instead a carbon–phosphorus bond cleavage occurs probably by an intramolecular nucleophilic substitution.

The reaction of the diarylphosphine oxide anion with oxiranes: a new synthesis of 1,2-ethylenebis(diarylphosphine oxides)

In an unusual double-substitution reaction, the diarylphosphine oxide anion reacts with oxiranes to give bis(phosphine oxides) that can have functional groups on the aryl ring and/or the bridging carbons between the PO groups.

Birch reduction of arylphosphines

In contrast to unsubstituted tri(aryl)phosphines, bis(p-dimethylaminophenyl)phenylphosphine is not cleaved by sodium in liquid ammonia; instead, the hitherto unknown Birch product is formed via an intermediary phosphinocyclohexadienyl anion.

The Reaction of the Diarylphosphine Oxide Anion with Oxiranes: A New Synthesis for 1,2-Ethanobis(Diaryl)Phosphines

Abstract The reaction of the diarylphosphine oxide anion with oxiranes gives bis-phosphine oxides in what is formally a double-substitution reaction but one which proceeds via a retro-aldol fragmentation and recombination process.

Oxidative addition of carboxylic acids to trans-carbonylhalogenobis-(tertiary phosphine)iridium(I) complexes

Complexes of the type trans-[lrX(CO)L2](L = PEt3,PMe2Ph, or PPh3; X = Cl, Br, or l) undergo rapid oxidative addition with carboxylic acids RCO2H (R = H, Me, CF3, Ph, or 1-naphthyl) to give iridium (III) complexes [lrXH(O2CR)(CO)L2] corresponding to both (formal)cis and trans addition of the carboxylic acid to the iridium(I) species. In solution these complexes undergo rapid anion exchange such that, at equilibrium, two additional hydrido-species, [lrX2H(CO)L2] and [lrH(O2CR)2(CO)L2], are present. In all these octahedral complexes the tertiary phosphine groups are mutually trans, the hydride and carbonyl groups mutually cis, and the carboxylic unit is unidentate. The ease of formation of the different complexes depends on the nature of the carboxylic acid. The cis adduct containing chloride and having hydride and carbonyl mutually trans can be prepared by the action of carbon monoxide on complexes [lrCl(H)(O2CR)L2] which contain a bidentate carboxylate ligand. With weak acids, e.g. acetic, conversion of the iridium(I) into the iridium(III) species is incomplete; the exchange between free and co-ordinated acid is, however, slow on the n.m.r. time scale over the range –60 to 30 °C. The adducts formed between trans-[lrX(CO)L2](X = Cl, Br, or I) and formic acid are smoothly converted on heating in solution into dihydrido-complexes [lrXH2(CO)L2] with expulsion of carbon dioxide; with L = PPh3 or PEt3, trihydrido-complexes [lrH3(CO)L2] are also formed.