Synthesis of 1,3-azaphosphol-2-ones. Crystal and molecular structures of [SP-4-2]-dichlorobis(3-phenyl-1,3-dihydrobenzo[1,3]azaphosphol-2-one-P)palladium(ii) and its chloro(methyl)platinum(ii) analogue?

Dalton Transactions Pub Date: 2009-11-10 DOI: 10.1039/B916913J

Abstract

Reaction of secondary phosphine (±)-(2-aminophenyl)phenylphosphine, (±)-app, with PCl5 in toluene gives the hydrochloride salt of the expected chlorophosphine (±)-(2-aminophenyl)chlorophenylphosphine, (±)-acpp.HCl, however, this is not the case with triphosgene. Rather the first example of a 1,3-azaphosphol-2-one is isolated, viz. (±)-3-phenyl-1,3-dihydrobenzo[1,3]azaphosphol-2-one, (±)-pbap. The hydrochloride salt (±)-acpp.HCl readily reacts with excess vinyl-, 2-methylphenyl- or 2-methoxyphenyl magnesium bromide to give the corresponding tertiary phosphines (±)-(2-H2NC6H4)PPhR (where R = CH[double bond, length as m-dash]CH2, 2-C6H4Me or 2-C6H4OMe). Hydrophosphination of the vinyl substituted tertiary phosphine with (±)-app in the presence of KOBut provides a synthetic route to the elusive P2N2 quadridentate ligand (RP*,RP*)- and (RP*,SP*)-(CH2)2(PPhC6H4NH2-2)2, albeit in low yield. The azaphospholone (±)-pbap can be readily deprotonated with KOBut in thf and subsequently alkylated with methyl iodide or benzyl bromide to give the analogous N-methyl or N-benzyl derivatives. Alkylation with 1,3-dibromopropane gives the bis(azaphospholone) (RP*,RP*)- and (RP*,SP*)-1,3-bis[1-{3-phenyl-1,3-dihydrobenzo[1,3]azaphosphol-2-one}]propane. The latter and the N-methyl substituted azaphospholone can also be synthesised by the reaction of the corresponding secondary phosphine, viz. (RP*,RP*)- and (RP*,SP*)-(CH2)3(NHC6H4PHPh-2)2 and (±)-(2-methylaminophenyl)phenylphosphine, with triphosgene. All three azaphospholones react with [PtClMe(1,5-cyclooctadiene)] in thf to give complexes of the type cis-[PtClMeL2] in which ligand L is coordinated via the P atom of the azaphospholones. The ligand (±)-pbap has also been complexed to palladium(II) via the reaction with Li2[PdCl4] in methanol to give cis-[PdCl2{(±)-pbap}2]. The structures of cis-[PtClMe{(±)-pbap}2] and cis-[PdCl2{(±)-pbap}2] have been confirmed by X-ray analysis.

Graphical abstract: Synthesis of 1,3-azaphosphol-2-ones. Crystal and molecular structures of [SP-4-2]-dichlorobis(3-phenyl-1,3-dihydrobenzo[1,3]azaphosphol-2-one-P)palladium(ii) and its chloro(methyl)platinum(ii) analogue
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