ABSTRACT
The first examples of an optically active Birch reduced tertiary phosphine, viz. (R(P))-(cyclohexa-2,5-dienyl)(3-pentyl)phenylphosphine, and successful hydrophosphination of the related racemic ligand (±)-(cyclohexa-2,5-dienyl)(2-propyl)phenylphosphine with PHPh(2) in the presence of KOBu(t) in thf to give a 1,2-cyclohexenebis(tertiary phosphine), viz. (±)-1,2-C(6)H(8)(PPh(2))(PPhPr(i)), are described; as confirmed by crystal structure determinations of [SP-4-4-(S(P),S)]-chloro[(cyclohexa-2,5-dienyl)(3-pentyl)phenylphosphine][2-{1-(dimethylamino)ethyl}phenyl-C,N]palladium(II) and [SP-4-3-(±)]-dimethyl[(1-diphenylphosphino)(2-isopropylphenylphosphino)cyclohexene]platinum(II).
ABSTRACT
Reaction of secondary phosphine (+/-)-(2-aminophenyl)phenylphosphine, (+/-)-app, with PCl(5) 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-H(2)NC(6)H(4))PPhR (where R = CH=CH(2), 2-C(6)H(4)Me or 2-C(6)H(4)OMe). Hydrophosphination of the vinyl substituted tertiary phosphine with (+/-)-app in the presence of KOBu(t) provides a synthetic route to the elusive P(2)N(2) quadridentate ligand (R(P)*,R(P)*)- and (R(P)*,S(P)*)-(CH(2))(2)(PPhC(6)H(4)NH(2)-2)(2), albeit in low yield. The azaphospholone (+/-)-pbap can be readily deprotonated with KOBu(t) 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) (R(P)*,R(P)*)- and (R(P)*,S(P)*)-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. (R(P)*,R(P)*)- and (R(P)*,S(P)*)-(CH(2))(3)(NHC(6)H(4)PHPh-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-[PtClMeL(2)] 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 Li(2)[PdCl(4)] in methanol to give cis-[PdCl(2){(+/-)-pbap}(2)]. The structures of cis-[PtClMe{(+/-)-pbap}(2)] and cis-[PdCl(2){(+/-)-pbap}(2)] have been confirmed by X-ray analysis.
ABSTRACT
The first structurally authenticated example of a hexadentate chelating tertiary phosphine in which all six donors are bound to a single metal centre is described. The multidentate ligand (RP*,RP*,RP*)- and (RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3 has been prepared in 80% yield via the reaction of five equivalents of sodium (2-aminophenyl)phenylphosphide (generated in situ from (2-aminophenyl)phenylphosphine and sodium in thf) with 1,1,1-tri(bromomethyl)ethane in thf. The diastereomeric mixture has been complexed to cobalt(III) and the resulting pair of complexes, viz. [Co{(RP*,RP*,RP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl3 and [CoCl{(RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl2, separated by ion exchange chromatography. The structure of the former (as the corresponding hexafluorophosphate salt) has been confirmed by X-ray crystallography and clearly shows all six donors of the P3N3 ligand coordinated to a single cobalt(III) centre. The related hexadentate ligand with internal N donors and terminal diphenylphosphino groups, viz. CH3C(CH2NHC6H4PPh2-2)3, has also been synthesised, albeit in low yield, via the reaction of [Li(tmeda)][2-NHC6H4PPh2] (generated in situ from (2-aminophenyl)diphenylphosphine, n-butyllithium and tmeda in diethyl ether) with 1,1,1-tri(iodomethyl)ethane in thf. No formation of a P3N3 ligand has been observed when either Na[2-PPhC6H4NH2] or [Li(tmeda)][2-NHC6H4PPh2] is reacted with the related tripodal substrate 1,1,1-tris(tolyl-4-sulfonyloxymethyl)ethane in thf. Rather the P-methyloxetane (+/-)-[3-{(2-aminophenyl)phenylphosphinomethyl}]-3-methyloxetane and the sulfonamide 2-(4-CH3C6H4SO2)NHC6H4PPh2 and the corresponding N-methyloxetane [3-{(2-diphenylphosphinophenyl)aminomethyl}]-3-methyloxetane have been isolated from the respective reactions. The structure of the sulfonamide has been confirmed by an X-ray analysis of the platinum(II) complex trans-[PtCl(CH3){2-PPh2C6H4NH(SO2C6H4CH(3-4)}2].