Synthesis and reactivity studies of palladium(ii) complexes containing the N-phosphorylated iminophosphorane-phosphine ligands Ph2PCH2P{NP(O)(OR)2}Ph2 (R = Et, Ph): application to the catalytic synthesis of 2,3-dimethylfuran

Dalton Transactions Pub Date: 2006-10-10 DOI: 10.1039/B609359K

Abstract

Reactions of [PdCl2(COD)] with 1 equiv. of the iminophosphorane-phosphine ligands Ph2PCH2P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OR)2}Ph2 (R = Et 1, Ph 2) lead to the novel Pd(II) derivatives cis-[PdCl2(κ2-(P,N)-Ph2PCH2P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OR)2}Ph2)] (R = Et 3, Ph 4). Pd–N bond cleavage readily takes place upon treatment of these species with a variety of two-electron donor ligands. By this way, complexes cis-[PdCl2(κ1-(P)-Ph2PCH2P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OR)2}Ph2)(L)] (R = Et, L = CNtBu 5a, CN-2,6-C6H3Me25b, py 5c, P(OMe)35d, P(OEt)35e; R = Ph, L = CNtBu 6a, CN-2,6-C6H3Me26b, py 6c, P(OMe)36d, P(OEt)36e) have been synthesized in high yields. The addition of two equivalents of ligands 1/2 to dichloromethane solutions of [PdCl2(COD)] results in the formation of complexes trans-[PdCl2(κ1-(P)-Ph2PCH2P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OR)2}Ph2)2] (R = Et 7, Ph 8), which can be converted into the dicationic species [Pd(Ph2PCH2P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OR)2}Ph2)2][SbF6]2 (R = Et 9, Ph 10) by treatment with AgSbF6. Complex 10 also reacts with CNtBu to afford trans-[Pd(κ1(P)-Ph2PCH2P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OPh)2}Ph2)2(CNtBu)2][SbF6]211. The structures of 4, 5b, 7 and 9 have been determined by single-crystal X-ray diffraction methods. In addition, the ability of these Pd(II) complexes to promote the catalytic cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has also been studied.

Graphical abstract: Synthesis and reactivity studies of palladium(ii) complexes containing the N-phosphorylated iminophosphorane-phosphine ligands Ph2PCH2P{ [[double bond, length as m-dash]] NP( [[double bond, length as m-dash]] O)(OR)2}Ph2 (R = Et, Ph): application to the catalytic synthesis of 2,3-dimethylfuran
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