Complexes of hydrophilic triphenylphosphines modified with gem-bis(phosphonate) moiety. An unusual simultaneous cis and trans arrangements in the Pt(II) dinuclear complex

New triphenylphosphines substituted with the gem-bis(phosphonate) moiety in the form of ethyl esters, tetraethyl [4-(diphenylphosphanyl)benzyl]methylene-bis(phosphonate) (2a) and octaethyl bis[4-(diphenylphosphanyl)benzyl]methylene-bis(phosphonate) (2b), and the corresponding free acids 3a and 3b were prepared by a multi-step synthesis and characterized by multinuclear NMR spectroscopy and mass spectrometry. The ester ligands 2a and 2b were conveniently purified through their borane adducts. The X-ray structure of 2b x 2BH3 x H2O was determined. Coordination properties of new ligands towards Rh(I), Pd(II) and Pt(II) ions were studied. 1H, 31P and 195Pt NMR spectroscopy showed that ligands 2a and 3a form the expected [RhCl(eta2:eta2-cod)(L)] (cod = cycloocta-1,5-diene) and [MCl2(L)2] (M = Pd, Pt) complexes. The compounds 2b and 3b behave as bridging bidentate ligands forming dinuclear complexes of the {[RhCl(eta2:eta2-cod)]2(mu-L-kappa2P,P')} and [M2Cl4(mu-L-kappa2P,P')2] (M = Pd, Pt) type. These findings are consistent with mass spectrometry and far-IR and Raman spectroscopy results. X-Ray structures of trans-[PdCl2(2a-kappaP)2] and cis,trans-[Pt2Cl4(mu-2b-kappa2P,P)2] were determined; the dinuclear complex exhibits a different arrangement on the Pt(II) centres which was observed for the first time in the solid state. Salts of complexes of the free acid 3a are highly soluble in water.

Probing the importance of the hemilabile site of bis(phosphine) monoxide ligands in the copper-catalyzed addition of diethylzinc to N-phosphinoylimines: discovery of new effective chiral ligands

The hemilabile ligand Me-DuPHOS(O) 2 has proven to be a successful ligand for the copper-catalyzed addition of diethylzinc to N-phosphinoylimines. The corresponding alpha-chiral amines were obtained in high yields (80-98%) and enantiomeric ratios (19.0:1 to 99.0:1 er). Furthermore, this Cu* 2 catalytic system has been shown to be effective in the addition of diethylzinc to nitroalkenes and in the reduction of beta,beta-disubstituted vinyl phenyl sulfones. This paper describes a general structure/selectivity study in which the three ligand subunits (chiral phospholane-linker-labile coordinating group (Z)) are systematically modified and tested in the copper-catalyzed addition of diethylzinc to the N-phosphinoylimine 1 derived from benzaldehyde. This study led to the discovery of a new class of effective chiral ligands that combine a chiral phospholane unit and an achiral phosphine oxide.

Enolphosphato−Phosphines: A New Class of P,O Ligands

The new bifunctional ligands Ph(2)PCH[double bond]CPh[OP(O)(OR)(2)] (1) (1a, R = Et; 1b, R = Ph) represent the first examples of P,O derivatives resulting from the association of a phosphine moiety and an enolphosphate group. The Z stereochemistry about the double bond provides a favorable situation for these ligands to act as P,O-chelates. Neutral and cationic Pd(II) complexes have been synthesized and characterized, in which 1a or 1b acts either as a P-monodentate ligand or a P,O-chelate, via coordination of the oxygen atom of the P[double bond]O group. In the latter case, it has been observed that phosphines 1a and 1b can display a hemilabile behavior, owing to successive dissociation and recoordination of the O atom. Competition experiments revealed that phosphine 1a presents a higher chelating ability than 1b, a feature ascribed to the more electrodonating properties of the ethoxy groups in 1a compared to the phenoxy groups in 1b. P,O-Chelation affords seven-membered metallocycles, which is unusual for P,O-chelates. Complexes trans-[PdCl(2)[Ph(2)PCH[double bond]C(Ph)OP(O)(OPh)(2)](2)] (2b), [PdCl[Ph(2)PCHdouble bond]C(Ph)OP(O)(OEt)(2)](mu-Cl)](2) (3a), [complex--see text] (8a'), and [complex--see text] (10a) have been structurally characterized. Interestingly, the seven-membered rings in 8a' and 10a adopt a sofa conformation with the double bond lying almost perpendicular to the plane containing the Pd, the two P, and the two O atoms.