Inorganic Chemistry, Vol.36, No.6, 1136-1142, 1997
Nitrogen-Coordination vs Carbon-Coordination of the Alpha-Cyano-Stabilized Phosphorus Ylide pH(3)P=c(H)CN - X-Ray Crystal-Structure of (Pd(DMBA)(P(OMe)(3))(N-C-C(H)=pph(3)))(ClO4)
The reaction of the solvated complexes [Pd(CN)(PR’(3))(THF)](ClO4) [CN = 2-((dimethylamino)methyl)phenyl-C’,N or dmba, 2-(1-(R)-(dimethylamino)ethyl)phenyl-C-1, or (R)-dmphea; PR’(3) = PPh(3), P(OMe)(3)] with a stoichiometric amount of Ph(3)P=C(H)CN (CPPY) (1:1 molar ratio), in THF at low temperature, gives the cationic derivatives {Pd(CN)(PR’(3))[N=C-C(H)=PPh(3)]}(ClO4), 4-6, in which the ylide ligand is N-coordinated to the Pd-II center and trans to the ortho-metalated C6H4 group, in an "end-on nitrile" coordination mode that is unprecedented for this ylide. The reaction of [Pd(CN)(NCMe)(2)](ClO4) (CN = dmba, (R)-dmphea) with Ph(3)P=C(H)CN (1:2 molar ratio) gives the bis(ylide) complexes [Pd(CN)(Ph(3)PCHCN)(2)](ClO4) (7, 8) in which one of the ylides is C-coordinated (trans to the NMe(2) group) and the other one is N-bonded (and trans to the C6H4 group). Either by reaction of [Pd(CN)(NCMe)(2)](ClO4) with Ph(3)P=C(H)CN (1:1 molar ratio) or by reaction of the bis(ylide) complexes [Pd(CN)(Ph(3)PCHCN)(2)](ClO4) with [Pd(CN)(NCMe)(2)](ClO4) (1:1 molar ratio), very insoluble materials of stoichiometry [Pd(CN)(Ph(3)PCHCN)(ClO4)] (9, 10) are obtained, which appear to be dinuclear derivatives with the ylide acting as a C,N-bridging group, [(CN)Pd(mu-C,N-Ph(3)PCHCN)(2)Pd(CN)-(ClO4)(2). At the same time, this ylide is shown to be sufficiently nucleophilic to promote the bridge-splitting of the dinuclear [Pd(mu-Cl)(CN)](2) complexes, giving the mononuclear derivatives [PdCl(CN)(Ph(3)PCHCN)I (11, 12) as a mixture of two isomers; in one of them, the ylide acts as a C-donor while in the other it acts as an N-donor. IR and NMR spectroscopies allow the unambiguous characterization of all of these products, and the X-ray crystal structure of {Pd(dmba)[P(OMe)(3)] [N=C-C(H)=PPh(3)]}(ClO4) (5) is reported. Complex 5 crystallizes in the monoclinic system, space group P2(1)/c, a = 12.5690(10) Angstrom, b = 17.857(2) Angstrom, c = 14.729(2) Angstrom, beta = 92.560(10)degrees, Z = 4, V = 3302.5(6) Angstrom(3), 4881 reflections with I > 2 sigma(I) for the refinement of 423 parameters and 30 restraints, R1 = 0.0384, wR2 = 0.0961, and GOF = 1.044.
Keywords:PALLADIUM(II) COMPLEXES;FUNCTIONAL PHOSPHINES;PLATINUM(II);CARBANIONS;REACTIVITY;NITRILES;METALS;ANION