MONONUCLEAR AND DINUCLEAR PALLADIUM COMPLEXES CONTAINING 2-PYRIDYLPHOSPHINE LIGANDS, INCLUDING X-RAY CHARACTERIZATION OF PD2I2(MU-PPH2PY)2 AND A DIMETHYLACETYLENEDICARBOXYLATE A-FRAME COMPLEX PD2CL2(MU-PPY3)2(MU-MEO2C.C=C.CO2ME) PY = 2-PYRIDYL

Dibromo- and diiodo[(2-pyridyl)phosphine]palladium(II) complexes are prepared by metathesis of cis-PdCl2(PPh3-npyn)2 species (n = 1-3) using the appropriate sodium halide; py = 2-pyridyl. NMR spectroscopy, particularly C-13{H-1}, is used to distinguish cis and trans isomers. The dinuclear complexes Pd2X2(mu-PPh3-npyn)2, X = halide, are synthesized via a conproportionation reaction using PdX2(PPh3-npyn)2 and Pd2(dba)3; dba = dibenzylideneacetone. Both Pd2I2(mu-PPh2py)2 and a dimethylacetylenedicarboxylate A-frame complex Pd2Cl2(mu-Ppy3)2(mu-MeO2C.C=C.CO2Me) are characterized crystallographically as head-to-tail isomers. The former crystallizes in the monoclinic space group C2/c with a = 30.992(3), b = 18.764(1), c = 13. 100(1) angstrom, beta = 100.676(5)-degrees, and Z = 8; the data were refined to R = 0.035 for 5874 reflections with I greater-than-or-equal-to 3-sigma(I). The A-frame compound is triclinic of space group P1BAR with a = 13.545(2), b = 15.064(2), c = 11.991(2) angstrom, alpha = 111.56(1), beta = 95.36(1), gamma = 97.63(1)-degrees, and Z = 2; R = 0.033 from 7128 reflections with I greater-than-or-equal-to 3-sigma(I). The Pd2X2(mu-PPhpy)2 complexes exist as a mixture of diastereomers because of chirality induced at the phosphorus atoms. The Pd2X2(mu-Ppy3)2 complexes in water generate the [Pd2(H2O)2(mu-PPY3)2]2+ dication, which is isolated as various salts. The mononuclear complexes in water generate aquo and hydroxo species.