Intramolecular and interionic structural studies of novel olefin palladium(II) and platinum(II) complexes containing poly(pyrazol-1-yl)borate and -methane ligands. X-ray structures of palladium five-coordinate complexes

Complexes [M(eta(1),eta(2)-C8H12OMe)(pz(2)-YH2)]((+)) (M = Pd, Y = C, 1; M = Pt, Y = C, 2; M = Pt, Y = B, 3) and [M(eta(1),eta(2)-C8H12OMe)(pz(3)-YH)]((+)) (M = Pd, Y = C, 4; M = Pd, Y = B, 5; M = Pt, Y = C, 6; M = Pt, Y = B, 7) were synthesized by the reaction of the dimers [M(eta(1),eta(2)-C8H12OMe)Cl](2) with the poly(pyrazol-1-yl)borate and -methane ligands. Complexes 1-7 were characterized in solution by multinuclear and multidimensional low-temperature NMR spectroscopy. The solid-state structures of olefinic five-coordinate Pd complexes 4 and 5 were investigated by X-ray single-crystal studies. The relative cation-anion position (interionic structure) was investigated in solution, for all cationic complexes at room and low temperature by (IF)-I-19, H-1-HOESY NMR spectroscopy, and in the solid state for 4. A remarkable specifity of the interionic contacts is observed in solution: the counterion is placed close to the peripheral protons of the pyrazolyl ligands probably due to the partial protection of the apical positions introduced by the nonplanar ligands and the delocalization of the positive charge on the pyrazolyl rings. In the case of complex 4 there is an excellent agreement between the solid state and solution results: the anion selectively interacts with the CH and five protons of the pz(3)-CH ligand via an assembly of hydrogen bonds.