PREPARATION AND CHARACTERIZATION OF PALLADIUM(II) AND PLATINUM(II) COMPLEXES WITH BIS(PYRAZOLYL)ALKANES - CRYSTAL AND MOLECULAR-STRUCTURES OF [PD(CH2(PZ)2)2][BF4]2 AND OF [PDCL2((CH3)2C(PZ)2)] (PZH=PYRAZOLE), A NEW EXAMPLE OF A PD=H-C AGOSTIC INTERACTION

Neutral and cationic complexes of general formulae (LL)MCl2 (M = Pd, (LL) = CH2(pz)2 (1); CH2(3,5-Me2pz)2 (2); (CH3)2C(pz)2 (3); M = Pt, (LL) = CH2(pz)2 (4); CH2(3,5-Me2pz)2 (5) and (LL)2M]2+ (M = Pd, (LL) = CH2(pz)2 (6); CH2(3,5-Me2pz)2 (7); (CH3)2C(pz)2 (8); M = Pt, (LL) = CH2(pz)2 (9); CH2(3,5-Me2pz)2 (10) have been prepared and characterized by IR and 1H NMR spectroscopy. The structures of 3 and 6 have been determined by X-ray diffraction; in both complexes the bis-(pyrazolyl)alkanes act as chelating ligands but the coordination around the palladium atom in the complex 6 is strictly square-planar whereas in 3 it is a slightly distorted towards pyramidal, with a significant Pd efHC agostic interaction. The six-membered rings in both the complexes adopt a boat-type conformations