Interaction of Palladium(II) with Polydentate Ligands, including the Synthesis and Structure of Bis[tris(pyrazol-1-yl)borato-N,N']paIladium(II) and the Cations [Pd(L)2]2+ [L = tris(pyrazo1-1-yl)methane-N,N' or tris(pyridin-2- yl)methane-N,N']

Palladium(II) forms the complexes [Pd{HB(pz)3}2] (1), [Pd{(py)3CH}2][NO3]2 (3), and [Pd{(pz)3CH}2]X2 [X = NO3-, BF4- (2), or CIO4-] on reaction of tetrachloropalladate(II) with tris(pyrazo1-1 -yl)borate {[HB(pz)3]-}, and removal of chloro- ligands from [Pd(L)CI2] {L = tris(pyridin-2-yl)methane [(py)3CH] or tris(pyrazo1-1-yl)methane [(pz)3CH]} by AgX followed by addition of a further mole of ligand L. The chloro- complexes [Pd(L)CI2] are prepared from [PdCI4]2- and (py)3CH in aqueous solution, and from [Pd(NCPh)2CI2] and (pz)3CH in benzene. X-Ray crystallographic studies show that for complexes (1 )-(3) the potentially tridentate ligands are present as N,N'-bidentates to give square-planar PdN4 geometry with a crystallographic centre of symmetry at palladium(II). 1H N.m.r. spectra are consistent with similar structures in solution, with facile interconversion between co-ordinated and unco-ordinated ring environments. Complex (3) crystallises in the monoclinic space group P21/c, with a = 8.478(1), b = 10.356(3), c = 17.443(4) A, beta = 96.35(2), Z = 2; complex (2) is isomorphous with (3), with a = 8.096(5), b = 10.226(7), c = 16.508(11) A, beta = 99.45(5), Z = 2; complex (1) crystallises in the triclinic space group P1 bar, with a = 9.960(2), b = 8.250(2), c = 7.523(2) A, alpha = 74.98(2), beta = 68.93(2), gamma = 89.32(2), and z= 1