Interaction of palladium(II) with polydentate ligands, including the synthesis and structure of bis[tris(pyrazol-1-yl)borato-N,N′]palladium(II) and the cations [Pd(L)2]2+[L = tris(pyrazol-1-yl)methane-N,N′ or tris(pyridin-2-yl)methane-N,N′]

Abstract

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 ClO₄^–] on reaction of tetrachloropalladate(II) with tris(pyrazol-1-yl)borate {[HB(pz)₃]^–}, and removal of chloro-ligands from [Pd(L)C1₂]{L = tris(pyridin-2-yl)methane [(py)₃CH] or tris(pyrazol- 1 -yl)methane [(pz)₃CH]} by AgX followed by addition of a further mole of ligand L. The chloro-complexes [Pd(L)Cl₂] are prepared from [PdCl₄]^2– and (py)₃CH in aqueous solution, and from [Pd(NCPh)₂Cl₂] 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)Å, β= 96.35(2)°, Z= 2; complex (2) is isomorphous with (3), with a= 8.096(5), b= 10.226(7), c= 16.508(11)Å, β= 99.45(5)°, Z= 2; complex (1) crystallises in the triclinic space group P, with a= 9.960(2), b= 8.250(2), c= 7.523(2)Å, α= 74.98(2), β= 68.93(2), γ= 89.32(2)°, and z= 1.