Syntheses of cationic, six-coordinate cadmium(II) complexes containing tris(pyrazolyl)methane ligands. Influence of charge on cadmium-113 NMR chemical shifts

Treating a thf (thf = tetrahydrofuran) suspension of Cd(acac)(2) (acac = acetylacetonate) with 2 equiv of HBF4 . Et(2)O results in the immediate formation of [Cd-2(thf)(5)](BF4)(4) (1). Crystallization of this complex from thf/CH2Cl2 yields [Cd(thf)(4)](BF4)(2) (2), a complex characterized in the solid state by X-ray crystallography. Crystal data: monoclinic, P2(1)/n, a = 7.784(2) Angstrom, b = 10.408(2) Angstrom, c = 14.632(7) Angstrom, beta = 94.64(3)degrees, V = 1181.5(6) Angstrom(3), Z = 2, R = 0.0484. The geometry about the cadmium is octahedral with a square planar arrangement of the thf ligands and a fluorine from each (BF4)(-) occupying the remaining two octahedral sites. Reactions of [Cd-2(thf)(5)](BF4)(4) with either HC(3,5-Me(2)pz)(3) or HC(3-Phpz)(3) yield the dicationic, homoleptic compounds {[HC(3,5-Me(2)pz)(3)]Cd-2} (BF4)(2) (3) and {[HC(3-Phpz)(3)]Cd-2}(BF4)(2) (4) (pz = 1-pyrazolyl). The solid state structure of 3 has been determined by X-ray crystallography. Crystal data: rhombohedral, R (3) over bar, a = 12.236(8) Angstrom, c 22.69(3) Angstrom, V = 2924(4) Angstrom(3), Z = 3, R = 0.0548. The cadmium is bonded to the six nitrogen donor atoms in a trigonally distorted octahedral arrangement. Four monocationic, mixed ligand tris(pyrazolyl)methane-tris(pyrazolyl)borate complexes {[HC(3,5-Me(2)pz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF4) (5), {[HC(3,5-Me(2)pz)(3)][HB(3-Phpz)(3)]Cd}(BF4) (6), {[HC(3-Phpz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF4) (7), and {[HC(3-Phpz)(3)][HB(3-Phpz)(3)]Cd}(BF4) (8) are prepared by appropriate conproportionation reactions of 3 or 4 with equimolar amounts of the appropriate homoleptic neutral tris(pyrazolyl)borate complexes [HB(3,5-Me(2)pz)(3)]Cd-2 or [HB(3-Phpz)(3)]Cd-2. Solution Cd-113 NMR studies on complexes 3-8 demonstrate that the chemical shifts of the new cationic, tris(pyrazolyl)methane complexes are very similar to the neutral tris(pyrazolyl)borate complexes that contain similar substitution of the pyrazolyl rings.