Syntheses of cationic lead(LT) and tin(IT) complexes containing tris(pyrazolyl)methane ligands. Control of stereochemistry by variation in ligand substitution

The addition of 2 equiv of HBF4 . Et(2)O to a THF suspension of Pb(acac)(2) (acac acetylacetonate) followed by addition of 1 molar equiv of the tris(pyrazolyl)methane ligand HC(3,5-Me(2)pz)(3) (pz pyrazolyl ring) results in the immediate precipitation of {[HC(3,5-Me(2)pz)(3)]Pb}(BF4)(2) (1) The complex {[HC(3,5-Me(2)pz)(3)]Pb-2}(BF4)(2) (2) was prepared by precipitation from an acetone solution of 1 containing an excess of HC(3,5-Me(2)pz)(3). Both {[HC(pz)(3)]Pb-2}(BF4)(2) (3) and {[HC(pz)(3)]Pb}(BF4)(2) (4) are prepared by the addition of the respective equivalent amounts of HC(pz)(3) to the HBF4 . Et(2)O-Pb(acac)(2) THF solution. The lead ion in 1 is three coordinate with normal Pb-N distances ranging from 2.379(14) to 2.434(16) Angstrom (average = 2.41 Angstrom). The six-coordinate lead ion in 2 is in a trigonally distorted octahedral environment with equivalent Pb-N bond distances (2.635(7) Angstrom). The lone pair on lead is stereochemically inactive and does not appear to influence the structure. The lead ion in 3 is in an asymmetric six-coordinate environment with disparate Pb-N bond distances ranging from 2.609(5) to 2.789(5) Angstrom (average 2.69 Angstrom) and very different interligand N-Pb-N bond angles. Reactions of equal molar amounts of 1 with either K[HB(3,5-Me(2)pz)(3)] or K[HB(pz)(3)] yield {[HC(3,5-Me(2)pz)(3)]Pb[HB(3,5-Me(2)pz)(3)]}(BF4) (5) and {[HC(3,5-Me(2)pz)(3)]Pb[HB(pz)(3)]}(BF4) (6). The highly asymmetric structure of 5 is best described as a distorted square base pyramid. The [HB(3,5-Me(2)pz)(3)](-) ligand is tridentate with Pb-N distances ranging from 2.375(7) to 2.475(8) Angstrom (average = 2.43 Angstrom), whereas the HC(3,5-Me(2)pz)(3) ligand is bidentate with long Pb-N distances of 2.745(7) and 2.827(7) Angstrom. Reaction of Sn(O3SCF3)2 With 1 molar equiv of HC(3,5-Me(2)pz)(3) in THF yields the complex {[HC(3,5-Me(2)pz)(3)]Sn}(O3SCF3)(2) (7).