SOLID-STATE STRUCTURES OF [HB(3-BUT-5-MEPZ)3]SNCL AND [HB(3-BUTPZ)3]CDCL (PZ = PYRAZOLYL RING) - STEREOCHEMICAL INFLUENCE OF A CENTRAL ATOMLONE-PAIR

The complexes [HB(3-Bu(t)-5-Mepz)3]SnCl and [HB(3-Bu(t)pz)3]CdCl(pz = pyrazolyl ring) have been prepared and their solid-state structures de termined crystallographically. The two structures allow a determinatio n of the impact of the lone pair on ligand geometry and on the metal-d onor atom distances for two metals with equivalent ionic radii. The ge ometry about tin in [HB(3-Bu(t)-5-Mepz)3]SnCl is best described as a d istorted trigonal bipyramid with the chloride ligand in an axial site and the tin lone pair occupying an equatorial position. The axial bond lengths are long, especially the Sn-Cl bond length at 2.601(l) angstr om. The structure of [HB(3-BU(t)PZ)3]CdCl is a distorted tetrahedron w ith nearly 3-fold rotational symmetry. The Cd-Cl bond length is 2.355( 2) angstrom, much shorter than the Sn-Cl distance in [HB(3-Bu(t)-5-Mep Z)3]SnCl. The lone pair on the central tin atom that is not present in the cadmium complex is stereochemically active and has the effect of increasing bond lengths, especially for the axial ligands. Crystal dat a: [HB(3-Bu(t)-5-MePZ)3]SnCl.1/2C6H6, monoclinic, P2(1)/n, a = 9.656(3 ) angstrom, b = 17.844(4) angstrom, c = 18.123(5) angstrom, beta = 99. 73(2)-degrees, V = 3077.7(14) angstrom3, Z = 4, R(F) = 4.19%; [HB(3-Bu (t)PZ)3]CdCl, orthorhombic, Pnma, a = 16.13n(5) angstrom, b = 15.985(4 ) angstrom, c = 9.885(3) angstrom, V = 2549.9(13) angstrom3, Z = 4, R( F) = 3.90%.