Volume 216, Issue 10

The structural features of over 460 anhydrous oxoborates that are described in literature were analysed. Lewis acid strengths were calculated for all cations other than B 3+ that were found in these structures, using the valences of the cations and their determined average coordination numbers. From the observation of a restriction of the occurrence of complex polyborate anions to specific ranges of cation Lewis acid strength in existing oxoborate compounds, the Lewis base strengths of the complex polyborate anions (not of the oxygen ligands) were inferred, using the idea that is at the bottom of the valence matching principle, that in the most stable compounds the Lewis acid strength of the cation nearly equals the Lewis base strength of the anion. From this, general inherent rules for the occurrence of the miscellaneous polyborate anions with respect to the ratio cation: boron (A:B), the Lewis acid strength(s) L a of the cation(s) other than B 3+ and the cation radii were developed. These rules offer the possibility for a prediction of the stoichiometry and the most probable polyborate structural group that will be adopted by a new anhydrous borate compound.

Large single crystals of optical quality and with dimensions up to 50 mm of double salts of the type X [C(NH 2 ) 3 ] Zr(N(CH 2 COO) 3 ) 2 ⋅ y H 2 O ( X = Rb, Tl, NH 4 , Cs, CH 3 NH 3 ) have been grown from aqueous solutions. They crystallize in the space group P 2 1 and exhibit quasi-isotypic structures. Complete elastic and thermoelastic tensors have been derived from ultrasonic resonances of plane-parallel plates. In addition, thermal expansion, pyroelectric, dielectric and piezoelectric properties have been measured. The maximum longitudinal piezoelectric effects d 222 exceed d 111 of α -quartz roughly by a factor of 7. The pyroelectric constants π 2 surmount π 3 of tourmaline by about a factor of 9. The structural and physical properties are closely related to those of the constituent salts.

Eu 8/7 TiS 3 and Sr 8/7 TiS 3 , two members in the hexagonal perovskite-like A x TiS 3 family, have been obtained as single crystals and their structure solved from twinned crystal X-ray data within the (3+1)-dimensional [(3+1)D] formalism. Eu 8/7 TiS 3 and Sr 8/7 TiS 3 crystallizes in the trigonal symmetry, R 3̅ m (00γ)0 s superspace group with the following lattice parameters: Eu 8/7 TiS 3 , a s = 11.3892(13) Å, c s = 2.989(2) Å, q = 0.5741(4) c * and V s = 335.8(3) Å 3 ; Sr 8/7 TiS 3 , a s = 11.480(5) Å, c s = 2.9940(13) Å, q = 0.5716(2) c * and V s = 341.7(5) Å 3 . The structures were considered as commensurate (P three-dimensional (3D) spacegroup) but refined within the (3+1)D formalism ( t = 0 section) to a residual factor: Eu 8/7 TiS 3 , R = 3.84% for 128 parameters and 4500 independent reflections; Sr 8/7 TiS 3 , R = 4.92% for 125 parameters and 2719 independent reflections. The two structures are isotypic and resemble that of Sr 9/8 TiS 3 . They differ from the structures of the oxide counterparts by the presence of original PO [TiS 6 ] units, intermediate between octahedra (Oh) and trigonal prisms (TP), and replacing the TP units found in the oxides. In addition, they are different from the Sr 9/8 TiS 3 structure by the occurrence of a particular twinning and the presence of two different [TiS 3 ] chain types, with two consecutive PO units in one of them.

A bicomplex of salicylaldehyde benzoylhydrazone ( SBH ) with Zn(II) was synthesized in ethanol and single crystals were obtained in DMSO. The compound crystallizes in the orthorhombic system with the space group Pna 2 1 (33) and crystal data: a = 22.573(3)Å, b = 6.1208(5) Å, c = 17.881(2) Å, V = 2470.5(5) Å 3 , Z = 4, d (calc) = 1.462 g⋅cm –3 , (2633 reflections with I > 2 σ ( I ); final R = 0.0509; R w = 0.1099). The asymmetric unit is a nearly planar bicomplex built up from one Zn atom linked to two monodeprotonated SBH ligands. The compound can be described as formed of chains extended along the b axis. This linear polymeric character results from the linking of each asymmetric unit to two neighbouring ones via four (2x2) covalent Zn-O bonds involving three Zn atoms and four phenolic oxygens. These covalent bonds are related to the very unusual Z configuration of the ligand. The three-dimensional cohesion of the compound is obtained by van der Waals forces be-tween the polymeric chains.

The title compound, Bis [N-(4-methoxybenzylidene)-2-mercaptoanilinato] Ni(II), [Ni(C 14 H 12 NO 2 S) 2 ]crystallizes in P 2 1 / n (no. 14) with a = 13.665(5), b = 12.983(5), c = 15.150(9)Å, β = 112.58(5)° and Z = 4. The Ni(II) atom is coordinated by two mono-anionic bidentate ligands through two N and two S atoms in cis-type fashion. Chemical and geometrical properties of this fashion and the results of energy minimisation studies in the gas phase support the expected molecular distorted square planar coordination around the Ni atom. The angle between the least-squares planes defined by N1, Ni, N1´ and S1, Ni, S1´ atoms is 12.1(5)°.