Band 229, Heft 7

The co-ordination number rule and the rule of hardness are developed in detail to rationalize inorganic co-ordination structures. We demonstrate how even very complex structures can be understood and sometimes predicted starting from primary co-ordination numbers of cations only. We remind the reader of relations between cation and anion co-ordination numbers and their use for the derivation of connectivity formulas of a Niggli type. We show how the hardness of the ions is responsible for their particular position within a structure. Furthermore, we derive a measure of segregation of the different ions within the structures and also of their electrostatic imbalance in relation to Pauling’s rule of charge sums, and we interpret such structural details in the context of simple numeric relations of co-ordination numbers together with specific “chemical” effects.

A series of five compounds, namely [Ba( trien ) 2 ] 3 [SbSe 4 ] 2 · trien (1) ( trien =diethylenetriamine), [(Se 3 )Cr( en ) 2 (Se 2 )Cr( en ) 2 (Se 3 )] 2 (2) ( en =ethylenediamine), [( pren ) 3 Eu(Te 3 ) 2 Eu( pren ) 3 ] (3) ( pren =1,3-diaminopropane), [( en ) 4 Ba( pren )Ba( en ) 4 ](Te 3 ) 2 (4) and [ en H] 4 [Sn 2 Se 6 ] (5) , which illustrate the transition of classical polychalcogenides to metalates, are presented, where mixed amine/(poly-)chalcogenide interaction with metal centers are in the focus of interest. A conventional aminothermal synthesis is discussed in comparison with ionothermal approaches. The compounds are considered useful precursors to study in situ interconversion of selenido- and telluridometalates under ionothermal conditions.

A new lithium borate, Li 3 B 11 O 18 , was synthesized by crystallization from glass, containing an excess of B 2 O 3 . The compound crystallizes monoclinic, P 2 1 / a , Z =4, a =9.766(5) Å, b =7.849(5) Å, c =17.899(9) Å, β =100.96(5)°, V =1347.0(13) Å 3 (R=0.06, wR=0.12). The structure is based upon two interpenetrating frameworks formed by triborate and pentaborate groups. The thermal behaviour of Li 3 B 11 O 18 was studied using DTA, DSC, and high-temperature XRD. Highly anisotropic thermal expansion and a new high-temperature phase were observed.

A new metastable compound Cr 3 Sb was synthesized as thin film starting from modulated elemental reactant layers. The new compound is cubic and crystallizes in the A15 structure (Cr 3 Si-type). A variation of the occupancy of the Sb position (0, 0, 0) was observed leading to a Cr-rich sample with formula Cr ∼6 Sb. In-situ X-ray diffraction and reflectivity investigations indicate an interdiffusion of the multilayers and crystallization of the new compound below 350°C. Calculations of the crystal structure and lattice parameter agree well with the experimental results. In addition the existence of a further metastable phase, a Heusler-like alloy, is discussed and supported by DFT calculations.

Important data sets of crystallographic van der Waals radii covering major portions of the Periodic Table are reviewed, including those originally published in Pauling’s pioneering work in the late 1930s, together with other more recent data sets. The van der Waals radii for rare gases are determined next from short contact distances in crystallographic data, as an illustration of the value of crystal structure databases for the direct determination of van der Waals radii for non-metallic elements. Then, van der Waals radii for the other non-metallic and metallic elements, as presented in the literature and having been determined using various approaches, are compared systematically. Finally, certain outstanding problems related to the derivation and application of van der Waals radii are discussed, and further investigations of crystallographic van der Waals radii are suggested.

The stannide SrPt 1.833 ☐ 0.167 Sn 2 was synthesized from the elements in a sealed niobium tube in a high-frequency furnace. Its structure was determined by and refined on the basis of single crystal X-ray diffraction data at 300 and 90 K. The refinement of 1177/1169 F 2 values with 34/37 variables leads to residuals [I≥3σ(I)] R M =0.026 (375) and R S =0.075 (53)/ R M =0.0211 (408) and R S =0.0503 (128) for the 300/90 K data sets, respectively. SrPt 1.833 ☐ 0.167 Sn 2 crystallizes with an orthorhombic (3+1)D structure with the supercentered superspace group C c mme ( 0β0 ) s 00 [ β =1/3 b * , a =655.25(15), b =656.7(4), c =2062.3(5) pm]. It is related to the tetragonal CaBe 2 Ge 2 type structure. The crystal chemistry is described and the structure solution is discussed based on (3+2)D–(3+1)D–3D group-subgroup relations in the Bärnighausen formalism. 119 Sn Mössbauer spectra at ambient temperature and 78 K revealed a single signal with isomer shifts of δ=1.78(1) and δ=1.83(1) mm s –1 with quadropole splitting of ΔE Q =0.71(1) and 0.86(1) mm s –1 , respectively reflecting the low-symmetric site symmetry of the tin atoms. SrPt 1.833 ☐ 0.167 Sn 2 was classified as a Pauli -paramagnet by magnetic susceptibility measurements. Its specific heat capacity is C pm =121.4(1) J mol –1 K –1 at 300 K.

The detailed X-ray structural elucidation of reaction products of a zinc(II) salt with O,O ′-dialkyldithiophosphate and nitrogen-containing heterocycles (N–N=1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy)) has been performed. Surprisingly, together with [Zn(S 2 P(OR) 2 ) 2 (N–N)] compounds, also ionic-type complexes having the formula of [Zn(N–N) 3 ](S 2 P(OR) 2 ) 2 have been obtained using the same molar ratios of the reactants. The prepared complexes have been characterized by elemental analysis and single-crystal X-ray analysis. The crystallographic analysis showed that the bond lengths and bite angles of the prepared complexes are in good agreement with those of similar compounds. The crystal packing of described complexes is formed via π–π stacking interactions and/or C–H···S non-covalent contacts.