Volume 37, Issue 11

By using chemical transport reactions with various transporting agents (HgCl 2 , NbCl 5 , Nb 3 O 7 Cl) a slightly substoiehiometric NbO 2 -phase, β-NbO 2 , was obtained from samples with O/Nb ∼ 1.5 (source; T > 1373 K) and with deposition temperatures > 1273 K (sink). The rango of composition of β-NbO 2 was found to exist from NbO 1.990 to NbO 1.998 . The structure of the tetragonal, column-shaped black crystals was determined by X-ray diffraction. It crystallizes tetragonally in the space group I4 1 with lattice constants a = 9.693(3) Å, c = 5.985(1) Å and Z = 10 formula units. The crystal structure of β-NbO 2 is shown to be a deformed rutile type. As in α-NbO 2 the Nb-atoms are grouped in pairs. However, both oxides are different with respect to their long-range order.

For the first time single crystals of LT-Li 2 PbO 3 have been prepared by decomposition of K 2 Li 6 [Pb 2 O 8 ] [Incompletely closed Ag cylinders, sealed in Supremax-glass ampoule, vacuum, 690 °C, 100 d]. The structure determination [533Io(hkl); four-circle-diffractometer PW 1100, ω - scan, Mo - K α , R = 4,86%, R w = 4,93% confirms space group C2/c with a = 544.52(7), b = 926.12(7), c = 547,56(8) pm, β = 111.216(13)°, Z = 4, d rö = 6.94 g · cm -3 , d pyk = 6.89 g · cm -3 . The NaCl-type structure variant is characterized by alternating layers of Li(2) + and Li(l) + /Pb 4+ cations. All atoms have octahedral coordination. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated.

1,3-Di-tert-butyl-2,2-dimethyl-1,3,2,4λ 2 -diazasilagermetidine (1) and its lead analogue (3), which have been synthesized from the dichlorides of germanium and lead and the dilithium salt of bis(tert-butylamino)dimetliylsilane, are compared with the corresponding tin compound 2 in their reactivity towards tert-butylamino. There is a clear dependence of the reaction rate on the nature of the element. The norcubane-like cage Ge 3 (N t Bu) 4 H 2 (5 a) and the cubane-like cages Ge 4 (N t Bu) 4 (6a) and Pb 4 (N t Bu) 4 (6c) result from these reactions. When 3 is treated with bis(methylamino)dimethylsilane, [(Me 2 Si) 2 (MeN) 3 Pb] n (7) precipi­tates from the reaction mixture. Sn 3 (N t Bu) 4 H 2 (5b) can be transformed into Sn 3 (N t Bu) 4 Ge (8a) and Sn 3 (N t Bu) 4 Pb (8b) when heated at high temperatures with 1 or 3, respectively. In these polycyclic compounds two low-valent elements of group IV are simultaneously present in one cage unit. As can be shown, 8b is less stable to bond cleavage than 8a and undergoes redistribution reactions at elevated temperatures to form Sn 4 (N t Bu) 4 (6b), Sn 2 Pb 2 (N t Bu) 4 (9). SnPb 3 (N t Bu) 4 (10) and Pb 4 (N t Bu) 4 (6c).

Triphenylphosphane 1, its oxide 2 and sulfide 3 undergo one-electron reduction at a mercury cathode in DMF to yield the corresponding radical anions. ESE analysis of the paramagnetic species is facilitated by deuteration and suggests a pyramidal geometry of the radicals. Reduction with potassium metal in DME at low temperature yields also radical anions for 2 and 3. The phosphane 1, however, reacts under phenyl cleavage and potassiumphenyl-assisted ring closure to the dianion of 5H-dibenzophosphole 4. This radical 4 · ⊖⊖ is also obtainod by alkali metal reduction of P-phenyldibenzophosphole o, and its spin distribution is compared to iso-.-π-electronic radicals containing CH, N, O, S, or Se links instead of the phosphorus atom.

The preparation of S 4 N 5 + MF 6- (5 a, b M = As, Sb) by decomposition of S 3 N 3 F 2 + MF 6- and by Cl - exchange in S 4 N 5 Cl with AgAsF 6 is described. The structure of 5a was de­termined from single crystal X-ray data.

Reactions of pentamethylantimony (CH 3 ) 5 Sb with carboxylic acids in the molar ratio 1:2 afford one equivalent of methane and essentially quantitative yields of crystalline tetramothylstibonium hydrogendicarboxylates. Six new compounds of this series have been synthesized using benzoic, o-phthalic, salicylic, 4-ethoxy-salicylic, oxalic, and malic acid, and characterized by analytical and spectroscopic data. An ionic structure with strong hydrogen bonds in the anionic components is proposed. The crystal structures of the hydrogen-dibenzoato (1), hydrogen-ortho-plithalato (2) and 4-ethoxy-hydrogen-salicylate (3) were determined by single crystal X-ray diffraction. The compounds can be described as having ionic lattices with some donor-acceptor inter­actions between the stibonium centers and the carboxylate oxygen atoms. The anions are characterized by strong hydrogen bonds O...H...O. Thus, the (CH 3 ) 4 Sb-tetrahedron in 1 is distorted by two benzoate oxygon atoms (at 304(2) and 340(2) pin). The cation in 2 is largely undistorted and the anion has a hydrogenphthalate hydrogen bond of d(O...H...O) = 232 pm. The cation-anion contact in 3 is as short as d(Sb-O) = 289 pm rendering the Sb atom pentacoordinate.

The structure of the known compound O,O-Diphenyl-N-chlorophosphoramidate has been determined by X-ray diffraction. It consists of dimers, in which the monomers are connected by N-H···O hydrogen bonds. The O,O-Diethyl-N-chlorophosphoramidate homologue can be synthesized by various methods. At room temperature it is part of an equilibrium mixture with O,O-Diethyl-phosphoramidate and O,O-Diethyl-N,N-dichloro-phosphoramidate.

The resonance Raman and electronic spectra of compounds Ni(en) 2 X 3 , Ni(dapn) 2 X 3 etc. and of compounds [Ni(en) 2 Pt(en) 2 X 2 ](ClO 4 ) 4 (where X = Cl or Br) show that those are mixed valence compounds with a metal halide chain (en = 1,2-diaminoethane, dapn = 1,2-diaminopropane).

The novel oxotribromosolcnate(IV) SeOBr 3- anion was prepared from the reaction of stoichiometric quantities of SeOBr 2 and bromide in acetonitrile solution, and it was isolated as the tetraphenylphosphonium and -arsonium salts in crystalline form. For the synthesis of the analogous SeOCl 3- as P(C 6 H 5 ) 4 SeOCl 3 , SeCl 4 was reacted in the presence of a small quantity of H 2 O with P(C 6 H 5 ) 4 Cl in acetonitrile. Complete X-ray structural analyses of P(C 6 H 5 ) 4 SeOCl 3 (space group P1̄, a = 10.981(3), b = 11.0511(3), c = 10.358(3) Å, α = 73.77(2)°, β = 83.33(2)°, γ = 80.51(2)°, V = 1187.9(6) Å 3 ) and of P(C 6 H 5 ) 4 SeOBr 3 (space group P 2 1 /c, a = 11.719(4), b = 16.088(4), c = 13.124(4) Å, β = 94.72(3)°, V = 2400(1) Å 3 ) show dimeric centrosymmetric Se 2 O 2 Cl 6 2- and Se 2 O 2 Br 6 2- anions being present in the solid. In the anions two square-pyramidal (Ψ-octahedral) SeOHal 4 groups are connected through a common Hal-Hal edge. The axial oxygen ligands (So-O: 1.597(4) and 1.584(0) Å) cause a pronounced stereochemical trans-activation of the inert pairs at the Se atoms. As(C 6 H 5 ) 4 SeOBr 3 is isotypic with P(C 6 H 5 ) 4 SeOCl 3.

Tetrabutylammoniumdodecatungstophosphate, [N(C 4 H 9 ) 4 ] 3 PW 12 O 40 exists in two different forms. The anion of the first one represents the regular “Keggin-Structure” (α-type) with T d -Symmetry. The second isomer, crystallizing in the triclinic space group P1̄ with lattice parameters a = 13.897 Å, b = 15.410 Å, c = 19.535 Å, α = 95.11°, β = 92.88°, γ = 90.46° contains a neutral W 12 O 36 moiety with centrosymmetric tungsten and oxygen positions built from tetragonal-pyramidal WO 5 units. In the central cavity a disordered PO 4 3- anion is enclosed. For the new isomer the term γ-type is proposed.

195 Pt NMR spectra for the pure anionic complexes [PtCl n Br 6-n ] 2- have been measured in acetone solution. The isomerization reactions cis-[PtCl n Br 6-n ] 2- → trans-[PtCl n Br 6-n ] 2- , n = 2, 4 and fac-[PtCl 3 Br 3 ] 2- → mer-[PtCl 3 Br 3 ] 2- are slow on the NMR time scale and these slow kinet ics allow an unambiguous assignment of the 195 Pt signals. The cis and fac complexes are found at slightly lower field (12-15 ppm) than their trails and mer counter­parts. There is a linear correlation of δ 195 Pt with the sum of the Allred-Rochow electronegatives of the halogen atoms.

Reactions of the ring systems (NPCl 2 ) 3 , (NPCl 2 ) 2 NSOX, and NPCl 2 (NSOX) 2 (X = Cl, Ph) with N,N′-dimethylethylenediamine lead to mono-, bis-, and tris(spirocyclic) com­pounds as the only characterizable products. The 1 H and 31 P NMR parameters are re­ported and briefly discussed.

The reactions of 1,2- and 1,3-dithioles, HSRSH, with Fo 3 (CO) 12 give the dinuclear compounds Fe 2 (CO) 6 (SRS) in good yields. With R = C 2 H 4 or R = C 3 H 6 the trinuclear compounds (CO) 3 Fe(SRS)Fe(CO)(SRS)Fe(CO) 3 containing an open Fe 3 chain are obtained.

Tris(diothyldithiophosphinato)-tris-μ-disulfido-μ 3 -thiotriangulo-trimolybdenum(IV)-di-ethyldithiophosphinate, [(et 2 PS 2 ) 3 Mo 3 S(S 2 ) 3+ (et 2 PS 2 ) - , crystallizes in two orthorhombic modifications with crystallographic parameters of A: a = 20.651(3), b=10.152(2), c = 19.019(2) Å, Pca2 1 , Z = 4 and B: a = 20.128(2), b= 15.655(2), c = 12.608(1) Å, Pinna, Z = 4. Both crystal structures were determined from 2886 (A) and 3414 (B) X-ray data with R factors of 0.058 and 0.045, respectively. The Mo atoms form a trinuclear Mo 3 S(S 2 ) 3 cluster with local symmetry close to C 3V in both modifications which differ in the packing of anions and cations and in the conformation of the ethyl groups. The av. distance Mo-Mo is 2.737 Å, the coordination number of the Mo atoms is 7 within the cluster and 9 on inclusion of the S atoms of the dithiophosphinato group.

SrAl 2 , forming at standard conditions the KHg 2 structure type, transforms at ~60 kbar and 1050 °C to a high pressure modification with the MgCu 2 structure (a = 832.5(5) pm).

The blue complex of L-ascorbic acid with Fe 3+ ions has been obtained and isolated. Various spectrographic and analytical techniques have been used to study this complex. A kinetic study was also carried out on L-ascorbic acid oxidation by Fe 3+ by means of the stoppod flow technique for rapid processes.

The title compound, C 25 H 20 BNO 2 · CH 3 OH, was examined by UV, IR, 1 H, and 13 C NMK spectroscopy as well as by thermogravimetry and X-ray structure analysis (Pbnb, a = 8.815, b = 17.309, c=28.992 Å, R= 5.5%). These investigations show the six-membered chelate ring (chelate A) to exist as formulated in [2] and not as a five-membered chelate ring B. One methanol molecule connects two chelate molecules by hydrogen bonds, resulting in an overall ratio of chelate to methanol of 1 : 1.

Triorganotin and -lead derivatives of X-benzoylglveine (BzGlyH) and N-formylglycine (ForGlyH), R 3 MBzGly and R 3 MForGly (M = Sn; R = Me, Ph. M = Pb; R = Ph) have been prepared from R 3 MOH and BzGlyH or ForGlyH, respectively. According to spectro­scopic data the Me 3 Sn groups are essentially planar; molecules of R 3 SnForGly are bridged by unidentate carboxylate groups and formyl-C = O groups in the solid state, while Ph 3 PbForGly and benzoylglycinates are bridged by bidentate carboxylate groups. NH does not coordinate to M. Pentacoordination and a polymeric nature in the solid state is also indicated by Mößbauer data of Me 3 SnForGly and Me 3 SnBzGly. In solution all compounds are monomeric.

The potentially curare-like silicon compounds 8a-8f wore synthesized and investigated with respect to their structure-activity relationships. The conformations of the com­pounds in the solid state and in solution were studied by X-ray diffraction analysis (8a-8e) and 1 H NMR spectroscopy (8a-8f), respectively. The muscle relaxing properties of 8a-8f were investigated on the mouse. The observed structure-activity relationships are not in accordance with the classical “14 Å model” for neuromuscular blocking agents.

Absorption, corrected emission spectra, fluorescence quantum yields, and preparation are reported for distyrylbenzene, distyrylstilbene and substituted derivatives. The Stokes shifts are measured in three solvents and correlated with quantum chemical calculations.

In continuation of studies on some extensions of von Braun BrCN reaction on organic bases, work on diisobutylamine and di-2-butylamine, has led to various substituted ureas and N-imino-ethyl ether derivatives. In contrast to previous observations, reduction of their cyanamides with zinc/HCl gave the amido derivatives instead of diamines.

The η 2 -ketenido (η 5 -C 5 H 5 )(CO)[P(CH 3 ) 3 ]W[O=C=C-C 6 H 4 CH 3 -(4)] reacts with thionyl chloride forming a sulfine O = S = C(COCl)C 6 H 4 CH 3 -(4).

The high pressure-high temperature phase of CaSi 2 is a representative of the α-ThSi 2 type of structure. Single crystals grown at 40 kbar and 1000 °C enabled a structural refinement which leads to interatomic distances Si-Si: 229.9(1) pm (1 × ) and 240.0(1) pm (2 × ), Ca-Si: 309.4(4) pm (4 x ) and 323.9(4) pm (8 × ), Ca-Ca: 400.3(3) pm (4 × ) and 428.3(3) pm (4 × ).

The 31 P NMR spectra of PCl 3 =N[PCl 2 = N] n PCl 2 =S (n = O-2) undergo significant changes in ν/2 and 4 J PP when the temperature is lowered. The effects are discussed in terms of T 1 relaxation effects which may re­flect the mobility of phosphorus in compounds 1-3. Bei 31 P-NMR-Untersuchungen an linearen Phosphorylphosphazenon der allgemeinen Struk­tur PCl 3 =N[PCl 2 =N] n PCl 2 =O (n=O-3) ha­ben wir eine höchst augenfällige Abhängigkeit der Parameter Kopplungskonstante, chemische Verschiebung und Halbwertsbreito ν/2 von Lö­sungsmittel und Temperatur festgestellt [1]. Die Änderungen von ν/2 betroffen dabei vor allem die ondständige PCls-Gruppo. Es konnte gezeigt werden, daß dieser Effekt wahrschein­lich durch Relaxation über den Spinrotations- Mechanismus (T1 SR ) zustande kommt. Um weiteres Untersuchungsmaterial in die Hände zu bekommen und um damit zu erkennen, in wel­chen Grenzen die beschriebenen Effekte auftreten, wurden nun auch die entsprechenden Thioanaloga in die Untersuchungen mit einbe­zogen.