Volume 56, Issue 12

The new germanates(IV) were synthesized via reaction of GeO 2 with AO 2 (A=K, Rb, Cs) and the elemental alkaline metals and their crystal structures have been determined from single crystal X-ray data. ß-K 4 GeO 4 / Rb 4 GeO 4 (monoclinic, P2 1 /c , a = 1047.6(3)/1103.2(2), b = 646.5(1)/673.3(1), c = 1048.1(3)/1084.5(2) pm, ß = 112.291(5) / 112.676(4)°, Z = 4) and Cs 10 Ge 2 O 9 (monoclinic, P2 1 /c , a = 1293.7(2), b = 1148.6(2), c = 1926.4(2) pm, ß = 128.05(8)°, Z = 4) contain isolated, A 6 Ge 3 O 9 (A = Rb / Cs: monoclinic, P 2 1 /c , a = 663.0(1) / 696.3(2), b = 1346.8(2) / 1403.1(3), c = 1666.6(2) / 1742.8(6) pm, ß = 107.47(2) / 107.88(2)°, Z = 2) cyclotrigermanate ions. In Cs 3 AlGe 2 O 7 (monoclinic, C2/c, a = 961.5(2), b = 1719.7(2), c = 761.7(1) pm, ß =126.5(1)°, Z = 4) digermanate ions are connected via [AIO 4 ] tetrahedra to form ribbons.

Treatment of the ligand l,3,5-tris[(diphenylphosphanyl)methyl]trimethylbenzene (P 3 ) with (tetrahydrothiophene)gold(I) chloride results in the symmetrical trigold complex [(P 3 )(AuCl) 3 ]. In the presence of sodium methoxide, [(P 3 )(AuCl) 3 ] reacts with thiocresol (HSC 6 H 4 Me-4) and 2-mercaptoquinoline (2-HSQn) to provide the complexes [(P 3 )(AuSC 6 H 4 Me-4) 3 ] and [(P 3 )(AuSQn) 3 ], respectively. Reaction of [(P 3 )(AuCl) 3 ] with KSCN also yields the expected product [(P 3 )(AuSCN) 3 ], however, treatment with 2-10 molar equivalents of NaSMe re­sults only in the unsymmetrical cationic complex [(P 3 )Au 3 (SMe) 2 ]Cl. Reaction between [(P 3 )(AuOTf) 3 ] (prepared in situ from [(P 3 )(AuCl) 3 ] and AgOTf) and sodium sulfide yields the complex [(P 3 )Au 3 S] + OSO 2 CF 3 - , the first example of a trigoldsulfonium unit coordinated to a tridentate phosphine. The tetrafluoroborate salt is obtained from [(P 3 )(AuCl) 3 ] and Na 2 S·9 H 2 O in the presence of NaBF 4 . The structure of [(P 3 )(AuSMe) 2 ]Cl has been determined and reveals that in the solid the two methylthiolate units bridge the three gold atoms, but the structure of the cation is fiuxional in solution according to NMR data.

New copper(II) complexes with 8-hydroxyquinoline-2-carbaldehyde-N-methylnitrone (HL 1 ) (1) and pyridine-2-carbaldehyde-N-methylnitrone (L 2 ) (2) have been synthesized. The crystal structure of compound 1 consists of binuclear molecules Cu 2 (L 1 ) 2 (NO 3 ) 2 with the oxygen atoms of the hydroxy groups acting as bridges between the copper ions. The nitrone ligand in 1 is coordinated in a tridentate fashion forming five-and six-membered chelate rings, and the copper ions have a square-pyramidal environment with the bridging oxygen atoms in apical positions. In compound 2 Cu(L 2 ) 2 (NO 3 ) 2 , the copper atom adopts a distorted octahedral environment with bidentately coordinated nitrone ligands. In both cases the nitrone groups are involved in coordination via the oxygen atom. Compounds 1 and 2 have been studied by EPR, UV-VIS and IR spectroscopy. The free nitrone HL 1 has also been studied by X-ray diffraction as well as by IR and UV spectroscopy.

o-Fluorophenyl glycine and alanine, 2-thienyl glycine and alanine form with dinuclear, chloro bridged metal complexes the chiral N, O-chelates (arene)M (Cl)(NH 2 CHRCO 2 ) (M = Ru, Rh, Ir; arene = cymene, Cp*) and (R 3 P)(Cl)M(NH 2 CHRCO 2 ) (M = Pd, Pt) as mixtures of diastereoisomers or cis/trans-isomers, respectively.

The new compounds Tm 2 NiAs 2 and Yb 2 NiAs 2 crystallize with a hexagonal structure similar to that reported for Zr 2 NiAs 2 . It was refined for Tm 2 NiAs 2 from single-crystal X-ray data in the polar space group P6 3 mc\ a = 408.4(1), c = 1374.2(3) pm, R = 0.044 for 176 structure factors and 16 variable parameters. The compounds Ln 2 NiAs 2 (Ln = Tb -Er) are confirmed to crystallize with an analogous structure from X-ray powder data. In contrast to the earlier structure refinement of Zr 2 NiAs 2 in the higher-symmetric space group P 6 3 /mmc, where the honeycomb layers of nickel and arsenic atoms are described as planar, these layers are puckered in Tm 2 NiAs 2 . These compounds are expected to undergo a displacive phase transition, with the centrosymmetric space group P6 3 /mmc to be correct at high temperature. Since the room temperature structure is polar, these compounds might be classified as ferroelectric from a symmetry point of view. The equiatomic title compounds LnNiAs and UNiAs crystallize with a related hexagonal structure corresponding to a superstructure of the AIB 2 type with lattice constants varying between a = 416.2(1), c = 1636.1(4) pm for LaNiAs and a = 401.9(2), c = 1488.5(5) pm for YbNiAs. The crystal chemistry of these hexagonal structures is briefly discussed. Using oxidation numbers chemical bonding in the lanthanoid containing compounds may be rationalized with the formulas (Ln +3 ) 2 Ni(As -3 ) 2 and Ln +3 NiAs -3 , thus suggesting semiconducting behavior.

Activation of Ni(acetylacetonate) 2 and Ni(2-ethylhexanoate) 2 with B(C 6 F 5 ) 3 and B(C 6 F 5 ) 3/ triethylaluminium leads to highly active catalyst systems for the vinyl polymerization of nor­bomene.

[Rh(CO) 2 Cl] 2 reacts with 1,3-diphenylcyclopentadienyl sodium or tetraphenylcyclopentadienyl sodium with formation of (1,3 -Ph 2 C 5 H 3 )Rh(CO) 2 (1) or (C 5 HPh 4 )Rh(CO) 2 (2), respectively. The reaction of 1 or 2 with PPh 3 yields the corresponding carbonyl-(cyclopentadienyl)(triphenylphosphane)rhodium complexes (1,3 -Ph 2 C 5 H 3 )Rh(CO)(PPh 3 ) (3) or (C 5 HPh 4 )Rh(CO)(PPh 3 ) (4). The 1 H and 1 C reported and discussed.

Sodium in dry methanol reduces 2-cyanopyridine in the presence of N(4)-dimethylthiosemicarbazide to produce 2-pyridyl-formamide N(4)-dimethylthiosemicarbazone, HAm4DM. Com­plexes with zinc(II) and cadmium(II) of formulae [M(Am4DM)(OAc)] 2 and [M(HAm4DM)X 2 ] (M = Zn or Cd, X = Cl, Br or I) have been prepared and characterized by spectro­scopic techniques. In addition, the crystal structures of HAm4DM, [Zn(HAm4DM)Br 2 ], and [Cd(HAm4DM)l 2 ] DMSO have been solved. HAm4DM is in the zwitterionic form with a hydrogen bonding interaction between the iminium hydrogen and the thiolato sulfur atom. Co­ ordination of the neutral thiosemicarbazone ligand is via the pyridyl nitrogen, imine nitrogen and thione sulfur atoms, while the anionic ligand in [M(Am4DM)(OAc)] 2 coordinates with the same two nitrogen atoms and a thiolato sulfur atom. The [M(HAm4DM)X 2 ] complexes are 5-coordinate with the tridentate thiosemicarbazone and two halogen ligands approaching a square pyramidal stereochemistry.

Previous studies on carbon supported Pt, Pt+W and Pt+Mo indicated that Pt+Mo was the most active electrocatalyst at low potentials and that Pt+W has similar properties as pure Pt in methanol oxidation. Those samples were thermally treated at 900 °C in a hydrogen gas atmosphere for 6 hours to observe the effect on metal particle sizes and on their distribution on carbon support. It was found that thermally treated Pt+Mo/XC-72 remains the most active catalyst at all potentials compared to the other heated samples. The heat treatment caused the sintering of small particles leading to a decrease in activity of the catalysts except Pt+Mo/XC-72. The heat treated samples were characterised by voltammetry, X-ray diffraction, transmission electron microscopy and energy dispersive X-ray analysis techniques. The methanol oxidation reaction was followed by in-situ FTIR spectroscopy to identify products and adsorbed species on the surface of electrode.

Ligand The asymmetric unit of crystal of the title compound, [Ni 2 (L)(C 3 H 3 N 2 )] (L = 1,3-Bis(2-hydroxy-4-methoxybenzylideneamino)propan-2-ol, C 3 H 3 N 2 = pyrazolate) contains two inde­pendent dinickel(II) complexes. In both molecules, the nickel(II) ions are bridged by the alkoxo group of the ligand and the N atoms of the pyrazolate group. Each nickel(II) ion is coordinated by two N and two O atoms, forming a square with trans-N 2 O 2 geometry.

The title compound was prepared from tri-n-butyl-chlorophosphonium chloride and N-tri-methylsilyl-tris(diethylamino)-phosphinimine. A low temperature X-ray crystal structure de­termination revealed PN bond lengths of 156.1(2) and 158.0(2) pm, with a PNP angle of 149.36(17)°.

Orange red crystals of Na 2 ZrSe 3 were obtained by the reaction of Na 2 Se, Zr and Se at 800 °C. The new compound is monoclinic, s. g. C2/m with a = 6.952(2), b = 12.01(1), c = 7.257(2) Å, ß = 108.81(2)°, Z = 4. Its crystal structure was determined from single crystal diffractometer data (Mo-K α -radiation) and refined to a conventional R of 0.016. It is characterized by layers based on a distorted ccp packing of Se-atoms where all metal atoms occupy octahedral voids in an ordered fashion. Zr atoms are located on the nodes of a 6 3 -net forming CrCl 3 type selenozirconate layer (d(Zr-Se) = 2.702 Å).

Tris(diphenylstibino)amine (Ph 2 Sb) 3 N (1) is formed in 49.5% yield by ammonolysis of Ph 2 SbCl in liquid NH 3 , and as a side product of the synthesis o f Ph 4 Sb 2 by reactions of Ph 3 Sb with Na and BrCH 2 CH 2 Br in liquid NH 3 . The structure of 1 was determined by single crystal X-ray diffraction. The crystals consist of molecules with an almost planar Sb 3 N core (sum of the angles at nitrogen: 352.14°).

Na 2 [M 2 (CO) 10 ] and GeCl 4 react to give the compounds [(CO) 5 MGeCl 3 ] - , 1a - 1c (M = Cr, Mo, W). From M(CO) 5 ·THF and Gel 2 in the presence of I - compounds [(CO) 5 MGeI 3 ] - , 2a - 2c (M = Cr, Mo, W) are obtained. Compounds 2a and 2c react with alkoholates or thiolates to produce the cage compounds [{(CO ) 5 Cr} 6 Ge 6 (μ 2 -OH ) 2 (μ 3 - O) 6 ] 2- , 3, [{(CO) 5 Cr} 6 Ge 6 - (μ 2 -OEt) 2 (μ 2 -O) 4 (μ 3 -O) 2 ] 2- , 4, and [{(CO) 5 W } 6 Ge 6 (OR) 2 (μ 2 - O) 2 (μ 3 -O) 4 ] 2- , 5. A structural pattern common to all these compounds is an idealised octahedral arrangement of six germanium atoms. Each of these six germanium atoms binds to an M(CO) 5 protective group. The germanium atoms are integrated in the core of the cage compounds by μ 3 -O , μ 2 -O and μ 2 -OH bridges. The co-ordination number of germanium is generally four, with one bond radiating to the external M(CO) 5 building block. In compounds 3 and 4 the remaining three germanium bonds radiate to the bridging groups within the cage. Compounds 5 contain two germanium centres which are linked to the cage by only two bonds and with the two remaining bonds to the external M(CO) 5 entity and to a terminal OR or SR group. Syntheses and structures of compounds 1 - 5 are described.

The evaporation of a solution of Au(OH) 3 and Na 2 So 4 in conc. sulfuric acid led to yellow single crystals of NaAu(SO 4 ) 2 (monoclinic, P2 1 /n, Z = 2, a = 469.1, b = 845.9, c = 831.2 pm, β = 95.7°). Analogous procedures with K 2 SO 4 or Rb 2 SO 4 instead of Na 2 SO 4 yielded single crystals of KAu(SO 4 ) 2 (monoclinic, C2/c, Z = 4, a = 1109.8, b = 724.2, c = 941.1 pm, β = 118.4°) and RbAu(S04)2, respectively, (triclinic, P1̄, Z = 1, a = 423.6, b = 497.5, c = 889.0 pm, a = 76.4°, β = 88.4°, γ = 73.5°). Although the crystal structures of the three sulfates are not isotypic they show similar structural features: The gold atoms are coordinated by four oxygen atoms in a square planar manner. These oxygen atoms belong to four SO 4 2- ions which link the [AUO 4 ] units to infinite chains according to 1 ∞ [Au(SO 4 ) 4/ 2 ] - . These chains are connected via the monovalent cations which show coordination numbers of 6 (Na + ), 10 (K + ) and 12 (Rb + ), respectively.

The absolute configuration of the conformationally flexible (4R,6S,7S)-serricornin, a non­ natural isomer of the female-produced sex pheromone of the cigarette beetle (Lasioderma serricorne), was determined by comparison of measured and calculated circular dichroism spectra. The rotational strengths were calculated by means of the semiempirical CNDO/2S-method. The total synthesis was accomplished by the SAMP/RAMP-hydrazone method.

Upon anodic oxidation tetrakis(4-N,N-dimethylaminophenyl)methane (3) fragments to give the stable species crystal violet (6), N,N,N′,N′- and Michler’s hydrol blue (12) that can be readily absorption bands.

Among 29 organic acids whose effects on the in vitro enzymatic substrate reducing activity on the MoFe-protein of nitrogenase have been investigated, 12 acids stimulate the in vitro C 2 H 2 -reducing activities in proportion to the H + -reducing activities. A second group com­ prised of eight acids significantly stimulates the H + -reducing activity but has only modest stimulatory effects on C 2 H 2 -and N 2 -reducing activities. A third group of nine acids causes only slight increases of MoFe-protein substrate reducing activities. The stimulatory effects of acids on MoFe-protein substrate reducing activity depend on their mode of interaction with molybdenum. Hydroxycarboxylic acids acting as bidentate ligands such as homocitric acid and its derivatives leave a sufficient number of molybdenum coordination sites available for interactions with the substrates, they have the highest stimulatory effects both on the C 2 H 2 -and N 2 -reducing activities, and their H + -reducing activities are not inhibited by CO. Acids acting as tridentate ligands, which include citric acid, have weaker stimulatory effects on the C 2 H 2 -and especially on the N 2 -reducing activities, and CO inhibits their H + -reducing activity. Whereas with the first group of acids the C 2 H 2 -reducing activities are linearly correlated with H + -reducing activities, the N 2 -reducing activities are directly correlated with H+-reducing activities in the presence of CO, and the association is exponential rather than linear. This exponential dependence is consistent with a stepwise mechanism of nitrogen reduction via diazene and hydrazine as the intermediates, the latter blocking one molybdenum coordina­tion site prior to its reduction to NH 3 . In the reduction of C 2 H 2 to C 2 H 4 , no such blockage occurs as product C 2 H 4 does not accumulate at the active site and is not reduced further.

4-Fluorobenzenesulfonyl chloride (1) and pentafluorobenzenesulfonyl chloride (2) are transformed into the corresponding N-sulfonylpyridinium triflates 4a-d by treatment with one equivalent of the reagent pair L/TMSOTf (L = 4-dimethylaminopyridine (DMAP), 4-ferf-butylpyridine (TBUPY), 1-methylimidazole (NMI); TMSOTf = trimethylsilyl triflate). Due to the electrostatic effect of the sulfonylonio function, SNAr reactions on these systems can be performed under mild conditions. So the reaction of 2 with excess DMAP/TMSOTf leads by way of peronio substitution to hexakis[(4-dimethylamino)-l-pyridinio]benzene hexa-kis(trifluoromethansulfonate) (7) [22] at room temperature. Additionally, a new reaction path to 4-(1-pyridinio)-substituted benzenesulfonamides, a class of pharmaceutically interesting substances, is shown.

The reaction of hexamethyldisilane with tellu­rium tetrachloride in carbon disulfide afforded polymeric (MeTeCl 3 ) n (1) that was characterized by TOF ES mass spectroscopy, 125 Te NMR spectroscopy, and X-ray crystallography. Pale brown, air-and moisture-sensitive crystals of 1 are monoclinic, space group P2 1 /n with a = 1030.69(5), b = 643.61(2), c = 1041.68(5) pm, ß = 119.236(5)°, V = 0.60299(5) nm 3 , and Z = 4. The crystal structure consists of infinite helical chains of the MeTeCl 3 units linked by bridging chlorine atoms. The polymeric chains are linked together by Te···Cl and Cl···Cl close contacts. The pos­sible routes for the formation of (MeTeCl 3 ) n are discussed.

A series of ferrocene sandwich compounds such as N-ferrocenyl amine, Fc-NH 2 (1), the Nsilylated derivatives Fc-NH -SiMe 3 (2), Fc- NH -SiMe 2 H (3), (Fc-NH ) 2 SiMe 2 (4), the N-silyl- N-boryl derivatives Fc-N(SiMe 3 )(9-BBN) (5) (9-BBN = 9-borabicyclo[3.3.1]nonyl) and Fc- N(SiMe 3 )BEt 2 (6), and the N-borylated derivatives Fc-NH -(9-BBN) (7) and Fc-NH -BEt 2 (8) were studied by 57 Fe NMR spectroscopy. The δ 57 Fe data reveal that C Fc N(pp)π interactions lead to 57 Fe nuclear magnetic deshielding (with respect to ferrocene) which is attenuated if competing BN(pp)π bonding becomes efficient (7, 8).

The structural parameters and IR frequencies of the following anionic fulminate complexes were computed at the density functional BPW91 level of theory using a 6-31++G(2d) basis for C, N, O, Co, Ni, and Zn and quasi-relativistic ECP60MWB core potentials for Pt, Au and Hg: [Co(CNO) 6 ] 3- (Oh), [Ni(CNO) 4 ] 2- (D 4h ), [Zn(CNO) 4 ] 2- (Td), [Pt(CNO 4 ] 2- (D 4h ), [Au(CNO) 2 ] - (D xh ) and [Hg(CNO) 4 ] 2- (Td). The structures were optimised within the symmetries stated above and were found to represent true minima (number of imaginary frequencies, NIMAG = 0). The agreement between the calcu­ lated structural parameters and characteristic asymmetric and symmetric CNO stretching fre­ quencies is very good for all complexes.