Gold-Stickstoff-Heterocyclen. 3. Synthese,Eigenschaften und Struktur von trimerem Amido-dimethylgold(III), [(CH3)2 AuNH2]3

Gold Nitrogen Heterocycles. 3. Synthesis, Properties, and Structure of Amido Dimethyl Gold(III), [(CH₃)₂ AuNH₂]₃ The reaction of [(CH₃)₂AuI]₂ with KNH₂ in liquid NH₃ yields tetrameric and trimeric amido dimethyl gold(III). The tetrameric form transforms at ambient temperature easily in the more stable trimeric complex. [(CH₃)₂AuNH₂]₃ forms air-stable, colorless crystals, which are sensitive against irridiation with light. It crystallizes in the orthorhombic space group Ama2 with the lattice constants a = 1653.4, b = 1844.4, c = 448.1 pm, Z = 4. In the trimeric complex the Au(CH₃)₂ groups are linked together by symmetrical amido bridges forming a six membered Au? N heterocycle in the chair conformation. The Au atoms exhibit a square-planar coordination of two CH₃ groups (Au? C = 203 pm) and two N atoms (Au? N = 215 pm) in a cis arrangement. The symmetry C_3v was confirmed for the complex in solution and in the solid state. The vibrational spectra as well as the H-NMR and mass spectra are discussed.     

A 2,2′-diphosphinotolane as a versatile precursor for the synthesis of P-ylidic mesoionic carbenes via reversible C–P bond formation

A metal-templated synthetic route to cyclic (aryl)(ylidic) mesoionic carbenes (CArY-MICs) featuring an endocyclic P-ylide is presented. This approach, which requires metal templates with two cis-positioned open coordination sites, is based on the controlled cyclisation of a P,P′-diisopropyl-substituted 2,2′-diphosphinotolane (1) and leads to chelate complexes coordinated by a phosphine donor and the CArY-MIC carbon atom. The C–P bond formation involved in the former partial cyclisation of 1 proceeds under mild conditions and was shown to be applicable all over the d-block. In the presence of a third fac-positioned open coordination site, the P–C bond formation was found to be reversible, as shown for a series of molybdenum complexes. DFT modelling studies are in line with an interpretation of the target compounds as CArY-MICs.

A metal-templated synthesis of cyclic (aryl)(ylidic)mesoionic carbene complexes (CArY-MICs) is presented. In the case of molybdenum carbonyls, the crucial P–C bond formation, which occurs during CArY-MIC formation, was found to be reversible.     

Die Kristallstrukturen von Triphenylarsin-p-toluolsulfonylimin und seines Donor-Akzeptorkomplexes [ZrCl4(Ph3AsNSO2Tol)]2

The Crystal Structures of Triphenylarsin-p-toluene Sulfonylimine and of its Donor-Acceptor Complex [ZrCl₄(Ph₃AsNSO₂Tol)]₂ The molecular structures of the title compounds are reported. In the donor-acceptor complex [ZrCl₄(Ph₃AsNSO₂Tol)]₂ the zirconium atoms are bridged by the oxygen atoms of the triphenylarsin-p-toluene sulfonylimine molecules, forming a centrosymmetric dimer with a puckered Zr₂O₄S₂ eight-membered ring in the chair conformation. Ph₃AsNSO₂Tol: Space group P1 , Z = 2, structure determination with 4 010 observed unique reflections, R = 0.036. Lattice dimensions at 19°C: a = 897.52(4), b = 1 071.82(6), c = 1 337,49(5) pm, α = 110.280(4)°, β = 98.814(4)°, γ = 109.872(4)°. [ZrCl₄(Ph₃AsNSO₂Tol)]₂: Space group P2₁/n, Z = 4, structure determination with 3 762 observed unique reflections, R = 0.078. Lattice dimensions at ?60°C: a = 1 387.3(4), b = 1 434.9(2), c = 1 404.7(4) pm, β = 92.71(1)°.     

Field-force alignment of disc-type pi systems.

The ability of electric fields to align nonpolar semiconducting molecules was demonstrated using hexa(para-n-dodecylphenyl)hexabenzocoronene (HBC-PhC12) as a model compound. A solution of HBC-PhC12 was applied to a glass surface by drop-casting and the molecules were oriented into highly ordered structures by an electric field during solvent evaporation. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) showed a long-range alignment where the disclike molecules were organized in columns perpendicular to the direction of the imposed electric field. The high anisotropy of the uniaxially aligned films was characterized by cross-polarized light microscopy. The birefringence of the HBC-PhC12 films was related to the presence of extended domains of unidirectionally aligned columns in which the aromatic cores of the HBC-PhC12 molecules were perpendicular to the columnar axis. The packing and the arrangement of the molecules in the field-force ordered films were proven by electron diffraction and X-ray analyses.     

New copper-mediated O-arylations of phenols with arylstannanes

A novel method for the synthesis of diaryl ethers with phenols and arylstannanes under mild conditions is described. This copper-mediated O-arylation is feasible using DMAP in acetonitrile and is complementary to the use of boronic acids as aryl donors. The reaction is tolerant of a wide range of substituents and sterically hindered coupling partners.     

Structure and reactivity of V(2)O(5): bulk solid, nanosized clusters, species supported on silica and alumina, cluster cations and anions

Vanadyl bond dissociation energies are calculated by density functional theory (DFT). While the hybrid (B3LYP) functional results are close to the available reference data, gradient corrected functionals (BP86, PBE) yield large errors (about 50 to 100 kJ mol(-1)), but reproduce trends correctly. PBE calculations on a V(20)O(62)H(24) cluster model for the (001) surface of V(2)O(5) crystals virtually reproduce periodic slab calculations. The low bond dissociation energy (formation of oxygen surface defect) of 113 kJ mol(-1)(B3LYP) is due to substantial structure relaxations leading to formation of V-O-V bonds between the V(2)O(5) layers of the crystal. This relaxation cannot occur in polyhedral (V(2)O(5))(n) clusters and also not for V(2)O(5) species supported on silica or alumina (represented by cage-type models) for which bond dissociation energies of 250-300 kJ mol(-1) are calculated. The OV(OCH(3))(3) molecule and its dimer are also considered. Radical cations V(2)O(5)(+) and V(4)O(10)(+) have very low bond dissociation energies (22 and 14 kJ mol(-1), respectively), while the corresponding radical anions have higher dissociation energies (about 330 kJ mol(-1)) than the neutral clusters. The bond dissociation energies of the closed shell V(3)O(7)(+) cation (165 kJ mol(-1)) and the closed shell V(3)O(8)(-) anion (283 kJ mol(-1)) are closest to the values of the neutral clusters. This makes them suitable for gas phase studies which aim at comparisons with V(2)O(5) species on supporting oxides.     

Neue Phosphor-verbrückte Übergangsmetallcarbonyl-Komplexe Die Kristallstrukturen von [Re2(CO)7(PtBu)3], [Co4(CO)10(PtBu)2], [Ir4(CO)6(PtBu)6] und [Ni4(CO)10(PiPr)6]

New Phosphorus-bridged Transition Metal Carbonyl Complexes. The Crystal Structures of [Re₂(CO)₇(P^tBu)₃], [Co₄(CO)₁₀(P^tBu)₂], [Ir₄(CO)₆(P^tBu)₆], and [Ni₄(CO)₁₀(PⁱPr)₆], (P^tBu)₃ reacts with [Mn₂(CO)₁₀], [Re₂(CO)₁₀], [Co₂(CO)₈] and [Ir₄(CO)₁₂] to form the multinuclear complexes [M₂(CO)₇(P^tBu)₃] (M = Re ( 1 ), Mn ( 5 )), [Co₄(CO)₁₀(P^tBu)₂] ( 2 ) and [Ir₄(CO)₆(P^tBu)₆] ( 3 ). The reaction of (PⁱPr)₃ with [Ni(CO)₄] leads to the tetranuclear cluster [Ni₄(CO)₁₀(PⁱPr)₆] ( 4 ). The complex structures were obtained by X-ray single crystal structure analysis: ( 1 : space group P1 (Nr. 2), Z = 2, a = 917.8(3) pm, b = 926.4(3) pm, c = 1 705.6(7) pm, α = 79.75(3)°, β = 85.21(3)°, γ = 66.33(2)°; 2 : space group C2/c (Nr. 15), Z = 4, a = 1 347.7(6) pm, b = 1 032.0(3) pm, c = 1 935.6(8) pm, β = 105.67(2)°; 3 : space group P1 (Nr. 2), Z = 4, a = 1 096.7(4)pm, b = 1 889.8(10)pm, c = 2 485.1(12) pm, α = 75.79(3)°, β = 84.29(3)°, γ = 74.96(3)°; 4 : space group P2₁/c (Nr. 14), Z = 4, a = 2 002.8(5) pm, b = 1 137.2(8) pm, c = 1 872.5(5) pm, β = 95.52(2)°).