H.-D. Hausen

Die kristall- und molekülstruktur des triphenylborans

Abstract The crystal structure of triphenylborane has been determined. The compound crystallizes in the orthorhombic space group Pbcn with Z = 4 and a = 17.265, b = 10.355, c = 8.03 A. In contrast to triphenylgallium and triphenylindium which belong to the same space group and have similar cell dimensions, no intermolecular interactions are found for the title-compound. The phenyl groups are tilted by about 30° with respect to the boron valence plane.

Präparative, spektroskopische und röntgenographische studien an bis(dimethylmetall)di(μ-1-propinylen) des aluminiums, galliums und indiums

Abstract Dimethylpropynylmetal compounds of Al, Ga and In are formed in 40–60% yield by the reaction of NaCCCH3 with (CH3)2MIIIHal (MIII  Al, Ga, In; Hal  Cl, Br). The IR, Raman, 1H and 13C NMR spectra of these, in solution dimeric, compounds are discussed. The indium derivative crystallizes in the orthorhombic space group Pnma with 4 formula units per unit cell. The lattice parameters are a  926.9; b  578.7 and c  1216.6 pm.

Die kristall- und molekúlstruktur der dimeren dimethylaluminium- und dimethylgallium-N,N′-dimethylacetamidine [(CH3)2M(NCH3)2CCH3]2 (M = Al, Ga)

Abstract Dimethylaluminium- and dimethylgallium- N,N ′-dimethylacetamidine (I and II) are doubly associated forming a puckered eight-membered ring. They crystallize isostructurally in the monoclinic space group P 2 1 / c with two dimers per unit cell. The lattice constants of I are a 8.187, b 7.266, c 14.778 A, β 103.58° and those of II a 8.163, b 7.277, c 14.835 A, β 103.46°. The MN and the NC bond lengths within the rings are nearly equal, their mean values are for I: AlN 1.925 A, CN 1.330 A and for II: GaN 1.979 A, CN 1.335 A. This is also true for the exocyclic bond lengths with average values AlC 1.975 A, NC 1.474 A, CC 1.509 A (for I) and GaC 1.998 A, NC 1.484 A and CC 1.507 A (for II). The metal atoms are tetrahedrally coordinated, and the distortion is only slight. The final R -values are 0.034 and 0.056, respectively.

Reaktion von (CH3)3SiNCNSi(CH3)3 mit aluminium-, Gallium- und Indium-Trimethyl

GaMe3 and InMe3 form distillable, liquid 11 adducts with bis(trimethylsilyl)-carbodiimide; Me3Al on the other hand forms a solid, monomeric insertion product Me2Al(NSiMe3)2CMe. The compound has C2v symmetry and has a planar AlN2C skeleton from NMR, IR and Raman data. Crystals of this acetamidine are in the triclinic space group P1− with Z = 2, the structure was refined to an R-value of 0.041.

Bis(dimethylmetall)-N,N′,N″,N‴-tetramethyloxamidine des aluminiums, galliums und indiums; synthese, spektren und röntgenstrukturen

N , N′ , N″ , N‴ -Tetramethyloxamidine, (HNMe) 2 C 2 (NMe) 2 , reacts with the trimethyl derivatives of Al, Ga and In, respectively, in a molar ratio. Monomeric bis(dimethylmetal)oxamidines, [Me 2 M] 2 C 2 (NMe) 4 with M = Al, Ga, In, and methane are formed. According to the vibrational spectra (IR and Raman) and the X-ray structure determinations of all three compounds these molecules consist of two fused five-membered rings, with an essentially planar structure. The results in the homologous series [Me 2 M] 2 C 2 O 4− x (NMe) x ( x = 0, 2 and 4 and M = Ga) are compared.

Different orbital occupation by an added single electron in 1,10-phenanthroline and its 3,4,7,8-tetramethyl derivative. Evidence from electron paramagnetic resonance spectroscopy of the anion radicals and of their dimesitylplatinum(II) complexes. X-Ray molecular structure of dimesityl(1,10-phenanthroline)platinum(II)

In contrast to the anion radicals of 1,10-phenanthroline (phen) or its 4,7-dimethyl derivative (dmphen) with their 2B1 ground state, the 3,4,7,8-tetramethyl derivative tmphen˙– has a 2A2 ground state as evident from EPR/ENDOR measurements. The small π spin population at the potentially metal-coordinating nitrogen centres in the 2A2 species as opposed to the 2B1 state causes distinct spectroscopic effects in corresponding diorganoplatinum(II) complexes. The neutral compound (phen)PtMes2, Mes = mesityl, has been structurally characterized as a square planar PtII complex with tightly protected axial sites: monoclinic, space group P21/c, Z= 4, a= 9.378(1), b= 15.791(2), c= 16.581(1)A, β= 103.18(1)°. All complexes (N ⁁ N)PtMes2, N ⁁ N = bpy (2,2′-bipyridine), phen, tmphen, dppz (dipyrido[3, 2-a : 2′,3′-c]phenazine) and pdo (1,10-phenanthroline-5,6-dione) are oxidized to EPR-silent platinum(III) species and reduced to anion radical complexes. The latter clearly contain PtII and heterocyclic anion radical ligands; however, they exhibit a trichotomous EPR behaviour. Whereas the radical complex [(phen)PtMes2]˙– shows a rather low giso-value of 1.983 and distinct g anistropy in frozen solution like the analogous complex of bpy˙–, the formally related [(tmphen)PtMes2]˙– has an isotropic g-factor (2.0030) much closer to the free-electron value and a distinctly smaller g anisotropy. The phenanthroline-derived radical complexes [(pdo)PtMes2]˙– and [(dppz)PtMcs2]˙– exhibit virtually no contribution from the coordinated heavy metal to the singly occupied MO (b1) which is mainly centred at the heteroatoms outside the phenanthroline π system.

Dialkylindium-thioacetate R2InOSCCH3 (R = CH3,C2H5), darstellung, eigenschaften und struktur

Abstract Dimethylindium thioacetate has been prepared and the vibrational spectra (IR and Raman) discussed. The X-ray structural determination shows that diethylindium thioacetate belongs to the orthorhombic space group Pnma . The unit cell with lattice constants a = 8.588, b = 13.834, c = 8.345 A contains four molecules. The indium—oxygen distance within the four-membered ring is nearly the same as the distance between the oxygen and the indium atom of the adjacent ring. Indium has therefore the coordination number 5.

Zur strukturellen flexibilität der “antiaromatischen” 1,4- dihydropyrazine. Kristall- und molekülstrukturen metallorganischer derivate

Abstract Molecular and crystal structures of the cyclic conjugated 8-π-electron systems 1,4-bis(trimethylgermyl)- and 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (I and II) and of 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (III) have been determined by X-ray crystallography at low temperatures. Whereas the first two species exhibit virtually planar six-membered ring conformations and very little pyramidalization at the nitrogen centers, the sterically more crowded tetramethyl derivative III has a pronounced boat conformation with a dihedral angle of about 140° between the ring halves. These structural results are in excellent agreement with theoretical calculations as well as spectroscopic data and illustrate the exceptional structural flexibility of the “antiaromatic” 1,4-dihydropyrazine system.

Trimethymetall-urotropinaddukte des aluminiums, galliums, indiums und thalliums

Abstract Reactions of urotropine (C6H12N4) with trimethylmetal derivatives of Al, Ga, In und Tl in various ( 1 1  1 4 ) molar ratios lead to stable and monomeric 1 1 , 1 2 or 1 3 adducts in good yields, but no 1 4 addition product could be isolated. The vibrational spectra (IR and Raman) of all compounds are recorded and partly assigned. Some characteristic frequencies of the C6N4-skeletons clearly show the symmetry changes in the series of the 1 1 → 1 2 → 1 3 adducts (C3ν → C2ν → C3ν). The X-ray structure determinations of C6H12N4·.GaMe3 (MeCH3) and C6H12N4·.2GaMe3, are in good agreement with the vibrational spectra. Both compounds crystallize in monoclinic space groups (P21 and C2/c). The GaN distances are around 214 pm, and the values for the C6N4-skeletons are not significantly different from those for free urotropine.

Die molekül- und kristallstruktur von bis-(dimethylgallium)-oxalat[(CH3)2Ga]2C2O4

Abstract Bis(dimethylgallium) oxalate crystallizes in the triclinic space group P 1 − . The unit cell has lattice constants a = 6.503 A, b = 8.014 A, c = 5.892 A, α = 77.6°, β = 114.5° and γ = 102.1° and contains one molecule. Gallium is surrounded by a distorted tetrahedron of two carbon atoms and two cis -standing oxygen atoms of the oxalate group. The Ga 2 C 2 O 4 -group forms an almost planar system composed of two fused five-membered rings. Interatomic distances and bond angles indicate that with respect to the bonding between the dimethylgallium- and oxalato group considerable ionic contributions have to be considered.