Brigitte Huber

Aromaten-Komplexe der p-Block-Elemente: eine tetramere η6-Koordinationsverbindung des Hexamethylbenzols mit Sn(AlCl4)Cl und Kristall-Chlorbenzol

Abstract The compound [η 5 -(C 6 Me 6 )SnCl(AlCl 4 )] 4 has been prepared from Sn(AlCl 4 ) 2 and hexamethylbenzene in chlorobenzene as solvent. Its crystal structure has been determined from single crystal X-ray diffraction. The structure is composed of dimeric units [η 6 -(C 6 Me 6 )SnCl(AlCl 4 )] 2 containing crystallographically nonequivalent monomers. These dimers are cross-linked to form centrosymmetrical tetramers. The C 6 Me 6 aromatic rings are η 6 -bonded to the tin atoms, while the crystalchlorobenzene molecules have no metal contacts. Pb(AlBr 4 ) 2 crystallizes from benzene as a polycoordinate network, in which the Pb 11 centers are eight-coordinate to the bromine atoms of four chelating AlBr 4 units. The solvating benzene has no metal contact.

Monomeric phosphinoboranes: the role of the B- and P-substituents for PB multiple bonding

The influence of the boron substituents on the structures of the first fully characterized monomeric diphosphinoboranes [(2,4,6-Me3C6H2)2P]B–X (X = OEt, Br) has been established; especially for X = Br, P–B multiple bonding may be clearly inferred from the molecular structure.

Synthesis and crystal structure of a mixed bis(arene)gallium(I) complex: Dimeric (η6-1,2,4,5-tetramethylbenzene) (η6-toluene)gallium(I) tetrachlorogallate(III)

Abstract The title compound (η6-1,2,4,5-tetramethylbenzene)(η6-toluene)gallium(I) tetrachlorogallate(III) (1) crystallizes from dilute solutions of equimolar quantities of gallium(I) tetrachlorogallate(III) and 1,2,4,5-tetramethylbenzene (durene) in toluene on slow cooling to 0°C. More concentrated solutions yield the 1 : 1 complex (1,2,4,5-C6H2Me4)Ga+Ga Cl4− (2). The crystals of compound 1 contain centrosymmetrical dimers, {[(η6-C6H2Me4)(η6-C6H5Me)Ga]GaCl4}2, in which each gallium(I) centre is hexahapto-bonded to one durene and one toluene molecule. The two aromatic hydrocarbons of these bent-sandwich moieties form an interplane angle of 58°. With a metal-to-ring distance of 2.642 A, the durene ring is much closer to the Ga+ atom than the toluene ring (3.039 A). The Ga+ atoms are bridged via two slightly distorted GaCl4− tetrahedra through contacts with three of the four chlorine atoms. The structure resembles that of the [(C6H6)2Ga]GaX4 complexes with X = Cl, Br.

Monomere Phosphinoborane: Synthese eines Tetraalkylphosphinoborans und seine Umwandlung unter Retro- und Re-hydroborierung zu einem dimeren Phosphinoboran sowie Synthese eines Triphosphinoborans

Abstract The first monomeric tetralakylphosphinoborane t Bu 2 BP t Bu 2 was synthesized from t Bu 2 BBr and LiP t Bu 2 . It decomposes above −20°C via double retro-hydroboration and elimination of isobutene, undergoes subsequent re-hydroboration and dimerisation to give stable bis(phosphinoborane)[ i Bu(H)BP t Bu 2 ] 2 , whose molecular structure was determined by X-ray diffraction. It contains a planar, almost square (BP) 2 four-membered ring. The BP distances are 2.004(4)/2.022(4) A. The first monomeric triphosphinoborane, Me 2 PB(PMes 2 ) 2 , was synthesized similarly. All compounds have been characterized by NMR spectroscopy.

1,2-Diphosphonio-diphosphirane / 1,2-Diphosphonio-diphosphiranes

The addition of AlCl3, to a dichloromethane solution of a triphosphenium tetrachloroaluminate R3P-P-PR3 AICI4 leads to chloromethylation of the latter, and in a subsequent reaction to the formation of 1,2-diphosphonio-diphosphirane tetrachloroalum inates. It is essential for this second step, that at least one R3P group of the two triphosphenium ions entering the reaction is aminosubstituted. The structure o f the diphosphonio-diphosphirane ions is established by NMR spectroscopy and in one case by X-ray investigation

Synthese und Kristallstruktur des Bis(benzol)gallium(I)-tetrabromogallat(III)-Dimeren / Synthesis and Crystal Structure of the Bis(benzene)gallium (I) Tetrabromogallate(III) Dimer

Anhydrous Ga[GaBr4] is readily dissolved in benzene. The resulting solutions show discrete 71Ga NMR signals for Ga(I) und Ga(III) centers. Narrow line-widths of the former indicate a small electric field gradient of the Ga(I) nucleus due to almost spherical shielding by the 4 s2 lone pair of electrons. Crystals obtained from the benzene solution on cooling have the stoichiometry [(C6H6)2Ga · GaBr4]2 ·3 C6H6, and are isomorphous with the analogous chloride compound: a = 9.390(2). b = 10.847(1), c = 13.118(2) Å; α = 85.54(1). β = 102.91(1). γ = 105.62(1)°; triclinic, space group Ρ1̄, Z = 1. The centrosymmetric dimers are composed of bis(benzene)gallium(I) and tetrabromogallate(III) units bridged by six bromine atoms. Only two bromine atoms are not engaged in coordinative bonding. The two benzene rings are both η6-bonded to the gallium(I) center, but not equidistant. They are enclined by 57.5°. The remaining benzene molecules are crystal benzene with no specific cation or anion contacts.

Strukturbestimmung von Ga[GaCl4] und α-Ga[GaBr4] nach Kristallisation aus Halogenbenzolen / Structure Determination of Ga[GaCl4] and α-Ga[GaBr4] Crystallized from Halobenzene Solvents

Single crystals of Ga[GaCl4] and α-Ga[GaBr4] have been obtained by crystallization from chlorobenzene and bromobenzene, respectively. The crystal structures of the two compounds, determined previously only on the basis of photographic data, were refined to a more satisfactory level of accuracy. The results confirm the presence of tetrahedral GaX4- anions as thecounterions to dodecahedrally coordinated Ga+ cations. The gallium-halogen distances in these dodecahedral arrays fall into four classes, thus resulting in a significant asymmetry of the Ga(I) center. This deviation from ideal S4 symmetry is also apparent in the 69Ga NMR spectra of the crystalline powder samples. Approximate calculation of the data leads to asymmetry parameters (η) of 0.44 and 0.27 for the chloride and bromide, respectively. Crystal data Ga[GaCl4]: Pnna (#52), a = 7.200(1), b = 9.625(1), c = 9.498(1) Å; Z = 4. For α-Ga[GaBr4]: Pnna, a = 7.528(1), b = 9.972(1), c = 10.010(1) Å, Z = 4.

Komplexe von Silber(l)-Salzen mit Naphthalino(cyclo)phanen, Strukturbestimmung von (rac-[2](1,5)Naphthalino[2]- paracyclophan)-silber(I)-perchlorat / Complexes of Silver(I) Salts with Naphthalino(cyclo)phanes, Structure Determination of (rac-[2](1,5)Naphthalino[2]- paracyclophane)silver(I) Perchlorate

Abstract The 1:1 complexes of Ag[GaCl4 ] with anti-[2.2](1 ,4)naphthalinophane and of Ag[ClO4 ] with [2](1.4)naphthalino[2]paracyclophane and rac-[2](1,5)naphthalino[2]paracyclophane have been prepared and characterized by elemental analyses and IR spectra. The crystal structure of the last compound, ([2](1,5)naphthalino[2]paracyclophane)silver(I) Perchlorate, has been determined by X-ray methods. It crystallizes in the centrosymmetrical space group P21/n with cell dimensions a = 12.495(2), b = 8.546(1), c =16.196(2) Å, β = 101.27(1)°. Both enantiomers of the ligands are present in the unit cell and related by centrosymmetry. Each silver atom is connected with the naphthalin systems of two ligands and with two Perchlorate anions, one of which is chelating, while the other is only monodentate. The cation/anion chains are linked through the organic ligands in such a way that a sheet structure is formed. The benzene rings of the cyclophanes are not involved in the metal coordination, the naphthaline rings are μ3 -bonded to the silver atoms, which are not ring-centered.

(η 2 -Me 4 C 5 H)Me 2 Si(η 5 -Me 4 C 5 )Ge + GeCl 3 − :: Alkene coordination at divalent germanium

Abstract The compound (η2-Me4C5H)Me2Si(η5-Me4C5)Ge+GeCl3− is the first example of alkene coordination at a main group element substantiated by X-ray crystallography. The complex was prepared from monometalated dimethylsilanediylbis(2,3,4,5-tetramethylcyclopenta-2,4-diene) and germanium dichloride-dioxane. The intramolecular interaction between the diene and the central germanium atom suggests that main group elements can coordinate with ordinary unsaturated hydrocarbons.

(η2-Me4C5H)Me2Si(η5-Me4C5)Ge+ GeCl3−:

Abstract The compound (η2-Me4C5H)Me2Si(η5-Me4C5)Ge+GeCl3− is the first example of alkene coordination at a main group element substantiated by X-ray crystallography. The complex was prepared from monometalated dimethylsilanediylbis(2,3,4,5-tetramethylcyclopenta-2,4-diene) and germanium dichloride-dioxane. The intramolecular interaction between the diene and the central germanium atom suggests that main group elements can coordinate with ordinary unsaturated hydrocarbons.