12] EHMO calculations were carried out using standard programs and parameters a)

When the cyclic bis(amino)stannylene Me(2)Si(NtBu)(2)Sn is allowed to react with metal halides MX(2) (M = Cr, Fe, Co, Zn; X = Cl, Br [Zn]) adducts of the general formula [Me(2)Si(NtBu)(2)Sn.MX(2)](n) are obtained. The compounds are generally dimeric (n = 2) except the ZnBr(2) adduct, which is monomeric in benzene. The crystal structures of [Me(2)Si(NtBu)(2)Sn.CoCl(2)](2) (triclinic, space group &Pmacr;1; a = 8.620(9) Å, b = 9.160(9) Å, c = 12.280(9) Å, alpha = 101.2(1) degrees, beta = 97.6(1) degrees, gamma = 105.9(1) degrees, Z = 1) and of [Me(2)Si(NtBu)(2)Sn.ZnCl(2)](2) (monoclinic, space group P2(1)/c; a = 8.156(9) Å, b = 16.835(12) Å, c = 13.206(9) Å, beta = 94.27(6) degrees, Z = 2) were determined by X-ray diffraction techniques. The two compounds form similar polycyclic, centrosymmetrical assemblies of metal atoms bridged by chlorine or nitrogen atoms. While in the case of the cobalt compound Co is pentacoordinated by three chlorine and two nitrogen atoms, in the zinc derivative Zn is almost tetrahedrally coordinated by three chlorine atoms and one nitrogen atom. The iron derivative [Me(2)Si(NtBu)(2)Sn.FeCl(2)](2) seems to be isostructural with the cobalt compound as can be deduced from the crystal data (triclinic, a = 8.622(7) Å, b = 9.158(8) Å, c = 12.353(8) Å, alpha = 101.8(1) degrees, beta = 96.9(1) degrees, gamma = 105.9(1) degrees, Z = 1). If NiBr(2), PdCl(2), or PtCl(2) is combined with the stannylene, the reaction product is totally different: 4 equiv of the stannylene are coordinating per metal halide, forming the molecular compound [Me(2)Si(NtBu)(2)Sn](4)MX(2), which crystallizes with half a mole of benzene per molecular formula. The crystal structures of [Me(2)Si(NtBu)(2)Sn](4).NiBr(2).(1)/(2)C(6)H(6) (tetragonal, space group I4(1)/a, a = b = 43.86(4) Å, c = 14.32(2) Å, Z = 16) and [Me(2)Si(NtBu)(2)Sn](4).PdCl(2).(1)/(2)C(6)H(6) (tetragonal, space group I4(1)/a, a = b = 43.99(4) Å, c = 14.318(14) Å, Z = 16) reveal the two compounds to be isostructural. The molecules have an inner Sn(4)M pentametallic core (mean distances: Sn-Ni 2.463 Å, Sn-Pd 2.544 Å) with the transition metal in the center of a slightly distorted square formed by the four tin atoms, the distortion from planarity resulting in a weak paramagnetism of 0.2 &mgr;(B) for the nickel compound. The halogen atoms form bridges between two of the tin atoms and have no bonding interaction with the transition metal. The nickel compound has also been prepared by direct interaction of Br(2) or NR(4)Br(3) with [Me(2)Si(NtBu)(2)Sn](4)Ni as a minor product, the main products being Me(2)Si(NtBu)(2)Sn(NtBu)(2)SiMe(2,) Me(2)Si(NtBu)(2)SnBr(2), NiBr(2) and SnBr(2). Other metal clusters have been obtained by the reaction of Me(2)Si(NtBu)(2)Sn with tetrakis(triphenyphosphine)palladium or by the reaction of Me(2)Si(NtBu)(2)Ge with RhCl(PPh(3))(3). In the first case Ph(3)PPd[Sn(NtBu)(2)SiMe(2)](3)PdPPh(3) (rhombohedral, space group R3c, a = b = 21.397(12) Å, c = 57.01(5) Å, alpha = beta = 90 degrees, gamma = 120 degrees, Z = 12) is formed and is character...

Within the development of a reliable numerical tool for the simulation of a whole rocket combustion chamber, real-gas thermodynamics have been implemented into two CFD codes, the in-house code INCA of the Institute of Aerodynamics and Fluid Mechanics at Technische Universität München and OpenFOAM, used by the Institute for Thermodynamics at Universität der Bundeswehr München. The present work, where Large Eddy Simulations (LES) are conducted for the transcritical injection of nitrogen, is part of the validation process. The comparison against experimental test data underlines that the results of both codes are in excellent agreement with each other as well as with the experiments. As a future task, further validation will be done by simulating the multicomponent mixing and combustion processes of coaxial injectors typically applied in rocket combustions engines.

A comprehensive numerical framework has been established to simulate reacting §ows under conditions typically encountered in rocket combustion chambers. The model implemented into the commercial CFD Code ANSYS CFX includes appropriate real gas relations based on the volume-corrected PengRobinson (PR) equation of state (EOS) for the §ow ¦eld and a real gas extension of the laminar §amelet combustion model. The results indicate that the real gas relations have a considerably larger impact on the §ow ¦eld than on the detailed §ame structure. Generally, a realistic §ame shape could be achieved for the real gas approach compared to experimental data from the Mascotte test rig V03 operated at ONERA when the di¨erential di¨usion processes were only considered within the §ame zone.

(tert‐Butylimino)stannylen (1) reagiert mit Chlorwasserstoff zu [tBuN(H)–SnCl]2 (2a), tBuNH2 · SnCl2 (3) und tBuNH3⊕ SnCl3⊖ (4). Da die Trennung der kristallinen Produkte Schwierigkeiten macht, ist man auf Alternativsynthesen von 2a, 3 und 4 angewiesen. Me2Si[N(tBu)H][N(tBu)]SnX (6a: X = Cl, 6b: X = Br, 6c: X = I) stellt eine Ausgangsstufe dar, die mit tert‐Butylamin zu 2a (X = Cl) und 2b (X = Br) quantitativ umgesetzt werden kann. 3 und 4 entstehen aus 2a u.a. durch HCl‐Addition. 6a, b und c zeigen unterschiedliche 1H‐NMR‐Spektren in Abhängigkeit von der Temperatur, was auf eine intramolekulare Ligandenumordnung hinweist. Die Röntgenstrukturanalysen von 6a (orthorhombisch, Raumgruppe P112121), 3 (monoklin, P21/c, und triklin, P1) und 4 (triklin, P1) weisen 6a als Molekül mit einer intramolekularen Donor‐Akzeptor‐Bindung [Sn–N = 2.347(6) Å], 3 in beiden Modifikationen als Addukt von SnCl2 an tBuNH2 [Sn–N = 2.334(4) Å (monoklin) bzw. 2.338(4) Å (triklin)] und 4 als Ionenpaar tBuNH3⊕ SnCl3− mit H–Cl‐Brücken im Kristall aus [Sn–Cl = 2.542 (Mittelwert), C–N = 1.515(6) Å].

Nur drei der vier Diethylethermoleküle werden von dem aus tert‐Butoxyaluminiumdihydrid und Diphenylsilandiol in Et2O erhaltenen Alumopolysiloxan 1 im Kristall über die OH‐Gruppen koordiniert. Die vierte Koordinationsstelle wird von zwei gegenüberliegenden OSi(Ph2)OSi‐(Ph2)O‐Brücken sterisch stark abgeschirmt. Mit Et3N statt Et2O wird der Polycyclus zweifach deprotoniert, und es können nur noch zwei Donormoleküle vom zentralen Achtring koordiniert werden.

When diphenyldihydroxysilane, Ph 2 Si(OH) 2 , is allowed to react with the aluminiumalkoxydihydride (tBu-O)AlH 2 , the polycyclic compound [(Ph 2 Si) 2 O,] 4 Al 4 (OH) 4 ,1, is formed. The compound is made up of five eight membered cycles, the central one originating from formal donoracceptor bonds between OH groups and Al atoms. The structure of 1 can be modified by reacting it with Lewis bases like Et,N, Et 2 O or C 5 H 5 N; in each case the basic structure of the polycycle is conserved, however serious changes are observed in the central A1 4 O 4 ring depending upon the basicity (the hydrogen withdrawing properties) of the oxygen or nitrogen atom. It is intriguing that the psendu host-guest behaviour of 1 is not the same for different bases and the 'shell' or 'basket' formed by the multiple phenyl groups and the shape of the Al-O-Si-skeleton is functioning as a selective trap such that the four OH groups accomodate two, three and four molecules of Et,N (2), Et 2 O (3) and C 5 H 3 N (4), respectively. The spatial consideration of the central part of the molecular unit for the incoming base i.e. an opening or closing effect is subjected to the steric requirements of the base employed. The replacement of hydrogen atoms in 1 by lithium atoms results in further cyclisation of the molecule to yield a higher polycyclic compound, [(Ph 2 Si) 2 O,] 4 O 4 Al 4 Li 4 , which can be isolated as a tetrakis(diethylether) adduct (5) or as a tris(diethylether) bis(ammonia) adduct (6). Nevertheless the connection of the atoms in 1 is retained in compounds 5 and 6. If the organic bases attacking 1 are replaced by the smaller and more acidic water molecule the new compound 7, [(Ph 2 Si) 2 O,] 6 AI 6 (OH),Al(OH) 6 *3OEt 2 , is formed, the structure of which is completely different from 1,2,3 or 4. In this case the starting molecule has been rearranged by the influence of water. 213 Downloaded by [University of Tennessee, Knoxville] at 22:47 26 December 2014 214 M. VEITH et al.

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