Die Strukturen der Heptahetero-Nortricyclene P7(Sime3)3 und P4(Sime2)3

The Structures of the Heptahetero-Nortricyclenes P₇(Sime₃)₃ and P₄(Sime₂)₃ Tris(trimethylsilyl)heptaphospha-nortricyclene P₇(Sime₃)₃ 1 and Hexamethyl-trisila-tetraphospha-nortricyclene P₄Si₃me₆ 2 are structural analogons to the hetero-nortricyclenes P and P₄S₃. 1 crystallizes in the space group P2₁ with a = 965.7 pm, b = 1746.5 pm, c = 693.3 pm, β = 99.61° and Z = 2 formula units. In the P₇ system tge P? P bond lengths differ functionally, namely 221.4 pm in the three-membered ring, 219.2 pm at the ring atoms and 217.9 pm at the bridgehead atom. The P? Si and Si? C bond lengths are 228.8 pm and 187.8 pm respectively. 2 crystallizes in the space group R3 with a_R = 1129.3 pm, α_R = 50.01° (hexagonal axes: a = 954.7 pm, c = 2956.9 pm) and Z = 2 formula units. In the P₄Si₃ systems the bond lengths are P? P = 220.2 pm, P? Si = 228.3 pm and 224.7 pm (to the bridgehead atom). The Si? C bond lengths are 187.3 pm. The structures are discussed with related compounds.     

Bildung siliciumorganischer Verbindungen. 92 [1]. Bildung und Struktur des Oktamethyl-hexasila-hexascaphans

Formation of Organosilicon Compounds. 92. Formation and Structure of Octamethylhexasila-hexascaphane By rearrangement and abstraction of CH₄ at the presence of AlBr₃ 2 forms 3 , and 6 forms 7 , which is also obtained reacting 8 and 9 under the same condition. Lithination of 1, 1, 3, 5, 5, 7, 7, 9, 9-Nonamethyl-1, 3, 5, 7, 9-pentasiladecaline yields 12 , which is trapped with me₃SiCl to form 6 . Convertation of 13 to 14 leads to 8 by reaction with ClSi(CH₂—Sime₃)₃. Compound 7 is characterized by NMR and mass spectroscopy as well as X-ray structural analysis. 1, 3, 5, 7, 9, 9, 11, 11-Octamethyl-1, 3, 5, 7, 9, 11-hexasila-hexascaphane 7 crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 3296.7 pm, b = 1536.2 pm, c = 891.9 pm, β 91.71° and Z = 8 formular units. Both crystallographic independent molecules have approximately the symmetry C₂. The differences of corresponding bond lengths, bond angles and torsion angles are unimportant. But there is a distinct dependence of the Si? C bond length relative to the function of the bond in the molecule (Averages: Si? C) (endo) = 188.4 pm, Si? C (exo) = 187.6 (pm).     

Bildung siliciumorganischer Verbindungen. 112. Über den Einfluß der Reaktionsbedingungen auf die Umsetzung von (Cl3Si)2CCl2 mit Silicium. Die Struktur von 2,2,3,3,5,5,6,6-Octachlor-1,4-bis(trichlorsilyl)-2,3,5,6-tetrasilabicyclo[2.1.1]hexan und 1,1,3,4,6,6-Hexakis(trichlorsilyl)hexatetraen

Formation of Organosilicon Compounds. 112. The Influence of Reaction Conditions on the Reaction of (Cl₃Si)₂CCl₂ with Silicon. The Structures of 2,2,3,3,5,5,6,6-Octachloro-1,4-bis(trichlorosilyl)-2,3,5,6-tetrasilabicyclo[2.1.1]-hexane and 1,1,3,4,6,6-Hexakis(trichlorosilyl)hexatetraene While reactions of (Cl₃Si)₂CCl₂ 1 with Si(Cu) in a fluid bed at 320°C exclusively yield products by silylation of the CCl₂ group in 1 does the reaction in a stirred bed preferrably give rize to chlorosilanes containing C? C double and triple bonds. Compounds 5, 6, 7, 8 and 9 in Tab. 1 belong to the first group, whereas 3 and 4 belong to the second one. The reaction of 1 with elemental copper under dehalogenation at carbon produces 3, 4 and 11 . In the reaction of 1 with CaSi₂ no additional Si? C bonds are formed, exclusively chlorosilanes with multiple C? C bonds as 3, 4 and 10 were found besides of SiCl₄. The bicyclo[2.1.1]hexane 6 (Tab. 1) crystallizes monoclinically in the space group C2/c (no. 15) with a = 1557.8, b = 857.4, c = 1727.3 pm, β = 104.34° und Z = 4 molecules per unit cell; the hexatetraene 10 (Tab. 1) crystallizes monoclinically in the space group C2/m (no. 12) with a = 1189.6, b = 1433.8, c = 983.5 pm, β = 98.75° pm, and Z = 2 molecules per unit cell. The skeleton of 6 is a system of high bond stress with 2-C₂ symmetry. The strongly folded (138.8°) four-membered ring (sum of angles = 344.2°) and the presence of both a Si? Si bond length of 238.2 pm and a Si? Si non-bonding distance of 255.1 pm are remarkable aspects of this feature. The mean bond lengths in the bicyclic compound were found to be d(Si? C) = 190.9 pm and d(Si? C) = 185.1 pm for exo- and endocyclic bonds, respectively. The skeleton of 10 is of the symmetry 2/m-C_2h. The six-membered chain is plane. The central C? C single bond length and the mean distance of the cumulated double bonds are 148.6 pm and 130.5 pm, respectively.     

Bildung siliciumorganischer Verbindungen. XXXI. Synthese des Brme2Si?CH2?Sime2?CC?Sime2?CH2-Sime2Br und dessen Abbau mit HBr

The synthesis of C₆H₅me₂Si? CH₂? Sime₂? C?C? Sime₂? CH₂? Sime₂C₆H₅ (a) is described, which forms Brme₂Si? CH₂? Sime₂? C?C? Sime₂? CH₂-Sime₂Br(b) with HBr. The reaction of (b) with HBr (1–4 moles at ?78°C) yields Brme₂Si? CH₂? Sime₂Br, as well as 1,2-dibromo-ethane (main products) and Brme₂Si? CH₂/? Sime₂CH = CHBr, Brme₂Si? CH₂? Sime₂CH₂? CHBr₂.     

Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe. 1. Die KristallStruktur des Diphosphasilirans (t-BuP)2SiPh2

Structural Chemistry of Phosphorus-containing Chains and Rings. 1. Crystal Structure of the Diphosphasilirane (t-BuP)₂SiPh₂ The three-membered P₂Si-heterocycle 1, 2-di-tert-butyl-3, 3-diphenyl-1, 2, 3-diphosphasilirane (t-BuP)₂SiPh₂ crystallizes monoclinic in the space group P2₁ with a = 1041.2 pm, b = 882.3 pm, c = 1158.1 pm, β = 91.33° and Z = 2 formula units. A special structural feature is the regular triangle built up by two P and one Si. Therefore the endocyclic bond angle at Si is as low as 60°. The average bond lengths are P? P = 222.6 pm, P? Si = 222.5 pm, P? C = 190.8 pm, Si? C = 186.6 pm, (C? C )ph = 139.0 pm, ( C? C )_t-Bu = 151.7 pm. The geometry of the substituents phenyl and tert-butyl is quite normal, the last ones are slightly disordered.     

Synthese und Struktur von Lithium-tris(trimethylsilyl)silanid · 1,5 DME

Synthesis and Structure of Lithium Tris(trimethylsilyl)silanide · 1,5 DME Lithium tris(trimethylsilyl)silanide · 1,5 DME 2a synthesized from tetrakis(trimethylsilyl)silane 1 [6] and methyllithium in 1,2-dimethoxyethane , crystallizes in the monoclinic space group P2₁/c with following dimensions of the unit cell determined at a temperature of measurement of ?120 ± 2°C: a = 1 072.9(3); b = 1 408.3(4); c = 1 775.1(5) pm; β = 107.74(2)°; 4 formula units (Z = 2). An X-ray structure determination (R_w = 0.040) shows the compound to be built up from two [lithium tris(trimethylsilyl)silanide] moieties which are connected via a bridging DME molecule. Two remaining sites of each four-coordinate lithium atom are occupied by a chelating DME ligand. The Li? Si distance of 263 pm is considerably longer than the sum of covalent radii; further characteristic mean bond lengths and angles are: Si? Si 234, Li? O 200, O? C 144, O?O (biß) 264 pm; Si? Si? Si 104°, Li? Si? Si 107° to 126°; O? Li? O (inside the chelate ring) 83°. Unfortunately, di(tert-butyl)bis(trimethylsilyl)silane 17 prepared from di(tert-butyl)dichlorsilane 15 , chlorotrimethylsilane and lithium, does not react with alkyllithium compounds to give the analogous silanide.     

Bildung siliciumorganischer Verbindungen. 84 [1]. Synthese und thermische Umlagerung von verschieden substituierten linearen und cyclischen Silanen

Formation of organosilicon compounds. 84. Synthesis and thermal rearrangement of some substituted linear and cyclic silanes In part IR we report on the synthesis of substituted silanes, and in part II on their thermal rearrangement. I: me₃i--Sime₃(me = CH₃) is formed by dropwise addition of THF to a suspension of Li powder in me₃SiCl; yield ～ 80%. The mixture me₃Si--Sime₂Cl, me₃SiCl, Li powder and THF reacts analogously to form me₂Si(Sime₃)₂; yield 80%. By the same type of reaction the following compounds are obtained: compound 1 from Brme₂Si? CH₂? Sime₂Br, 1 from Brme₂Si? CH₂? Sime₂Br, 2 from Brme₂Si? Sime₂? CH₂? Sime₂Br 16 and 3 from Bret₂Si? CH₂? CH₂? Siet₂Br (et = C₂H₅). 2 decomposes during its isolation from THF. 16 is formed from phme₂Si? Sime₂? CH₂? Sime₂ph 17 (ph = C₆H₅) by reaction with HBr, 17 either from phme₂SiLi and Clme₂SiCH₂Cl or from phme₂Si? Sime₂Br and LiCH₂? Sime₂ph. II: me₂Si(Sime₃)₂ rearranges at 440 °C (56 h) with insertion of the CH₂ group (Si? H formation) into the Si? Si bond and the formation of me₃Si? Sime₂? CH₂? Sime₂H, me₂HSi? CH₂? Sime₂? CH₂? SiHme₂, and me₃Si? CH₂? Sime? CH₂? Sime₂H. 1 reacts analogously. Methylated halogenated disilanes like Brme₂Si? Sime₂Br react with separation of: Sime₂ and its insertion into the Si-halogen bond to form trisilanes. Different from both are the phenylated derivatives, though phme₂Si? Sime₂ph still forms phme₂Si? Sime₂? Sime₂ph. 3 reacts with separation of C₂H₄, formation of the Si? H group and insertion of C₂H₄ into the Si? Si bond.     

Die Strukturen der 1,3,5-Trisilacyclohexan-Eisendicarbonyl-cyclopentadienylkomplexe C3H6Si3Cl5Fe(CO)2πcp und C3H6Si3Cl4(Fe(CO)2πcp)2

Structures of the l,3,5-Trisilacyclohexane-Iron Dicarbonyl-cyclopentadienyl Complexes and C₃H₆Si₃Cl₅Fe(CO)₂πcp and C₃H₆Si₃Cl₄(Fe(CO₂)πcp)₂ Trisilapentachlorocyclo-hexyl-dicarbonylcyclopentadienyliron C₃H₆Si₃Cl₅Fe(CO)₂πcp 1 and Trisilatetrachlorocyclohexyl-bis(dicarboncyclopentadienyliron)C₃H₆Si₃Cl₄(Fe(CO)₂πcp)₂ 2 are 1,3,5-Trisilacyclohexane complexes substituted by dicarbonylcyclopentadienyliron at one and two silicon atoms of the six-membered ring, respectively. The crystal and molecular structures were determined from single crystals ( 1 ; space group P2₁/a (No. 14); a = 1100.5 pm; b = 2033.9 pm; c = 843.3pm; β = 98.58°; Z = 4; MoKα-radiation; 3142h k l; R = 0.036. 2 ; space group P1 ; (No. 2); a = 1231.1 pm; b = 1267.3 pm; c = 1045.9 pm; α = 113.23°; β = 83.93°; γ = 115.00°; Z = 2; Mokα-radiation; 4196 h k 1; R = 0.065). In both complexes the six-membered rings of the carbosilane ligands are in skew-boat conformation. The bond lengths Fe? Si are 226.4 pm and 228.1 pm, respectively. The distances Si? C and Si? Cl are 186 pm and 206 pm in 1 and 187 pm and 209 pm in 2 . Their different lengths depend on the position in the ligand system and can be explained with the concept of bond orders.     

Bildung siliciumorganischer Verbindungen. 96. Bildung und Struktur von P-Yliden des 1,3,5-Trisilacyclohexans (Einfluß der Substituenten)

Formation of Organosilicon Compounds. 96. Preparation and Structure of P-Ylides of the 1,3,5-Trisilahexanes (Influence of the Substituents) The influence of the substituents at the silicon atoms on formation and structure of ylides of 1,3,5-trisilacyclohexanesis investigated. The reactions of 1 , 2 , 3 with Me₃Si? PMe₂ lead via cleavage of the Si? P bond and subsequent rearrangement to the ylides 4 , 5 and 6 . The x-ray structure determination reveals, that the atoms of the ylid part of 4 are in a plane with the shortened bond distances d(C? P) = 168.6 pm and d(Si? C) = 180.1 pm, whereas the other endocyclic Si? C distances remain nearly unaffected by the ylid formation. Only the endocyclic bond angles C? Si? C of the Si atoms of the ylid are enlarged (116°). In the molecule 6 d(C? P) = 164.6 pm is much shorter, but d(P? Br) = 236.6 pm is enlarged. This enlargement is coupled with a deviation of 17 pm for the ylidic C atom from the ylid plane. Distances and angles are normal in the methylated trisilnhexane. The ring in 6 has boat conformation, in 4 a flat chair conformation.     

Bildung siliciumorganischer Verbindungen. 94. Die Kristallstruktur des Hexaphenyltrisilacyclohexans Si3C39H36

Formation of Organosilicon Compounds. 94. Crystal Structure of Hexaphenyltrisilacyclohexane Si₃C₃₉H₃₆ 1.1.3.3.5.5-Hexaphenyl-1.3.5-trisilacyclohexane crystallizes monoclinically in the space group P2₁/n (No. 14) with a = 1718.3 pm, b = 1769.2 pm, c = 1091.4 pm, β = 90.72° and Z = 4 molecules per unit cell. The trisilacyclohexane sceleton is present in a flattened twist boat conformation with mean bond angles of 110.0° at the Si atoms and 117.9° at the C atoms, respectively. The mean bond lengths are d(Si? C) = 187.1 pm in the six membered ring and 187.9 pm to the substituents.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXXIII. Die Struktur des Bis(triphenylsilyl)sulfids

Contributions to the Chemistry of Silicon Sulphur Compounds. XXXIII. Structure of Bis (triphenylsilyl)sulphide The condensation of triphenylsilanethiol yielded bis(triphenylsilyl)sulphide ( 1 ). The compound is remarkable resistent to hydrolysis. 1 crystallizes monoclinically [P2₁/n (No. 14): a = 1707.8 pm; b = 1454.6 pm; c = 1225.0 pm; β = 97.27°; Z = 4; 4470 h k l; R = 0.053]. The molecule is bent with a bond angle Si? S? Si = 112.0°. The mean bond distances Si? S and Si? C are 215.2 pm and 187.4 pm, respectively. Some structural details are discussed.     

Bildung siliciumorganischer Verbindungen. 85 [1]. Bildung,Reaktionen und Struktur des 1,1,3,3-Tetramethyl-2,4-bis(trimethylsilyl)-1,3-disilabicyclo[1, 1, 0]butans

me₃Si? CCl₂?Sime₂Cl (me ? CH₃) läßt sich mit n-buLi (bu ? C₄H₉) bei–100°C (Lösungsmittel THF/Äther) in me₃Si? CCl(Li)? Sime₂Cl a überführen. das mit meJ me₃Si? CClme? Sime₂Cl bildet. Wird a in Abwesenheit eines Abfangreagenzes langsam erwärmt, so bildet sich unter Abspaltung von LiCl (Cl aus der SiCl-Gruppe) über eine reaktive Zwischenstufe des Bicyclobutans b . Die Struktur von b ist durch NMR-Untersuchung, Röntgenstrukturanalyse und Abbaureaktionen gesichert. Mit HBr bzw. CH₃OH werden die Si? C-Bindungen der Dreiringe in b gespalten, so daß sich me₃Si? CH₂? C(Sime₂X)₂Sime₃ (X ? Br, OCH₃) bildet. Formation of Organosilicon Compounds. 85. Formation, Reactions, and Structure of 1,1,3,3-Tetramethyl-2,4-bis(trimethylsilyl)-1,3-disilabicyclo[1, 1, 0]butane me₃Si? CCl₂? Sime₂Cl (me ? CH₃) with n-buLi (bu ? C₄H₉) at –100°C (solvent: THF/ether) yields me₃Si? CCl(Li)? Sime₂Cl a , which forms me₃Si? CClme? Sime₂Cl with meI. By warming a slowly in absence of any trapping reagent the bicyclobutane b is obtained via a reactive intermediate under elimination of LiCl (Cl from the SiCl group). The structure of b is established by nmr investigations, X-ray structure determination and chemical derivatisation.     

Das 1,3,5,7-Tetraphospha-2,4,6,8,9-dekamethyl-2,4,6,8,9-pentasilabicyclo(3.3.1)-nonan. Struktur und Reaktionen

1,3,5,7-Tetraphospha-2,4,6,8,9-decamethyl-2,4,6,8,9-pentasila-bicyclo (3.3.1)-nonan. Structure and Reactions The structure of the title compound 1 (white quad-shaped crystals, mp. 193°C) obtained by reaction of Li₂PH with Me₂SiCl₂, is identified by ³¹PNMR and mass spectra as well as X-ray structure analysis. Compound 1 crystallizes in the monoclinic space group C2/c (No. 15) with a = 1563.6(28) pm, b = 1166.7(9) pm, c = 2556.0(27) pm, = 87.07(12)° and Z = 8 formula units in the elementary cell. The molecule has approximately mm (C_2v) symmetry. The boat-boat conformation characterizes 1 as direct precursor of the dodecamethyl-hexasila-tetraphospha-adamantane. The bond lengths and bond angles are normal with d?(P? Si) = 224.5 pm and d?(Si? Me) = 186.0 pm. The H bonded to P are directed exocyclic. 1 reacts with (CO)₄CrNBD (NBD = Norbornadiene) (bidentate ligand) to (SiMe₂)₅P₂(PH)₂Cr(CO)₄ 2 while closing the structure of compound 1 to the adamantane structure via the inserted Cr(CO)₄.     

Bildung und Struktur des iso-Tetraphosphans P[P(SiMe3)Me]3

Formation and Structure of iso-Tetraphosphane P[P(SiMe₃)Me]₃ The reaction of MeP(SiMe₃)₂ with PCl₃ (molar ratio 3:1, ?78°C, n-pentane) yields by cleaving of the P? Si bond P[P(SiMe₃)Me]₃ 1 with Cl₂P? P(SiMe₃)Me and ClP[P(SiMe₃)Me]₂ as intermediates. The reaction rate decreases by the increase of phosphorylation. The last reaction step (formation of 1 ) occurs while warming up to room temperature. 1 forms colorless hexagonal crystals, melting point 65 ± 1°C. Tris(trimethylsilyl-methyl-phosphino)phosphane 1 crystallizes monoclinically in the space group Cc (No. 8) with Z = 8 formula units per unit cell. The molecules possess approximated C₃ symmetry and have (RRR) and (SSS) configurations, respectively. The bond distances d?(P? P) = 220.1 pm, d?(P? C) = 186.5 pm, and d?(P? Si) = 225.2 pm are normal and within the expected range of known distances. According to repulsive interactions between the non bonded electron pairs of the terminal P atoms and the protons of the methyl groups the angles at the central and terminal P atoms are enlarged to ? P P P = 105.1° and ? P P C = 106.9°, respectively.     

Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe. 2. Die Kristall- und Molekülstruktur des Diphosphaborirans (t-BuP)2BNEt2

Structural Chemistry of Phosphorus-containing Chains and Rings. 2. Crystal and Molecular Structure of the Diphosphaborirane (t-BuP)₂BNEt₂ The three-membered P₂B-heterocycles 1,2-di-tert-butyl-3-diethylamino-1,2,3-diphosphaborirane, (t-BuP)₂BNEt₂, crystallizes triclinic in the space group P1 with a = 935.5 pm, b = 985.4 pm, c = 987.4 pm,α = 81.55°, β = 89.40°, γ =69.07°, and Z = 2 formula units. The main structural feature is a short B? N-bond length (138.2 pm) inside a plane P₂BN-group. The endocyclic bond angles are 54.0° on phosphorus and 72.0° on boron. The (average) bond lengths are P? P = 222.5 pm, P? C = 189.5 pm, P? B = 189.3 pm, B? N = 138.2 pm, N? C = 147.2 pm, C? C = 152.6 pm, and C? H = 98 pm. The geometry of the substituents ethyl and tert-butyl is quite normal.     

[WCl4(Me3Si?CC?SiMe3)]2 Synthese,IR-Spektrum und Kristallstruktur

[WCl₄(Me₃Si? C?C? SiMe₃)]₂. Synthesis, I.R. Spectrum, and Crystal Structure The title compound is obtained from tungsten hexachloride and bis-trimethylsilyl acetylene in the presence of C₂Cl₄ in dichloro methane, forming green crystals. The complex is characterized by the mass spectrum, the i.r. spectrum, and by a structural analysis with the aid of X-ray diffraction data. [WCl₄(Me₃Si? C?C? SiMe₃)]₂ crystallizes triclinic in the space group P1 with one dimeric formula unit per unit cell (2 231 observed, independent reflexions, R = 4.6%). The cell dimensions are a = 928, b = 938, c = 1 080 pm; α = 115.3°, β = 91.9°, γ = 100.0°. The complex forms centrosymmetric dimers, the units being linked by chloro bridges of bond lengths W? Cl 244 and 272 pm. The trans-position to the long W? Cl bridge is occupied by the acetylene ligand which is bonded side-on with identical W? C bond lengths of 203 pm. Together with the three terminal chlorine ligands (mean W? Cl distance 231 pm) the tungsten atom achieves coordination number seven.     

Bildung und struktur der Cyclophosphane P4(CMe3)2[P(CMe3)2]2 und P4(SiMe3)2[P(CMe3)2]2

Formation and Structure of the Cyclophosphanes P₄(CMe₃)₂[P(CMe₃)₂]₂ and P₄(SiMe₃)₂[P(CMe₃)₂]₂ n-Triphosphanes showing a SiMe₃ and a Cl substituent at the atoms P¹ and P², like (Me₃C)₂P? P(SiMe₃)? P(CMe₃)Cl 3 or (Me₃C)₂P? P(Cl)? P(SiMe₃)₂ 4 are stable only at temperatures below ?30°C. Above this temperature these compounds lose Me₃SiCl, thus forming cyclotetraphosphanes, P₄(CMe₃)₂[P(CMe₃)₂]₂ 1 out of 3 , P₄(SiMe₃)₂[P(SiMe₃)₂]₂ 2a (cis) and 2b (trans) out of 4 . The formation of 1 proceeds via (Me₃C)₂P? P?PCMe₃ 5 as intermediate compound, which after addition to cyclopentadiene to give the Diels-Alder-adduct 6 (exo and endo isomers) was isolated. 6 generates 5 , which then forms the dimer compound 1 . Likewise (Me₃C)₂P? P?P-SiMe₃ 8 (as proven by the adduct 7 ) is formed out of 4 , leading to 2a (cis) and 2b (trans). Compound 1 is also formed out of the iso-tetraphosphane P[P(CMe₃)₂]₂[P(CMe₃)Cl] 9 , which loses P(CMe₃)₂Cl when warmed to a temperature of 20°C. 1 crystallizes monoclinically in the space group P2₁/a (no. 14); a = 1762.0(15) pm; b = 1687.2(18) pm; c = 1170.5(9) pm; β = 109.18(5)° and Z = 4 formula units in the elementary cell. The molecule possesses E conformation. The central four-membered ring is puckered (approx. symmetry 4 2m; dihedral angle 47.4°), thus bringing the substituents into a quasi equatorial position and the nonbonding electron pairs into a quasi axial position. The bond lengths in the four-membered ring of 1 (d (P? P) = 222.9 pm) are only slightly longer than the exocyclic bonds (221.8 pm). The endocyclic bond angles \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \beta $\end{document}(P/P/P) are 85.0°, the torsion angles are ±33° and d (P? C) = 189.7 pm.     

Molekül- und Kristallstruktur des 1,4-Bis[tris(tetrahydrofuran)lithium]-octaphenyltetrasilans

Molecular and Crystal Structure of 1,4-Bis[tris(tetrahydrofuran)lithium]-octaphenyltetrasilane 1,4-Dilithium-octaphenyltetrasilane prepared from octaphenyl-cyclo-tetrasilane and lithium in tetrahydrofuran (THF) [4], can be isolated from tetrahydrofuran/n-pentane as an adduct with six molecules of tetrahydrofuran per formula unit. The orange-red compound crystallizes in the triclinic space group P1 {a = 1159.6(3); b = 1268.4(2); c = 1367.8(3) pm; α = 92,23(2)° β = 113.79(2)° γ = 111.62(2)° at ?5 ± 3°C; Z = 1}. An x-ray structure determination (R_w = 0.046) shows the existence of a centrosymmetric molecule with an extended planar Li? Si₄? Li unit; either lithium atom is bound to silicon and to the oxygen atoms of three molecules of tetrahydrofuran. Characteristic bond lengths and angles are: Li? Si 271; Si? Si 241 and 243; Si? C 190 to 192 pm; Li? Si? Si 126°; Si? Si? Si 127°. ²⁹Si and ⁷Li n.m.r. measurements at low temperatures indicate the presence of three different adducts.     

Phosphaniminato-Komplexe des Schwefels. Synthese und Kristallstrukturen von [O3SS(NPPh3)2] · CH3CN, [SO(NPPh3)2] und [SCl(NPMe3)2]Cl

Phosphorane Iminato Complexes of Sulfur. Syntheses and Crystal Structures of [O₃SS(NPPh₃)₂] · CH₃CN, [SO(NPPh₃)₂], and [SCl(NPMe₃)₂]Cl The title compounds have been prepared by the reaction of Me₃SiNPPh₃ with SO₂ and SOCl₂, respectively, and by the reaction of Me₃SiNPMe₃ with S₂Cl₂. They form colourless, moisture sensitive crystals, which were characterized by IR spectroscopy and by crystal structure determinations. [O₃SS((NPPh₃)₂)] · CH₃CN : Space group Pca2₁, Z = 4, structure solution with 4016 observed unique reflections, R = 0.050. Lattice dimensions at ?60°C: a = 1865.1, b = 1168.4, c = 1569.0 pm. The compound has a zwitterionic structure with a S? S bond length of 218.2 pm and bond lengths S? N of 161.2 and P? N of 160.1 pm. [SO(NPPh₃)₂] : Space group P2₁/c, Z = 4, structure solution with 2854 observed unique reflections, R = 0.113. Lattice dimensions at ?50°C: a = 1173.1, b = 1585.6, c = 1619.2 pm, b? = 98.13°. The compound forms monomeric molecules, in which the positions of S and N atoms are disordered in two positions. The bond lengths are S? N 166 pm and P? N 163 pm in average. [SCl(NPMe₃)₂]Cl : Space group P1 , Z = 2, structure solution with 2416 observed unique reflections, R = 0.038. Lattice dimensions at 20°C: a = 613.2, b = 1030.3, c = 1111.4 pm, α = 88.48°, b? = 88.01°, γ = 83.10°. The compound forms ions [SCl(NPMe₃)₂]⁺ and Cl^?. In the cation the sulfur atom is ?-tetrahedrally coordinated with a long S? Cl distance of 246.9 pm and bond lengths S? N of 155.3 pm and P? N of 164.3 pm in average.     

Trimethylsilyl-imido-Vanadiumtrichlorid,Me3Si?NVCl3 Synthese,Eigenschaften und Kristallstruktur

Trimethylsilyl-Imido-Vanadium Trichloride, Me₃Si? N?VCl₃. Synthesis, Properties, and Crystal Structure Me₃Si? N?VCl₃ is prepared from VCl₄ and trimethylsilyl azide, forming volatile orange-red crystals extremely sensitive to moisture. Reactions with 2,2′-dipyridyl and PPh₄Cl, resp., lead to the complexes [Me₃SiNVCl₃(dipy)] with six-coordinated vanadium and PPh₄[Me₃SiNVCl₄] with five-coordinated vanadium. The i.r. spectra are reported. Me₃SiNVCl₃ was characterized by X-ray crystal structure determination. The compound crystallizes orthorhombic in the space group Pnma with four formula units per unit cell and with the lattice dimensions a = 1628 pm, b = 1041 pm, c = 635 pm at 20°C (440 observed, independent reflexions, R = 0.043). Me₃Si? N?VCl₃ forms monomeric molecules with an almost linear axis SiNV (177.5°); the bond lengths are: Si? N 179 pm and V?N 159 pm, indicating a VN triple bond. The molecular geometry (C_s) deviates slightly from the trigonal prisma (C_3v).