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.     

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.     

Bildung siliciumorganischer Verbindungen. 97. Über den Einfluß der Si-Substituenten (Me,Cl) auf Bildung und Reaktion von Yliden

Formation of Organosilicon Compounds. 97. About the Influence of the Si-Substituents (Me, Cl) upon the Formation and the Reactions of Ylides 1,3-disilapropanes with different grade of chlorination or methylation at the silicon atoms and containing a CCl₂ group cleave the Si? P bond of Me₃SiPMe₂. By subsequent rearrangement ylides with ? PMe₂Cl group are formed. The reactivity of the CCl₂ group depends on the grade of Si-chlorination resp. Si-methylation. Si-methylation decreases the reactivity of the CCl₂ group. The reaction of 1,3-disilapropanes and Me₃SiPMe₂ (molar ratio 1:1) runs in a sequence shown in “Inhaltsübersicht”. Ylid C is able either to react with the initial compound A forming B, or in competition decomposes forming D. Reacting Si-perchlorinated carbosilanes, the decomposition forming D is not to be observed. In Si-methylated ylides like (Me₃Si)₂C?PMe₂? PMe₂ and (Me₃Si)₂C?PMe₂? P(Me)SiMe₃ the ylid carbon atom is able to abstract a proton of the P? CH₃ group resp. P? H groups of the trivalent phosphorus forming (Me₃Si)₂C(H)PMe₂. The rearrangement is proved by deuterated derivatives. The different behaviour is due to the increased basicity of the ylid-C atom in Si-methylated phosphorus ylides. Quite the same behaviour show the phosphorus ylides of 1,3,5-trisilacyclohexane.     

Bildung siliciumorganischer Verbindungen. 83. Bildung,Reaktionen und Struktur von Yliden aus perchlorierten Carbosilanen

Formation of Organosilicon Compounds. 83. Formation, Reactions, and Structure of Ylides Generated from Perchlorinated Carbosilanes The CCl-moiety in perchlorinated carbosilanes as (Cl₃Si)₂ a, Cl₃Si? CH₂? SiCl₂? CCl₂? SiCl₃ b, (Cl₃Si? CCl₂)₂SiCl₂ c or (Cl₂Si? CCl₂)₃ d, e.g., cleaves the Si? P bond of me₃Si? Pme₂ e (me = CH₃); and by subsequent rearrangement ylides are formed. Such, treating e with a yields (Cl₃Si)₂CPme₂Cl 1, which also results from the reaction of me₂P? Pme₂ with a. The ylides also can be obtained by means of treating the carbosilanes a, b, c or d with LiPme₂. Thus, c with one mole of LiPme₂ yields Cl₃Si? CCl₂? SiCl₂? C(Pme₂Cl)? SiCl₃ or Cl₃Si? C(Pme₂Cl)? SiCl₂? C(Pme₂Cl)? SiCl₃, resp., with two moles of LiPme₂. The corresponding Si-methylated derivates do not form ylides; (me₃Si)₂CCl₂, e.g., with e in benzene yields me₃Si? CH(Pme₂)? Sime₃. One mole of Lime methylates 1 to yield (Cl₃Si)₂CPme₃ 11. With either LiPme₂, me₃Si? Pme₂ or Me₂P? Pme₂ 1 forms (Cl₃Si)₂CPme₂-Pme₂. Reacting 1 with CH₃OH/(C₂H₅)₂NH, (Cl₃Si)[SiCl₂(OCH₃)]CPme₂(OCH₃) is formed. Ylides also result from the reactions of partially C-chlorinated 1,1,3,3,5,5-hexachloro-1,3,5-trisilacyclohexanes with me₃Si? Pme₂, (Cl₂Si? CCl₂)₃ with three moles of me₃Si? Pme₂ or LiPme₂, resp., yields (Cl₂Si? CPme₂Cl)₃ 16, the 1,1,3,3,5,5-Hexachlor-2,4,6-tris(chlordimethylphosphoranyliden)-1,3,5-trisilacyclohexan, which crystallizes with one mole of monoglyme. X-ray structure determinations revealed that 1, 11 and 16 are planar. As well the (P? C) as the (Si? C) bond lengths are remarkably shortened; in 1 (P? C) to 173.3 pm, (Si? C) to 173.3 pm, (Si? C) to 179.5 pm, in 16 (P? C) to 168.7 pm, (Si? C) to 180 pm. The (Si? C) and (P? C) bond orders amount to about 1.33, and are relatively equally distributed. Therefore, the charge of the formal carbanion is equally distributed, which shall be expressed by means of the following kind of writing for 1 and 16 see “Inhaltsübersicht”.     

Übergangsmetallphosphidokomplexe. VIII. Strukturuntersuchungen an Übergangsmetallphosphor-Vier- und Sechsringkomplexen. Die Strukturen von [(CO)4MnPH2]2, [(CO)4MnPH2]3 und [cpNiPH2]3

Transition Metal Phosphido Complexes. VIII. X-Ray Diffraction Studies of Transition Metal Phosphorus Four- and Six-Membered Ring Complexes. Structures of [(CO)₄MnPH₂]₂, [(CO)₄MnPH₂]₃, and [cpNiPH₂]₃ [(CO)₄MnPH₂]₂ 1 crystallizes triclinic in the space group P1 with a = 680.4 pm, b = 706.4 pm, c = 919.1 pm, α 110.5°, β = 91.92°, γ 115.65°, and Z = 1 formula unit. The molecule exhibits a centrosymmetrical structure. The bond angles within the planar four-membered (Mn? P)₂-ring are 76.1° at the Mn atoms and 103.9° at the P atoms, respectively. The average Mn? P bond distance is found to be 235.1 pm. [(CO)₄MnPH₂]₃ 2 crystallizes monoclinic in the space group P2/n with a = 905.2 pm, b = 974.8 pm, c = 1264.2 pm, β = 109.1°, and Z = 2 formula units. The framework of the six-membered (Mn? P)₃-ring can be described as having a twist boat conformation. The average endocyclic bond angles are with 89.1° at the Mn atoms and 130.1° at the P atoms, respectively, largely widened compared to 1 . The average Mn? P bond distance, which is found to be 238.5 pm, is also slightly increased compared to 1 . [cpNiPH₂]₃ 3 crystallizes rhombohedral in the space group R3. The cell constants (hexagonal setting) are a = b = 1686.1 pm, c = 561.1 pm and Z = 3 formula units. The six-membered (Ni? P)₃-ring exhibits a chair conformation. The endocyclic bond angles are with 92.3° at the Ni atoms and 124.3° at the P atoms, respectively, comparable with those of the six-membered ring compound 2 . The Ni? P bond distance is found to be 215.2 pm. The eyclopentadienyl ligands are disordered and have been refined as rigid groups.     

Bildung siliciumorganischer Verbindungen. 95. Die Kristallstruktur eines Hexadecamethyl-octasila-dispiro-[5.1.5.1]-tetradecans,Si8C22H65

Formation of Organosilicon Compounds. 95. Crystal Structure of a Hexadecamethyloctasila-dispiro [5.1.5.1]tetradecane, Si₈C₂₂H₅₆ 1,1,3,3,5,5,7,7,9,9,11,11,13,13,14,14-Hexadecamethyl-1,3,5,7,9,11,13,14-octasila-dispiro[5.1.5.1]tetradecane crystallizes monoclinically in the space group P2₁/n (No. 14) with a = 1352.4 pm, b = 1215.5 pm, c = 1001.2 pm, β = 92.11° and Z = 2 molecules per unit cell. The dispiro system is formed by a central disilacyclobutane and two C-spiro connected trisilacyclohexane rings. The symmetry of the molecule is 2/m, with flattened six membered rings in chair conformation. The Si? C bonds are enlarged (192 pm) at the strained spiro region whereas the Si? C bonds are distinctly shortened (186 pm) at the opposite Si atoms in the six membered rings.     

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. 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).     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXXV. Das dimere Thallium(I)-tri-tert-butoxysilanthiolat

Contributions to the Chemistry of Silicon-Sulfur Compounds. XXXV. The Dimeric Thallium(I)-tri-tert-butoxysilanethiolate Thallium(I)-tri-tert-butoxysilanethiolate is formed as a dimer by reaction of tri-tert-butoxysilanethiol with TlNO₃. The compound crystallizes as colourless triclinic plates. F.I. mass spectra show only the mass of the dimeric species (m/e = 968), in the E.I. mass spectra, however, also the peak for the monomeric unit (m/e = 484) is observed. The molecule is of 1 /C_i symmetry. The central four-membered ring is plane, the bond distances and angles therein are d (Tl? S) = 289 pm and S/Tl/S = 91.5°. The Tl atoms are additionally coordinated by an oxygen atom of the tri-tert-butoxysilyl group (d(Tl? O) = 280 pm). The mean bond angle at the threebonded sulfur atom was found to be 90° (d(S? Si) = 207.8 pm). Related details of the structure are discussed (space group P1 ; a = 927.5 pm, b = 1395.1 pm, c = 882.1 pm; α = 108.43°, β = 116.77°, γ = 90.98°; Z = 2; R = 0.032; 2887 reflections hkl).     

Molekül- und Kristallstruktur des Dimeren Magnesium-bis[bis(trimethylsilyl)amids]

Molecular and Crystal Structure of the dimeric Magnesium bis[bis(trimethylsilyl)-amide] The magnesium bis[bis(trimethylsilyl)amide] crystallizes as a dimeric molecule in the space group C2/c with {a = 1821.0(4); b = 1494.4(4); c = 1859.6(6) pm; β = 121.10(2)°; Z = 4 dimers}. The cyclic planar Mg₂N₂ moiety shows endocyclic NMgN angles of 95.8°. The bond lengths within this ring system to the four-coordinate, bridging nitrogen atoms N^b are 215 pm, whereas the distances between the magnesium atom and the terminal, three-coordinate nitrogen atom N^t display values of approximately 198 pm. These different coordination numbers of the nitrogen atoms affect the NSi bond length (N^tSi 171, N^bSi 177 pm).     

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.     

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.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXX. Die Struktur des Tetra-t-butoxy-1,3,2,4-dithiadisiletans

Contributions to the Chemistry of Silicon-Sulfur Compounds. XXX. Structure of Tetra-t-butoxy-1,3,2,4-dithiadisiletane Alcoholysis of silicon disulfide by t-butanol yielded the title compound. [(t-BuO)₂SiS]₂ crystallizes orthorhombically in the space group Pbca (no. 61) with a = 1708.4(5), b = 1560.8(3), c = 907.1(3) pm and Z = 4 molecules per unit cell. The molecule has the crystallographic 1 –C_i point symmetry and consequently the Si₂S₂ four-membered ring is rigid plane. The bond distances of this ring are Si? S = 214.2 and 213.1 pm and the bond angles S? Si? S = 97.8° and Si? S? Si = 82.2°. Related details of the structure are discussed.     

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.     

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.     

Acyl- und Alkylidenphosphane. XXII [1]. Synthese und Struktur des 1, 3-Dimethyl-2,2,4,4-tetrakis-(trimethylsilylsulfano)-1,3-diphosphetans

Acyl- and Alkylidenephosphines. XXII. Synthesis and Structure of 1, 3-Dimethyl-2,2,4,4-tetrakis(trimethylsilylsulfano)-1,3-diphosphetane At ?30°C methylbis(trimethylsilyl)phosphine reacts with carbon disulfide to give a red adduct first which rearranges to [bis(trimethylsilylsulfano)methylidene]methylphosphine 1a . In contrast to the thermally stable phenyl derivative 1b [2], this compound with its insufficiently shielded P?C group dimerizes fast with increasing temperature. 1,3-Dimethyl-2,2,4,4-tetrakis(trimethylsilylsulfano)-1,3-diphosphetane 2a formed by this reaction, crystallizes in the triclinic space group P1 with following dimensions of the unit cell, determined at a temperature of measurement of ?80 ± 3°C: a = 1024.7(3); b = 1360.2(5); c = 1326.3(6)pm; α = 117.85(4); ß = 111.05(3); γ = 72.09(3)°; Z = 2. Due to ring folding at the P1? P2 axis of 149.1°, the molecule shows pseudosymmetry C_s. Characteristic averaged bond lengths and angles obtained at an R_w-value of 0.030, are: P? C(endocyclic) 188 and 191; P? CH₃ 184; C? S 183; S? Si 216 pm; C? P? CH₃ 105; P? C? S 113; S? C? S 114; C? S? Si 108; P? C? P 90 and C? P? C 86°.     

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.     

Trimethylsilylverbindungen der Vb-Elemente. II. Molekül- und KristallStruktur des Tetrakis(trimethylsilyl)-diarsans

Trimethylsilyl Derivatives of Vb-Elements. II. Molecular and Crystal Structure of Tetrakis(trimethylsilyl)diarsine Pale yellow tetrakis(trimethylsilyl)diarsine 1 which is easily obtained from lithium bis(trimethylsilyl)arsenide · 2 tetrahydrofurane (THF) and 1,2-dibromoethane crystallizes in a trigonal, acentric space group. The dimensions of the unit cell determined at ?95 ± 5°C are: a = 974.2(2); c = 2 080.0(4) pm; Z = 3. Considering anomalous dispersion the refinement of structural data in space group P3₁21 converges at an R-value of 0.060, in its enantiomorph P3₂21, however, at 0.031. With a dihedral angle Si2′? As′? As? Si1 of ?125.7° the molecule adopts gauche conformation. Both bis(trimethylsilyl)arsino groups are symmetry-related by the crystallographic operation of the diad. Characteristic bond lengths and angles are: As? As 245.8(1); As? Si 236.5(1) and 236.2(2) pm; Si? As? Si 100.90(5); As? As? Si 93.87(3) and 113.63(4)°. The shortest intermolecular As? As distance is found to be 662 pm.     

Bildung siliciumorganischer Verbindungen. LIV. Die Kristall- und Molekülstruktur des Tetramethyl-octasila-dodecascaphans Si8C17H36

Formation of Organosilicon Compounds. LIV. Crystal and Molecular Structure of Tetramethyl-octasila-dodecascaphan 3,7,11,15-Tetramethyl-1,3,5,7,9,11,13,15-octasila-dodecascaphan crystallizes in the cubic space group F4 3c–T with a = 17.074(10) Å. In the unit cell there are four molecules of each of the two chiral forms which are arranged in the way of the NaCl-structure. The molecules have the symmetry 23-T with torsion angles of 19° in the twelve six-membered rings with skew-boat conformation. In the polycyclic skeleton the bond length Si? C are nearly the same (1.885(2) Å, 1.893(5) Å and 1.888(6) Å), whereas the bond length Si? CH₃ is slightly shorter (1.874(8) Å). The shortest distances between H-atoms are 2.59 and 2.68 Å (intramolecular) and 2.72 and 2.73 Å (intermolecular) respectively. The thermal motions of all atoms can be reduced to a rigid-body motion. Diffuse scattering (dependent on temperature) is observed and discussed.     

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.