Trimethylsilylverbindungen der Vb-Elemente. V. Molekül- und Kristallstruktur des Lithium-bis(trimethylsilyl)-arsenids · DME

Trimethylsilyl Derivatives of Vb-Elements. V. Molecular and Crystal Structure of Lithium Bis(trimethylsilyl)arsenide · DME Lithium bis(trimethylsilyl)arsenide · DME 1 obtained from tris(trimethylsilyl)-arsine and n-butyl or methyl lithium in 1,2-dimethoxyethane crystallizes monoclinic with {a = 1813(3); b = 1327(3); c = 968(1) pm; β = 119.3(1)°; Z = 4} at +20°C. Experimental conditions unfavourable for an X-ray structure determination caused high standard deviations of all structural parameters. The refinements of these values calculated with respect to the centrosymmetric space group C2/m converged at a relatively high R-value of 0.090. In contrast to the homologous antimonide lithium bis(trimethylsilyl)arsenide · DME 1 is found to be dimeric in solution as well as in the solid state. The four-membered ring built up by bis(trimethylsilyl)arsino groups and DME-coordinated lithium atoms in alternating sequence is planar; the carbon atoms statistically occupy positions on both sides of a mirror plane. Characteristic bond lengths and angles are: As? Si 230.7(7); As? Li 259(2); Li? O 205(4) and 215(4) pm; Si? As? Si 103.2(4)°; Li? As? Li 81(1)°; As? Li? As 99(1)° and Li? As? Si 115(1)°.     

Molekül- und Kristallstruktur von Magnesium-bis[bis(trimethylsilyl)phosphanid] · DME

Molecular and Crystal Structure of Magnesium Bis[bis(trimethylsilyl)phosphide] · DME Magnesium bis[bis(trimethylsilyl)phosphide] crystallizes in the tetragonal space group I4 c2 with a = 1652.9(2); c = 2282.6(5) pm and Z = 8. The magnesium atom is distorted tetrahedrally surrounded by two oxygen and two phosphorus atoms with Mg? P- and Mg? O-bond lengths of 248.7(2) and 204.7(5) pm, respectively. The phosphorus atom displays a trigonal pyramidal coordination.     

Metallderivate von Molekülverbindungen. IV. Synthese,Struktur und Reaktivität des Lithium-[tris-(trimethylsilyl)silyl]tellanids · DME

Metal Derivatives of Molecular Compounds. IV Synthesis, Structure, and Reactivity of Lithium [Tris(trimethylsilyl)silyl]tellanide · DME Lithium tris(trimethylsilyl)silanide · 1,5 DME [3] and tellurium react in 1,2-dimethoxyethane to give colourless lithium [tris(trimethylsilyl)silyl]tellanide · DME ( 1 ). An X-ray structure determination {-150 · 3·C; P2₁/c; a = 1346.6(4); b = 1497.0(4); c = 1274.5(3) pm; β = 99.22(2)·; Z = 2 dimers; R = 0.030} shows the compound to be dimeric forming a planar Li? Te? Li? Te ring with two tris(trimethylsilyl)silyl substituents in a trans position. Three-coordinate tellurium is bound to the central silicon of the tris(trimethylsilyl)silyl group and to two lithium atoms; the two remaining sites of each four-coordinate lithium are occupied by the chelate ligand DME {Li? Te 278 and 284; Si? Te 250; Li? O 200 pm (2X); Te? Li? Te 105°; Li? Te? Li 75°; O? Li? O 84°}. The covalent radius of 154 pm as determined for the DME-complexed lithium in tellanide 1 is within the range of 155 ± 3 pm, also characteristic for similar compounds. In typical reactions of the tellanide 1 [tris(trimethylsilyl)silyl]tellane ( 2 ), methyl-[tris(trimethylsilyl)silyl]tellane ( 4 ) and bis[tris(trimethylsilyl)silyl]ditellane ( 5 ) are formed.     

Trimethylsilylverbindungen der Vb-Elemente. VII. Die Kristallstrukturen von Lithium-bis(trimethylsilyl)bismutid · DME und Tetrakis(trimethylsilyl)dibismutan sowie Bemerkungen zur Kristallstruktur des Bis(4-methoxyphenyl)ditellans

Trimethylsilyl Derivatives of Vb Elements. VII. Crystal Structures of Lithium Bis(trimethylsilyl)bismuthide · DME and of Tetrakis(trimethylsilyl)dibismuthane as well as Some Comments on the Crystal Structure of Bis(4-methoxyphenyl)ditellane Colourless lithium bis(trimethylsilyl)bismuthide · DME

1 1,2-Dimethoxyethan (DME); Tetrahydrofuran (THF)

1 and green, metallic lustrous tetrakis(trimethylsilyl)dibismuthane 2 crystallize isotopic to their antimony homologues [1, 2]. As it is shown by crystal structure determinations { 1 : ?90°C; I 4 2d; a = 1017,3(4); c = 3738,0(26) pm; Z = 8; R _w = 0,065; 2 : + 20°C; P2 ₁ /c; a = 680,9(4); b = 1704,8(13); c = 1197,9 (10) pm; β = 119,46(6)°; Z = 2; R _w = 0,084} both compounds form chains which in the case of bismuthide 1 are built up as screws of alternating bismuth and lithium atoms; bonding further to two trimethylsilyl groups or to the chelating DME ligand both atoms gain coordination number 4 {Li? Bi 292(3); Bi? Si 263.3(14) pm; Bi? Li? Bi 132(1); Li? Bi? Li 148(1); φ(Li? Bi? Li? Bi) 83°}. In the case of dibismuthane 2 the centrosymmetric molecules are strung, their Bi-Bi groups forming nearly linear zigzag chains with shortened intermolecular contact distances {Bi-Bi 303.5(3); Bi …? Bi 380.4(3); Bi? Si 268 pm; Bi? Bi …? Bi 169; Bi? Bi? Si 97.4(5) and 92.0(5)°}. Structure and properties of 2 are compared with those of similar compounds; the crystal structure of brown, green metallic lustrous bis(4-methoxyphenyl)ditellane 5 already published by Ludlow and McCarthy[3] is reinvestigated with respect to very short intermolecular Te…?Te contacts.     

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).     

Metallderivate von Molekülverbindungen. VI. Lithium- und (Tetrahydrofuran)lithium-cyantrimethylsilylamid — Synthese und Struktur

Metal Derivatives of Molecular Compounds. VI. Lithium and (Tetrahydrofuran)lithium Cyanotrimethylsilylamide — Syntheses and Structures At different temperatures N,N′-bis(trimethylsilyl)carbodiimide ( 1 ) and lithium methanide react either under addition or substitution. When compound 1 , however, is treated at ?40°C with an equimolar amount of (1,2-dimethoxyethane-O,O′)lithium phosphanide ( 2 ) in 1,2-dimethoxyethane, only exchange of one trimethylsilyl group versus lithium is observed and in addition to phosphane and tris(trimethylsilyl)phosphane a very pure lithium derivative insoluble in n-pentane can be isolated. The vibrational spectra prove the compound to be lithium cyanotrimethylsilylamide ( 3 ). Recrystallization from tetrahydrofuran (+40/+20°C) yields (tetrahydrofuran)lithium cyanotrimethylsilylamide ( 3 ′). As shown by an X-ray structure analysis {C2/c; a = 2 261.1(5); b = 1 106.4(2); c = 1 045.9(2) pm; β = 113.63(1)°; Z = 8 formula units}, compound 3 ′ is polymeric in the solid state. Coordinative Li? N2′ bonds allow a head-to-tail addition of two monomeric units each to give an eight-membered heterocycle with two linear N1? C2≡N2 fragments (N1? C2 126.1; C2≡N2 117.5; N1? Si 171.4; Li? N1 203.2; Li? N2′ 206.1 pm; C2? N1? Li 109.0; N1? Li? N2′ 115.9; N2≡C2? N1 177.2°). Forming planar four-membered Li? N2? Li? N2 rings (Li? N2″″ 198.3 pm; Li′? N2? Li″ 80.3; N2′? Li? N2″″ 99.5°) these heterocycles polymerize to slightly folded tapes.     

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.     

Synthese und Molekülstruktur von Barium-bis[N,N′-bis(trimethylsilyl)benzamidinat] · DME · THF

Synthesis and Molecular Structure of Barium Bis[N,N′-bis(trimethylsilyl)benzamidinate] ° DME ° THF Barium bis[N,N′-bis(trimethylsilyl)benzamidinate] · thf · dme crystallizes in the monoclinic space group P2₁/n with a = 1 122.0(2), b = 2 190.7(4), c = 1 840.2(3) pm, β = 98.04(1)° and Z = 4 containing a metal center in a distorted monocapped trigonal prismatic surrounding. The barium dibenzamidinate moiety is sent with an angle of 120°, although this leads to different Ba? N distances of 273 and 282 pm originating from the interligand repulsion of the trimethylsilyl groups and the dme substituent. The 1,3-diazaallyl fragment with C? N bond lengths of 132 pm shows a delocalisation of the anionic charge.     

Trimethylsilylverbindungen der Vb-Elemente. VI. Synthese,Molekül- und Kristallstruktur des Tetrakis(trimethylsilyl)distibans im Vergleich mit Tetraphenyldistiban

Trimethylsilyl Derivatives of Vb-Elements. VI. Synthesis, Molecular and Crystal Structure of Tetrakis(trimethylsilyl)distibine Compared with Tetraphenyldistibine Tetrakis(trimethylsilyl)distibine already isolated by Breunig et al. [9] from cleavage reactions of tris(trimethylsilyl)stibine may also be obtained in high yields from lithium bis(trimethylsilyl)antimonide · 2THF and 1,2-dibromoethane in n-pentane. This compound intensely red in the solid state, but only slightly yellow in solution or in the melt crystallizes in the monoclinic space group P2₁/c with a = 680.6(1); b = 1672.8(2); c = 1190.0(1) pm; β = 119.01(5)°; Z = 2 at +20°C. An X-ray structure determination (R = 0.017) shows the bis(trimethylsilyl)-stibino groups to be arranged in a transoid position. Characteristic bond lengths and angles are: Sb? Sb 286.7(1); Sb? Si 259.4 pm; Si? Sb? Si 94.46(3); Sb? Sb? Si 98.68(3) and 94.43(3)°. As in similiar 2,2′,5,5′-tetramethyldistibolyl published recently by Ashe III et al. [8] this crystal structure, too, is characterized by a nearly linear sequence of Sb? Sb groups. Compared with the sum of van-der-Waals radii the intermolecular Sb-Sb contact in such a chain is shortened from 440 to 399 pm. This probably allows electronic interactions of unknown type responsible for the colour of the crystals. In keeping with this assumption an analogous formation of chains is not found in solid, only yellow tetraphenyldistibine 5 the structure of which has already been studied by Rehder et al. [44].     

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.     

Metallderivate von Molekülverbindungen. V. Synthese und Struktur von Hexakis{lithium-[tris(trimethylsilyl)silyl]tellanid}—Cyclopentan (1/1)

Metal Derivatives of Molecular Compounds. V. Synthesis and Structure of Hexakis{lithium-[tris(trimethylsilyl)silyl]tellanide}—Cyclopentane (1/1) . Lithium [tris(trimethylsilyl)silyl]tellanide—DME (1/1) [1 b] prepared from lithium tris(trimethylsilyl)silanide—DME (2/3) [3] and tellurium, reacts with hydrogen chloride in toluene to form [tris(trimethylsilyl)silyl]tellane ( 1 ) [1 b]. Subsequent metalation of this compound with lithium n-butanide gives lithium [tris(trimethylsilyl)silyl]tellanide ( 2 ) free of coordinating solvent. Pale yellow crystals are obtained from cyclopentane solution. An X-ray structure determination {P1 ; a = 1 558.5(7); b = 1 598.4(8); c = 1 643.5(6) pm; α = 117.64(4); β = 91.63(3); γ = 117.19(3)°; Z = 1; R = 0.032} shows them to be the (1/1) packing complex ( 2 ′) of hexakis{lithium-[tris(trimethylsilyl)silyl]tellanide} and disordered cyclopentane molecules —{Li? Te? Si[Si(CH₃)₃]₃}₆ · C₅H₁₀.     

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.     

Bildung und Eigenschaften von Aoylphosphinen. III. Molekül- und KristallStruktur von Dipivaloylphosphin

Syntheses and Properties of Acylphosphines. III. Molecular and Crystal Structure of Dipivaloylphosphine In the reaction of tris(trimethylsilyl)phosphine with pivaloyl chloride two Si? P bonds are cleaved and dipivaloyltrimethylsilylphosphine is formed. Reaction with methanol yields dipivaloylphosphine. N.m.r. investigations show a tautomeric equilibrium between keto and enol form as in β-diketones. The substance crystallizes in the orthorhombic space group Pmmn with molecules in two crystallographically different sites [cell parameters: a = 14.04(1), b = 13.82(1), c = 6.28(2) Å]. An X-ray structure determination (R = 5.0%) proves the existence of the enol form in the solid, in that (1.) the molecular symmetry is mm 2(C_2v), (2.) P? C bonds are shortened and C? O bonds are elongated, and (3.) we find a symmetric hydrogen bridge with a very short O? O distance. Bond lengths and angles are compared with those of other β-diketones. The packing of molecules is studied in detail.     

Molekül- und Kristallstruktur von Ytterbium(III)-triaqua-trinitrat,Yb(H2O)3(NO3)3

Molecular and Crystal Structure of Ytterbium(III)-triaqua-trinitrate, Yb(H₂O)₃(NO₃)₃ Yb(H₂O)₃(NO₃)₃ crystallizes from a concentrated solution of Yb₂O₃ in nitric acid in a vacuum desiccator at ambient temperature as colourless single crystals. The crystal structure was determined from single crystal four-circle diffractometer data (R3 , Z = 6, a = 1175.5(1), c = 1117.7(2) pm, V_m = 134.25 cm³/mol, R = 3.0%, R_w = 2.9%). The structure may be viewed at as a heavily compressed packing of [Yb(H₂O)₃(NO₃)₃] molecules. Yb³⁺ is coordinated by three bidentate nitrate ligands and three water molecules so that a tricapped trigonal prism (C.N. 9) of oxygen atoms results as the coordination polyhedron.     

Acyl- und Alkylidenphosphane. XIX. Molekül- und Kristallstruktur des 2,4-Bis(dimethylamino)-1,3-diphenyl-1,3-diphosphetans

Acyl and Alkylidenephosphines. XlX. Molecular and Crystal Structure of 2,4-Bis (dimethyl-amino) ?1,3-diphenyl-l, 3-diphosphetane 2,4-Bis(dimethylamino)-1,3-diphenyl-1,3-diphosphetane 2a which is isolated as a byproduct in the synthesis of (E)-(dimethylamino)methylidene-phenylphosphine 1a crystallizes in the monoclinic space group P2₁/c. The dimensions of the unit cell determined at ?65 ± 5°C are: a = 1 004(1); b = 1 018(3); c = 1 873(2) pm; β = 105.15(8)°; Z = 4. As it is shown by a low temperature X-ray structure determination (R_g = 3.5%) the phenyl groups are placed above and the dimethylamino groups below the folded 1,3-diphosphetane ring; the molecule with its differently twisted substituents, however, deviates considerably from point symmetry mm2. The dihedral angle between the P1? C1n? P2 planes (n = 1 or 2) is found to be 153°. The relatively long Pn? C1n bond distances (187 to 191 pm) indicate a strained ring system; in solution 2a decomposes to some extent and forms monomeric 1a again. Further characteristic average bond distances and angles are: Pn? C4n (phenyl) 184; C? N 146 pm; P1? C1n? P2 93°; C11? Pn? C12 84° and Pn? C1n? Nn 116°.     

Metallderivate von Molekülverbindungen. VII. Bis[1,2-bis(dimethylamino)ethan-N,N′]lithium-disilylphosphanid — Synthese und Struktur

Metal Derivatives of Molecular Compounds. VII. Bis[1,2-bis(dimethylamino)ethane-N,N′]lithium Disilylphosphanide — Synthesis and Structure Crystalline lithium phosphanides studied so far show a remarkably high diversity of structure types dependent on the ligands at lithium and the substituents at phosphorus. Bis[1,2-bis(dimethylamino)ethane-N,N′]lithium disilylphosphanide ( 1 ) discussed here, belongs to the up to now small group of compounds which are ionic in the solid state. It is best prepared from silylphosphane by twofold lithiation with lithium dimethylphosphanide first and subsequent monosilylation with silyl trifluoromethanesulfonate, followed by complexation. As found by X-ray structure determination (wR = 0.038) on crystals obtained from diethyl ether {monoclinic; space group P2₁/c; a = 897.8(1); b = 1 673.6(2); c = 1 466.8(1) pm; β = 90.73(1)° at ?100 ± 3°C; Z = 4 formula units}, the lithium cation is tetrahedrally coordinated by four nitrogen atoms of two 1,2-bis(dimethylamino)ethane molecules. Characteristic parameters of the disilylphosphanide anion are a shortened average P? Si bond length of 217 pm (standard value 225 pm) and a Si? P? Si angle of 92.3°.     

Pseudoelementverbindungen IX. Organostannylierung von Cyanamidonitrat — Molekül- und Kristallstruktur von N-Trimethylstannyl-N′-nitro-carbodiimid

Considered under the aspect of its ambidence, the reactivity of cyanamidonitrate [NO₂NCN]⁻ towards triorganostannyl chlorides was investigated. The reaction products of type R₃Sn-NCN-NO₂ were characterized by ¹H-NMR, ¹³C-NMR, ¹¹⁹Sn-NMR and IR spectroscopy. While cyanamides of the type [R_nE(Y)NCN]⁻ (R_nE(Y) = RC(O), RC(NCN), R₂ P(O), R₂P(S), R₂P(NCN), RSO₂) are coordinated exclusively either via the terminal nitrogen (monodentately) or via both the nitrile group end on and the chalcogen atom (bidentately), we found N-triorganostannyl-N′-nitro-carbodiimides as the first example in which the NCN group acts as a bidentate bridge with metal-N bonds in 1- and 3-position. For Me₃Sn-NCN-NO₂ the crystal structure was determined.

Zusammenfassung

Unter dem Aspekt der Ambidenz wurde die Reaktivität von Cyanamidonitrat [NO₂NCN]⁻ gegenüber Triorganostannylchloriden untersucht. Die Reaktionsprodukte des Typs R₃Sn-NCN-NO₂ wurden ¹H-NMR-, ¹³C-NMR-, ¹¹⁹Sn-NMR- sowie IR-spektroskopisch charakterisiert. Während Cyanamide des Typs [R_nE(Y)NCN]⁻ (R_nE(Y) = RC(O), RC(NCN), R₂P(O), R₂P(S), R₂P(NCN), RSO₂) ausschlieβlich über das terminale Stickstoff- (einzähnig) bzw. über das Nitrilstickstoff- und das Chalkogenatom (zweizähnig) gebunden werden, fanden wir mit N-Triorganostannyl-N′-nitro-carbodiimiden erstmalig Beispiele, in denen die NCN-Gruppe zweizähnig verbrückend in 1- und 3-Position koordiniert wird. Für Me₃Sn-NCN-NO₂ liegt eine Kristallstrukturbestimmung vor.