Acyl- und Alkylidenphosphane. XXVI. 2, 4-Bis(phenylimino)-1,3-diphosphetane aus Thiocarbamoyl- und Carbamoyltrimethylsilylphosphanen

Acyl-and Alkylidenephosphines. XXVI. 2, 4-Bis (phenylimino)-1, 3-diphosphetanes from Thiocarbamoyl- and Carbamoyltrimethylsilylphosphines . Bis(trimethylsilyl)phosphines R? P[? Si(CH₃)₃]₂ 1 (R = H₃C a, H₅C₆ b, (H₃C)₃C e, H₁₁C₉ d) and phenyl isothiocyanate give insertion compounds which were identified as [CN-phenyl, N-trimethylsilyl)thiocarbamoyl]trimethylsilylphosphines 3 ? 2 in solution as well as in the solid state [2]. In the presence of small amounts of solid sodium hydroxide the phenyl derivative 3 ? 2b eliminates bis(trimethylsilyl) sulfane, whereas the tert-butyl 3 ? 2c and the mesityl compound 3 ? 2d show the same reaction even without a catalyst. The unstable [(phenylimino)methylidene]phosphines 6 formed first, dimerize rapidly to give 2, 4-bis(phenylimino)-1,3-diphosphetanes 7 which in solution exist as mixtures of the E and Z isomers. Via a NaOH-catalyzed elimination of hexamethyldisiloxane these cyclic phosphines 7 can also be obtained from the adducts of phenyl isocyanate and bis(trimethylsilyl)phosphines 1. Taking the thermally sufficiently stable tert-butyl derivative 7 c as an example, the temperature dependence of n.m.r. spectra is discussed in detail.     

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°.     

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°.     

Acyl- und Alkylidenphosphane. XXXIII. Lithoxy-methylidenphosphan · DME und -methylidinphosphan · 2 DME — Synthese und Struktur

Acyl- and Alkylidenephosphines. XXXIII Lithoxy-methylidenephosphine · DME and -methylidynephosphine · 2DME — Syntheses and Structures Lithium dihydrogenphosphide · DME(¹) and ethyl formate in a molar ratio of 2 : 1 react in 1,2-dimethoxyethane to give liquid lithium formylphosphide · DME in 87% yield. Since lithium complexed by the chelate ligand DME is bound to the oxygen atom of the carbonyl group, the compound has to be considered as lithoxy-methylidenephosphine · DME ( 1 ). According to x-ray structure analyses of crystalline derivatives [5, 6], molecules of this type dimerize forming a four membered Li O Li O ring. Characteristic nmr-data show the presence of an E- and Z-isomer (δ¹ H  P: 3.87 and 4.49; ¹ J _HP: 150.8 and 136.5; δ¹ H  C: 11.4 and 10.05; ² J _HP: 6.1 and 81.2; ³ J _HH: 6.6 and 13.9; δ³¹ P : 38.6 and 8.8; δ¹³ C P: 225.0 and 215.4 ppm; ¹ J _CP: 41.2 and 65.0 cps); in 1,2-dimethoxyethane an E : Z ratio of 1.86 : 1 is found. In a similar reaction of lithium bis (trimethylsilyl)phosphide · 1.6 THF(¹) with excess dimethyl carbonate lithoxy-methylidynephosphine · 2DME ( 2 ) is formed via an up to now poorly understood mechanism. The compound can also be prepared from lithium dihydrogenphosphide · DME; it crystallizes in the monoclinic space group P2₁/n {a = 880.6(2); b = 1296.6(2); c = 1267.4(2) pm; β = 96.07(2)° at −100 ± 3°C; Z = 4}. An x-ray structure analysis (R_w = 0.052) gives a P C distance of 155.5 pm which is typical for a triple bond. The C O bond length of 119.8 pm, however, is extremely short compared to the standard value of a single bond (139 pm). Angles of 178.5° and 170.7° at the carbon and oxygen correspond with the expected linear configuration of the PC O Li backbone of the molecule, Characteristic nmr-data are as follow: δ³¹ P -384.2; δ¹³ C 166.6ppm; ¹J_cp 41.5 cps.     

Acyl- und Alkylidenphosphane. XXIII [1]. Synthese und Struktur der [Bis(trimethylsilylsulfano)methyliden]phosphane

Acyl- and Alkylidenephosphines. XXIII. Synthesis and Structure of [Bis(trimethylsilylsulfano)methylidene]phosphines Analogous to the phenyl derivative 1a [2] tert-butyl- 1b , mesityl- 1c and methylbis-(trimethylsilyl)phosphine 1 d react with carbon disulfide to give the corresponding [bis(trimethylsilylsulfano)methylidene]phosphines 4 . Only in case of the mesitylphosphine 1 c the intermediate compounds 2 and 3 could be detected by n.m.r. spectroscopic methods; thermally unstable [bis(trimethylsilylsulfano)methylidene]methylphosphine 4 d dimerizes rapidly [1]. [Bis(trimethylsilylsulfano)methylidene]phenylphosphine 4 a crystallizes in the monoclinic centrosymmetric space group P2₁/c with following dimensions of the unit cell determined at ?95 ± 3°C: a = 1386.4(8); b = 1036.0(7); c = 1281.7(8) pm; ß = 101.23(4)°; Z = 4. An X-ray structure determination (R = 0.032) proves the constitution of this compound as already derived from its nmr spectra. Characteristic bond lengths and angles are: P?C 170; P? C(phenyl) 183; C? S 176; S? Si 219 pm; C? P?C 107; P?C? S 124 and 120; S? C? S 116 and C? S? Si 111°.     

Acyl- und Alkylidenphosphane. XVI. (Dimethylaminomethyliden)- und (Diphenylmethyliden)phosphane

Acyl- and Alkylidenephosphines. XVI. (Dimethylaminomethylidene)- and (Diphenylmethylidene) phosphines Alkyl- or arylbis(trimethylsilyl)phosphines 1 (R = mesityl, C₉H₁₁ a ; (CH₃)₃C b ; C₆H₅ c ; CH₃ d ) react only very slowly with dimethylformamide 2 and benzophenone 4. After repeated addition of small amounts of solid sodium hydroxide, however, the reaction-time is shortened from several months to a few days. The reactions between 1 a or 1 b and 2 yield the (dimethylaminomethylidene)phosphines 3 a and 3 b ; from 1 a and 4 mesityl-(diphenylmethylidene)phosphine 5 a is obtained. The formation of the thermally labile phosphines 3 d and 5 c is proved by NMR spectroscopy; these compounds dimerize very fast to give 2,4-bis(dimethylamino)-1,3-dimethyl- 10 d and 1,2,2,3,4, 4-hexaphenyl-1,3-diphosphetane 15 c. Similarly the lithium trimethylsilylphosphides 6 a , 6 c and 6 e (R = (CH₃)₃Si) react with 2 or 4 to form 3 a and 5 c as well as (diphenylmethylidene)-trimethyl-silylphosphine 5 e .     

Acyl- und Alkylidenphosphane. XIII [1]. Molekül- und Kristallstruktur des 2,4-Di(tert.butyl)-2,4-bis-(trimethylsiloxy)-1,3-diphosphetans

Das Gemisch aus dem E- und Z-Isomeren des [2,2-Dimethyl-1-(trimethylsiloxy)propyliden]phosphans ist bei 20°C im diffusen Tageslicht nicht beständig; im Laufe einiger Wochen scheidet sich das Dimere 2,4-Di(tert.butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetan 1 ab. Die Verbindung kristallisiert triklin in der Raumgruppe P1 mit a = 1044,5(3); b = 647,8(2); c = 883,8(2) pm; α = 100,39(2); β = 102,84(2); γ = 93,70(2)°; Z = 1. Wie die Röntgenstrukturanalyse (R = 3,7%) zeigt, besitzt das Molekül als kristallographisches Symmetrieelement ein Inversionszentrum. Die mit 190,3 und 189,5 pm langen P? C? Abstände weisen auf eine beträchtliche Ringspannung hin; in Lösung zerfällt das Diphosphetan wieder leicht in das E- und Z-isomere Monomere. Weitere charakteristische Bindungsabstände und -winkel sind: C1? O 140,8; Si? O 163,5 pm sowie P? C1? P' 92,7; C1? P? C1′ 87,3; C1? O? Si 146,2° Acyl and Alkylidene Phosphines. XIII. Molecular and Crystal Structure of 2,4-Di(tert.-butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetane Kept at 20°C in diffuse daylight the mixture of the E and Z isomer of [2,2-dimethyl-1-(trimethylsiloxy)propylidene]phosphine is not stable; within several weeks the dimer 2,4-di(tert.-butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetane 1 precipitates. The compound crystallizes triclinic in the space group P1 with a = 1044.5(3); b = 647.8(2); c = 883.8(2) pm; α = 100.39(2); β = 102.84(2); γ = 93.70(2)°; Z = 1. As shown by an x-ray structure determination (R = 3.7%) the molecule has a centre of symmetry. The long P? C distances (189.5 and 190.3 pm) indicate a strained ring-system; in solution the diphosphetane decomposes again to form the E and Z isomeric monomer. Further characteristic bond distances and angles are: C1? O 140.8; Si? O 163.5 pm as well as P? C1? P' 92.7; C1? P? C1′ 87.3; C1? O? Si 146.2°.     

Bildung Siliciumorganischer Verbindungen. 103. Bildung und Struktur von cis- und trans-2,4-Dichloro-2,4-bis(trimethyl-silyl)-1,1,3,3-tetramethyl-1,3-disilacyclobutan

Formation of Organosilicon Compounds. 103. Formation and Structure of cis and trans 2,4-Dichloro-2,4-bis(trimethylsilyl)-1,1,3,3-tetramethyl-1,3-disilacyclobutane The reaction of Me₃Si? CCl₂? SiMe₂Cl with LiBu in THF yields 1,1,3,3-Tetramethyl-2,4-bis(trimethylsilyl) 1,3-disilabicyclo[1.1.0]butane. The product of the first reaction stage is Me₃Si? CCl(Li)-SiMe₂Cl. The 1,3-Disilacyclobutane 2 and 3 were isolated, when Me₃Si? CCl₂? SiMe₂Cl was treated with LiBu in Et₂O. This way the proof is given that 2 and 3 are intermediates of the formation of product 1 . The further products are 4 and 5 (CCl in 2 and 3 substituted by CH) and Me₃Si? CH₂? C(SiMeCl)₂SiMe₃. 2 crystallizes orthorhombically in the space group Fdd 2 (no. 43) with a = 2149.1 pm, b = 2229.2 pm, c = 1763.6 pm and Z = 16 molecules per cell. The central ring of disilacyclobutane is slightly folded (17.9°). The configuration of the C-Atoms in this four membered ring gets closer to a sp² configuration built up by three Si? C bonds. The Cl-atoms approximately have orthogonal positions to these CSi₃ arrangements. The extension of the C? Cl bonds (184.6 pm) and the mutual approximations of the Cl-atoms in the cis-position indicate a high reactivity of the molecule.     

Die Synthese von 1,3-Bis(dichlorcarbo)-2,4-bis(dihalogen)cyclo-diborazanen

Zusammenfassung 1,3-Bis(dichlorcarbo)-2,4-bis(dihalogen)cyclodiborazane wurden durch Umsetzung von Rhodantrichlorid mit Trihalogenboranen dargestellt. Die Massenspektren und IR-Spektren bestätigen die Struktur der Verbindung, für welche die Punktgruppe D_2h angenommen wird.

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From the reaction of thiocyanogen trichloride with trihaloboranes 1,3-bis(dichlorcarbo)-2,4-bis(dihalogeno)cyclodiborazanes have been obtained. IR and mass spectra confirm the structure of these compounds, for which a D_2h symmetry is proposed.

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Mit 1 Abbildung     

Acyl- und Alkylidenarsane. IV [1] Molekül- und Kristallstruktur des 2,4-Di(tert. butyl)-1,3-dimethyl-2,4-bis(trimethylsiloxy)-1,3-diarsetans

Bis-Nitridochloro Complexes Cl₃PO? (Cl₄)M?N? C₂Cl₄? N?M(Cl₄)? OPCl₃ with M = Mo, W, Re By the reaction of cyanogen with tungstenhexachloride, as well as by the reactions of cyanogen and chlorine with molybdenum-, tungsten- and rheniumpentachloride, in POCl₃ solution the POCl₃ solvated bis-nitridochloro complexes Cl₃PO? (Cl₄)M?N? C₂Cl₄? N?M(Cl₄)? OPCl₃ can be obtained. The i.r. spectra indicate that the complexes contain metal nitrogen triple bonds with a linear M?N? C arrangement. The O atoms of the POCl₃ molecules are coordinated in trans-position to the M?N triple bond.     

Acyl- und Alkylidenphosphane. XVII. Triacetylphosphan aus Tris(trimethylsilyl)phosphan

Acyl- and Alkylidenephosphines. XVII. Triacetylphosphine from Tris(trimethylsilyl)-phosphine Tris(trimethylsilyl)phosphine reacts at 0°C with excess acetyl chloride in cyclopentane to form chlorotrimethylsilane and triacetylphosphine 3a . In contrast to the corresponding 2,2-dimethylpropionyl derivate (Z)- 5b the intermediate compounds (E)- and (Z)-acetyl-[1-(trimethylsiloxy)ethylidene]phosphine 5a are thermally instable. They could not be isolated in a pure state, but were characterized by NMR spectroscopic methods only. The isomers differ scarcely in their chemical shift values, but very much in their coupling constants. If the solution is cooled unsufficiently diacetyl-[1-(trimethylsiloxy)vinyl]phosphine 7 and the keto-enol-tautomers of diacetylphosphine K-/E- 2a are formed to a greater extend. ¹H-{³¹P}-INDOR experiments allowed the correlation between ¹H- and ³¹P-NMR resonances and hence the correct identification of the phosphines formed. Within days the compounds 2a and 7 also react at +20°C with an excess of acyl halide to give triacetylphosphine 3a .     

Acyl- und Alkylidenphosphane. XII [1]. Synthese und Eigenschaften des 2,2-Dimethylpropionylphosphans und einiger Derivate

Acyl and alkylidene phosphines. XII. Syntheses and properties of 2,2-dimethylpropionylphosphine and of some derivatives At ?25°C bis(trimethylsilyl)phosphine 1b and 2,2-dimethylpropionyl chloride form (2,2-dimethylpropionyl)trimethylsilylphosphine 2b . As this compound is thermally more stable than similar acyltrimethylsilylphosphines, it might be treated at ?55°C with methyllithium to form the correspondig lithium phosphide 2d ; after the addition of chlorotrimethylsilane [2,2-dimethyl-1-(trimethylsiloxy)propylidene]-trimethylsilylphosphine 3c is obtained. At +20°C 2b rearranges to the E and Z isomer of [2,2-dimethyl-1-(trimethylsiloxy)propylidene]phosphine 3b . The NMR data of E- 3b and Z- 3b differ mostly in the coupling constants. Kept in the diffuse daylight for several days 3b dimerizes to form 2,4-di(tert.butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetane 10 . In solution 10 is unstable and decomposes again to a mixture of the E und Z isomer of 3b . Reacting 3b or 3c with alcoholes all trimethylsilyl groups are replaced by hydrogen atoms and unstable 2,2-dimethylpropionylphosphane 4b is formed. Lithium(2,2-dimethylpropionyl)phosphide 4d , synthesized at ?60°C from 4b and methyllithium, crystallizes with one molecule 1,2-dimethoxyethane per formula unit and is dimeric in benzene. As shown by the NMR data 4d has the structure of an alkylidene-phosphine with the lithium atom bound to oxygen. At ?50°C 4d and chlorotrimethylsilane react to form 3b .     

Synthese und struktur von 2,2-bis(trifluormethyl)4-dimethyl-amino-1,3-diazolon

Cyanogen, O-(trimethylsilyl)hexafluoracetone cyanhydrin and dimethylformamide react to yield a five-membered heterocycle of composition (CH₃)₂NC₃N₂H(O) (CF₃)₂. The composition and the molecular structure were determined on the basis of mass spectra and a single-crystal X-ray analysis. The compound crystallizes in the space group P2₁/n with a = 9.469(1), b = 11.540(2), c = 10.205(4) Å, β = 106.O2(2)^o. The final R_w(F) is 0.047 for 1168 observed reflections.     

Synthese und Struktur von Vanadium(III)- und Vanadium(IV)-silanolaten

Synthesis and Structures of Vanadium(III) and Vanadium(IV) Silanolates The syntheses of the new and partially known vanadium(III)-silanolate complexes [{V(OSiMe^t₂Bu)₃}₂(THF)] ( 1 ), [Li(THF)₂V(OSiMe^t₂Bu)₄] ( 2 ), [V(OSiMe^t₂Bu)(lut)] ( 3 ), V(OSiPh₃)₃(THF)₃ ( 4 ), [Li(THF)₄][V(OSiPh₃)₄](THF)₂ ( 5 ), [Li(DME)VMes(OSiMe^t₂Bu)₃] ( 7 ), [Li(THF)₄][VMes · (OSiPh₃)₃] ( 8 ), [Li(THF)₄][VMes₃(OSiMe^t₂Bu)] ( 9 ), and Na[VMes₃(OSiPh₃)](THF)₄ ( 10 ) as well as the vanadium(IV) compounds [V(OSiPh₃)₄] ( 6 ), [VMes₃(OSiMe^t₂Bu)] ( 11 ) and [VMes₃(OSiPh₃)] ( 12 ) are reported. In most cases the vanadium atom displays a coordination number of four. The dimeric structure of 1 with coordination numbers of four and five, respectively, has been deduced from molecular mass measurements, mass spectrometry and its magnetic properties. The crystal structures of compounds 2 , 4 , 5 , 9 and 11 were resolved. Complex 2 resembles a bridged contact ion pair in which both metal centres are in a tetrahedral coordination environment. In 4 the ligands are arranged trigonal bipyramidally with the THF molecules in the axial positions. Complexes 5 and 9 crystallize in separated ion paires with the vanadium in a tetrahedral coordination sphere. The crystal structure of 11 is analogous to that of 9 but with consequences due to the higher oxidation state. Oxidation of the vanadates(III), e. g. 5 , 9 and 10 , yields the corresponding vanadium(IV) compounds 6 , 11 and 12 .     

Synthese,Struktur und Reaktivität eines 2,4-Diphosphino-1,3-diphospha-2,4-disilacyclobutans

Synthesis, Structure, and Reactivity of a 1,3-Diphosphino-2,4-diphospha-1,3-disilacyclobutane Pentamethylcyclopentadienyltrichlorosilane reacts with Li[Al(PH₂)₄] to give the stable 1,3-diphosphino-2,4-diphospha-1,3-disilacyclobutane 4 . Treatment of 4 with Lithium alkyls affords the Lithium phosphide 5 via regiospecific metalation of a ring phosphorus atom, and reaction with t-Bu₂Hg proceeds via oxidative P? P bond formation to yield the 1,4-disila-2,3,5,6-tetraphospha-bicyclo[2,1,1]-hexane 6 . Cleavage of pentamethylcyclopentadiene is observed during thermolysis of 4 at 200°C. 4–6 were characterised by NMR-spectroscopy, and 4 by an additional crystal structure determination.     

Acyl- und Alkylidenphosphane. XXXII [1, 2]. Di-cyclo-hexoyl- und Diadamant-1-oylphosphan — Keto-Enol-Tautomerie und Struktur

Acyl- and Alkylidenephosphines. XXXII. Di-cyclohexoyl- and Diadamant-1-oylphosphine – Keto-Enol Tautomerism and Structure Lithium dihydrogenphosphide · DME (¹) [12] and cyclo-hexoyl or adamant-1-oyl chloride react in a molar ratio of 3:2 to give lithium di-cyclo-hexoylphosphide · DME and the corresponding diadamant-1-oylphosphide.2THF (¹) resp. Treatment of these two compounds with 85% tetrafluoroboric acid. diethylether adduct yields di-cyclo-hexoyl- ( 1b ) and diadamant-1-oylphosphine ( 1c ). In nmr spectroscopic studies 1b over a range of 203 to 343 K, a strong temperature dependence of the keto-enol equilibrium is found; thermodynamic data characteristic for the formation of the enol tautomer (ΔH⁰ = ?4.3 kJ. mol^?1; ΔS⁰ = ?9.2 J. mol^?1. K (^?1) are compared of 1,3-diketones. The enol tautomer of diadamant-1-oylphosphine ( E-1c ) as obtained from a benzene solution in thin colourless plates, crystallizes in the monoclinic space group P2₁/c {a = 722.2(2); b = 1085.5(4); c = 2434.8(5) pm; ß = 96.43(2)° at –100 ± 3°C; Z = 4}. An X- ray structure analysis (R_w = 0.033) shows bond lengths and angles to be almost identical within the enolic system (P? C 179/180; C? O 130/129; C? C(adamant-1-yl) 152/153 pm; C? P? C 99°; P? C? O 124°/124°; P? C? C 120°/120°; C? C? O 116°/116°. The geometry of the very strong, but probably asymmetric O‥H‥O bridge is discussed (O? H 120/130, O‥O 245 pm).     

Synthese und Struktur von Au(OTeF5)3

Syntheses and Structure of Au(OTeF₅)₃ Stable and crystalline Au(OTeF₅)₃ is prepared from AuF₃ and B(OTeF₅)₃. The crystal structure analysis of the monoclinic single crystals, space group C2/c, a = 1893.8(4), b = 847.3(2), c′ = 564.6(2) pm, β = 94.30(5), gave the OTeF₅ positions, but the gold positions only in a statistical manner. Interpretation of weak diffuse super structure reflections resulted in a three times magnified c-axis and produced molecular units of the X₂AuX₂AuX₂ type. This is the first time that bridging OTeF₅ ligands have been observed.     

Acyl- und Alkylidenarsane. VI. Vergleichende Untersuchungen zur Struktur von Bis (2,2-dimethylpropionyl) phenylarsan und -phosphan

Acyl- and Alkylidenearsines. VI. Comparative Studies on the Structures of Bis(2,2-di-methylpropionyl)phenylarsine and -phosphine . Bis(2,2-dimethylpropionyl)phenylarsine 1a [19] and -phosphine 1b [20] prepared from the corresponding bis(trimethylsilyl) derivative and 2,2-dimethylpropionyl chloride, crystallize in the monoclinic space group P2₁/c with following dimensions of the unit cell determined at a temperature of measurement of ?70 ± 3°C/?73 ± 3°C: a = 1449.3(7)/1468.3(3); b = 1050.0(5)/985.9(2); c = 1138.5(4)/1159.4(4) pm; β = 108.27(3)/105.61(3)°; Z = 4. X-ray structure determinations (R_w = 0.044/0.044) reveal distances of 205 and 191 pm between the pnicogen and the carbon atom of the carbonyl group which, as in similar trifluoromethyl compounds [2], are definitely elongated with respect to standard values of 194 and 183 pm. Further characteristic mean bond lengths and angles are: As? C(phenyl) 194; P? C(phenyl) 184; C?O 119/121; C(O)? C 153/154; C(O)? As? C(O) 91; C(O)? P? C(O) 95; As? C? O 120; P? C? O 120; As? C(O)? C 117 and P? C(O)? C 118°.