Frank Ruthe

Tuning seleniumiodine contacts: from secondary soft–soft interactions to covalent bonds

Selenium to iodine contacts ranging from the sum of the Se and I van der Waals distances to strong covalent bonds are reviewed with the help of recent structural determinations of compounds exhibiting SeI distances from 384 to 244 pm, with emphasis on ‘less clear-cut’ cases, in terms of different extents of ‘hypervalent’ 3c–4e (10-Se-3) and (10-I-2) interactions. Within a continuum of SeI interactions from undisturbed single bonds via n->σ*(SeI) interactions and typical 3c–4e XSeI or SeIX systems to van der Waals contacts, any desired SeI distances can be tuned by an appropriate choice of the particular substituents and ligands attached to the SeI moiety.

Iodophosphonium salt structures: homonuclear cation–anion interactions leading to supramolecular assemblies

Abstract The structures of iodophosphonium cations R n PI 4− n + depend significantly on the nature of their counteranions, which act as nucleophiles towards electrophilic iodine atoms bonded to the formally charged phosphorus atom. This nucleophilic attack leads to P–I bond lengthening, that can be understood as consequence of ( n → σ *) donor–acceptor interactions, i.e. population of the σ * energy level of the attacked P–I bond. For a given cation, anion ‘iodophilicity’ correlates well with P–I and I–I distances: the phosphane and the anion compete for coordination with the central linearly coordinated iodine atom. When different iodophosphonium cations are compared, however, P–I/I–I correlations are not always that straightforward, since specific effects of the peculiar substituents like size, electronic properties and packing preferences do also play a role. In di- and triiodophosphonium ions, bi- and trifunctionality of the soft Lewis acids R 2 PI 2 + and RPI 3 − and the ability of iodide ions to bridge up to five cations allows the formation of rings, chains, columnar, layer and 3D net structures, which are all due to I⋯I interactions. Comparison of several structures involving the same cation confirms, that I 3 − is a much weaker donor than I − , and indicates, that in solid compounds bridging I − anions ‘spread’ their donor ability over several iodophosphonium acceptors; i.e. the individual cation is less affected. This allows to understand, why compounds RPI 4 (R=Me, i -Pr, t -Bu) are stable as solids, but dissociate in inert solvents into RPI 2 and molecular iodine.

Novel Mesityltellurium Cations from Selenenation and Tellurenation Reactions of Dimesityl Telluride in the Presence of the Br2/AgSbF6 Reagent

The reaction of dimesityl telluride (2) with bis(pentafluorophenyl) diselenide (1), Br2 and AgSbF6 provides small amounts of crystalline [Mes2TeSeC6F5][SbF6] (3). The main products, however, are [Mes2TeTeMes][SbF6] (4) and MesSeC6F5 (5). Reactions of 2 with Br2 and AgSbF6 provide − depending on the stoichiometric ratio − 4 and [Mes3Te][SbF6] (6) or [Mes2TeBr][SbF6] (7). 2, Mes2Te2, Br2 and AgSbF6 provide 4 in a fair yield. Addition of 2 to 4 leads to the tritellurium salt [Mes5Te3][SbF6] (8). Cation−anion interactions due to the α-heteroatom electrophilicity of RSe-, RTe- and Br-substituted telluronium salts are followed by structure determinations of 3, 4, 6, 7 and 8 and by Raman-spectroscopic observations of the Te−Te vibrations in compounds 4 and 8.

DIMERE DIALKYLPHOSPHANYLGERMYLENE : YLIDISCHE DIPHOSPHADIGERMETANE

Wahrend der Dichlorgermylen-Triphenylphosphan-Komplex (1) mit Di-t-butyl(trimethylsilyl)phosphan (2 a) stets nur im Mengenverhaltnis 1 : 1 reagiert, wobei unter Abspaltung von Chlortrimethylsilan und Triphenylphosphan Chloro(di-t-butylphosphanyl)germylen (3 a) entsteht, reagiert 1 mit zwei Aquivalenten an Diisopropyl(trimethylsilyl)phosphan (2 b) glatt zu der neuen Verbindung Bis(diisopropylphosphanyl)germylen (5 b), die als gelbe Kristalle isoliert wird. Kernresonanzspektren und Strukturbestimmungen belegen, das die Phosphanylgermylene 3 a und 5 b in Losung und in festem Zustand aufgrund verbruckender Phosphanylgruppen als ylidische Diphosphadigermetane vorliegen; terminale Chloratome (in 3 a) und Phosphanylgruppen (in 5 b) sind zueinander trans-orientiert. Dimeric Dialkylphosphanylgermylenes: Ylidic Diphosphadigermetanes The dichlorogermylene triphenylphosphane complex (1) reacts with di-t-butyl(trimethylsilyl)phosphane (2 a) only in a 1 : 1 stoichiometry providing dimeric chloro(di-t-butylphosphanyl)germylene (3 a); with two equivalents of diisopropyl(trimethylsilyl)phosphane (2 b), however, 1 (or the dichlorogermylene dioxane complex) provide straightforwardly dimeric bis(diisopropylphosphanyl)germylene (5 b) as yellow crystals. The trans-dimeric structures of 3 a and 5 b are confirmed by spectroscopic data and by X-ray diffraction. Dialkylphosphanylgermylenes 3 a and 5 b are ylide-type diphosphadigermetanes in solution and in the solid state.

Trichlorosilylation of chlorogermanes and chlorostannanes with HSiCl3/Net3 followed by base-catalysed formation of (Me3Ge)2Si(SiCl3)2 and related branched stannylsilanes

Abstract Chlorotrimethylgermane 1 and dichlorodimethylgermane 4 react with trichlorosilane and triethylamine to provide trichlorosilylgermanes Me4−nGe(SiCl3)n (n=1: 2; n=2: 5) in fair yields, as distillable liquids. The formation of 2 is followed by base-catalysed decomposition reactions leading to novel solid (Me3Ge)2Si(SiCl3)2 3. Chlorotrialkylstannanes 6a–c (6a: R=CH3, 6b: R=C2H5, 6c: R=n-C4H9) react with trichlorosilane and triethylamine providing the branched silylstannanes (R3Sn)2Si(SiCl3)2 7a–c and traces of silylstannanes R3SnSiCl3 8a–c. Only 7a was isolated in a pure state. Heating 7a or crude 7b and 7c with benzyl chloride leads to the formation of benzyltrichlorosilane (10). The constitution of compounds 2, 3, 5 and 7a was confirmed by MS, NMR and analytical data. The structures of C6D6-solvated 3 and C6H6-solvated 7a were determined by X-ray diffraction, and shown to be isotypic.

Syntheses, Structures, and Reactions of C-Methoxycarbonyl-Functionalized Small- and Medium-Sized P-Heterocycle Complexes

Thermal ring-opening of [{2-bis(trimethylsilyl)methyl-3- phenyl-2H-azaphosphirene-ĸP}pentacarbonyltungsten(0)] (8a) in the presence of dimethyl acetylenedicarboxylate (DMAD) led to the 2,3-bifunctionalized 1H-phosphirene complex 9a and the 4-phenyl-substituted 2H-1,2-azaphosphole complex 10a, the latter as a by-product. If a small amount of benzonitrile was added, complex 10a was obtained as the main product, along with a small amount of the decomplexed 2H-1,2-azaphosphole 11, which could not be isolated. Reaction of complex 10a with elemental sulfur furnished the corresponding PV sulfide 13. When the ring-opening of complex 8a was performed in the presence of two equivalents of DMAD and two equivalents of dimethyl cyanamide, we obtained the 4-dimethylamino-substituted 2H-1,2-azaphosphole complex 10b, together with the diastereomeric Δ3-1,3,2-oxazaphospholene complexes 14a,b. On reaction of [{2-pentamethylcyclopentadienyl-3-phenyl-2H-azaphosphirene-ĸP}pentacarbonyltungsten(0)] (8b) and DMAD in toluene, the corresponding 1H-phosphirene complex 9b was only formed as a transient species and the P-coordinated P,C-cage compound 15 was the final product. Using benzonitrile as solvent, the 4-phenyl-substituted 2H-1,2-azaphosphole complex 10c was obtained, together with the 7-aza-1-phosphanorbornadiene complex 16, the latter through partial decomposition of 10c coupled with rearrangement and a Diels–Alder reaction; the ratio 10c/16 was found to depend strongly on the molar ratio of complex 8b to DMAD. A cycloaddition reaction of the 2,3-bifunctionalized 1H-phosphirene complex 9a with 2,3-dimethylbutadiene furnished the bicyclic phosphirane complex 19, along with a small amount of the noncoordinated bicyclic phosphirane 20. Reaction of complex 9a with diethylamine yielded the phosphirane complex 21 as a 1,2-addition product, the diorganophosphane complex 22 through ring-opening of 9a, and the 3,4-functionalized 1,2-dihydro-1-phosphet-2-one complex 23 through an unprecedented ring-expansion reaction; the products 21, 22, 23 were formed in a ratio of ca. 1:1:1. The structures of the 1H-phosphirene complex 9a, the 4-dimethylamino-substituted 2H-1,2-azaphosphole complex 10b, the bicyclic phosphirane complex 19, the phosphirane complex 21, and the 1,2-dihydro-1-phosphet-2-one complex 23 have been determined by single-crystal X-ray diffraction analysis.

Synthese und Strukturen von N-Bis(diisopropylamino) phosphanyl-substituierten Aminocarbenkomplexen der Metalle Chrom, Molybdän und Wolfram

Abstract Aminocarbene complex anions [(CO)5MC(NH)R]− (M = Cr, Mo, W; R = Me, Ph) (1a–f), generated in situ by reaction of their conjugate acids with n-BuLi or MeLi, react with bis(diisopropylamino)chlorophosphane (2) to give lithium chloride and N-phosphanylsubstituted metal—carbene complexes [(CO)5M C(N(H)PR′2)R] (R′ = N′Pr2; R = Me, Ph) (3a–f), the first derivatives of this class of compounds. X-ray structure analysis of the chromium derivatives (3a: R = Me; 3d: R = Ph) and of the molybdenum complex (3b: R = Me) reveal M C(R) N units with structural data typical of both aminocarbene and iminiumacylmetallate complexes.

Coordination and oxidation of phosphine selenides with iodine: from cation pairs [(R3PSe)2I+]2 to (iodoseleno)phosphonium ions [R3PSeI]+ existing as guests in polyiodide matrices

An X-ray crystallographic study of adducts of trialkylphosphine selenides with >1 equivalent of diiodine reveals that solid But3PSeI3 consists of cation pairs [(But3PSe)2I+]2 intercalated between I5– layers and that solid R2R′PSeI7 (R = But or Pri, R′ = Pri) contains [R2R′P–Se–I]+ cations with weak secondary I‥I interactions to polyiodide networks.

Syntheses of 3-Heteroaryl-2H-Azaphosphirene Tungsten Complexes

The syntheses of 3-heteroaryl-substituted 2H-azaphosphirene pentacarbonyltungsten complexes are reported. The products were characterized by multinuclear NMR spectroscopy (1H, 13C, 15N, 31P, 183W); the structure of the 3-N-methylpyrryl-substituted 2H-azaphosphirene complex was determined by single-crystal X-ray structure analysis.

Catalytic and selective ring expansion reactions of o-phenyl-substituted 2H-azaphosphirene tungsten complexes

Abstract ortho -Phenyl-substituted ethoxy- and aminocarbene pentacarbonyltungsten complexes 2a – c and 3a – c are synthesized and the latter are reacted with chloromethylenephosphane 4 in diethyl ether in the presence of triethylamine to yield the ortho -phenyl-substituted 2 H -azaphosphirene complexes 6a – c via elimination of triethylammonium chloride; remarkable are the prolonged reaction times in the case of the methoxy- and dimethylamino-substituted complexes 6b , c . The 2 H -azaphosphirene complexes 6a – c and 7d are reacted with benzonitrile in dichloromethane in the presence of ferrocenium hexafluorophosphate to furnish the 2 H -1,2,4-diazaphosphole complexes 8a – d ( 8a : R=Me, 8b : R=OMe, 8c : R=NMe 2 , 8d : R=H); the reaction course will be discussed. All complexes were unambiguously confirmed by NMR spectroscopy and elemental analysis and, additionally complexes 2b , 5 and 6b by X-ray analysis.