Wolf-W. du Mont

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.

Iodophosphane Selenides: Building Blocks for Supramolecular Soft–Soft Chain, Helix, and Base‐Pair Arrays

A novel type of P=Se⋅⋅⋅I−P bridging is found in the solid-state structures of iodophosphane selenides. These molecules can be viewed as new building blocks for the design of directed donor–acceptor interactions (see diagram) within chains, helices and “soft–soft” base pairs.

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.

Telluration and de-telluration: New ways for the cleavage and formation of P-P bonds

Abstract Phosphanes react with tellurium much more selectively than with oxygen, sulfur and selenium. Tertiary phosphanes give “phosphane tellurides” that can equivalently be described as coordination compounds of the phosphanes with Te(O); these are kinetically labile to (phosphane) ligand substitution reactions in the nmr time scale.1

Soft–Soft Interactions of Iodide and Triiodide Ions with Triphenyltelluronium Cations

The crystal structures of triphenyltelluronium iodide and of triphenyltelluronium triiodide were solved by X-ray diffraction. Triphenyltelluronium iodide consists of ladder-like tetrameric units involving dicoordinated iodine atoms, bridging penta- and hexacoordinated tellurium atoms, and tri-coordinated central iodines that bridge one pentacoordinated and two hexacoordinated tellurium atoms. Triphenyltelluronium triiodide is made up of extended chains that are generated by pairwise interaction of Ph3Te-I3 units through weak Te···I contacts involving one terminal atom from each triiodide ion, and by connection of these four-membered units through both terminal atoms of the triiodide ions. This asymmetric contribution of the two terminal iodine atoms of the triiodide ion to the soft–soft network correlates with a significant difference of the two I‒I bond lengths (2.847 and 2.984 A).

Diastereoselective Reactions of Sulfur- and Selenium-Bridged Bisphosphaalkenes with Tetrachloro-o-benzoquinone

2,4-Diphospha-3-thia- and 3-selenapentadienes [(Me 3 Si) 2 C = P] 2 E ( 1a : E = S; 1b : Se) react as bifunctional phosphaalkenes with two equivalents of cyclopentadiene and of tetrachloro-o-benzoquinone (TOB), furnishing 2a and 2b from double [2+4] cycloaddition reactions of the diene and 3a and 3b from the reactions of TOB with the P = C double bonds. The phosphanorbornane-related chalcogenophosphinous anhydrides 2a and 2b are obtained as pairs of isomers, whereas the reactions with TOB proceed diastereoselectively. X-ray crystallographic data confirm that bis-dioxaphospholene-related 3b consists of a mixture of (RR) and (SS) enantiomers. A third equivalent of TOB can be added oxidatively to one phosphorus atom of 3a and 3b , furnishing the spirocyclic compounds 6a and 6b with P(σ < eqid1 > λ < eqid2 > 5 < eqid3 > 5 ) connectivity. 3a and 6a are configurationally stable at room temperature, whereas the selenium derivatives 3b and 6b undergo slow isomerisation in solution.

Metastable P-Tellurium-Substituted Phosphaalkenes: Formation, 125Te- and 31P-NMR Spectroscopic Characterization, and Decomposition

Abstract The formation and decomposition of P-tellurium-substituted phosphaalkenes was followed by 31P- and 125Te-NMR spectroscopy. Acyclic compounds with C˭P-Te moieties are in general thermally labile, but bulky substituents enhance the lifetime of a number of species. The P-chlorophosphaalkene (Me3Si)2C˭PCl (1a) reacts with the disilyltelluride (iPrMe2Si)2Te (2) leading to the mixed-substituted telluride (Me3Si)2C˭PTeSiMe2iPr 3a which reacts with another equivalent of 1a furnishing the tellurobis(phosphaalkene) [(Me3Si)2C˭P]2Te (4a). 4a is a shortlived compound decomposing thermally with precipitation of elemental tellurium, leading to a known diphosphabicyclobutane 5a. In a similar way, the bulkier P-chlorophosphaalkene (iPrMe2Si)2C˭PCl (1b) reacts with (iPrMe3Si)2Te furnishing [(iPrMe2Si)2C˭P]2Te (4b), which loses tellurium much more slowly than 4a and can be kept in cold solutions for an extended time. Reactions of in situ-prepared lithium aryltellurolates LiTeAr 6 – 9 [Ar˭Ph: 6, Ar˭2,4,6-Me3Ph (˭Mes): 7, Ar˭2,4,6-iPr3Ph (˭TIP): 8, Ar˭2,4,6-tBu3Ph (˭Mes*): 9] with 1a provide P-aryltellurophosphaalkenes 10 – 13, which decompose with the loss of diarylditellurides leading to 5a. After a 2 + 4 cycloaddition trapping experiment of 12 with cyclopentadiene, a metastable P-aryltelluro phosphanorbornene 14 was detected by 31P-NMR. Reactions of elemental tellurium with P-phosphanylphosphaalkenes (Me3Si)2C˭PPR′R′;′ 15 – 17 (R′, R′′˭iPr: 15; R′˭iPr, R′′˭tBu: 16; R′, R′′˭tBu: 17) lead to metastable insertion products (Me3Si)2C˭PTePR′R′′ 18 – 20 that decompose with formation of the tellurobisphosphanes (R′R′′P)2Te 21 – 23, and of the bicyclic diphosphane 5a, which isomerises thermally to the diphosphabicyclooctane 24. The P-di-i-propylphosphanyl-phosphanorbornene 25 dismutates under the action of tellurium into the symmetric diphosphanes iPr4P2 and bis-phosphanorbornene 26. The tellurium-free products 24 and 26 were characterized by X-ray crystallography. GRAPHICAL ABSTRACT

The first trialkylphosphane telluride complexes of Ag(I): molecular, ionic and supramolecular structural alternatives

The structures of the first phosphane telluride complexes of silver(I), obtained from i-Pr3PTe (1) with AgNMs2 [Ms = SO2CH3] and with AgSbF6, reveal the superior coordinating ability of 1, particularly as a bridging ligand, compared with related i-Pr3PS and i-Pr3PSe ligands.

Insertion and 2+2 Dismutation Reactions Including P-P, Te-Te and Se-Se Bonds

Abstract Reactions of diphosphanes and cyclophosphanes with selenium, tellurium and organic ditellurides have been studied.

P-functional phosphaalkenes with C-isopropyldimethylsilyl groups, and a sterically stabilized P-cyano phosphaalkene

GRAPHICAL ABSTRACT ABSTRACT The dehydrochlorination of the dichlorophosphane (iPrMe2Si)2C(H)PCl2 (2) with 1,4-diazabicyclo[2.2.2]octane (DBO) provides the P-chlorophosphaalkene (iPrMe2Si)2C=PCl (3). Halide exchange reactions of 3 with AgBF4, with Me3SiBr, and with Me3SiI lead to the P-halogenophosphaalkenes (iPrMe2Si)2C=PX (X = F: 4; X = Br: 5; X = I: 6). From the reaction of 3 with AgCN, the sterically stabilized P-cyanophosphaalkene (iPrMe2Si)2C=P-CN (7) was isolated. The structures of the related P-fluorenylphosphaalkene 9 (from 3 with fluorenyllithium) and of the P-selenophosphaalkenes (iPrMe2Si)2C = PSe(2,4,6-tBu3C6H2) (10) and [(iPrMe2Si)2C=P]2Se (11) were determined by X-ray crystallography.