George A. Fisher

The Structures of the Group 15 Element(III) Halides and Halogenoanions

Publisher Summary This chapter deals with the solid-state structures of the element(III) halides and halogenoanions of arsenic, antimony, and bismuth. The element halogenoanions are a structurally diverse group of compounds and are considered in the chapter according to common structural types. The simplest species results from formal addition of one halide anion to one EX, molecule to give the [EX4]− anion. Such species usually dimerize or polymerize, but a significant example of a discrete mononuclear species is found in the structure of [Et4N][PCl4]. The most commonly encountered form of the [EX4]− unit is as a one-dimensional polymer, which may be represented as [{EX4}n]n−, in which the coordination about the group 15 element has increased to six and the geometry is approximately octahedral. There are a number of compounds that contain discrete anions of the formula [E3X12]3−and these are found in two distinct forms. One type is described as linear and a second type of [E3X12]3−structure is found in the complexes [Et3-NH]3[As3Br12]and [Me3NH]3[As3I12].

Dibismuth as a four-electron donor ligand. Synthesis and molecular and electronic structure of [M2(CO)4(η-C5H4Me)2(µ-η2-Bi2)](M = Mo or W)

The compounds [M2(CO)4(η-C5H4R)2(µ-η2-Bi2)](M = Mo or W, R = H or Me) have been prepared by the solid-state thermolysis or solution-state photolysis of [Bi{M(CO)3(η-C5H4R)}3]. The structures of the methylcyclopentadienyl derivatives were determined by X-ray crystallography and show a M2(CO)4(η-C5H4Me)2 unit in which the M–M vector is transversely bridged by a Bi2 ligand so as to give a tetrahedral M2Bi2 core. The Bi2 ligand acts as a four-electron donor. The electronic structure of [Mo2(CO)4(η-C5H5)2(µ-η2-Bi2)] has been examined by extended-Huckel molecular orbital calculations and compared with the related diphosphorus complex [Mo2(CO)4(η-C5H5)2(µ-η2-P2)]. Substantial differences are found in the nature of those frontier orbitals which are localised primarily on the P2 and Bi2 units. These are consistent with the observed differences in the chemistry of P2vs. Bi2 ligands in general. The chromium complexes [BiCl{Cr(CO)3(η-C5H5)}2] and [Bi{Cr(CO)3(η-C5H5)}3] are also described.

Anionic, four-coordinate, 10-electron bismuth complexes

The synthesis and structures of [PPN][BiCl 2 {Fe(CO) 2 (η-C 5 H 5 )} 2 ] and [PPN][BiCl 2 {MO(CO) 3 (η-C 5 H 5 )} 2 ] (PPN  Ph 3 PNPPh 3 ) are described; both bismuth complexes adopt structures intermediate between tetrahedral and equatorially vacant trigonal bipyramidal, possible electronic reasons for which are presented and discussed.

Alkyl and aryl dimetalla-bismuthine complexes

The reaction between [BiCl{Mo(CO)3(η-C5H5)}2, 5 and one equivalent of K[BHEt3] affords, as one of the products, the bismuth ethyl complex [BiEt{Mo(CO)3(η-C5H5)}2], 7, which has been characterised by X-ray crsytallography. Aspects of the possible mechanism of this reaction are discussed. The phenyl bismuthine complexes [BiPh{Mo(CO)3(η-C5H5)}2], 8, and [BiPh{Co(CO)3(PPh3)}2], 9, have also been synthesised from the reaction between PhBiBr2 and two equivalents of Na[Mo(CO)3(η-C5H5)] and K[Co(CO)3(PPh3)] respectively.

Structural studies on organotransition-metal-bismuth complexes

The X-ray single-crystal structures are reported for [BiX{M(CO)3(η-C5H5)}2](M = W, X = Cl 2; M = Mo, X = Br 3; M = Mo, X = I 4). Compounds 2 and 3 exhibit linear polymeric structures involving intermolecular Bi ⋯ X interactions and are isomorphous with the previously reported [BiCl{Mo(CO)3(η-C5H5)}2]1. In contrast, the iodide derivative 4 exists in the solid state as a weakly bound dimer. Analysis of Bi-LIII-edge and M-K-edge or LIII-edge extended X-ray absorption fine structure (EXAFS) spectra for [BiCl{M(CO)y(η-C5H5)}2](M = W or Mo; y= 3 2, 1: M = Fe; y= 2 5) and [Bi{M(CO)3(η-C5H5)}3](M = W 6 or Mo 7) in solid (1, 2, 5, 7) and solution (1, 5) phases also shows evidence for oligo- or poly-merisation through Bi ⋯ Cl interactions in solid 1, 2 and 5. In tetrahydrofuran (thf) solutions of 1 and 5 these interactions are disrupted, and the monomeric species formed show co-ordination of solvent to bismuth. The BiM3 species 6 and 7 show metal–metal distances consistent with a pyramidal geometry at bismuth. EXAFS data for BiCl38 in the solid and in thf solution showed only indirect evidence for disruption of the weaker Bi ⋯ Cl contacts present in the solid on solvation.

Synthetic and structural studies on organotransition metal–bismuth nitrates

The reaction between Bi(NO3)3·5H2O and 2 equivalents of K[Fe(CO)2(η-C5H5)] affords the iron–bismuth complex [Bi(NO3){Fe(CO)2(η-C5H5)}2]1 which was characterised by X-ray crystallography. Complex 1 comprises a bismuth atom in a trigonal-pyramidal co-ordination geometry bonded to two Fe(CO)2(η-C5H5) fragments and the oxygen atom of a monodentate nitrate group. In addition there is a longer secondary intermolecular contact between the bismuth and a nitrate oxygen of an adjacent molecule which is approximately trans to the primary Bi–O bond. The complexes [Bi(NO3)(MLn)2][MLn= Fe(CO)2(η-C5H4Me)2, Ru(CO)2(η-C5H5)3, Mo(CO)3(η-C5H5)6, Mo(CO)3(η-C5H4Me)7, W(CO)3(η-C5H5)8, W(CO)3(η-C5H4Me)9 or Cr(CO)3(η-C5H5)10] have also been prepared and characterised by spectroscopic and analytical methods. Data are also presented on the synthesis and characterisation of the ruthenium complexes [Bi{Ru(CO)2(η-C5H5)}3]4 and [BiCl{Ru(CO)2(η-C5H5)}2]5 and on the reactions between bismuth nitrate and 2 equivalents of K[Mn(CO)5] or K[Co(CO)3(PR3)](R = Ph or OPh).

Structure of BiBr2Ph: a solid-state architecture involving secondary bonding and π-π interactions

The X-ray crystal structure of the compound BiBr2Ph comprises one-dimensional chains in which the bismuth centres are linked through bromine bridges: these chains form a two-dimensional layer as a result of π-π interactions between interleaved phenyl groups in adjacent chains. All atoms lie in special positions, on mirror planes or two-fold rotation axes.

Structural studies on phenyl bismuth halides and halogenoanions

Structural studies by X-ray crystallography have been carried out for a range of phenyl bismuth halides and halogenoanions. The complexes [BiPhBr2(thf)]1 and [BiPhI2(thf)]2(thf = tetrahydrofuran) form one-dimensional polymeric chains with a single asymmetrically-bridging halide between each pair of adjacent bismuth atoms. The co-ordination geometry around the bismuth centre is that of a square-based pyramid with the phenyl group in the apical position and two cis halides, a bridging halide from an adjacent monomer unit and a thf ligand in the basal plane. Addition of [NEt4]I to 2 affords the ionic species [NEt4]2[Bi2Ph2I6]·Et2O 3 which contains the discrete dimeric [Bi2Ph2I6]2– anion. This anion comprises two edge-shared square-based pyramids with an angle of 105.2° between the basal planes. As with 1 and 2, the phenyl group occupies the apical site with the basal sites around each bismuth occupied by two terminal and two bridging iodides. The complex [BiPh2Br(thf)]5 is monomeric and has an equatorially vacant trigonal-bipyramidal co-ordination geometry around the bismuth centre in which the phenyl groups occupy the equatorial sites and the bromine and thf ligand the axial sites. The structure of [PPh4][BiPh2Br2]6 contains monomeric [BiPh2Br2]– anions with a geometry similar to that found in 5. Comparisons are made, where appropriate, with related tellurium(IV) compounds, and the nature of the bonding in the complexes is discussed particularly with regard to the details of the secondary, intermolecular bonds observed in the structures of 1–3.

Structural studies on phenyl bismuth halides and halogenoanions. Part 2. X-Ray crystal structures of [BiPhCl2(thf)](thf = tetrahydrofuran), [NBun4]2[Bi2Ph2Br6] and [NEt4][BiPh2I2]

Structural studies by X-ray crystallography have been carried out on the complexes [BiPhCl2(thf)]1(thf = tetrahydrofuran), [NBu4n]2[Bi2Ph2Br6]4 and [NEt4][BiPh2I2]6. Complex 1 comprises a chloridebridged polymeric chain with each bismuth centre in a square-based pyramidal co-ordination environment. A phenyl group occupies the apical site whilst the four basal positions are occupied by three chlorine atoms, one terminal and two bridging, and the oxygen of a co-ordinated thf molecule. The chloride bridges are quite asymmetric and a comparison is made with the increasing trend towards symmetric bridges found in the previously characterised bromide and iodide derivatives. The structure of the anionic part of 4 comprises a centrosymmetric [Bi2Ph2Br6]2– dianion with a planar Bi2Br6 unit and trans phenyl groups with each bismuth centre also adopting a square-based pyramidal co-ordination geometry with apical phenyls. Comparisons are made with similar bismuth, antimony and tellurium complexes and the differences discussed. The structure of the anion of 6 can be described as disphenoidal or equatorially vacant, trigonal bipyramidal with axial iodides and equatorial phenyls. This is similar to the previously known bromide complex except that 6 exists in the solid state as a weakly bound centrosymmetric dimer. All of the above structures are compared with those of related compounds and the various trends which are apparent are discussed.

Synthetic and structural studies on bismuth(III) thiocyanate and selenocyanate complexes

The reaction between either BiCl3 or Bi(NO3)3·5H2O and 3 equivalents of KSCN afforded a yellow material which has not been fully characterised but which reacts as a source of Bi(SCN)3A. Compound A and 2 equivalents of K[Mo(CO)3(η-C5H5)] afforded the green complex [Bi(SCN){Mo(CO)3(η-C5H5)}2] which has been characterised by X-ray crystallography and consists of trigonal-pyramidal bismuth centres co-ordinated to one SCN group through sulfur, and two Mo(CO)3(η-C5H5) fragments with additional intermolecular Bi ⋯ NCS interactions resulting in a one-dimensional polymer. The reaction between A and [K(18-crown-6)]SCN (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane) afforded an orange and a yellow crystalline material both of which have been characterised by X-ray crystallography and shown to be isomers. In the orange compound a potassium cation is located between two potassium cations co-ordinated by 18-crown-6 ligands and an octahedral [Bi(SCN)6]3– anion is present. These ions are organised into two-dimensional sheets in which each [Bi(SCN)6]3– anion is surrounded by four K[K(18-crown-6)]2 units and vice versa. In the yellow compound the structure has the same basic cationic and anionic units but the thiocyanatobismuth anion has four S-bonded and two trans N-bonded thiocyanate ligands with the anions arranged in parallel columns separated (within columns) by potassium cations. The remaining two potassium cations are co-ordinated by 18-crown-6 ether ligands and are positioned between the columns. The reaction between BiCl3 and 3 equivalents of KSeCN afforded dark red crystals of a complex formulated as Bi(SeCN)3. The reaction between Bi(SeCN)3 and 2 equivalents of [Bi{Mo(CO)3(η-C5H5)}3] afforded [Bi(SeCN){Mo(CO)3(η-C5H5)}2]. The reaction of [N(PPh3)2][BiCl4] and 4 equivalents of KSeCN afforded a dark red crystalline compound K[N(PPh3)2]2[Bi(SeCN)6] the structure of which was also established by X-ray crystallography and comprises isolated [N(PPh3)2]+ cations and columns of [Bi(SeCN)6]3– anions separated by potassium cations in a similar manner to that found in yellow K[K(18-crown-6)]2[Bi(SCN)4(NCS)2].