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The magnitude of the stability constants (K) for the formation of X3– from X– and X2 (X = Cl, Br, I) in aqueous and nonaqueous solution depends strongly on both X and solvent. Thermodynamic arguments establish that for aqueous solutions this is not the result of differing bond strengths in the X3– anion but rather depends on the solvation energies of the relevant anions and halogens. The experimental results for K in different organic solvents can also be rationalized in terms which emphasise solvation effects. Electrospray ionization mass spectrometry (ESI-MS) has been used to qualitatively probe relative bond strengths in the absence of solvent.Key words: trihalides, stability constants, solvation, electrospray ionization, mass spectrometry.

The reactions of indium monohalides, InX with haloforms, CHX3, in 1,4-dioxane (diox), produce the dioxane adducts of dihalogeno–dihalogenomethyl–indium(III), X2In(diox)nCHX2 (X = Cl, Br, n = 1; X = I, n = 2) compounds. The ionic derivative [(C2H5)4N] [Cl3InCHCl2] was prepared and its crystal structure determined by X-ray means. The reactions of the X2In(diox)nCHX2 compounds are significantly different from those of the related X2InCH2X compounds. The dihalogenomethyl derivatives react with strong electrophiles suggesting dihalogenomethyl substituents of mild nucleophilic character, while the carbon atoms in the halogenomethyl derivatives are electrophilic.

Complexes of lead(II) of the type Pb(O 2 R) where R is a substituted aromatic group, can be prepared by the direct electrochemical oxidation of a lead anode in a non-aqueous solution of the appropriate substituted catechol, R(OH) 2 . The products, which are colourless, air-stable, insoluble materials, and presumably cross-linked in the solid state, can be oxidised to the corresponding lead(IV) derivatives by iodine or tetrahalogeno- o -quinones. The direct reaction of elemental lead with an o -quinone in refluxing hexane or toluene yielded identifiable products in only two cases; with 2,5- tert -butyl-1,2-benzoquinone, the corresponding lead(II) catecholate was obtained, while with phenanthrenequinone the semiquinonate Pb(PSQ ) 2 was isolated. These latter reactions are shown by electron spin resonance spectroscopy to proceed via free radical intermediates, and the spectra are analysed to give information on the species present in the reaction media.

Solutions of I2 + X− (X = Cl, Br, I. NCS) in both water and acetonitrile have been studied by electrospray mass spectrometry in order to identify the anions present. For I2/I−, there is no evidence of the I5− anion proposed earlier to explain deviations from ideality in the formation of I3− in aqueous solution; rather, the equilibrium I3− + I− ⇌ I42− is shown to be compatible with the mass spectrometric results, and with the earlier literature. With Cl−, Br− and NCS−, both classes of solution contain members of the series X3− ⇌ X2I− ⇌ XI2− ⇌ I3−; this is ascribed to rapid redistribution processes rather than to the redox and/or photochemical reactions suggested by earlier workers. There is little qualitative difference between aqueous and acetonitrile solutions, except that aqueous I2/Cl− systems contain the ICl4− anion, whose decomposition in the gas phase produces the previously unknown ICl3˙− radical anion. No I2X− adducts were identified when X = OH−, NCO−, N3− or NO2−.

Laser desorption/ionisation mass spectrometry of the elements sulfur, selenium, tellurium and phosphorus has shown a range of polynuclear ions in both positive and negative ion modes. Three-dimensional topographical surfaces are used to display changes in the speciation of sulfur ions with increasing laser power under laser desorption/ionisation conditions, using a technique described as energy-dependent laser desorption/ionisation mass spectrometry; the positive and negative ion spectra of sulfur are both dominated by singly-charged ions, with S5 and S3 showing particular intensity. Similar results are also reported for the other title elements. # 2002 Elsevier Science B.V. All rights reserved.

The bis-1,4-dioxane (diox) adduct of bromomethyl-dibromo-indium(III), Br 2 In(diox) 2 CH 2 Br, reacts with triphenylphosphine oxide, triphenylphosphine sulfide and benzyl sulfide to produce the compounds Br 2 In[OP(C 6 H 5 ) 3 ] 2 CH 2 Br and Br 3 InCH 2 L (L=benzyl sulfide, triphenylphosphine sulfide). The crystal structures of these new organoindium compounds have been solved by X-ray diffraction methods. The structural results are compared with those for related organoindium compounds. Quantum mechanical calculations, by the PM3 method, satisfactorily predict the measured bond distances and angles in all compounds, and hence furnish reliable net atomic charge maps, which demonstrate the presence of a sulfur ylid ligand, H 2 C δ−  δ+ S(CH 2 C 6 H 5 ) 2 , and a triphenylphosphonium-sulfur methylide ligand, δ− CH 2 S δ+ P(C 6 H 5 ) 3 , in the Br 3 InCH 2 L compounds. Mass spectra and thermal decomposition studies establish that Br 3 InCH 2 S(CH 2 C 6 H 5 ) 2 decomposes via an intramolecular nucleophilic attack of a bromide ligand, either to the InCH 2 carbon atom to produce benzyl sulfide, or to the C 6 H 5 CH 2 carbon to yield benzyl bromide and benzyl-methyl-sulfide.

The 27Al and 71Ga NMR spectra of mixtures of M2X6 and M2Y6 (M = Al, Ga; X ≠ Y = Cl, Br or I) in benzene are reported. All these systems show rapid inter-halogen exchange, and in some cases stable intermediates M2XnY6 − n can be characterised spectroscopically. In particular, the results are used to identify the predominant species present in solutions prepared by mixing (i) Al2Br6 and Ga2Cl6, and (ii) Al2I6 and Ga2Br6, in benzene in various mole ratios. The expected M2X3Y3 intermediates are found for M = Al or Ga, X ≠ Y = Cl, Br, but with other mixed halide systems, unsymmetric structures predominate, and possible reasons for this are discussed. The experimental results are in agreement with thermodynamic predictions, and with arguments based on maximizing the M–X, Y electronegativity differences.

Germanium powder reacts slowly with 3,5-di-tert-butyl-1,2-benzoquinone (dbbq) in refluxing toluene to give products whose composition depends on the initial mole ratio of the reactants. When Ge ∶ dbbsq = 1 ∶ 2, the solid product is a monoradical + diradical species, but in non-aqueous solvents this converts to a diamagnetic oligomer. Treatment with 2,2′-bipyridine, or monodentate nitrogen donors (= L) gives diamagnetic germanium(IV) derivatives Ge(dbc)2L2 (dbc2− = 3,5-di-tert-butylcatecholate dianion). When the initial Ge ∶ dbbq mole ratio = 1 ∶ 3, the product is the diradical Ge(dbbsq˙)2(dbc). The reaction of Ge and 4 dbbq, or the treatment of GeX4 (X = Cl, Br) with 4 moles of Na(dbbsq˙), gives a product identified as Ge(dbbsq˙)2(dbc)(dbbq), but the structure of this compound is unclear. The solid state and solution properties of these unusual compounds are discussed in the light of 1H NMR and electron spin resonance (ESR) spectroscopy.

The reaction of InBr with CH2Br2 in 1,4-dioxane or acetonitrile yields the corresponding solvate of Br2InCH2Br, which on reaction with E(C6H5)3 (E=P, As, Sb) gives the indium(III)-Group 15 dimetallo-methane derivatives, Br3InCH2E(C6H5)3. The crystal structures of the two related compounds (E=As, Sb) have been determined by X-ray crystallography. For Br3InCH2As(C6H5)3, cell constants a=15.553(7), b=21.646(8), c=12.920 (10) A; space group Pbca, Z=8, R=0.064, Rw=0.054, and for Br3InCH2Sb(C6H5)3, a=15.439(6) A, b=22.016(4) c=13.138(5) A; space group Pbca, Z=8, R=0.062, Rw=0.049. Results are also reported for I3InCH2As(C6H5)3 (cell constants a=12.0122(2), b=15.8526(3), c=13.4180(3) A, β=109.933(1)°; space group P21/n, Z=4, R=0.0481, Rw=0.0431) and Br3InCH2N(C2H5)3 (a=7.362(2), b=14.700(2), c=13.049(1) A, β=98.90(1)°; space group P21/n, Z=4, R=0.0418, Rw=0.0368). The structural results are compared with those for other organoindium ylids with the same general structure Br3InCH2L (L=P(C6H5)3; 1,1,3,3,-tetramethyl-2-thiourea; N,N,N′,N′-tetramethylethanediamine). Semi-empirical quantum mechanical calculations, using the PM3 method, were carried out on the series Br3InCH2E(C6H5)3 (E=P, As, Sb), and the calculated structural parameters are compared with the values determined by X-ray crystallography. The presence of an ylid ligand H2Cδ−δ+E(C6H5)3 in the organoindium compounds is confirmed. Mass spectra and thermogravimetric analysis strongly suggest that the thermal decomposition of the compounds occurs via fission of the indiumcarbon bond, leading to the corresponding ylid, which can be trapped by reacting the X3InCH2E(C6H5)3 compounds with HBr to produce the onium derivative [CH3E(C6H5)3]+ [InX4]− (E=P, As; X=Br, I).

Solutions prepared by equibrating solid AlCl3 and benzene have been studied by 27Al NMR spectroscopy. Evidence of hydrolysis of AlCl3 is found, both under nominally anhydrous conditions and in the presence of added H2O. Results are also reported for systems containing added gaseous HCl. The deconvoluted spectra show signals from rapidly exchanging ionic species, identified as H[AlCl4] and H[AlCl3(OH)], and a non-ionic species, formulated as [Cl2Al(OH)]2, and based on an Al2O2 core, is also postulated. This species is structurally related to compounds reported by others in preparative work carried out in nominally anhydrous AlCl3 and benzene. The solution probably also contains Al2Cl6, identified as a very broad resonance whose chemical shift is estimated at approximately 98 ppm, relative to [Al(H2O)6]3+=0.

The interactions of gallium, indium and thallium with 3,5-di-tert-butyl-1,2-benzoquinone (TBQ) and its reduced derivatives TBSQ − (=3,5-di-tert-butyl-1,2-benzosemiquinonate anion) and TBCAT2− (=3,5-di-tert-butyl-catecholate) are discussed in terms of inter- and intramolecular electron transfer processes. The gallium(III) complex Ga( TBS Q )(TBCAT)(Bupy)2 (Bupy=3-n-butylpyridine), which is a rare example of a metal ion coordinated by both semiquinonate and catecholate ligands, has been characterized crystallographically; monoclinic, space group P21, a=10.3718(1), b=16.0047(1), c=14.8006(1) A, β=110.151(1)°, Z=2, Rw=0.069 for 5784 unique reflections. Electron spin resonance (ESR) spectroscopy shows that this substance undergoes intermolecular electron transfer in toluene. Gallium also forms Ga( TBS Q )I2, which is thermally unstable, releasing I2; the solid and solution properties of this, and related compounds, have been studied by ESR spectroscopy. In all the systems investigated, gallium is in the Ga(III) state. Attempts to prepare derivatives of In or Tl in this oxidation state were unsuccessful, and all products have the metal as M(I). For gallium, electron transfer is only detected as an inter-ligand process, while for indium and thallium, ligand↔metal transfer predominates.

The electrochemical oxidation of gallium in a cell containing a solution of 3,5-di-tert-butylcatechol (H2dbc) in a mixture of liquid ammonia and diethyl ether gives rise to the complex Ga(dbqdi)2, where dbqdi is a tridentate ligand formed by the condensation of two molecules of H2dbc and ammonia. The same paramagnetic molecule can be prepared by treating GaCl3 with H2dbc in ethanol with concentrated aqueous ammonia, with subsequent aerial oxidation. The crystal parameters are triclinic, space group P[Formula: see text], a = 11.6140(8), b = 12.3415(9), c = 20.765(1) Å, α = 89.491(1)°, β = 74.287(1)°, γ = 75.748(1)°, Z = 2, and R = 0.0542 for 7578 unique reflections. The structure, which is based on a GaO4N2 kernel, is discussed on the basis of crystallographic and ESR results.Key words: gallium, electrochemical synthesis, electron spin resonance, X-ray crystallography.

Adducts of aluminium(III) chloride with 9-fluorenone, xanthenone and dibenzosuberenone have been characterised spectroscopically and by single crystal X-ray crystallography. These coloured pseudo-tetrahedral species, which are diamagnetic in both solid and solution states, serve as models for 1∶1 adducts of AlCl3 with substituted p-quinones. These latter compounds undergo intramolecular one-electron transfer in non-aqueous solution, giving rise to paramagnetic species which have been characterised by electron spin resonance spectroscopy. The 1∶1 adducts of AlCl3 with o-quinones show similar behaviour, although the solution chemistry reflects the differences between mono- and bi-dentate ligands.

(Bromomethyl)dibromoindium(III), Br2InCH2Br, reacts with tetraethylammonium bromide, 1,4-dioxane (diox), or tetrahydrofuran (thf) to produce addition compounds of the general formula Br2In(L)nCH2Br...

The non-aqueous solution chemistry of GaAlCl4 has been investigated by 27Al and 71Ga NMR spectroscopy. In dilute solution in benzene, the solute species are of the form {[RnGa]+[ClxAlCl4–x]–}m (R = arene; x = 1–3, n, m undetermined), while in concentrated solutions the dominant interactions involve aggregates of ion pairs. Dilute solutions of the salt in n-heptane have also been studied, together with n-heptane–benzene mixtures, solutions of GaAlCl4 and Ga2Cl6 in n-heptane, solutions of GaAlBr4 and GaAlI4 in benzene, and mixed GaAlCl4–GaAlBr4 systems. The hydrolysis of GaAlCl4 in benzene is shown to involve reaction at both Ga and Al centres.

The primary process in the reaction of hexaphenylditin with various substituted orthoquinones (Q) is shown to involve attack by the quinone at a phenyl ligand. The intermediate thus formed decomposes to yield Ph3Sn(SQ·), where S(Q·−) is the corresponding semiquinonate. Rearrangement of these species in solution gives rise to biradicals, while intramolecular electron transfer may lead to the formation and precipitation of Ph2Sn(CAT), where CAT2− is the corresponding substituted catecholate. The identification of these processes depends in part on electron paramagnetic resonance spectroscopy. The reaction of Ph3SnCl or Ph2SnCl2 with Na(TBSQ·) (TBSQ·−=3,5-di-tert-butyl-orthobenzosemiquinonate) results in the formation of Ph2Sn(TBSQ·), which can undergo redistribution and intramolecular electron transfer, so that the solution chemistry of these latter systems is similar to that of the products of the Sn2Ph6+Q reaction.

The interactions of substituted ortho- and para-quinones with indium(III) halides and the InI4– anion have been studied in non-aqueous solution. para-Quinones and InI3 give rise to stable 1∶1 adducts, which are diamagnetic in the solid state, but which decompose in solution to form (p-sq)InI2 derivatives, where p-sq˙– is the corresponding semiquinonate. With ortho-quinones, the reaction products are (o-sq)InI2 which react with 4-methylpyridine (pic) to form (o-sq)InI2pic2. The electron spin resonance spectra of these products, and their solution chemistry, are discussed. The reactions involve intramolecular one-electron transfer, resulting in oxidation of the iodide ligand. In contrast, the reaction of 3,5-di-tert-butyl-1,2-benzoquinone with InI4– apparently involves intermolecular electron transfer; in this case, the products are I3– and the corresponding catecholate (dbc), isolated as the solid InI(dbc)pic2. The mechanisms of these various processes are discussed.

The reaction of phenyllithium with p-quinones (1,4-benzoquinone, 2,6-di-tert-butyl-1,4-benzoquinone, 1,4-naphthoquinone) in tetrahydrofuran gave the phenyl radical, which goes to biphenyl, and the corresponding lithium semiquinonate. The latter can also be obtained by direct reaction between lithium and the p-quinone. Electron spin resonance spectroscopy showed that a solution of the lithium derivative contains both monomeric and dimeric species. Adducts with 4-methylpyridine have also been prepared. Quantum-mechanical calculations were consistent with the ESR results. Related experiments with potassium derivatives were also performed.

Tris(tropolonato)samarium(III), SmT3, and tris(tropolonato)neodymium(III), NdT3, have been prepared in high yields by the electrochemical oxidation of samarium and neodymium metal anodes in acetonitrile solution of 2-hydroxy-2,4,6-cycloheptatrienone (tropolone, HT). The unusual divalent Ln(II) complexes are formed at the one step of the electrochemical reaction. The final products, Sm(C7H5O2)3 and Nd(C7H5O2)3, have been characterized by microanalyses and IR, Raman, 1H and 13C NMR spectral studies. Referee I: I. Murase Referee II: K. Sakata

The electrochemical oxidation of a sacrificial metal anode (M = Zn, Cd, Cu) in an acetonitrile solution of 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone, lapachol, C15H14O3 (=HL) gives ML2. The results are in keeping with earlier work on direct electrochemical synthesis in related systems. Adducts with 2,2′-bipyridine (bpy) and N,N,N′,N′-tetramethylethanediamine (tmen) have also been prepared. The structure of the 2,2′-bipyridine adduct of Cu(lapacholate)2 has been established by X-ray crystallography. The parameters are triclinic, space group [Formula: see text], a = 12.748(59) Å, b = 13.859(49) Å, c = 11.770(59) Å, α = 108.30(4)°, β = 108.08(3)°, γ = 68.94(3)°, Z = 2, R = 0.059 for 2256 unique reflections. The copper atom is in a distorted CuN2O2O2′ environment. The mechanism of the formation of this Cu(lapacholate)2 is discussed. Keywords: electrochemical synthesis, lapachol, X-ray crystallography, copper(II) complex.

The solid state structures of the compounds GaI3•PPh3 and Ga2I6•dppe ( dppe = 1,2-bis(diphenylphosphino)ethane ) have been determined. For the former, in which the GaI3P core has C3v symmetry, the structure is trigonal, with a = 14.961(2) Å, c = 16.509(3) Å, V = 3199.5(4) Å3, Z = 6, space group [Formula: see text]. In Ga2I6•dppe, the ligand bridges two GaI3P centres; the structure is monoclinic, a = 10.196(7) Å, b = 15.363(1) Å, c = 23.027(9) Å, β = 98.735(4)°, V = 3565.1(3.2) Å3Z = 4, space group P21/n The use of 31P NMR spectroscopy shows that GaI3•PPh3 is slightly dissociated in nonaqueous solution, and the effect of adding Ph3P or I− has been investigated. Similar studies with Ga2I6•dppe are also reported. In each system, four-coordination at gallium is dominant; an equally important factor is the dimerization of uncomplexed GaI3 to Ga2I6 in these solutions. Keywords: gallium(III) iodide, complexes, phosphorus, NMR, crystallography.

Indium(III) iodide forms both 1:1 and 1:2 adducts with triphenylphosphine, depending on the reaction conditions, and especially on the solvent used. The complex InI3•PPh3 involves four-coordination at indium; the structure is trigonal, with a = 15.105(4) Å, c = 16.769(7) Å, V = 3313(2) Å3, Z = 6, and space group [Formula: see text]. Crystals were also obtained in which InI3•PPh3 and InI3(PPh3)2 are present in a 1:1 ratio; these are also trigonal, a = 15.473(4) Å, c = 41.701(7) Å, V = 8646.1(1.8) Å3,Z = 3 + 3 and space group [Formula: see text]. The 1:2 adduct has approximately D3h symmetry in the InI3P2 kernel. The bond distances and angles are discussed; in particular, the In—P bonds are extremely weak in the 1:2 adduct. This compound has been shown by 31P NMR to undergo complete dissociation in solution to InI3•PPh3 and PPh3. The addition of R4NI (R = n-C3H7, n-C4H9) causes quantitative conversion to InI4− and free Ph3P. Similar experiments are reported for the compound InI3(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane), whose structure is an infinite chain of InI3 units linked through In-P-C2H4-P-In coordination. The crystal structure showed that InI3(dppe) cocrystallizes with an equimolar quantity of dppe; these crystals are cubic, a = 41.445(14) Å, b = 15.944(8) Å, c = 16.533(11) Å, p = 102.02(4)°, V = 10 685(9) Å3, Z = 4 + 4, space group C2/c, Solid state and solution phase results are discussed in terms of the coordination chemistry of indium(III). Key words: indium, phosphorus, coordination chemistry, multinuclear NMR, X-ray crystallography.

The six-coordinate adduct InI 3 (pic) 3 (pic = 4-methylpyridine) has been prepared, and studied by X-ray crystallography. The crystals are monoclinic, space group P 2 1 / n , with a =11.430(3), b =13.951(3), c =15.332(2) A, β =96.913(15)°, Z =4, R =0.062 for 4471 unique reflections. The InI bond distances are compared with those for a number of related compounds, as with other indium(III) systems, there is a pronounced relationship between r (InI) and the coordination number at indium.

The 71Ga NMR spectra of solutions of gallium tribromide in different aromatic solvents have been recorded, and dependences of chemical shift on concentration, temperature and solvent observed. Such effects are absent in the corresponding solutions of Me3Ga. The 71 Ga chemical shift changes are consistent with the dissociation of the dimeric form of gallium tribromide to the monomer, as observed in the gas phase, but a study of effect of added H2O or Et2O indicates that solutions of gallium tribromide contain no monomeric species and the changes are best accounted for in terms of rapid chemical exchange between two different dimeric forms of gallium tribromide, one closed and the other half-open. With increasing solvating power of the aromatic solvent, the equilibrium between these dimeric structures favours the half-open solvated species.

Indium(I) halides, InX (X = Cl, Br, I), react with haloforms, CHX3, to give X2InCHX2 derivatives. Treatment of the latter with (C2H5)4N+X- gives the 1:1 electrolytes [(C2H5)4N][X3InCHX2], but with neutral ligands L (L = dimethylsulfoxide (dmso), 1,1,3,3-tetramethyl-2-thiourea (tmtu), triphenylphosphine), the products were the adducts of the corresponding indium trihalide, InX3Ln (X = Cl, L = tmtu, n = 2; X = Cl, L = Ph3P, n = 2; X = Cl, L = dmso, n = 3; X = Br, L = dmso, n = 3; X = I, L = Ph3P, n = 2: X = I, L = tmtu, n = 1). [(C2H5)4N][X3InCHX2] (X = Br, I) reacts with InX to give, after the addition of (C2H5)4NX, the salts [(C2H5)4N]2[X3InCHXInX3].

The reaction between phenyllithium and substituted o-quinones (3,5-di-tert-butyl-1,2-benzoquinone (TBQ), 1,2-naphthoquinone, 9,10-phenanthrenequinone) results in the oxidation of C6H5- to C6H5•, wi...

The condensation of two molecules of 3,5-di-tert-butylcatechol (dbc) with ammonia under oxidizing conditions is believed to proceed via a keto-imine radical. Further condensation, and subsequent reaction with tin(II) or lead(II) halides, yields complexes of identical composition, M[dbqdi]2, where dbqdi is 3,5-di-tert-butyl-1,2-quinone-1-(2-hydroxy-3,5-di-tert-butylphenyl)imine anion; this name is used without prejudice as to the actual structure of the ligand. The two compounds differ in crystallographic and magnetic properties, and ESR measurements show that the tin compound has a triplet ground state. Both involve six-coordination of the metal in a distorted environment; tin is in the +IV state, but lead is +II, and there are corresponding differences in the form of the ligand. For SnIV(dbqdi)2, the crystal parameters are orthorhombic, space group C2221, a = 19.597(4), b = 24.375(4), c = 23.755(6) Å, Z = 8, and R = 0.073 for 1405 unique reflections. For PbII(dbqdi)2, monoclinic, space group P21/n, a = 14.56(1), b = 25.967(9), c = 15.13(1) Å, β = 99.81(7)°, Z = 4, R = 0.065 for 4911 unique reflections. The different complexation behaviour is shown to be a consequence of the redox properties of the two metallic elements. Keywords: tin, lead, ESR, coordination chemistry, electron transfer.

The reaction of InX3 (X  Cl, Br, I) with 2 mol of Na+TBSQ·− (TBSQ·− =3,5-di-t-butyl-o-benzosemiquinonate anion) yields solutions of the diradicals InX(TBSQ)2, whose EPR spectra have been recorded. Addition of pyridine or γ-picoline (L) to such solutions produces adducts of the 3,5-di-t-butylcatecholate-indium(III) halide, of the type In(TBC)XLn. The mechanism of these reactions, and of the related ligand replacement and disproportionation equilibria, is discussed in terms of internal one-electron transfer processes. The compound In(TBC)(pic)2·DMF has been the subject of an X-ray crystallographic study. The substance forms monoclinic crystals, space group P21/n with a=12.992(5), b=13.923(4), c=18.491(4) A, β=98.82(2)o, Z=4, R=0.053 for 3244 unique reflections. The molecule is dimeric, with a central In2O2 ring, involving six-coordinate indium(III).

The reaction between tetrahalogeno- ortho -benzoquinones (X 4 C 6 O 2 - o ; X  Cl, Br) and diphenyl ditelluride gives the unusual tellurium(IV) derivatives [(X 4 C 6 O 2 )TeC 6 H 5 ] 2 O. Crystallographic studies show that tellurium is coordinated by a substituted catecholate, a phenyl group, and a bridging oxygen. The mechanism of the reaction probably involves initial formation of a semiquinone-tellurium- phenyl species, since ESR spectroscopy identifies the presence of o -semiquinone radicals. A similar reaction was observed with (C 6 H 5 ) 2 Te 2 and 3,5-di-tert-butyl- ortho -benzoquinone.

71 Ga NMR spectra of solutions of GaCl 3 and Me 3 Ga, and of binary mixtures of GaCl 3 Me 3 Ga, in n-heptane have been recorded. The resonance signals for both Me 3 Ga and GaCl 3 are unchanged on dilution over the temperature range 20–100°C. Mixtures of GaCl 3 and Me 3 Ga show only one resonance signal, whose chemical shift is determined predominantly by the nature of the coordination at gallium, indicating rapid chemical exchange of the species involved. The results of studies of methanolysis and hydrolysis, and of adduct formation, are also discussed. The 71 Ga resonances of several possible external standards in the temperature range 20–100°C are also reported. The 71 Ga NMR signal of a solution of GaCl 4 − in 6 M aqueous hydrochloric acid, for which δ( 71 Ga) = 250 ± 0.5 ppm downfield from the signal of a 1 M solution of [Ga(H 2 O) 6 ] 3+ [ClO 4 ] 3 − in 1 M HClO 4 , is recommended as a temperature-independent external standard for gallium NMR studies.

The compound Ga(TBSQ . ) 3 (TBSQ . =3,5-di-tert-butyl- 1,2-benzosemiquinonate anion) has been prepared by two synthetic routes and its structure determined by X-ray analysis. The crystals are rhombohedral, with a=16.408(6) A, c=13.898(4) A, V=3240(2) A 3 , Z=3, and space group R3(h); R=0.050; T=23 o C. The molecule has a distorted octahedral GaO 6 kernel, with bidentate TBSQ .- ligands. The compound and its solutions in noncoordinating solvents are stable for months, even when exposed to air

The electrochemical oxidation of a number of metals in acetonitrile solutions of PPh2H gives rise to M(PPh2)n compounds (M = Co, Zn or Cd, n= 2; M = Cu, Ag or Au, n= 1). With anodic nickel the product is Ni(PPh2)·PPh2H. In the presence of elemental sulphur such oxidation reactions yield [M(S2PPh2)2](M = Co, Zn or Cd). The electrochemical processes involved have been identified. The crystal structure of the addition compound [Cu4(PPh2)4(dppm)2]·4MeCN 1[dppm = bis(diphenylphosphino)methane] has been determined by X-ray crystallography, which reveals a Cu4P4 ring, capped by Cu2PCP'2 rings. Crystal parameters: triclinic, space group P, a= 14.719(4), b= 13.649(5), c= 17.112(5)A, α= 112.40(3), β= 106.22(2), γ= 115.39(2)° and Z= 1; R= 0.0632 for 3622 observed reflections [I 3σ(I)]. The compound Ni(PPh2)·PPh2H is oxidized by elemental oxygen, sulphur or selenium to give [Ni(E2PPh2)2](E = O, S or Se), and also reacts with PhNCS to yield [Ni{PPh2(SCNPh)}2]2. Crystal parameters: triclinic, space group P, a= 8.950(6), b= 9.745(4), c= 10.366(7)A,α= 112.28(4), β= 99.09(5), γ= 90.88(4)° and Z= 1. Disorder prevented this structure from being refined beyond R= 0.1612, but the essential features of the square-planar NiS2P2 core were identified. The crystal parameters of [Ni(O2PPh2)2(HO2PPh2)2(MeCN)2]3 are monoclinic, space group P21/c, a= 12.420(5), b= 9.737(7), c= 20.729(16)A, β= 100.29(5)° and Z= 2. The nickel atom is co-ordinated by two monodentate Ph2PO(O)– ligands and two monodentate Ph2(O)OH ligands which are hydrogen-bonded to their anionic analogues, and by two MeCN molecules, to give a NiO2O′2N2 core.

A. Introduction B. M-M bonded compounds C. Oxidative addition reactions of indium(1) compounds. .. D. Quinones as oxidants for Main Group species ....... (i) Reactions of InX or SnX, with o-quinones. ...... (ii) The oxidation of non-metallic compounds ....... (iii) Oxidation of metallic and non-metallic elements ... E. Conclusions Acknowledgement References . . . . . . .

The reaction between tetrahalogeno- ortho -benzoquinones (X 4 C 6 O 2 - o ; X  Cl, Br) and diphenyl ditelluride gives the unusual tellurium(IV) derivatives [(X 4 C 6 O 2 )TeC 6 H 5 ] 2 O. Crystallographic studies show that tellurium is coordinated by a substituted catecholate, a phenyl group, and a bridging oxygen. The mechanism of the reaction probably involves initial formation of a semiquinone-tellurium- phenyl species, since ESR spectroscopy identifies the presence of o -semiquinone radicals. A similar reaction was observed with (C 6 H 5 ) 2 Te 2 and 3,5-di-tert-butyl- ortho -benzoquinone.

A. Introduction B. M-M bonded compounds C. Oxidative addition reactions of indium(1) compounds. .. D. Quinones as oxidants for Main Group species ....... (i) Reactions of InX or SnX, with o-quinones. ...... (ii) The oxidation of non-metallic compounds ....... (iii) Oxidation of metallic and non-metallic elements ... E. Conclusions Acknowledgement References . . . . . . .

Electrochemical oxidation of indium in solutions containing a dihalogenomethane also yields InX (X=Cl, Br, I) and that in the case of X=Br or I further reaction leads to X 2 InCH 2 X compounds. Some interesting adducts of these species have been prepared and structurally characterized

Analysis of the EPR of mixtures of M(TBSQ) 2 (M=Mg, Zn, and Cd) and L (L=py, bipy, and tmed) in frozen solutions has demonstrated the existence of biradical species in which the interaction between two semiquinone ligands is purely dipolar in nature. For the monodentate ligand py both cis and trans isomers are identified, with the cis isomer by far the more abundant. Only the cis isomer is found for the bidentate ligands bipy and tmed. The tmed ligand produced additional species for M=Mg, Cd, and Ba, which are proposed as five-coordinate for M=Mg and eight coordinate of M=Cd and Ba

The electrochemical oxidation of copper in an acetonitrile solution of an aromatic diol (R(OH)2 = catechol, tetrachloro-1,2-dihydroxybenzene, 2,2'-dihydroxybiphenyl) gives soluble copper(I) products which are reduced to copper at a platinum cathode. In the presence of R(OH)2 + L (L = 2,2'-bipyridine, triphenylphosphine, bis(diphenylphosphino)methane (= dppm)), the products are adducts of copper(I) species in which the anionic ligand is [R(O)OH]−. The crystal structure of Cu2[OC6Cl4(OH)]2(dppm)2 is triclinic, with a = 22.418(5) Ǻ b = 1.784(4) Ǻ, c = 13.492(4) Ǻ, α = 61.63(2)°, β = 86.66(2)°, γ = 80.61(2), V = 3093(2) Ǻ3, Z = 2, and space group [Formula: see text] The molecule consists of a Cu—P—C—P—Cu—P—C—P ring, with copper ligated by [R(O)OH]− groups external to this. Intramolecular O—H—O hydrogen-bonding contributes to the stabilization of this novel complex. Key words: Copper, electrochemical synthesis, hydrogen bonding, aromatic diols, crystal structure.

Indium(I) halides (InX; X=Cl, Br, I) react with 3,5-di-tert-butyl-o-quinone (TBQ) in toluene/tmen solution to give the corresponding semiquinone-indium(III) derivatives (TBSQ)InX 2 •tmen (tmen=N,N,N',N'-tetramethylethanediamine). Related species have been prepared by the reaction between Na + TBSQ − and InX 3 , and the presence of the semiquinone has been confirmed by X-ray crystallography in the case of (TBSQ)InBr 2 •2CH 3 C 5 H 4 N•0.5 (N,N-dimethylformamide), which is monoclinic

The electrochemical oxidation of a metallic sacrificial anode (M = Zn, Cd, Sn, In, Cu) in a non-aqueous solution of 3-hydroxy-2-methyl-4-pyrone (= HL) yields the MLn complexes (M = Zn, Cd, Sn, Cu, n = 2; M = In, n = 3). Adducts of the type ML2•B (M = Zn, Cd, B = N,N,N′,N′-tetramethylethylenediamine (tmen); M = Cu, B = triphenylphosphine) were obtained by the reaction between the appropriate ligand (B) and the previously synthesized complexes (M = Zn, Cd), or by arranging for the initial electrolytic phase to include the base (M = Cu). The tin(II) compound shows the typical reactions of such low oxidation state species by reacting with iodine and ortho-quinones by oxidative addition. All compounds were characterized by elemental analysis and by IR, 1H and 13C nmr spectroscopy. The structure of CdL2•tmen was determined by X-ray crystallography, which identified the CdO4N2 kernel, and partial electron delocalization within the pyronate ring. Keywords: electrochemical synthesis, cadmium complexes, zinc complexes, tin(II) oxidation, 3-hydroxy-2-methyl-4-pyrone.

The electrochemical oxidation of a sacrificial anode (M = Zn, Cd, Hg, In, Sn) in non-aqueous solutions of 3-hydroxyflavone, 1′-hydroxy-2′-acetonaphthone, or 2-ethoxyphenol (= HL) gives ZnL2, CdL2, HgL, InL3, or SnL2 (not all combinations). Adducts with 2,2′-bipyridine (bpy) or N,N,N′,N′-tetramethylethanediamine (tmen) have also been prepared in some cases. Certain zinc and cadmium compounds produce paramagnetic species on exposure to the atmosphere. The structure of Zn(C15H9O3)2tmen has been determined; the crystals are orthorhombic, space group Pbcn, cell dimensions a = 18.817(2) Å, b = 13.886(3) Å, c = 12.567(3) Å, Z = 4, R = 0.0758 for 773 unique observed reflections. The corresponding data for Cd(C12H9O2)2bpy are orthorhombic, space group Pbca, cell dimensions a = 20.338(4) Å, b = 30.473(5) Å, c = 9.316(2) Å, Z = 8, R = 0.0457 for 2623 unique observed reflections. Both molecules have MO4N2 kernels, but each shows significant differences in the two M—O bond lengths to the dioxo ligand, and there are concomitant effects in the C—O and C—C bond distances in the ligands. Keywords: electrochemical synthesis, d10 metal ions, X-ray crystallography, zinc complex, cadmium complex.

Presentation globale de travaux concernant la chimie de l'aluminium, du gallium et de l'indium combines avec les halogenes et concernant principalement le degre d'oxydation II. Parametres thermodynamique de formation d'halogenures et proprietes spectrales derives halogenes