far-IR Spectra Research Articles

Lattice dynamical study of an internal charge transfer molecular crystal: 4-nitropyridine N-oxide and its deuterated derivative

Phonon dispersion curves, far-IR and low-frequency Raman spectra (below 200 cm −1) of 4-nitropyridine N-oxide (NPO) including results at high pressure and low temperature are reported and interpreted with the help of a lattice-dynamical calculation using atom—atom Buckingham-type potentials and a multipole expansion up to the quadrupole. The charge transfer process is analysed through its manifestations on the model parameters of some short intermolecular interactions. The good agreement between calculation and experience is confirmed by using the same model to interpret the experimental results of inelastic neutron scattering along the b ∗ direction of a deuterated NPO- d4 single crystal.

Structural and vibrational spectroscopic studies of complexes of trimethylphosphine with copper(I) and silver(I) halides

New copper(I) halide–trimethylphosphine adducts were prepared by reaction of CuX with PMe3 in benzene suspension, and characterized by room-temperature single-crystal X-ray studies and vibrational spectroscopy. [(Me3P)2Cu(µ-I)2Cu(PMe3)2], monoclinic, space group P21/c, a= 9.296(2), b= 16.206(7), c= 9.577(3)A, β= 113.76(2)°, Z= 2 dimers, conventional R on |F| 0.040 for 1369 ‘observed’[I > 3σ(I)] reflections at convergence; [{Cu4Cl4(PMe3)3}∞], rhombohedral, space group R3c, a= 17.776(2), c= 11.708(7)A(hexagonal setting), Z= 6, R= 0.045 for 820 observed reflections. The latter is a novel one-dimensional polymer of quasi-cubanoid Cu4Cl4 units disposed with their body diagonals coincident with the crystallographic 3-axis and linked by Cu–Cl bonds between the four-co-ordinate apical atoms of successive Cu4Cl4 units. Unlike the related [{Cu4I4(NEt3)3}∞] polymer, however, the off-axis copper atoms are planar three- rather than four-co-ordinate, having (µ-Cl)2CuP environments. The far-IR and Raman spectra of the compounds, and of the 1 : 1 Agl–PMe3 complex with the proposed tetrameric ‘cubane’ structure [Ag4I4(PMe3)4], have been recorded and assigned. The frequencies and activities of the v(MX) modes correlate well with the observed or proposed structures, and a comparison of the Raman spectra for the series of three compounds allows the first rational assignment of v(MP) modes for multinuclear complexes of this type.

High-resolution IR spectroscopy of jet-cooled CF3CH2F

The mid-IR spectrum of HFC-134a, CF3CH2F, entrained in a supersonic jet expansion has been measured at high and low resolution and the rotational structure of the C-type bands ν14(1204 cm–1) and ν15(974 cm–1) has been analysed along with the hot band ν15+ν18â†�ν18. Rotational constants have been obtained and used to simulate the band structure, enabling the rotational temperature in the jet to be estimated at 65 K. In addition, low-resolution far-IR spectra of CF3CH2F in a room-temperature gas cell have been recorded and the vibrational fundamentals more completely assigned. These results are compared with previous experimental values and those predicted from molecular orbital calculations.

ChemInform Abstract: Synthesis, Structure and Properties of the Polychalcogenides (M4Te12)4‐ (M: Cd, Hg).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis, structure and properties of the polychalcogenides [M 4Te 12] 4− (M=Cd, Hg)

The cluster anions, [M 4Te 12] 4− (MCd, Hg) are reported. (Et 4N) 4[Cd 4Te 12] ( I) was prepared by the reaction of CdI 2, K 2Te 2 and Et 4NBr in a 2:3:2 molar ratio, in DMF. I crystallizes in the orthorhombic space group Cmca (No. 64) with a = 15.482(5), b = 22.563(4), c = 18.027(4) Å, V = 6297(5) Å 3 and Z = 4. The black rectangular platelet crystals of (Me 4N) 4[Hg 4Te 12] ( II) were obtained from the reaction of HgCl 2 and K 2Te in a 2:5 molar ratio in DMF. II crystallizes in the monoclinic space group P2 1/ n (No. 14) with a = 10.324(3), b = 21.851(6), c = 11.125(4) Å, β = 110.63(3)°, V = 2348(3) Å 3 and Z = 2. [M 4Te 12] 4− is a cluster with two Te 2−, two Te 2 2− and two Te 3 2− ligands connecting a planar array of four tetrahedral M 2+ metal centers. Its shape may be described as a basket, consisting of an {M 4(Te 2) 2Te 2} core with two side Te 3 2− handles. The average M-Te and Te-Te distances are 2.85(8) and 2.74(2) Å for I, respectively, and 2.86(12) and 2.73(1) Å for II, respectively. The far-IR spectra show two absorptions at 173 and 160 cm −1 for I and at 167 and 148 cm −1 for II. Thermal gravimetric analysis data are reported.

The assignment of the Raman and far-infrared spectra of Ph3SnX(X  Cl, Br, I) and Ph4Sn; a reaffirmation

Abstract Complete solid state Raman (460-50 cm−1) and far-IR (460-100 cm−1) spectra are reported for Ph3SnX(X  Cl, Br, I) and Ph4Sn. The assignments reaffirm and clarify those given earlier, particularly for ν SnX and are consistent with all Ph3SnX being monomeric. Preliminary results from X-ray analysis show Ph3SnI is triclinic, space group P 1 , with Z = 4. The Ph3SnI molecules have almost trigonal symmetry around the tin while shortest intermolecular d(Sn---I) values are > 6.3 A.

Microwave and far-IR spectra, conformational stability, molecular structure, barriers to internal rotation and ab initio calculations for the anticlinal conformer of trans-1-fluoro-2-butene

The microwave spectrum of trans-1-fluoro-2-butene, trans-(CH 3)HCCH(CH 2F), has been recorded in the region of 18.0–39.0 GHz. Both a-type R- and b-type Q-branch assignments have been made for the ground and first two vibrationally excited states of the asymmetric torsion for the gauche (anticlinal) conformer. The ground state rotational constants for this conformer are found to have the following values: A = 19,938.33±0.48, B = 2071.37±0.01, C = 2022.17±0.01 MHz. From an analysis of the internal rotational splittings of the Q-branches, the three-fold rotational barrier for the methyl group is determined to be 596±7 cm −1 (1.70±0.02 kcal/mol). From the Stark effect the dipole moment components for the gauche conformer were determined to be |μ a | = 1.86±0.01, |μ b | = 1.16±0.01, |μ c | = 0.31±0.05, and |μ t = 2.21±0.01 D. The fundamental asymmetric torsion for the cis (synclinal) conformer has been observed in the far-IR spectrum of the vapor at 123.95 cm −1 whereas that for the gauche conformer has been determined to occur at 82.8±5 cm −1 based on relative intensity measurements obtained from the microwave spectrum. From these data the potential function which governs the internal rotation of the asymmetric top has been determined and the following potential constants have been evaluated: V 1 = −191±10, V 2 = 598±10, V 3 = 786±13, V 4 = 59±5, and V 6 = 79±5 cm −1. These data are consistent with the more stable conformer having the fluorine atom cis (synclinal) to the double bond and lying 300±33 cm −1 (858±94 cal/mol) lower in energy than the gauche rotamer. Utilizing ab initio calculations with the MP2/6-31G* basis set and the three rotational constants, r 0 structural parameters are estimated. Also, the barriers to conformer interconversion have been calculated with the RHF/3-21G, RHF/6-31G*, and MP2/6-31G* basis sets. All of these results have been compared to the similar quantities of some corresponding molecules.

Spectra and structure of silicon compounds. XVII Raman and infrared spectra and vibrational assignment for hexamethyldisilane and ab initio calculations for disilane and hexamethyldisilane

The IR spectra of gaseous and solid hexamethyldisilane between 4000 and 25 cm −1 and the far-IR spectrum of the liquids from 450 to 25 cm −1 have been recorded. The Raman spectra have been recorded from 3500 to 10 cm −1 for all three physical phases. Assisted by ab initio calculations, the vibrational spectrum of hexamethyldisilane has been assigned under D 3 d symmetry and the results of a normal coordinate analysis are discussed. No spectral features indicative of free internal rotation have been observed. Gradient ab initio calculations have been carried out for the disilane and hexamethyldisilane molecules using different types of basis sets. The structural parameters, rotational constants, unscaled and scaled frequencies and harmonic force constants have been reported for both disilane and hexamethyldisilane.

X-ray photoelectron and vibrational spectroscopic studies of TeC:H films for optical disk memory

The valence band spectrum of a Te C: H film was found to be essentially the same as that of amorphous elemental tellurium using X-ray photoelectron spectroscopy. Raman and Fourier transform far-IR spectra were examined based on the phonon density of states for tellurium, and the far-IR peak corresponding to the vibration of amorphous tellurium was identified at 150 cm −1. Organic TeC bonding was found in the Te C: H film, and the origin of this bonding is discussed by taking into consideration the deposition process, including surface reaction on the tellurium target. The chemical sputtering process is suggested to contribute to the deposition of Te C: H film.

Far-IR spectrum, conformation stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of 3-chloro-2-methylpropene

The far-IR spectrum from 375 to 30 cm −1 of gaseous 3-chloro-2-methylpropene, CH 2=C(CH 3)CH 2Cl, has been recorded at a resolution of 0.10 cm −1. The fundamental asymmetric torsional mode for the gauche conformer is observed at 84.3 cm −1 with three excited states falling to lower frequency. For the higher energy s-cis conformer, where the chlorine atom eclipses the double bond, the asymmetric torsion is observed at 81.3 cm −1 with two excited states falling to lower frequency. Utilizing the s-cis and gauche torsional frequencies, the gauche dihedral angle and the enthalpy difference between conformers, the potential function governing the interconversion of the rotamers has been calculated. The determined potential function coefficients are (in reciprocal centimeters): V 1=189±12, V 2=−358±11, V 3=886±2 and V 4=−12±2 with an enthalpy difference between the more stable gauche and s-cis conformers of 150 ±25 cm −1 (430 ± 71 cal mol −1). This function gives values of 661 cm −1 (1.89 kcal mol −1), 1226 cm −1 (3.51 kcal mol −1) and 812 cm −1 (2.32 kcal mol −1), for the s-cis to gauche, gauche to gauche, and gauche to s-cis barriers, respectively. From the methyl torsional frequency of 170 cm −1 for the gauche conformer, the threefold barrier of 678 cm −1 (1.94 kcal mol −1) has been calculated. The asymmetric potential function, conformational energy difference and optimized geometries of both conformers have also been obtained from ab initio calculations with both the 3–21G * and 6–31G * basis sets. A normal-coordinate analysis has also been performed with a force field determined from the 3–21G * basis set. These data are compared with the corresponding data for some similar molecules.

Far-IR spectra, barriers to internal rotation, r0 structural parameters and ab initio calculations of chloromethyl methyl ether

The far-IR spectra from 350 to 50 cm −1 of gaseous chloromethyl methyl ether, ClCH 2OCH 3, along with three of the deuterium isotopomers, have been recorded at a resolution of 0.10 cm −1. The fundamental asymmetric torsional and methyl torsional modes are extensively mixed and have been observed at 180 and 133 cm −1, respectively. An estimate is given for the potential function governing the asymmetric torsion. On the basis of a one-dimensional model the barrier to internal rotation of the methyl moiety is determined to be 556 ± 5 cm −1 (1.59 ± 0.01 kcal mol −1). Utilizing previously reported rotational constants for seven isotopomers, r 0 structural parameters are determined. The heavy atom parameters (distances in ångströms angles in degrees) are: r(C 1−Cl) = 1.818 ± 0.003; r(C 1−O) = 1.371 ± 0.004; r(C 2−O) = 1.430 ± 0.001; ∢ClC 1O = 113.01 ± 0.07;∢ClOC 2 = 114.03 ± 0.10 and dihedral ClC 1OC 2=70.20 ± 0.15. A complete vibrational assignment is given for the ClCD 2OCD 3 molecule. The fundamental vibrational frequencies, barrier to internal rotation and structural parameters which have been obtained experimentally are compared with those obtained from ab initio Hartree-Fock calculations employing the 3–21G * and 6–31G * basis sets along with the 6–31G * basis set with electron correlation at the MP2 level. All of these results are discussed and compared with the corresponding quantities obtained for some similar molecules.

Torsional spectra of molecules with two C3v rotors—XXV. Rotational and vibrational spectra, r0 structure, barriers to internal rotation and ab initio calculations for 2,2-difluoropropane

The microwave spectra of two isotopic species of 2,2-difluoropropane, (CH 3) 2 13CF 2 and (CD 3) 2 12CF 2, have been recorded from 26.5 to 40.0 GHz and the b-type R-branch transitions have been observed and assigned for the ground state. Utilizing the rotational transitions for these two isotopomers along with those for the normal species the following r o structural parameters have been determined: r(C-H) = 1.091±0.002Å, r(C-C) = 1.510 + 0.005 Å, r(C-F) = 1.378±0.005 Å, ∢CCH = 109.26±0.05°, ∢CCC = 116.44±0.54° and ∢FCF = 105.15±0.50°. The carbon-hydrogen distances have also been obtained from the frequency of the isolated carbon-hydrogen frequency in the IR spectrum. The far-IR spectra of 2,2-difluoropropane- d 0 and - d 6 in the gas were recorded at a resolution of 0.10 cm −1 and the torsional fundamentals, along with several hot band transitions, have been assigned. From these data the barrier to internal rotation of the coupled rotors is 1103±48cm −1 (3.15±0.14kcalmol −1). The IR spectra (3600–50cm −1) of gaseous and solid and the Raman spectra (3600–10 cm −1) of gaseous, liquid and solid (CD 3) 2CF 2 have been recorded. A complete vibrational assignment is proposed for both the normal and d 6 molecules based on depolarization values, relative intensities, isotopic shifts and normal coordinate calculations. The structural parameters, barriers to internal rotation and fundamental vibrational frequencies which have been determined experimentally are compared with those obtained from ab initio Hartree-Fock gradient calculations utilizing both the 3–21G and 6–31G* basis sets along with electron correlation at the MP2 level, and to the corresponding quantities obtained for some similar molecules.

Spectra and structure of small ring compounds—LXL. IR and Raman spectra, vibrational assignment, conformational stability and ab initio calculations of cyclopropylmethylsilane

The IR (3500–50 cm −1) and Raman (3500–20 cm −1) spectra of gaseous and solid cyclopropylmethylsilane, c-C 3H 5-CH 2SiH 3, have been recorded. Additionally, we have obtained the Raman spectrum of the liquid and the IR spectrum of the sample trapped in an argon matrix. From these data a complete assignment of the normal vibrational modes is provided. The spectra of the gaseous and liquid phases have been interpreted on the basis of the predominance of a conformation having a gauche structure and this form exists exclusively in the solid. Ab initio Hartree-Fock structural optimizations with the 3–21G* and 6–31G* basis sets are consistent with the gauche rotamer lying ~800 cm −1 lower in energy than the cis conformation which has the SiH3 group eis to the cyclopropyl ring. The force fields obtained with the 3–21G* basis set have been used to perforin a normal coordinate analysis. The cyclopropyl torsion has been observed as an IR band of hybrid contour centered at 80 cm −1 in the far-IR spectrum of the gas. Combination band spectra in the 2300–2000 cm −1 region of the mid-IR spectrum of the gas can be attributed to sum and difference bands of the SiH3 and cyclopropyl torsional modes with an SiH3 stretching mode. Analysis of these data leads to a barrier governing internal rotation of the silyl group of 687±50 cm −1. These results are compared with corresponding quantities in some similar molecules.

Low frequency vibrational spectra of crystalline and glassy metaborates Ba 2M II(B 3O 6) 2 (M II  Mg, Ca, Ni, Co, Cd)

The low frequency vibrational spectra (Raman and IR) of crystalline metaborates Ba 2M II(B 3O 6) 2 (M II  Mg, Ca, Ni, Co, Cd) are interpreted on the basis of a factor group analysis and with the help of 24Mg 26Mg and 40Ca 44Ca isotopic shifts. The far-IR spectra of the glasses appear as the envelope of the spectra of the corresponding crystalline compounds for M II  Mg, Ca and Cd, but they exhibit an additional broad absorption centred near 400 cm −1 for M II  Co, Ni and Zn. This absorption is assigned to a fourfold coordination of part of the M II cations, the remaining being in sixfold coordination (as in the crystal) and responsible for a broad absorption in the 300-200 cm −1 region. The possible existence of correlations between coordination and vibrational frequencies is discussed for either alkali and alkaline-earth cations, or transition elements.

A comparative analysis of the internal rotation in acetone and trans-dimethylglyoxal: Application to the fundamental frequencies and torsional modes

The large-amplitude internal rotations in trans-dimethylglyoxal (DMG or biacetyl) were considered as a pair of interacting methyl rotors which were completely decoupled from the torsion of the acetyl groups around the central C-C bond. The potential energy surface for methyl rotation was determined by performing ab initio RHF calculations for seven conveniently chosen conformations of the methyl groups. In these calculations a 6-31G(d,p) basis set was used, and the geometry of each conformation fully optimized. The set of energy values were fitted to a symmetry-adapted Fourier series as a function of the rotation angles, which was used to construct a potential energy function for the double rotations and combined with the kinetic energy. The energy levels and the transition energies calculated for DMG were compared with the hot band intervals observed in the warm-jet laser fluorescence excitation spectrum. The acetyl torsion around the central bond was studied in a similar way and the frequencies were compared to the far-IR spectrum. The effects of interacting methyl groups were explored by comparing the dynamics of the remotely situated methyl groups in the DMG system with the sterically coupled methyl groups of acetone.

Synthesis, Characterization and Reactivity of New Hetero-Bimetallic Complexes

Abstract Heterobimetallic complexes of the type [Cu(TETA) C12MCl2] where M = Si, Ge, Sn, Ti or Zr, TETA-H2 = (triethylene tetramine) have been synthesized and characterized by elemental analysis, EPR spectra, electronic spectra, IR spectra, far-IR spectra and conductivity measurements. The complex [Cu(TETA)Cl2 SnPh2] has also been prepared. The results indicate that the compound [Cu(TETA-H2)]Cl2 is square planar and ionic in nature, while its bimetallic complexes, [Cu(TETA)Cl MCl2] and [Cu(TETA)Cl2SnPh2], have an octahedral environment around the Cu(II) ion. Another series of compounds of the type [Cu(TETA)C12M(TMDTC)2] has been prepared by the direct interaction of [Cu(TETA)Cl MCl2] with tetramethylenedithiocarbamate (TMDTC) in a 1:2 ratio in methanol. In these complexes, an octahedral stereochemistry around the Group IV metal has been observed in which the TMDTC acts as a bidentate ligand.

A vibrational spectroscopic study of tris triphenyl phosphine rhodium (I) chloride

In this work we report the first Raman spectrum of tris triphenyl phosphine rhodium (I) chloride. The vibrational spectrum of triphenyl phosphine has also been recorded under similar conditions to facilitate comparisons. FT-Raman spectra and diffuse reflectance mid-IR and far-IR spectra are presented and a full skeletal vibrational assignment is made.

Syntheses and characterization of the first thallium polysulfide anions

The reaction of potassium tetrasulfide with thallium chloride in dimethylformamide (DMF) was investigated. The addition of the cations Ph[sub 4]P[sup +], Et[sub 4]N[sup +], and Me[sub 4]N[sup +] to this reaction afforded six new soluble thallium(I) polysulfide complexes. Surprisingly, all the complexes (I-VI) stabilize the same [Tl[sub 2](S[sub 4])[sub 2]][sup 2][sup [minus]] anions. Despite their different colors II and III are structurally identical. The anion features two trigonal pyramidal Tl[sup +] centers each chelated by a tetrasulfide ligand and the third coordination site is satisfied by bonding a terminal sulfur atom of another TlS[sub 4] unit, forming a dimer. This bonding mode of the S[sub 4][sup 2][sup [minus]] ligands results in a new condensed inorganic ring system with a central, strickly planar, four-membered Tl[sub 2]S[sub 2] rhombic unit and two five-membered TlS[sub 4] rings in an envelope configuration. The envelope configuration of the five membered TlS[sub 4] ring in the [Tl[sub 2](S[sub 4])[sub 2]][sup 2][sup [minus]] anions results in either the boat-boat or the chair-chair conformation. The reaction of potassium tetrasulfide with thallium chloride in acetonitrile afforded orange red crystals of K[sub 0.68]Tl[sub 1.32]S[sub 5] (VII). Compound VII is isostructural to the known K[sub 2]S[sub 5] and Tl[sub 2]S[sub 5]more » and consists of a S[sub 5][sup 2][sup [minus]] chain with Tl[sup +] and K[sup +] as charge-compensating cations. VII can be considered as a solid solution of the two known compounds. All complexes show similar UV/vis spectra in DMF with two absorptions at [approximately]432 and [approximately]617 nm. The solid-state far-IR spectra of all compounds exhibit strong absorptions in the 500-100-cm[sup [minus]][sup 1] region due to the S-S and M-S stretching frequencies; tentative assignments are reported.« less

A detailed infrared and far-infrared spectral investigation of the alkyl- and (non-alkyl)cobalt(III) complexes of 3,8-dimethyl-5,6-benzo-4,7-diazadeca-3,7-diene-2,9-dione dioxime and a study of ground state trans-effect in tetragonally distorted octahedral cobalt(III) complexes by far-infrared and electronic absorption spectroscopy

The tetraaza quadridentate chelate, 3,8-dimethyl-5,6-benzo-4,7-diazadeca-3,7-diene-2,9-dione dioxime [(DOH) 2bzo], forms stable tetragonally distorted octahedral cobalt(III) complexes with monodentate ligands such as halogens, pseudohalogens and Lewis bases in the axial sites besides forming pseudooctahedral alkylcobalt(III) complexes. A detailed IR and far-IR spectral investigation has been made for nine alkyl- and nineteen (non-alkyl)cobalt(III) complexes, reported recently. These complexes exhibit IR absorptions such as ν(OH), ν(CH), ν(NO), ν(CN), ν(CC), ν(CN), ν(CC) and CCH 3 symmetric and asymmetric deformation vibrations characteristic of the (DO)(DOH)bzo ligand framework and absorptions characteristic of the axial ligands. In the case of the complexes of aromatic Lewis bases vibrations such as ring deformation, ring breathing mode, ring stretchings and ring torsion characteristic of the aromatic rings are observed. Spectral evidence is obtained for the formation of an intramolecular hydrogen bond. The effect of hyperconjugative electron release and π-backbonding are manifested in the spectra of the complexes of 4-methylpyridine and triphenylphosphine, respectively. The far-IR spectra show vibrations such as ν(CoN), ν(CoBr), ν(CoC) and ν(Co-base) (Lewis base in the axial site). The ground state trans-effect in a series of tetragonally distorted octahedral (non-alkyl)cobalt(III) complexes of the type [LCo((DO)(DOH)bzo)Br] + (where L=a Lewis base such as pyridine, imidazole, methylimidazole, 4-methylpyridine, benzimidazole, 5,6-dimethylbenzimidazole, ethylamine, diethylamine, triethylamine, 2-aminopyridine, triphenylphosphine) is studied by following the variation of the CoBr stretching frequency on the field strength, Dq z , of the Lewis base in the axial site, trans to Br −. A plot of ν(CoBr) frequency versus Dq z is linear and as the Dq z increases ν(CoBr) frequency decreases. As the electron donating power of the axial Lewis base increases it transmits more electron density to Co 3+ with a concomitant transmission of electron density to Br −, trans to the Lewis base, thereby weakening the CoBr bond. This is the first report of the ground state trans-effect being studied using a quantitative measure of the electron donating ability of a series of test ligands on the ground state property of a probe ligand involving a heavy atom in six-coordinate cobalt(III) complexes.

Crystal structure, infrared and 31P nuclear magnetic resonance studies of complexes of tris(2,4,6-trimethoxyphenyl)phosphine with mercury(II) halides

The 31P NMR spectra of 1:1 solutions of tris(2,4,6-trimethoxyphenyl)phosphine (tmpp) and mercury(II) halides HgX2(X = Cl, Br or I) in acetonitrile reveal the presence of the ionic complexes [HgX(tmpp)]+ and [Hg(tmpp)2]2+. The amount of the first of these two species relative to the second increases from X = Cl to I. The solids which crystallize from tmpp–HgX2 solutions in acetonitrile contain mixtures of ionic compounds which contain both of these cationic complexes. The first species was identified in the solid state by the observation of ν(HgX) bands in the far-IR spectra. In the X = Cl case, crystals of the complex [Hg(tmpp)2]2+[Hg2Cl6]2– were isolated from the solid product and the structure of this complex was determined by single-crystal X-ray diffraction [monoclinic, C2/c, a= 32.767(5), b= 11.500(2), c= 23.814(4)A, β= 133.57(1)°, Z= 4 formula units; R= 0.047 for 3461 ‘observed’ reflections]. The cation has C2 symmetry and the mercury atom environment in this ion is dominated by a close association with the phosphorus atoms of the two attached ligands in a quasi-linear P–Hg–P array, but significant deviations from linearity arise, presumably because of contacts with the methoxy oxygen atoms [Hg–P 2.389(5)A, P–Hg–P 166.51(9)°]. The Hg ⋯ O contacts involving the nearest ortho-methoxy oxygen atoms on the three phenyl groups in each ligand are 2.726(9), 2.938(7), 3.044(9)A. The [Hg2Cl6]2– anions have a structure of Ci symmetry in which two mercury atoms with tetrahedral HgCl4 co-ordination are linked by sharing two bridging Cl atoms. The structural parameters for this anion are similar to those found previously for this species in compounds with other cations. The far-IR spectra of the solids obtained from the other mercury halides reveal the presence of [Hg2X6]2– species in these compounds also. For X = I, the product is predominantly [Hgl(tmpp)]2[Hg2I6].