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Raman and far-i.r. spectra for single crystals of tetrakis(thiourea)nickel(II) dichloride have been obtained at ca. 120 K and at ambient temperature. The results allow unambiguous assignment to A, B, and E species (in C4 symmetry). Descriptions of many of the internal modes are also offered.

Vibrational spectra of the ions [MCl6]2–(M = Cr, Mn, Fe, In, or lr) and [MCl6]3–(M = Mn or Ce) are assigned. The ν3 values show the effect of the differences in electronic structure of the metal atoms, being very low for M = Fe (t2g3eg2) and high for M = MnIII(Jahn–Teller distorted). Further spectra of tetrahalogenothallates are reported and show some differences at low frequencies from those previously published.

Far-infrared (60—4000 cm.–1) and laser-Raman spectra of solid complexes MI2[MCl6](M = Sn and Pb) are reported. Force constants are calculated on the basis of a modified Urey–Bradley force field and show a general decrease with increase in cation size. Some cation lattice modes are reported and found to decrease with increase in cation mass.

The far-infrared spectra (70–400 cm.–1) of tellurium tetrachloride show that its structure in the solid state differs from that in benzene solution, in which a molecular form is most probable. The solid bromide has a similar structure to the chloride.

An outline is given of an Algol computer programme for normal co-ordinate analysis. Some improvements in the force-constant refinement process are reported. The spectra of diborane, and of six halides of the formula M2X6(M = Al, Ga, or ln), have been analysed. In each case the force field is built up from the SVFF by adding interaction terms one by one, only those that are determined by the data being accepted. Force fields for all of the M2X6 molecules can be constructed by choosing 10 or more force constants from a set of 13; the force field for diborane differs considerably from these. A B–B force constant of 2·511 mdynes/A was found for diborane. In contrast, calculations for the M2X6 molecules became unstable when an M–M force constant was included, contrary to a previous report. An error in our previous calculations on auric chloride is corrected.

Copper(II) halides form complexes of the type CuX2L2(L is 2,3-diphenyl- and 2-methyl-quinoxaline) and CuX2L (L is 2,3-dimethylquinoxaline) with substituted quinoxaline. The 2,3-diphenylquinoxaline complexes appear to be monomeric whereas the others are polymeric. The 2-methylquinoxaline complexes have halide bridges and the 2,3-dimethyquinoxaline complexes are square-planar with organic ligand bridges. These structures are deduced from reflectance and far-infrared spectra and an examination of molecular models. Some copper(II) nitrate complexes of these ligands are described.

Partial or complete Raman and i.r. spectra are reported for WOCl4, WOBr4, MoO2Cl2, MoO2Br2, and WO2Cl2 as solids. A full assignment is given for WOCl4, and possible structures for the dioxide dihalides are discussed. A normal-co-ordinate analysis of WOCl4 is made.

A simple modification of the Bhagavantam–Venkatarayudu method is used to calculate the contribution of each atom in a unit cell to a representation of the factor group. Results have been computed for all sites in all 230 space groups, but only a few are given here in illustration of the method. The use of these data is illustrated for ionic, complex ionic, and molecular crystals as well as for polymers and layer structures. By its nature the method also yields the results of equivalent analyses for 32 of the point groups.

I.r. (and a few Raman) spectra are reporeted for the series M2I[MX5(H2O)], M2I[MX4(H2O)2], MX2,2H2O, and MX2,6H2O. From shifts in frequency with change of cation, metal, and halogen (X) the wagging mode of coordinated water is assigned at higher frequency than the rocking mode, contrary to currently accepted wisdom. Use of deuteriation has enabled identification of ν(Mâ†�OH2) and δ(M–O) modes in many cases. It is suggested that CoBr2,6H2O has the structure [CoBr2(H2O)4],2H2O and does not contain the hexa-aquo ion.

Raman and far-infrared spectra of solid halogenotellurates, M2I[TeX6], are reported and discussed. ν3 Is unusually broad and sometimes split, but the splitting is not different in origin from those shown by other [MX6]2– ions. It is concluded that there is no static distortion due to the lone pair but that the breadth of ν3 is associated with its presence in a symmetric orbital, as suggested by Urch. His description also accounts for the anomalous ratio of the bond-stretching force constants, K(Te–Br)/K(Te–Cl), which we find.

Infrared and partial Raman data are reported and assigned for the title compounds. A normal-co-ordinate analysis has been made for auric chloride. The most significant result of the calculation is that the bridge bond stretching force constant in auric chloride is 73% that of the terminal bond, whereas it is approximately 50% in aluminium chloride; this difference is rationalised and generalised.

The i.r.- and Raman-active fundamentals in the spectra of K2PtCl4 are unambiguously assigned from measurements on single crystals.

Single-crystal Raman spectra have enabled the identification and assignment to be made of nearly all the predicted factor-group fundamentals derived from internal modes of the anion in potassium chromate. Single-crystal i.r. and Raman methods were also used to study the lattice modes of this compound.

Nearly all the unit cell modes predicted by a factor-group analysis of tetrakis(thioacetamido)copper(I) chloride have been observed for single crystals in both Raman and i.r. spectra. The results show that the very simple i.r. spectrum of the Nujol mull is produced by the overlap of a large number of bands of different symmetry and similar frequency.

Single-crystal Raman spectra are reported and assigned for (NMe4)CdCl3, NH4CdCl3, (NH3Me)MnCl3, CsCuCl3, CsMnCl3,2H2O, and CsMnCl3,2D2O. Polarised far-i.r. studies have been made for (NMe4)CdCl3. Cscucl3, CsMnCl3,2H2O, and CsMnCl3,2D2O. With the exception of NH4CdCl3, which has a complicated double-chain structure, the results are discussed in terms of factor group analysis. Line group analysis suffices for NH4CdCl3.

The complexes Fe(CO)3L2, (L = Ph3P, Ph3As, Ph3Sb), react with mercuric halides to form 1 : 1 adducts; spectroscopic and conductivity evidence suggests their formulation as metal–donor complexes L2(CO)3Fe → HgX2. A 1 : 2 complex is formed by Fe(CO)3{(PhO)3P}2 and consists of a 1 : 1 compound plus a molecule of mercuric halide. Analogous structures are suggested for Fe(CO)5,nHgX2, (n= 1, 2).Features of the low-frequency spectra of the parent compounds and the adducts are discussed. Mercury–halogen frequencies are correlated with various structural situations.

Almost all the optically active modes of K2CuCl4(H2O)2 predicted by factor group analysis have been observed and assigned using single-crystal Raman and far-i.r. techniques. Less complete data are reported for K2CuCl4(D2O)2 and (NH4)2CuCl4(H2O)2. The spectrum of the trans-CuCl2(H2O)2 molecules present is strikingly similar to that reported for CuCl2,2H2O single crystals by Beattie, Gilson, and Ozin, showing that the effect of the ‘long-bonded’ interactions in both compounds is similar.

Infrared and laser-Raman spectra of WF5Cl are reported and assigned on the basis of C4v symmetry. A tungsten–chlorine bond distance of 2·10 A is estimated from the P–R separation of ν1. This, and the high value of ν1, suggests the presence of some π-contribution to the W–Cl bond.

New Raman data for solutions, powders, and oriented single crystals are reported which allow a consistent assignment of the vibrational spectra of the title compounds. The four Raman-active ν(CO) modes for Mn2(CO)10 are at 2116(a1), 2024(e2), 1997(a1), and 1981(e3) cm–1. Low-frequency spectra of considerably improved quality are also presented. All of the a1 bands have been located for Re2(CO)10 and all but one for Mn2(CO)10 for solutions.

Infrared spectra have been obtained over the range 70–4000 cm.–1 for complexes of the types InX3L3 and InX3L2, where X = Cl, Br, and I and L = donor ligand. The evidence indicates a pentaco-ordinate monomeric structure for the InX3L2 series [L = Ph3PO, Ph3P, or ½(Ph2P·C2H4·PPh2)] in the solid state, the trans-octahedral form for InX3(dimethyl sulphoxide)3, and the cis-octahedral structure for InX3py3.

Far-infrared spectra (60–400 cm.–1) of the ions [M2X6]2–(M = Pd, Pt; X = Cl, Br, or I), are assigned. Normal-co-ordinate analyses have been made for the in-plane infrared-active modes. Bond-stretching force constants for the bridge bonds vary from 75 to 100% of those for terminal bonds.

The observation of Raman and far-i.r. spectra of oriented single crystals of [Et4N]2[InCl5] has enabled a probable assignment to be given for the anion.

Raman and i.r. spectra are reported and assigned for the compounds Mn2(CO)10, Mn(CO)5X (X = Cl or Br), and Hg[Mn(CO)5]2.

Far-i.r. reflectance spectra of M2IMCl6 complexes where M = Sn, Pt, or Te, have been used to estimate the half-bandwidths of the v3 vibration of the [MCl6]2– ions. The values are substantially lower than those found from absorption spectra of powdered samples but those for the tellurates are greater than those for the platinates and stannates. An earlier interpretation of the mull i.r. spectra is supported by these results.