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Infrared reflectance spectra are reported for oriented single crystals of MAMC and PAMC with the electric vector parallel to the anionic sheets for temperatures from 50 to 295K. Single-crystal Raman spectra were also obtained at similar temperatures. The main features of the spectra, particularly for the ambient temperature phases, are assigned with the aid of a factor group analysis. This phase for MAMC, although orthorhombic, behaves spectroscopically as pseudo-tetragonal, but PAMC is plainly orthorhombic. Modes above 260 cm-1 are attributed to cation internal modes, including torsions. The phase III (tetragonal) to phase IV (monoclinic) transition is distinguished in the Raman spectra by disappearance of an intense broad features at about 35 cm-1/.

The far-infrared spectra of platinum(IV) complexes of the types cis- and trans-[PtX4L2](X = Cl, Br, or I; L = donor ligand) are assigned and discussed. For the trans complexes the halogen-sensitive modes occur near those of the related [PtX4]2– species whilst the ν(Pt–X) pattern for the cis complexes covers a wide range which includes that of ν(Pt–X) in bridging situations in platinum(II) compounds. Assignments are given for ν(Pt–P), ν(Pt–As), ν(Pt–S), and for the associated bending modes.

Raman and i.r. spectra of the title compounds are reported and assigned for both solids and solutions. ν(C–H) modes show correlationsplitting, but the remainder of the internal modes of the π-allyl ligands can be discussed in terms of Cs local symmetry. ν(C–C–C) modes of the allyl skeleton are placed ca. 1383 and 1020 cm.–1 in the parent complex.

The far-infrared spectra (70–400 cm.–1) of 36 thiourea and ethylenethiourea (imidazolidine-2-thione) complexes, embracing several different stereochemical types, are assigned and discussed. Metal–sulphur stretching frequencies, v(M–S), lie in the range 298–205 cm.–1 for the transition-metal complexes, and vary with co-ordination number and electron configuration in the manner now familiar from the behaviour of metal–hylogen stretching frequencies, v(M–X). For Group metals v(M–S) has been found as low as 170 cm.–1. The similarity between the spectra of thiourea complexes and those of thiocyanates has led to an assignment of the published data for thiocyanates. Some interesting variations in halogen-sensitive vibrations have been encountered.

I.r. spectra (70–4000 cm.–1) of nickel complexes of the type [Ni(S2C2R2)2]n–(R = H, CF3, or CN) and of [M(S2C2(CN)2)2]n–(M = Co, Cu, Zn, Pd, or Pt) are discussed. Vibrations containing a large (ν(M–S) contribution are found in the range 465–295 cm.–1. Frequency and intensity variations are consistent with the molecular orbital description of the bonding.For dithiophosphate complexes of three types of stereochemistry ν(M–S) is assigned in the region 330–220 cm.–1; the variation is mainly due to the differing masses of the metal.These results, together with other published work, lead to correlations for ν(M–S) for various ligands in the range 504–205 cm.–1.

Raman single-crystal spectra are reported for eight hydrates and deuteriates [MCl5(H2O)]2–(M = In or Fe). Many fewer lattice modes were found than predicted, but for the anion internal modes factor-group predictions accord well with observation. A complete assignment in terms of anion C4v symmetry is deduced. Deuteriation enabled identification of all skeletal modes associated with oxygen-atom motions. The most unusual feature of the assignments is that π(MCl4) modes come above δ(MCl4) modes. Comparison with single-crystal assignments for [InCl5]2– show that the largest change is in the A1π(InCl4) mode which is raised upon aquation of the complex.

The far-infrared spectra of some halogenocuprates of the types [CuX4]2–(planar and tetrahedral), [Cu2X6]2–, CsCuX3, and M2ICuCl4,2H2O have been studied. Complexes of the type CuX2L2(X = Cl or Br; L = donor ligand) are also considered. v(Cu–Cl) lies in the range 368—222 cm.–1 and v(Cu–Br) between 278 and 168 cm.–1. The spectra admit of a consistent interpretation without the need to postulate the presence of v(Cu–X) modes in the normal region due to stretching of copper–halogen “long” bonds. Bridging v(Cu–X) frequencies have been assigned but the range is severely overlapped by that of terminal v(Cu–X).

The ν(CO) spectra of Mo(CO)4 bipy (bipy = 2,2′-bipyridyl), cis-[W(CO)2{o-C6H4(PEt2)2}2],Cr(CO)3(π-mesitylene), and Cr(CO)3(π-C6H5·CO2Me) are examined in solution in n-hexane–chloroform or –nitrobenzene mixtures; the ν(NO) spectrum of Fe(NO)(S2CNMe2)2 is studied in benzene–nitromethane mixtures. Structure observed on the ν(CO) bands is discussed in terms of formation of solvent–solute complexes.

Raman and i.r. spectra are reported and assigned for X2Sn[Co(CO)4]2,X2Sn[Fe(CO)2(π-C5H5)]2(X = Cl, Br, and I), and M-SnCl3, (M = Mo(CO)3(π-C5H5); Rh(NBD)2; Ir(COD)2), and for a number of related compounds. Metal–metal stretching frequencies are in the range 165–235 cm.–1 and are intense in the Raman spectra.

Far-i.r. spectra of A2[PdCl4] and A2[PtCl4](A = K, NH4, or ND4) have been investigated at temperatures below 100 K for the first time. Several new bands occur in the 200–360 cm–1 region on cooling to ca. 20 K. These and other features are discussed with the aid of single-crystal polarised-transmission measurements on [NH4]2[MCl4](M = Pd or Pt) in the range 60–180 cm–1, which yield evidence for the positions of the translatory modes. A theoretical analysis is given of the space groups to which these solids might transform at low temperatures. Among the structural possibilities considered are out-of-plane distortions of the anions.

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.

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.

The complex Raman and i.r. spectra of ruthenocene at ambient and liquid-nitrogen temperatures have been interpreted with the aid of solution and Raman single-crystal data to yield a complete assignment, including inactive modes. The polarisation property of the π(C–H) modes in ferrocene has been determined for the first time. Contrary to the accepted order, the i.r.-active ring ‘tilt’ mode of ruthenocene comes at lower frequency than the M–ring bond stretch.

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.

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

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.

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.

The long-sought ν4(a1′) mode of (PNCl2)3 has been located at 172 cm–1 in solution and its symmetry species confirmed by a Raman Study of an oriented single crystal. Experimental evidence from the crystal spectra also allowed distinction between e′ and e″ species. A reassignment of the spectrum is offered.

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 spectroscopic evidence for solutions and oriented single crystals is presented from which a reassignment is made for the ν(CO) frequencies of the title compounds.

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.