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In an astonishingly short period in September 1939, while on a brief visit from England, F.P. Bowden (FRS 1948) conceived the need, and obtained the approval of the Australian Council for Scientific and Industrial Research (CSIR), to establish a wartime friction and bearings research laboratory within the University of Melbourne. He recruited a galaxy of young talent, which during the following six years made major contributions to four very diverse defence-related problems. The infant laboratory survived the peace and eventually evolved into the internationally admired Division of Tribophysics. Many of the original members of the group went on to distinguished careers in Australia, the UK and elsewhere. The story of the exciting early days of the laboratory and the subsequent achievements of its staff are briefly described.

A high-resolution IR study of the Mg(HCCH) complex in helium droplets revealed νCH centred at 3277.9204(15) cm−1.1

Recent work has shown that most transition metals and post-transition metals can be incorporated as vertices in polyhedral metalloborane cluster compounds. Numerous synthetic routes have been devised and structural studies on the resulting clusters have revealed an astonishing variety of geometrical forms. Most boranes and borane anions from B2 to B12 now have metalloborane analogues in which one or more of the various boron atoms in the cluster of the parent borane are replaced by a metal centre. In addition, the flexibility introduced into the bonding by the differing connectivities, coordination numbers, and oxidation states of the various metals enables many unprecedented clusters to be generated. Examples of these novel cluster geometries include con juncto[ (PMe2Ph) 2 (Pt2B8H14)J, con juncto[ (PMe2Ph) 2 (Pt2B12H18) 1, iso—nido{ (PPh3) 2 (IrB9H10 .PPh3) 1, iso—closo-[H(PPh3) (PPh2a6H4) (Ir9H8) 1, iso—closo-[H(PMe3) 2(IrB8H7C1) 1, con juncto{ (PMe2Ph) (PtB16H18 . PMe2Ph) 1, and several conjuncto-PtB18 and -Pt2B18 species some of which feature the construction by cluster rearrangement of an unusual confacial triangular fusion between the two subclusters.

The Mossbauer spectra of the mono-, di-, tri- and tetra-nuclear iron carbonyl anions and carbonyl hydride anions are reported and compared with the known spectra of the neutral binary carbonyls. Increase in anionic charge in the sequence 0, –1, –2 results in progressively lower values of chemical isomer shift δ for each series. In addition, there is a systematic increase in δ as the co-ordination number of iron increases from 4 to 7. These trends are interpreted in terms of changes in the bonding in these compounds. Systematic variations in the quadrupole splitting Δ are also discussed.The effects on δ and Δ of substituting carbon monoxide by tertiary phosphines are investigated and the structure and bonding in the unusual new compound [(OC)3FePMe2Ph]3 are discussed. The Mossbauer spectra of the tetrameric species [π-C5H5FeCO]4 and [π-C5H5FeCO]+4 are also investigated.

The structure of the compound [Ph3MeP]2[Zn(B10H12)2] has been determined by X-ray diffraction analysis; 4569 reflections were measured on a four-circle diffractometer. Crystals of the salt are monoclinic, space group C2/c with Z= 8 in the unit cell of dimensions a= 41·549(34), b= 10·071(8), c= 23·500(18)A, and β= 99·20(5)°. The structure was solved by Fourier methods and refined by least-squares calculations to a final R of 8·9%; all 121 atoms were located. The anionic complex can be considered to comprise two bidentate B10H122– ligands co-ordinated tetrahedrally to zinc(II). The distortions in the boron cluster due to the large size of the zinc atom are discussed. The cadmium and mercury analogues were shown to be isostructural.

The products of the reaction between tris(primary amino)boranes and boron trifluoride have been shown to depend on the nature of the alkyl group present. When R = Pri or But the product is the primary aminoboron difluoride dimer, (RNHBF2)2, whereas when R = Me, Et, Prn, or Bui the product is the corresponding primary amine–boron trifluoride adduct together with various substituted borazines. Likewise tris(ethylamino)borane undergoes a novel reaction with boron trichloride to a quantitative yield of ethylamine—boron trichloride and B-trichloro-N-triethylborazine, (EtNBCl)3. Some transammination reactions of diethylamino-boron difluoride are also described.The proton, boron, and fluorine nuclear magnetic resonance spectra of these compounds are recorded. The occurrence of long-range proton–boron coupling is discussed and it is also shown that the alkyl groups in isopropylaminoboron difluoride dimer are in the trans configuration with respect to the plane of the ring.

The Mossbauer spectra of 32 iron dithiolene complexes have been measured at 77°K and at a higher temperature, usually 295°K. The structural implications of the observed chemical isomer shifts and quadrupole splittings are discussed. The variations of these parameters in several isostructural series of complexes as the nature of the ligand is systematically varied or as the charge state of the species is altered are interpreted in terms of the detailed electronic bonding. The complexes are unusual in that changes in the dithiolene ligand which are several atoms removed from the iron atom frequently have a marked influence on the quadrupole splitting whilst leaving the chemical isomer shift virtually unaltered. The tetrachlorobenzene-1,2-dithiolato-complexes [Fe{S2C6CI4}2]22– and [Fe py {S2C6CI4}2]– have the largest quadrupole splitting yet reported for low-spin FeIII compounds (3·02 mm. sec.–1).

A Mossbauer investigation of the disproportionation of quenched samples of Fe1–xO between 300 and 700 K has been carried out. At temperatures above 500 K the prior rearrangement of Fe1–xO into Fe1–x–yO and Fe1–x+yO (see Part I) was too rapid to be recorded on the Mossbauer spectra, but the observed reduction in the quadrupole splitting as a function of time at constant temperature can be discussed in terms of the reaction: (1–4z)Fe1–xO →(1–4x)Fe1–zO +(x–z)Fe3O4 In the limit, z becomes very small and the monoxide approaches stoicheiometry. The phase Fe0·99O had a Neel temperature of 196 ± 3 K and a range of hyperfine magnetic fields of 340 ± 20 kG at 77 K. At temperatures above about 570 K further disproportionation of Fe1–zO itself becomes rapid and the spectrum of metallic iron begins to appear, according to the reaction: 4Fe1–zO →(1–4z)Fe + Fe3O4 The rate of precipitation of Fe3O4 at a given temperature was found to depend not only on the initial composition of Fe1–xO, but also on the temperature from which the initial samples were quenched during preparation. The effect is interpreted in terms of the defect aggregations present in the initial samples.

The sign of the quadrupole coupling constant, e2qQ, has been determined for 119Sn in the following six compounds: [Mn(CO)5SnCl3], [Mn(CO)5SnCl2Me], [Fe(π-C5H5)(CO)2SnCl3], [Fe(π-C5H5)(CO)2SnBu3], [{Fe(π-C5H5)(CO)2}2SnCl2], and [{Fe(π-C5H5)(CO)2}2Sn(NCS)2]. It was found to be positive for all of the compounds except [Fe(π-C5H5)(CO)2SnBu3], which has a small negative value for e2qQ. In those compounds containing iron, the sign of e2qQ for 57Fe was also determined and found to be positive in each case. The nature of the bonding in these and similar compounds is discussed in relation to results obtained from other physical methods.

One of the prerequisites to a full understanding of the nature of coordination compounds is a knowledge of the strength of the donor-acceptor bonds which hold them together. In many complexes the situation is complicated by the presence of several such bonds; for example the compound may be 4-, or 6-co-ordinate so that several terms go to make up the total heat of formation of the complex. For this reason it was decided to study simple 1 : I and I : 2 addition compounds rather than the usual octahedral, square, or tetrahedral complexes. In this way we hoped to be able to interpret the various energy terms more satisfactorily and so arrive at a sequence of strengths of donor-acceptor bonds between a given ligand and a series of electron acceptors, or between a given acceptor and a series of ligands. The systems we have been most interested in are those in which the electron acceptor is an element of Group III and this paper reviews the results obtained on the I : I complexes of boron trichloride and tribromide and the I : 1 and I : 2 complexes of gallium trichloride and tribromide. Two methods have been used to determine the heat of formation of a crystalline complex: equilibrium vapour pressure measurements and direct reaction calorimetry. These give the heat offormation of the solid complex and from these, the heats of formation in the gas phase can be obtained in those cases where the relevant heats of sublimation and vaporization are known. The equilibrium vapour pressure method is normally restricted to those cases where a solid complex dissociates either into a solid and a gas or into two gases. Experimentally the method simply involves synthesizing the complex in a vacuum line and then measuring its vapour pressure directly or on a spiral gauge. In this work it has been used mainly to cross-check the calorimetric measurements. As an example of its independent use, the dissociation pressure of triphenylmethyl tetrachloroborate was determined: PhaC+BCI4-(c.)~ PhaCCI(c.) + BCla(g.)

The structure of the title compound has been determined by X-ray diffraction analysis by use of diffractometer data. Crystals are triclinic, space-group P with Z= 2 in the unit cell of dimensions a= 5·686(4), b= 8·780(6), c= 10·690(10)A, α= 88·32(5), β= 113·80(5), and γ= 97·47(5)°. The structure was solved by Fourier methods and refined by least-squares calculations to a final R of 7·0% for 2817 independent reflections; all 24 atoms were located. The anion contains three BH2 groups and two B–H–B groups in the open face of the icosahedral fragment of the B9 cluster (2613 topology).

The structure of the compound of empirical formula (Et2O)2Cd(B10H12) has been investigated by X-ray diffraction techniques from diffractometer data. Crystals are triclinic, space-group P1 with one dimeric unit in the unit cell of dimensions a= 9·386(13), b= 10·854(18), c= 10·202(17)A, α= 90·07(9)°, β= 105·60(9)°, and γ= 102·80(8)°. Because of disorder in the positions of the ethyl carbon atoms, the structure was not solved completely (final R 9·8 % for 3423 independent reflections), but the dominant features have been elucidated; the molecules are dimeric, each cadmium atom being bonded (via three-centre bonds) to two B10H12 icosahedral fragments. The co-ordination environment of each cadmium is completed by two ether ligands. The two B10H12 units therefore act as bridges between the metal atoms and can be considered to be related to decaborane by replacement of two bridging hydrogen atoms by the cadmium atoms.

Mossbauer spectra have been obtained for a series of organotin compounds in which the tin atom is covalently bonded to another tin or other metal atom. Compounds studied include Ph4Sn, (Ph3Sn)2, (Ph3Sn)2SnPh2, (Ph3Sn)4Sn, (Ph3Sn)4Ge, and (Ph3Sn)4Pb. Despite the absence of a regular tetrahedral environment for the tin atom in most of these compounds, no observable quadrupole effect was detected. This unexpected result is discussed in terms of structures and bonding.

Reaction of halogenomagnesium derivatives of decaborane(14), B10H13MgX, (X = Br, l), with alkylmercury(II) halides, RHgY, (R = Me; Y = Cl, Br, l: R = Et, Prn; Y = Cl), in ether solvents, yields the solvated double salts of magnesium, (MgY2)x{Mg[Hg(B10H12)2]}(solvent)y, which dissolve in water to form the ion, [Hg(B10H12)2]2–, a formal mercury(II) complex of the dodecahydro-nido-decaborate(2-) ion, B10H122–. Physical data (including 28·87 MHz and 80·53 MHz 11B n.m.r. spectra) for tetramethylammonium and triphenylmethylphosphonium salts of the anions, [Zn(B10H12)2]2–, [Cd(B10H12)2]2–, and [Hg(B10H12)2]2– are presented and correlated with their known structures in the solid state.

The lambda transition in ammonium chloride at 242 K has been investigated using 57Fe2+ impurity atoms. These probably reside on interstitial sites in an effective [FeCl4(H2O)2]2– complex. The temperature dependence of the quadrupole splitting reveals a larger tetragonal distortion of the impurity site in the low-temperature ordered state of the NH4Cl.

Trimethylamine–alane, Me3N,AIH3, reacts with decaborane to give the trimethylammonium salt of a new anion (B10H12AIH2–),nEt2O, where n= 1·5 to 2. This is the first example of 6,9 internally bridged derivative of B10H122– and contains direct Al–B bonds. Related reactions of decaborane with adducts of chloro- and alkyl-substituted alanes are also discussed. Controlled hydrolysis of the anion (B10H12AIH2–),nEt2O, liberates only one molar equivalent of hydrogen, and salts of the anion B10H15– were isolated from the hydrolysis mixture. The properties and structure of these compounds are considered.

The reactions of [Fe(CO)3SR]2(R = Me or Et) with the ditertiary phosphines L = Ph2P·[CH2]N·PPh2(n= 1 or 2), cis-Ph2P·C2H2·PPh2 and Ph2P·NEt·PPh2 and the ditertiary arsines L = Ph2As·[CH2]n·AsPh2(n= 1 or 2) under various experimental conditions have been studied. A number of different types of products have been isolated. These include [Fe2(CO)5L(SR)2] and [Fe(CO)2LSR]2 in which the ligands are monodentate, [{Fe(CO)2SR}2L] in which the ligand bridges two iron atoms, [Fe(CO)3(SR)2Fe(CO)L] in which the ligand is chelated to a single iron atom and [Fe2(CO)3L2(SR)2] in which one ligand is bidentate and the other monodentate. The nature of the product is shown to depend on the ligand and the reaction conditions. The reactions of [Fe(CO)3SMe]2 with the ligands L′= PEt3, PPh3, P(OMe)3, AsPh3, and SbPh3 have also been studied and the mono-substituted [Fe2-(CO)5L′(SMe)2], bis-substituted [Fe(CO)2L′SMe]2, and tris-substituted [Fe2(CO)3L′3(SMe)2] derivatives have been isolated.Mossbauer and i.r. spectroscopy have been used to elucidate the structures of the above derivatives as well as those of the products of the reactions of [Fe(CO)3SPh]2 with various tertiary and ditertiary phosphines. Systematic variations in the chemical isomer shift and quadrupole splitting are discussed in relation to the bonding in these compounds.

The Mossbauer spectra of a large number of hexaco-ordinate tin(IV) compounds have been investigated. No quadrupole interaction is observed even when the six atoms bonded to tin are not all the same, provided that all six have non-bonding pπ electrons. When some of the attached groups have no such pπ electrons (e.g., methyl) then substantial quadrupole splitting is observed. Isomer shifts show the expected trend with electronegativity of the halogen but are somewhat insensitive to the nature of the chelating ligand. The results have been used to draw structural conclusions about several compounds whose detailed structures have not previously been established unambiguously. Among these are the adducts of the tin(IV) halides with 8-hydroxyquinoline, with [Ph2P(O)]2NH, and with dinitrogen tetroxide.

Spectroscopic and magnetic studies have been made on Fe3+ ions in a variety of oxide host lattices, namely NaSc1–xFexTiO4, NaFeSnO4, CaSc2–xFexO4, Sc2–xFexTiO5, NaFeTi3O8, α-NaSc1–xFexO2, CsxScx–yFeyTi2–xO4, β-NaAl1–xFexO2, CsxScx–yFeyTi4–xO8, LiFeTiO4, and CsFeSi2O6. The 119Sn Mossbauer spectra of NaFeSnO4 and NaScSnO4 were also recorded. In most of these lattices the crystal fields at the iron sites depart significantly from cubic symmetry and we have found that isolated Fe3+ ions give rise to a strong e.s.r. signal at g′= 4·3 and a magnetic Mossbauer spectrum. These spectra are strongly concentration and temperature dependent. We conclude that the magnetic Mossbauer spectra are the result of a pure spin-alignment effect, while the g′= 4·3 e.s.r. signal is the result of ground-state splitting which occurs even when the spins are not strictly aligned. The electronic spectra of these compounds have been analysed and the bands corresponding to a particular transition are found to be remarkably constant. Only those transitions which correspond to the two lowest levels, and whose energies are crystal-field dependent, show significant changes in band position.

Room-temperature Mossbauer spectra of rapidly quenched samples of nonstoicheiometric Fe1–xO (0·053 < x < 0·109) show an envelope of overlapping resonances which, for small values of x, can be resolved into five broad Lorentzian peaks assignable to a series of Fe2+ quadrupole doublets and an Fe3+ doublet at a lower velocity. As the phase deviates further from stoicheiometry the range of site symmetries produces a more complicated envelope which cannot be resolved into the sum of a small number of Lorentzian peaks. The influence of initial temperature and of quench rate have also been studied over the full range of composition and variations correlated with the known phase diagram for the system. Samples of Fe0·947O which had been most rapidly quenched from 1520 K into water showed negligible disproportionation during quenching. Their spectra, when compared with those predicted for various possible defect structures, suggested the presence of clusters of four vacant cation sites around a tetrahedral Fe3+. Changes in the spectra as the Fe3+ content was increased reflected the increase in the defect cluster size towards that previously proposed for Fe0·90O (13 vacant cation sites with 4 tetrahedral Fe3+). Fe3+ was present as a quadrupole doublet and no evidence was found for electron hopping between Fe2+ and Fe3+. Spectra of the magnetically ordered oxide phases at 77 K were consistent with this interpretation.

The Pople-Segal-Santry SCMO method is used to calculate the electronic structures of a selected series of compounds of Sn(IV) with basis sets including 5s, 5p, and 5d orbitals on tin. The occupation number of the 5s orbital of tin in each compound is correlated with their known experimental chemical shifts and an approximately linear relationship is found. The 5s electron density at the tin nucleus, calculated from the Fermi-Segre equation using a modified form of Burns' screening rules, also exhibits a linear relation with the observed shifts. The inclusion of 5d orbitals does not appear to exert a marked effect on the calculated s-electron densities. From the results the value of ΔR/R for the 119Sn nucleus on excitation to the 23.8 keV level is 3.5 × 10–4. The differential contribution, due to 5s screening, of 4s electron density to the total at the nucleus is calculated for the series. Finally, the occupation numbers of the three individual 5p orbitals lead to a qualitative understanding of experimental quadrupole splitting data.

The diffusive line broadening of the Mossbauer spectrum of Fe1–xO has been studied at 1074 and 1173 K and leads to activation energies for the jump process of 140 ± 20 kJ mol–1 for Fe0·940O and 135 ± 20kJ mol–1 for Fe0·910O. The observed reduction in the average cation-jump frequency from 42 MHz to 30 MHz over the range Fe0·940O to Fe0·910O at 1074 K has been compared with the number of atoms statistically able to jump in random and clustered defect configurations, but the observed behaviour can only be simulated by the incorporation of an activation energy of jumping which increases with increasing cluster size. The absolute magnitude of the derived self-diffusion coefficient was in general agreement with values obtained from radioactive tracer studies.