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Dipole moments have been determined for iron(III), cobalt(III), nickel(II), palladium(II), platinum(II) and copper(II) complexes of the mercapto-β-diketones RC(SH):CH·C(O)R′[R = Me or Ph, R′= Ph; R = Me, C4H3S (2-thienyl), Ph. p-MeC6H4, or p-BrC6H4, R′= CF3] from both static-polarization and dielectric-relaxation measurements. The moments clearly indicate cis-square-planar configurations for the nickel, palladium, platinum, and copper complexes, but do not distinguish unequivocally between facial- and meridional-octahedral configurations for the iron and cobalt complexes. Group dipole moments for the R substituents, except 2-thienyl, in the square-planar complexes have been derived from the dipole-moment data. The effect of the CF3 group is discussed in terms of its influence on the electron density in the chelate ring.

Nickel perchlorate hexahydrate Ni(ClO4)26H2O is found to undergo a new type of phase change from C2v7 to P21c/ symmetry as in the case of Fe(ClO4)26H2O. The mean susceptibility and the anisotropy of the crystal have been measured between 80K and 300K. An abrupt break in the mean moment square and anisotropy curves is observed at (225+or-1)K. The Mossbauer studies of this crystal diluted with Fe2+ ions showed anomalies in the ( Delta EQ) values at about 120K. Below Tc( approximately=225K) the ionic susceptibility Kperpendicular to becomes greater than K/sub /// and the trigonally distorted octahedron becomes tetragonally distorted. It is also found that on cooling through Tc, the value of the zero field splitting D changes sign and magnitude.

The rigorous resonance Raman effect was observed for the octahedral PtBr and PtI ions. The enhancement of the Raman intensity occurred for the totally symmetric ν1 band and for the non-totally symmetric ν2 band simultaneously in both cases of the two ions. The overtone bands of ν2 appeared in the spectra in addition to the ordinary long overtone progression of the ν2 vibration. The results are discussed in relation to the two closely lying electronic levels of the ions.

The steric course for Hg2+ and NO+ promoted aquation of some bis(ethylenediamine)cobalt(III) cations has been accurately determined at 23° C. Some are re-examinations of other work for which precision has been improved or different results obtained. Previous discussion related to the factors affecting aquation stereochemistry is amplified in the light of new results and some new correlations are noted.

The electronic and i.r. spectra of the complex biguanide bases of V, Cr, Mn, Co, Ni, Cu and Zn are studied and assignments of the chief bands are made. Spectral data conform to distorted octahedral structures for the V, Cr, Mn and Co complexes, square planar structures for Ni and Cu and a tetrahedral configuration for Zn.

Growth patterns on cube and octahedral faces of PbS crystals grown in silica gels at room temperature, and the etch pattern of growth strata on a crystal cleavage are described. The observations are discussed in relation to the mechanism and conditions of crystal growth.

Salicylaldehyde salicylhydrazone (SSH) complexes M(SSHH) 2 , M = Cu(II), Co(II), Mn(II), VO(IV), TiO(IV); M′(SSH2H), M′ = Cu(II), Ni(II), Co(II), and Cu 1 (SSHH) have been synthesised and characterised by analysis, infrared and electronic spectra and magnetic measurements, They are insoluble in common solvents and decompose above 250°C without melting. Subnormal magnetic moments have been observed in some of them. Comparison of electronic absorption bands of SSH and metal complexes show the presence of ligand-metal charge transfer bands. Cu(II) complexes are square planar while Ni(II) and Co(II) complexes have octahedral stereochemistry. In M′ (SSH2H) complexes, infrared spectra indicate the involvement of -OH, >CO and >CN groups. In others, only -OH and >CN appear bonded. Metal-metal interactions via oxo-bridge structures have been discussed in the light of magnetic, electronic and infrared data.

Free energies of sinusoidal and antiferromagnetic spin density waves (SDW) are calculated with the model of energy bands proposed in a previous paper. The calculation for the sinusolidal SDW is made by an interpolation method. It is shown that the commensurate-incommensurate transition (denoted by C-I transition) in Cr-Mn alloys arises from the cooperation of the effect of entropy and the effect of a flow of electrons between the octahedral Fermi surfaces of electron and hole bands and the other free Fermi surfaces. The C-I transition in a helical SDW is also studied. Finally the origin of the C-I transition in Cr-Fe alloys is qualitatively discussed.

It is proposed that the orientation relationships of carbides and nitrides in steels are best considered in terms of a simple correspondence between the metal atoms which coordinate the interstitial atoms in the precipitate and the octahedron of metal atoms which surround carbon and nitrogen in the parent phase. The known orientation relationships are rationalised in terms of the model which also allows unestablished relationships to be predicted.

The mineral brazilianite, NaAI3(PO4)2(OH)4, is monoclinic, space group P21/n, with a = 11.233 (6), b = 10"142 (5), c=7-097 (4) ,& and fl=97.37 (2) A~. With Z = 4 the calculated density, 2.998 (4), compares well with the measured density, 2.98 (1) gcm -3. The structure was solved by direct phasing and Fourier techniques. Of the 2276 unique reftexions collected by counter methods, 2033 with I> 3a(l) were used in the least-squares refinement to R=0-030 (wR=0-050). Brazilianite is composed of chains of edgesharing AI-O octahedra linked by P-O tetrahedra, with Na located in cavities in the framework.

Die fruher an den gemischten Komplexsalzen des Typs K2[OsClnY6–n], Y = Br, J; n = 1–5 experimentell bestimmten kinetischen Daten fur die intramolekulare Isomerisierung bzw. den intermolekularen Ligandenaustausch im festen Zustand werden auf die reinen Hexahalogenokomplexe extrapoliert. Bereits unter 100°C beginnt die Umlagerung innerhalb der einzelnen Oktaedergruppen, der intermolekulare Austausch der Liganden setzt erst bei deutlich hoheren Temperaturen ein. Fur die Reaktionsgeschwindigkeiten gelten folgende Reihen: intramolekular: K2[OsCl6] < K2[OsBr6] < K2[OsJ6], intermolekular: K2[OsJ6] < K2[OsCl6] < K2[OsBr6]. Ligand Exchange in Solid Complex Salts. III. Mobility of Ligands in Pure Hexahalo Complexes of Osmium(IV) The kinetical dates of intramolecular isomerization and intermolecular ligand exchange in solid-state, formerly determined experimentally for mixed-ligand complexes of the type K2[OsClnY6–n], X = Br, I; n = 1–5, are now extrapolated to pure hexahalo-complexes. Already below 100°C the rearrangement within the octahedral groups begins, the intermolecular ligand exchange just arises at distinct higher temperatures. For the rates the following series are valid: intramolecular: K2[OsCl6] < K2[OsBr6] < K2[OsI6], intermolecular: K2[OsI6] < K2[OsCl6] < K2[OsBr6].

High temperature behaviour of the electrical conductivity and the Seebeck effect in MnFe2O4 single crystals is studied both experimentally and theoretically. Various heat cycles in the temperature range 300–600 °C lead to marked changes in the temperature dependences of electrical properties. A two donor level model of electrical conduction is used to explain the observed behaviour. The influence of the cation migration between the tetrahedral and the octahedral sites of the spinel lattice on electrical properties of Mn ferrites is demonstrated.

Most of the bands predicted by a group theoretical analysis have been observed in the i.r. and Raman spectra of a number of ordered, cubic perovskites A2BIIBVIO6. With the help of cartesian symmetry coordinates, and from the wealth of experimental data including 24Mg26Mg, 40Ca44Ca and 122Te130Te isotopic frequencies, it appears that the separation of the observed vibrations in internal and external modes is a good approximation for the high-frequency bands, which are assigned to the stretching vibrations of the BVIO6 octahedron. This approximation is not so satisfactory for the corresponding bending vibrations, since these vibrations may be more or less mixed up with translational, external modes which belong to the same symmetry species (T1u in i.r.; T2g in Raman). The behaviour of the totally symmetric A1g mode has been investigated in some detail: its frequency is predominantly determined by the nature of the hexavalent BVI cation; but it is also influenced by the nature of the bivalent BII octahedral cation, acting through its bonding force and ionic radius, and by the size of the large A cation, because of its influence on the BIIO distance. Abnormal values of the A1g frequency are observed when the BII cation is rather large: this is qualitatively explained by a displacement of the oxygen towards the BVI cation, with or without distortion of the structure.

Complexes [IrHX2(Ph3P)3], [IrX(Ph3P)3] (X = Cl and Br), [IrHCl(C6H4PPh2)(Ph3P)2], and [IrCl (Ph3P)(C8H12)] (C8H12 = 1,5-cyclo-octadiene) were reacted with ligands (o-Ph2LC6H4)3L′ (L′ = P and As; L = P and As), L′L3. The isolation of complexes of the types [IrHX(L′L3)][BPh4], octahedral, [IrX (L′L3)], trigonal bipyramidal, and unusual [Ir(Ph3P) (L′L3)][BPh4], also trigonal bipyramidal, is reported. The proton and phosphorus-31 n.m.r. spectra and the electronic spectra of some of the complexes are recorded.

EPR measurements have been made of the spin Hamiltonian parameters of Mn2+ at the three different sites in each of the four diamagnetic garnets LuAlG, YAlG, LuGaG and YGaG. The temperature variation of all the second order crystal field parameters together with those of the fourth order crystal field parameter and the hyperfine splitting parameter for octahedral sites in YGaG have been followed over a range 4·2-550°K. The magnitude of the various parameters and their temperature variations are discussed.

The ordered structure of the V8N subnitride was studied by X-rays, electron diffraction and electron microscopy. V8N exists in two different modifications (α′ and α″). The vanadium sublattice of both phases is pseudo-tetragonal, in reality triclinic, with lattice parameters: αo = bo = 3.114 A, co = 2.994 A, αo = βo = 90.5o ± 0.1o, γo = 90o. The proposed unit cell of α′-V8N has dimensions: a = 2√2 ao, c = 2co and corresponds to V32N4. Doublets of nitrogen atoms occupy two sets of octahedral cavities whose shortest axes are aligned along the x and y directions of the sublattice in an ordered fashion. The α″-V8N phase is a periodically twinned modification of the α′-V8N, the twin plane being of the (001) type. The V8O suboxide has the same structure as the α″-V8N, the sublattice parameters being: ao = bo = 3.11 A, co = 2.994 A, αo = βo = 90.3o ± 0.1o, γo = 90o.

We examine the consequences for the Mossbauer spectrum of coupling between asymmetric vibrational modes and an electronic state having orbital degeneracy – the Jahn-Teller (JT) effect. Characteristic modifications of the quadrupole coupling by a spontaneous JT distortion (« static JT effect ») and by a dynamic coupling of electronic and vibrational motions (« dynamic JT effect ») are discussed with the aid of a simplified model. The importance of small crystal strains in determining the type of spectrum observed is discussed, as is also the role of thermally induced transitions in causing motional averaging of the spectrum. Examples are given of JT effects as observed or anticipated in the Mossbauer spectrum of Fe2+ in crystal sites with tetrahedral and octahedral coordination.

The reaction of dialkyl(chloromethylene)ammonium chlorides (R2NCHCl)+Cl–, (R = Me, Et, Pri, or Bun), with RhI substrates [RhCl(PPh3)3], [RhCl(CO)PPh3]2, or [RhCl(CO)2]2 affords RhIII secondary carbene complexes, [L′RhCl3CHNR2]n[L′= CO, n= 2; L′=(PPh3)CO, n= 1; L′=(PEt3)2 or (PPh3)2, n= 1], via a three-fragment oxidative-addition reaction. The secondary carbene RhIII complexes are characterised by a high degree of CN double-bonding, greater than in tertiary carbene complexes or carboxylic acid dialkylamides. The Ccarb–H1H n.m.r. resonance is at low field (τca. –1), ν(Ccarb–H) at ca. 3050 cm–1, and ν(Ccarb[graphic omitted]N) at ca. 1600 cm–1; coupling of Ccarb–H resonances are identified: 2J(103Rh–1H), 3J(31P–1H), and cis- and trans-4J(C1H3N–1H). A single-crystal X-ray analysis of [RhCl3(PEt3)2CHNMe2] has been carried out to R= 0·050; the complex has an approximately octahedral Rh environment with mutually trans-phosphine ligands. Bond distances (A) are Rh–Ccarb= 1·961(11), Ccarb–N = 1·289(14), Ccarb–H = 1·14(4), Rh–P = 2·368(3) and 2·372(3), Rh–Cl (mutually trans)= 2·357(4) and 2·364(3), Rh–Cl (trans-carbene)= 2·445(4). The high trans-influence of the secondary carbene ligand is discussed in terms of X-ray, i.r., and n.m.r. data, and it appears to have the highest trans-influence of a neutral ligand of RhIII.

Ligand–ligand repulsion energies have been calculated for [M (bidentate)3(unidentate)]x± complexes using a ‘normalised bite’ of 1·22, which is the appropriate value for bidentate β-diketonate ligands attached to a lanthanoid element. (‘Normalised bite’ is defined as the distance between the two donor atoms of the same bidentate ligand divided by the metal atom–donor atom distance.) Three minima of closely similar energies appear on the potential-energy surfaces. The first two correspond to a capped octahedron (C3v symmetry) and an irregular polyhedron (C1 symmetry), and are the structures observed for compounds whose structures have been determined, and where the unidentate ligand is water or a carbonyl compound. The third minima (Cs symmetry) corresponds to a stereochemistry intermediate between a pentagonal bipyramid and a capped trigonal prism, and it is predicted that it will be formed only with unidentate ligands which form particularly stable ligand → lanthanoid bonds.

The crystal structures of the title compounds have been determined from three-dimensional X-ray diffractometer data by conventional Patterson and Fourier methods. Both compounds crystallize in the orthorhombic space group P212121, with Z= 4; cell parameters for the ammonia derivative (II) are: a= 10·540(5), b= 13·147(6), and c= 10·443(5)A; those of the triphenylphosphine derivative (I) are: a= 17·211(8), b= 14·225(6), and c= 10·656(5)A. The structures were refined by least-squares methods to R 0·038 [(II), 1651 observed reflections] and 0·049 [(I), 1429 observed reflections]. Evidence for trans-influence in this type of octahedral cobalt(III) complex is discussed.

Ammonium titanyl oxalate monohydrate, (NH4)2 TiO(C2O4)2·H2O, is monoclinic with cell parameters A = 13.473(2), B = 11.329(1), C = 17.646(2) A, β = 126.66(1)°. The space group is P21/c with Z = 8, dc = 1.808 g cm−3 and dm = 1.80 g cm−3. The crystal structure was determined from single-crystal diffractometer data and refined by least-squares methods using isotropic thermal parameters. The conventional R factor was 7.0% for 2466 used reflections. The anions consist of cyclic tetranuclear complexes [TiO O (C2O4)2]48− with symmetry. The titanium atoms are six-coordinated with two bridging oxygen atoms cis to one another and four oxygen atoms of bidentate oxalate groups, together forming a distorted octahedron. The titanium atoms of the tetramer are linked through oxygen atoms at two neighbouring apices of each octahedron. The actual name of the compound should therefore be: ammonium cyclotetra-di-μ-oxo-cis-dioxalatotitanate(IV)tetrahydrate. The di-μ-oxo-tetratitanium unit is an eight-membered ---O---Ti---O--- ring with Ti-O distances of successively 1.840(7), 1.785(7) and 1.855(6), 1.788(8) A, repeated by the centre of symmetry, and the orientation of the atoms suggests the presence of dπ---pπ 3-center 2-electron bonds in each Ti---O---Ti set. The Ti---O distances trans to the bridging oxygen atoms are much longer: 2.060(7), 2.101(7), 2.081(7) and 2.116(7) A respectively, as is to be expected from the charge displacement due to the dπ---pπ bonding. Most O---Ti---O angles in the distorted octahedra differ considerably from 90°. As was found by difference Fourier synthesis and thermal analysis, half of the crystal water is held very loosely compared to the other half.

The influence of relativistic effects on the positions of charge-transfer bands in octahedral hexahalo species is considered and it is demonstrated that in the 5d series spin-orbit contributions are frequently comparable in magnitude to the changes in spin-pairing energy which accompany a given dq → dq+1 transition. The inclusion of spin-orbit corrections is found significantly to improve the correlations between χopt, the optical electronegativity, and q, the orbital occupation number, and to allow a better rationalization of the positions of the π → f2g bands in terms of the spin-pairing energy concept.

The study of rates and mechanisms of ligand exchange reactions in coordination compounds has received a great deal of attention in the literature.1,2 A volume of evidence has been accumulated to indicate that in the ligand substitution reactions of octahedral transition metal ion complexes, bond breaking is more important than bond formation in the determination of the reaction rate. Unfortunately, nearly all studies of this type carried out on octahedral complexes have been done in the free ligand as solvent.2 Under these conditions there is no opportunity to study definitively the role of the free ligand in the exchange mechanism. Ideally, the study of the ligand exchange reaction should be carried out in an inert solvent so that the concentration of the free ligand can be varied with no fear of the solvent participating in the exchange reaction.

The molecular orbital orientation of the angular overlap model has been developed to describe the d-d electronic spectra, anisotropic molecular magnetic susceptibilities, and esr g values of orthorhombically distorted octahedral copper(II) complexes. By systematically varying the σ and π perturbation energy parameters good agreement is reached between the experimental properties and the corresponding calculated values with particular reference to the potassium copper Tutton's salt (KCu(HO)(SO)).

An olive-green and a violet form of Ni(C 5 H 6 NO 3 ) 2 , a pyridine adduct Ni(C 5 H 6 NO 3 ) 2 . 2Py and orange-red Ni(C 5 H 7 N 2 O 2 ) 2 have been prepared from Ni(II) salts and isonitrosoacetylacetone in addition to the Ni(CH 3 COO)(C 5 H 7 N 2 O 2 ) and Ni(C 5 H 7 N 2 O 2 ) 2 already reported in the literature. Magnetic and spectral measurements reveal that the two forms of Ni(C 5 H 6 NO 3 ) 2 , Ni(C 5 H 6 NO 3 ) 2 . 2Py and Ni(CH 3 COO).(C 5 H 7 N 2 O 2 ) have octahedral or pseudooctahedral structures, whereas the two varieties of Ni(C 5 H 7 N 2 O 2 ) 2 have square-planar configurations. PMR studies suggest that at least three structural isomers of Ni(C 5 H 2 N 2 O 2 ) 2 exist in CDCl 3 solution.

The morphology of natural rounded rhombic dodecahedral diamonds has been studied optically and by scanning electron microscopy, and their internal structures have been investigated by X-ray topographic techniques. That this rounded habit arises from dissolution of a sharp-edged octahedral growth form is indicated both by theoretical considerations and experimental evidence. The hypothesis that these diamonds grew throughout their history as rounded rhombic dodecahedra is directly refuted by the X-ray topographic studies. The information on dislocation distribution revealed by X-ray topographs also provides strong evidence against a current variant of the growth hypothesis, that the rounded rhombic dodecahedral habit developed upon an octahedral core. The manner by which dissolution of surfaces of rounded dodecahedral diamonds proceeds can be described on an atomic scale by motion of kinks along stable monomolecular steps parallel to 〈110〉 directions. It is shown that this process leads to the development of edges parallel to the minor diagonals of the rhombic surfaces, in accord with observation.

The hexagonal ordered perovskite-like compounds Ba4Ta3LiO12 and Ba4Nb3LiO12 have been prepared. The structure of Ba4Ta3LiO12 has been determined by profile analysis of a powder neutron diffraction pattern. The structure is based on an eight layer (ccch) stacking sequence of the BaO3 layers (space group P6 3 mmc ) with the lithium atoms confined to the face-shared octahedral sites. The relationship of this structure to that of Ba5Ta4O15 is discussed.

Cubic, disordered phases of the compounds MSbO 3 (M = Li, Na, K, Rb, Tl, and Ag) have been investigated. KSbO 3 is readily synthesized in the disordered, cubic structure at high pressure, and the other isomorphic compounds were obtained by ion exchange. The structures of NaSbO 3 and AgSbO 3 , which have space group Im 3, were solved by X-ray single-crystal analysis. The structures contain an essentially rigid SbO 3 subarray consisting of pairs of edge-shared octahedra sharing common corners. Within this subarray, face-shared octahedra form 〈111〉 tunnels that intersect at the origin and body center of the unit cell, and the M + ions are randomly distributed over two positions within these tunnels. Ordered, cubic phases have the primitive-cubic space group Pn 3. The two M positions are different for Na + and for Ag + ions. At one of the Ag + -ion positions, the AgO bond length is only 2.26 A, consistent with the gray-black color of AgSbO 3 . Deformation of the 4 d 10 Ag + -ion core by 4 d -5 s hybridization appears to be induced by AgO covalent bonding. This conclusion is compatible with the observation that ion exchange is reversible for all compounds but AgSbO 3 . Several properties of these compounds are compared with the super ionic conductors M 2 O·11Al 2 O 3 β-alumina.

The M\"ossbauer spectra produced by ${10}^{\ensuremath{-}4}$-at.% ${\mathrm{Co}}^{57}$ and 0.5-at.% ${\mathrm{Fe}}^{57}$ doped in the normal spinels ${\mathrm{Co}}_{3}$${\mathrm{O}}_{4}$, Co${\mathrm{Rh}}_{2}$${\mathrm{O}}_{4}$, Co${\mathrm{Cr}}_{2}$${\mathrm{O}}_{4}$, Co${\mathrm{Mn}}_{2}$${\mathrm{O}}_{4}$, and Zn${\mathrm{Co}}_{2}$${\mathrm{O}}_{4}$ have been obtained. Based on properties of the spinel structure and on correlations with M\"ossbauer data from the natural-iron spinels, these spectra are interpreted in terms of the daughter and impurity iron being located on the tetrahedral and octahedral lattice sites. The charge state of the daughter iron is not always the same as that of the parent cobalt; instead, it is generally that of natural iron in the parallel spinel compounds ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, Co${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$, Fe${\mathrm{Co}}_{2}$${\mathrm{O}}_{4}$, Fe${\mathrm{Cr}}_{2}$${\mathrm{O}}_{4}$, Fe${\mathrm{Mn}}_{2}$${\mathrm{O}}_{4}$, and Zn${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$. From this and other evidence, we propose that the daughter-iron's valence is determined primarily by the chemical bonding properties of iron (as distinct from cobalt) in the environment where it is created. Of the several models of spinel crystal chemistry, that of Goodenough and Loeb roughly accounts for our conclusions.

X-ray diffraction studies of single crystals of (Cr0.01V0.99)2O3 have shown that the transition from the low to high temperature rhombohedral forms of this material proceeds without changing the orientation of the unit cell axes. The structures of both the high and low temperature forms have been determined at 23°C using single crystal x-ray diffraction techniques. Both forms are isomorphous with V2O3, but upon heating the M-M distance across the shared octahedral face increases from 2.700(1) A to 2.747(1) A while the M-M distance across the shared edge increases from 2.884(1) A to 2.917(1) A. The M-O distances increase by a maximum of 0.011A. The low temperature form of (Cr0.01V0.99)2O3 is isostructural with V2O3 while the high temperature form is isostructural with (Cr0.038V0.962)2O3.

Low temperature spectroscopy and spectral analysis by Robinson and Fournier of the Yb 3+ spectrum in an alkali alkaline earth silicate glass has shown that this ion is sixfold coordinated in a site whose symmetry approaches octahedral. A similar analysis is performed for Er 3+ doped into the same alkaline earth glass. The level separations within the 4 F 9 2 , 4 I 9 2 , 4 I 11 2 , 4 I 13 2 and 4 I 15 2 multiplets are fitted to the diagrams of Lea, Leask and Wolf using the operator equivalent factors of Erath. The crystal field parameters values A 4 〈 r 4 〉 = 288 cm −1 and A 6 〈 r 6 〉 = 15.2 cm −1 provide the best agreement for the five multiplets. The degeneracy of the 4 F 9 2 multiplet is completely lifted, and the analysis correctly identifies the Γ 8 states. In the other multiplets, good agreement is obtained where the Kramers doublets are distinguishable. It is concluded Er 3+ is in a site whose symmetry approaches octahedral.

The crystal structure of [(Me2N)2TiF24 has been determined by single-crystal X-ray diffraction. The crystals are tetragonal, I 4 , a = b = 11.313(5), c = 12.862(4) A, Z = 2. The titanium atoms display a distorted octahedral coordination and are linked by TiFTi and TiNMe2Ti bridges to form a tetramer, which possesses a crystallographic inverse tetrad axis at its centre. One fluorine and one dimethylamino group do not participate in the bridging. The principal bond lenghts are TiF(bridging) 2.00(2) and 2.06(2), TiF (terminal) 1.77(2), TiN(bridging) 2.14(3) and 2.19(3), TiN(terminal) 1.99(30) A. The structure has been refined to R = 0.077 for 231 visually estimated unique reflections.

Solution studies of the reactions of bis(dimethylthiocarbamato)nickel(II) and bis(di-n-propylthiocarbamato)-nickel(II) with a variety of primary, secondary, and aromatic amines have been conducted. Primary amines yield either octahedral bis or tetrakis amine adducts, the latter presumably containing monodentate oxygen-bonded thiocarbamate ligands. Normal secondary amines yield bis adducts in equilibrium with a pentacoordinate species, while α-hindered secondary amines yield an anomalous compound of undetermined structure. Aromatic amines yield bis adducts, with the exception of 2,6-lutidine, which exhibits an equilibrium with a pentacoordinate species. The PMR contact shifts and Ai values are reported for the amine protons.

Bis adducts of n -hexyl, n -octyl, n -undecyl and n -hexadecylamine with the trifluoroacetyl-acetonates of nickel(II) and cobalt(II) have been prepared. They are octahedral complexes similar to compounds previously reported. Mono adducts of hexamethylenediamine, 1,11-diaminoundecane and 1,12-diaminododecane with the acetylacetonates and trifluoroacetylacetonates of nickel(II) and cobalt(II) and with the dipivaloylmethanate of nickel(II) have been prepared. Spectral properties and molecular weights indicate a polymeric, pseudo-octahedral structure for these complexes.

The reaction of an imidoyl chloride R1C(Cl):NR2 with the RhI complex [Rh(CO)2Cl]2 in the rigorous absence of hydrogen chloride affords the RhIII carbene chelate Cl3(OC)[graphic omitted]R2. The chloride ligands are replaceable by Br– or I–, and the chelate bridge is cleaved by reaction with a tertiary phosphine. A single-crystal X-ray analysis of (IV) I3(OC)[graphic omitted]Me by the heavy-atom method has been refined to R 0·047 for 2400 independent terms measured on a diffractometer: the complex has an approximately octahedral Rh environment, with Rh–C(carb) 1·968(13), C(carb)–N 1·328(16), Rh–N 2·047(9), Rh–I 2·662(4)—2·774(4), and Rh–C(O) 1·892(14)A. Crystals are monoclinic, a= 10·83(1), b= 17·24(2), c= 11·52(1)A, β= 97·3(2)°, Z= 4, space group P21/n.

We have carried out a study of nickel-zinc ferrite of composition Zn0.218Ni0.752Fe2.03O4+y, with varying oxygen nonstoichiometry y. The method used was to measure the intensity of three groups of X-ray reflections on single crystal specimens with subsequent division of the amounts of mean-square dynamic and static displacement of the ions on the sublattices. From the amount of static displacement compared to two calculated models, one of which was based on an ionic approximation while the other was based on approximation of an elastically isotropic continuum, the character and distribution of point defects in the spine structure was determined. It was established that in nickel-zinc ferrite with y 0 vacancies appear in the octahedral cation sublattice.

Spectroscopic measurements are reported on single crystals of the high-${\mathrm{Nd}}^{3+}$-concentration perovskite ${\mathrm{Cs}}_{2}$NaNd${\mathrm{Cl}}_{6}$ [$\ensuremath{\rho}(\mathrm{Nd})=3.2\ifmmode\times\else\texttimes\fi{}{10}^{21}$ ${\mathrm{cm}}^{\ensuremath{-}3}$] and on ${\mathrm{Cs}}_{2}$Na${\mathrm{Nd}}_{0.01}$${\mathrm{Y}}_{0.99}$ ${\mathrm{Cl}}_{6}$.The room-temperature fluorescence lifetimes are 1.23 and 4.1 msec, respectively, which are the longest reported so far for ${\mathrm{Nd}}^{3+}$ in any environment. This compound shows weak concentration quenching of fluorescence comparable to that observed in Nd${\mathrm{P}}_{5}$${\mathrm{O}}_{14}$ which has $\ensuremath{\rho}(\mathrm{Nd})=4\ifmmode\times\else\texttimes\fi{}{10}^{21}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. This is related to the isolation of the ${\mathrm{Nd}}^{3+}$ ions which are located in discrete Nd$\mathrm{Cl}_{}^{3\ensuremath{-}}{}_{6}{}^{}$ octahedra and have a minimum separation of 0.77 nm. The long fluorescence lifetime results from the strict octahedral coordination of ${\mathrm{Nd}}^{3+}$ which discourages electric-dipole electronic transitions. Absorption and emission of the $^{4}\mathrm{F}_{3/2}$ - $^{4}\mathrm{I}_{9/2}$ and $^{4}\mathrm{F}_{3/2}$ - $^{4}\mathrm{I}_{11/2}$ levels are found to be dominated by phonon-assisted vibronic transitions. The ground state to the $^{4}\mathrm{F}_{3/2}$ no-phonon line is observed in absorption at 1.8 \ifmmode^\circ\else\textdegree\fi{}K, and the phonon-assisted spectra at shorter wavelengths are used to interpret the $^{4}\mathrm{F}_{3/2}$ to $^{4}\mathrm{I}_{9/2}$ emission spectra at 1.8 \ifmmode^\circ\else\textdegree\fi{}K. The phononassisted spectra associated with the $^{4}\mathrm{F}_{3/2}$ to $^{4}\mathrm{I}_{11/2}$ emission are not the same as observed for the $^{4}\mathrm{F}_{3/2}$ to $^{4}\mathrm{I}_{9/2}$ emission but a tentative assignment has been made. Due to the reduction of the phonon populations at lower temperatures the emission cross sections are reduced and the lifetimes of the concentrated and dilute crystals increase to 5 and 11 msec, respectively, at 77 \ifmmode^\circ\else\textdegree\fi{}K. A comparison with YAG: Nd and Nd${\mathrm{P}}_{5}$${\mathrm{O}}_{14}$ indicates that \ensuremath{\sim} 5% of absorbed photons are emitted into the $^{4}\mathrm{I}_{11/2}$ levels in ${\mathrm{Cs}}_{2}$NaNd${\mathrm{Cl}}_{6}$ at room temperature, and an approximate peak emission cross section of 1.2 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}21}$ ${\mathrm{cm}}^{2}$ is calculated for the $^{4}\mathrm{F}_{3/2}$ to $^{4}\mathrm{I}_{11/2}$ emission. This is \ensuremath{\sim} 100 times lower than found for Nd${\mathrm{P}}_{5}$${\mathrm{O}}_{14}$ and indicates a low gain in pulsed laser operation. Because of the far longer lifetime, however, the gain per ion under cw operation is predicted to be \ensuremath{\sim} 10 times lower than for Nd${\mathrm{P}}_{5}$${\mathrm{O}}_{14}$ and \ensuremath{\sim} 7 times lower if diluted samples of the two compounds are compared with each other.

Transparent single crystals of AgNiF 3 up to 3 mm on an edge have been grown by slow cooling from AgF flux. The crystals are tetragonal, space group D 6 4 -p4 2 2 1 2, with cell constants a = 5.56 A and c = 7.86 A . The material has an optical absorption spectrum typical of divalent nickel in octahedral coordination with fluoride ions. A noncollinear antiferromagnetic transition at 197°K is observed.

Most of the Al3+ entering the pyroxenes does so by substituting for tetrahedral Si4+. This creates a charge imbalance that requires the simultaneous entry of Cr3+, Ti4+, Fe3+ or Al3+ into octahedral sites. Cr3+, because of its high crystal field stabilisation energy (CFSE), is the most important of these elements to enter the early-formed pyrosenes but it is replaced by Ti4+ later in fractionation when the Cr3+ content of the melt becomes depleted. The dependence of Cr3+ and Ti4+ on charge balance controls their partition between coexisting pyroxenes and olivines. Ca-rich pyroxene which contains more Al3+ than Ca-poor pyroxene also has more Ti4+ and Cr3+ whereas olivine, which contains negligible Al3+, has low Cr3+ and Ti4+.

The following coordination compounds of Manganese(II) with urea have been prepared: MnU2X2 (with X = Cl, Br), MnU4X2 (X = Cl, Br), MnU6X2 (X = Br, I and ClO4) and MnU10X2 (X = Br, I). I.R. spectra (4000–200 cm−1), electronic spectra, paramagnetic susceptibility and powder diffraction patterns were studied. All these compounds are high-spin octahedral with urea coordinated through oxygen. MnU2X2 has chain-like structure with bridging halogen atoms. MnU4X2 is trans-octahedral; MnU10X2 is to be considered as [MnU6]X2·4U, the four extra urea molecules being hydrogen bonded to the MnU62+ cation.

The reactions of [(Ph 3 P) 4 Ni], [(Ph 3 P) 3 CoN 2 ], [(dp) 2 Ni], [(dp) 2 CoH], [(dp) 2 Fe(C 2 H 4 )] or [(dp) 2 FeH 2 ] (dp = Ph 2 PCH 2 CH 2 Ph 2 P) with Ph n SiCl 4- n ( n = 1, 2, or 3), Ph n SiH 4- n , X 3 SiH (X = Cl or Et), or R 2 ClSiH (R = Ph or Me) have been investigated. Solid complexes were isolated which, for the most part, were insoluble in non-polar solvents. Assignments of structures are therefore incomplete, and are based on microanalysis, IR spectra, analogies with established reactions, and (in some cases) chemical degradation. Evidence is presented for the following: (i) for Ni II , products from [(Ph 3 P) 4 Ni] and HSiXX′X″ (XX′X″ = Ph 3 , Ph 2 H or PhH 2 ), the cyclic [(Ph 3 P) 2 NiSiCl 2 ] 2 , and the five-coordinate [(dp) 2 -NiX] + [SiCl 3 ] - (X = H or Cl 3 Si); (ii) for Co III , the six-coordinate cis -octahedral [(dp) 2 CoH 2 ] + [SiXX′X″] - (XX′X″ = Cl 3 , Cl 2 Me, ClMe 2 , or ClPh 2 ); and for Fe II , the four-coordinate [(dp)FeH(SiCl 3 )] and the six-coordinate [(dp) 2 Fe(X)SiCl 3 ] (X = H, Cl, or Cl 3 Si).

The cation distribution in NiAl2O4 and in the solid solutions NixMg1−xAl2O4 with x ranging from 0.01 to 0.55 has been studied by X-ray analysis, magnetic susceptibility and reflectance spectroscopy. The relative X-ray intensities of various reflections for each compound were measured and compared with intensities calculated for various models of cation distribution. Lattice parameters, magnetic moments of Ni2+, and the position of nickel absorption bands have also been measured. The results show that all specimens have a predominantly octahedral distribution for their nickel ions, and that there is a small change towards a random distribution when the quenching temperature is increased from 1273 to 1673°K. Both X-ray and magnetic results show that the fraction, α, of Ni2+ ions on tetrahedral sites varies with nickel content. For samples quenched from 1273°K, NiAl2O4 is 78% inverse, but between x = 1.0 and x = 0.25 the value of α decreases from 0.22 towards 0.1. Thus, the fraction of nickel on octahedral sites in the solid solutions is higher than in NiAl2O4. The effect is linked with an increase in Dq for the Ni2+ ion. Below x = 0.25, there is tentative evidence that α may increase. In nickel-dilute solutions the matrix as a whole is nearly normal, and it is suggested that Madelung energy may then be more effective in counteracting the octahedral stabilization of nickel. The same trend is observed in the specimens quenched from 1673°K.

The low temperature 19F n.m.r. spectra of the mixtures TiF62−−TiX62− (X = Cl−, Br−, NCS−, NCO−) in sulfur dioxide solution have been examined. When X = Cl− or Br− rapid fluorine exchange is occurring even at the lowest accessible temperature, but when X = NCS− or NCO− the spectra of the individual mixed species TiF6−xXx2− are observed. In the latter two cases the solutions also contain fluorine-bridged dimers in stable equilibrium. The 19F chemical shifts of TiF6−xXx2− (X = NCS− or NCO−) and of some related mixed complexes are reasonably represented by the equation δ = pC + qT where C and T are constants characteristic of the substituent X and p and q are the number of ligands X cis and trans respectively to the resonating fluorine. The constants T appear to be a measure of the π-donor ability of the ligand X in these complexes, supporting the idea that the chemical shift of a fluorine in fluorotitanates is determined largely by the extent to which fluorine-to-titanium back donation occurs.

The crystal structure of Si5O[PO4]6 has been determined and refined by least-squares, using three-dimensional X-raydata fromWeissenberg photographs: space group R 3;a=7.869 andc=24.138 A;Z=3; 418 independent reflections;R=6.0%. The crystal structure consists of isolated [SiO6] octahedra and [Si2O7] groups which are linked by [PO4] tetrahedra forming a three-dimensional network. The average interatomic distances are: Si[6]−O=1.768, Si[4]−O=1.607 and P−O=1.52i A. The compound is isotypic with Ge5O[PO4]6.

Neutron-scattering experiments have elucidated the mechanism of the successive phase transitions of CsPb${\mathrm{Cl}}_{3}$ at 47, 42, and 37\ifmmode^\circ\else\textdegree\fi{}C. These phase transitions are basically associated with the condensation of rotational modes of Pb${\mathrm{Cl}}_{6}$ octahedra around the three principal axes. The phase transition at 47\ifmmode^\circ\else\textdegree\fi{}C is caused by the condensation of the nondegenerate ${M}_{3}$ phonon mode at the zone boundary along the [110] direction of the cubic lattice. The axis of rotation of the Pb${\mathrm{Cl}}_{6}$ octahedra is along the [001] axis. The second phase transition at 42\ifmmode^\circ\else\textdegree\fi{}C is associated with the condensation of one of doubly degenerate modes ${Z}_{5}^{x}$ and ${Z}_{5}^{y}$ at the zone boundary along the [001] direction of the tetragonal lattice, which are derived from the triply degenerate ${R}_{25}$ mode in the cubic phase. The direction of the rotation axis is along the [100] axis when we assign ${Z}_{5}^{x}$ as the condensing mode. The third phase transition at 37\ifmmode^\circ\else\textdegree\fi{}C is caused by the condensation of the remaining ${Z}_{5}^{y}$ mode. The crystal systems and the space groups of three low-temperature phases were determined from the eigenvectors of the condensing modes as tetragonal ${D}_{4h}^{5}$, orthorhombic ${D}_{2h}^{17}$, and monoclinic ${C}_{2h}^{2}$ in the sequence of decreasing temperature. These are consistent with the previous experimental results on nuclear-quadrupole-resonance spectra of ${\mathrm{Cl}}^{\ensuremath{-}}$ ion. A phenomenological theory has been developed to explain these successive phase transitions caused by the condensation of the ${M}_{3}$ and ${R}_{25}$ zone-boundary phonons. The observed phase-transition schemes can be qualitatively explained by a suitable choice of the parameters in the free-energy expansion with respect to order parameters.

The hexagonal RCo5 compounds form several orthorhombic hydrides which are structurally closely related. A neutron-diffraction study of βI, βII and βIII types, as found for e.g. PrCo5D3·6, PrCo5D2·9 and CeCo5D2·55 respectively, revealed that the deuterium atoms occupy both octahedral and tetrahedral interstices. In the simplest of these, βI, the occupancy of the interstices is equal; its space group is Cmmm. In both βII and βIII the c-axis is doubled compared with βI. In βII, space group Im2m, the octahedral positions have a uniformly reduced occupancy, which leads to appreciable ordered shifts of the metal atoms. In βIII (Cccm) half of the octahedral positions are vacant, giving a limiting stoichiometric composition CeCo5H3. The magnetizations of the (ferromagnetic) hydrides decrease with increasing hydrogen content. Results of neutron-diffraction analysis are in fair agreement with the magnetization measurements.

The i.r. and Raman spectra of complexes of Δ2-tetrazaborolines are consistent with the geometry of (Me2N4BMe)2SnCl4 at tin of a trans-disubstituted octahedron, and that of Me2N4BMe, SbCl5 of the molecular structure of a substituted octahedron (Me2N4BMe)SbCl5. In complexes formed by tetrazaborolines with titanium tetrachloride and aromatic hydrocarbons, the aromatic group is only loosely held in the crystal lattice since the vibrational frequencies of the aromatic molecules are little changed from the gas-phase molecules.

Optical spectm were recorded for (NEt/sub 4/)/sub 2/PaCl/sub 6/ and (NEt/ sub 4/)PaBr/sub 6/ two ligand field parameters and the spin- orbit coupling constant. Similar interpretations are provided for data available on uranium (V)- hexahalogeno complexes and NpF/sub 6/. Trends in the ligand field parameters can be explained qualitatively in terms of molecular orbital theory with large variations in sigma bonding dominating the total ligand field splittings as the halide ion is varied. (auth)