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The reaction of oxobis(acetylacetonato)vanadium(IV) with 1,10-phenanthroline in methylene chloride under aerobic conditions afforded diamagnetic dioxo(acetylacetonato)(1,10-phenanthroline)vanadium(V). The cis configuration of this compound was concluded on the basis of IR and Raman data, and confirmed by the single crystal X-ray analysis. The geometry of this mixed ligand complex is a distorted octahedron. The V-O(oxide anion) distances are 1.613(4) and 1.670(5)Å, the O-V-O angle being 105.5(2)°. The appreciable trans influence of the oxide anion is reflected on the V-N and V-O(acetylacetonate) distances.

A triangular tungsten(IV) aqua ion with sulfur bridges, W3O2S24+has been prepared and characterized. X-ray structure analysis of a derivative complex, [W3O2S2(Hnta)3]2-(H3nta = nitrilotriacetic acid) has revealed that its core is of structure of W3(µ2-O)2(µ2-S)(µ3-S). The electronic spectrum of the aqua ion has an absorption peak at 506 nm (e = 381 M-1cm-1per trimer; 1 M = 1 mol dm-3).

The triethylenetetraminepalladium(II) perchlorate and the potassium triethylenetetraminepalladium(II)tris-(hexafluorophosphate) were prepared; the X-ray structure analysis has been carried out for the latter compound. The crystal of [Pd(trien)](PF6)2·KPF6is orthorhombic, with space group Pbca: a=21.645 (5), b=20.873 (5), c=9.541 (2) Å, and Z=8. The structure has been determined from X-ray diffractometer data and refined to R=0.091 (1166 reflections). The Pd atom has a planar coordination of 4N atoms disposed in a somewhat trapezoidal form. The complex cation has a pseudo symmetry plane which is perpendicular to the 4 N plane and bisects the H2N–Pd–NH2angle. In the quadridentate triethylenetetramine ligand, each of the terminal H2N–CH2–CH2–NH– fragments forms a 5-membered chelate ring with the asymmetric envelope conformation, whereas the chelate ring formed by the middle –NH–CH2–CH2–NH– fragment has the symmetric envelope conformation. The electronic spectrum of [Pd(trien)]2+is presented.

Di-μ-sulfido tungsten(V) dimers, [W2O2S2(cys)2]2−(1) and W2O2S2(aq)2+(2) have been prepared and characterized. The structure of the former has been determined by the X-ray crystal structure analysis. The W–W bond distance is 2.843(1) Å. Peak positions of electronic spectra are : 428 nm (ε=259 M−1cm−1per dimer; 1 M = 1 mol dm−3), 330sh(3920), and 276 (10760) for 1; 435 (144), 320 (2640), and 263 (7180) for 2.

A molybdenum(IV) aqua ion with sulfur bridges, Mo3OS34+, has been prepared and characterized. An X-ray structure analysis of the iminodiacetato complex prepared from the aqua ion has revealed the core structure of Mo3(μ-O)(μ-S)2(μ3-S).

Two cubane-type molybdenum aqua compounds, [Mo4OS3(H2O)12](CH3·C6H4·SO3)5·14H2O and [Mo4OS4(H2O)12](CH3·C6H4·SO3)5·14H2O have been prepared, and characterized by X-ray crystallography, electronic spectroscopy, and cyclic voltammetry. Their reduced species, [Mo4OS3(H2O)12]4+and [Mo4S4(H2O)12]4+, have also been characterized.

The crystal structures of (pyH)4[Mo2O2S2(NCS)6] (1) (pyH=pyridinium ion) and (pyH)4[Mo2O3S(NCS)6]·2H2O (2) have been determined from the diffractometer data. The 1and 2structures were refined by the least-squares method to R0.041 and 0.064 for 2728 and 2349 non-zero reflections respectively. The two structures are isomorphous. Each Mo(V) ion has a distorted octahedral coordination, and two coordination octahedra share a common edge to form a binuclear complex. The binuclear complex contains a mirror plane through two bridging atoms. The two terminal oxo ligands on each Mo(V) are cisto each other and cisto the bridging oxo or sulfido. The Mo–N(NCS) bond length transto the Mo–Ot(terminal oxo) is ca.0.1 Å longer than the other Mo–N(NCS) bond lengths, showing the large transeffect of the Otligand.

The bis((S,S)-2,4-pentanediamine)platinum(II) chloride monohydrate crystallizes in the space group P212121with four formula units in a unit cell of dimensions a=12.089(3), b=13.547(3), c=10.697(2) Å. The crystal structure has been determined from diffractometer data and refined to R=0.052 for 1903 independent reflections. The Pt atom has a square planar coordination by four N atoms, the average value of the Pt-N distance being 2.05 Å. The complex has a pseudo two-fold axis which is perpendicular to the coordination plane defined by the four N atoms. The 6-membered chelate ring is of a chair conformation and one methyl group is axial with respect to the chelate ring, while the other is equatorial. From a comparison of the circular dichroism spectra of the diammine-(S,S)-2,4-pentanediamineplatinum(II) and the bis((S,S)-2,4-pentanediamine)platinum(II) ions, the effect of the (S,S)-2,4-pentanediamine on the rotatory strength of the Pt(II) complex has been found to be not additive.

Green-to-blue six-coordinate mixed complexes, Cu(acac)2(en) and Cu(etac)2(diamine)(acac=acetylacetonate anion; etac=ethyl acetoacetate anion; diamine=ethylenediamine, trimethylenediamine, 2,2′-bipyridine or 1,10-phenanthroline) have been isolated by the reactions of the respective parent β-diketonate with the corresponding diamine in dry dichloromethane. On the other hand, the reaction of Cu(acac)2with en in the mole ratio of one-to-two in dichloromethane saturated with water has resulted in purple crystals of Cu(acac)2(en)2·2H2O. This compound has been shown by X-ray analysis to consist of a square-planar copper(II) cation, coordinated by two ethylenediamine molecules, and two planar acetylacetonate anions, the plane of which is not perpendicular to, but slanted against, the CuN4plane. One oxygen atom of the anion participates in the N–H···O hydrogen bonding with an NH2group of the ethylenediamine molecule, while the other occupies the axial position of Cu(en)22+(Cu···O: 2.79(1) Å). Therefore, the compound can be designated by the formula [Cu(en)2]·(acac)2·2H2O. The water hydrogen atoms seem to take part in the hydrogen bonding with the anion oxygen atoms.

The title compound was synthesized and characterized by means of absorption, circular dichroism, and its NMR spectra as well as X-ray structure analysis. The crystals are monoclinic, with a P21space group, a=9.175(3), b=12.423(5), c=7.434(3) Å, ß=108.1(4)°, and Z=2. The structure was determined from the diffractometcr data and refined by a least-squares method to R=0.041 for 1732 observed reflections. The Pt atom has an essentially planar coordination with 4 N atoms. The disposition of the four donor atoms is not rectangular, but trapezoidal; it is, moreover, slightly tetrahedral. The quadridentate ligand forms three 5-membered chelatc rings with the Pt atom. The two terminal rings are of a d asymmetric envelope conformation, while the middle ring has a ? symmetric skew conformation. Both of the secondary N atoms possess a Rconfiguration. The complex ion has a pseudo-two-fold axis by which the two terminal rings are related to each other. The circular dichroism spectrum reflects mainly the conformations of the 5-membered chelate rings. The features of the absorption and circular dichroism spectra are discussed on the basis of the geometry of the PtN4chromophore.

(+)589-Bis(l-ornithinato)cobalt(III) nitrate monohydrate was isolated by ion-exchange chromatography from a reaction mixture of trinitratotriamminecobalt(III) with l-ornithine at pH 9, and was assigned to the cis-(O)trans(Na)cis(Nd) isomer on the basis of the absorption and circular dichroism spectra. Then, the geometry of the complex was confirmed by X-ray structure analysis. The red crystal is orthorhombic, with these cell dimensions: a=14.380, b=16.493, and c=6.787 Å. The space group is P212121, and Z=4. The crystal structure was solved by the Patterson and Fourier techniques and was refined by the least-squares method to R0.099. The Co atom is surrounded by 2 O and 4 N atoms, the former being in cispositions. Each of the l-ornithinato ligands assumes the facial coordination, and the complex cation has an approximate two-fold axis by which the ligand are correlated.

The crystal structures of Na2[Mo2O4(R-pdta)]·3H2O (1), Na2[Mo2O3S(R-pdta)]·4H2O (2), and Na2[Mo2O2S2(R-pdta)]·4H2O (3) have been determined from difTractometer data collected by the use of Mo Kα radiation. The structures of 1, 2, and 3were refined by the least-squares method to R0.064, 0.040, and 0.058 for 1370, 2794, and 2141 nonzero reflections respectively. Each Movion has a distorted octahedral coordination, and the two coordination octahedra share a common edge to form a binuclear complex. Two terminal oxo ligands are cisto the bridging oxide or sulfide. The R-pdta4−ligand bridges two Movions, yielding a Mo–N–CH2–CH(CH3)–N–Mo ring with an equatorial methyl group, the N and carboxyl O atoms occupying the axial (transto the terminal O) and equatorial positions respectively. A specific distortion of the donor-atom disposition is observed, which is represented as the twist (Δ) of the terminal O–O edges in the (Remark: Graphics omitted.) portion about the axis passing through the mid-points of the O–O edges (Δdenotes the absolute disposition of two skew edges or bonds), and as the twist (Δ) of Mo–N bonds about the Mo–Mo axis. The O=Mo bonds of the O=Mo–Mo=O segment in 1twist in Δ, but those in 2and 3are virtually parallel. The distortion of donor-atom disposition is discussed on the basis of the strain due to chelate-ring formation.

A new complex, aquaoxo[N-(2-pyridylmethyl)iminodiacetato]vanadium(IV) dihydrate [VO(pmida)(H2O)]·2H2O has been synthesized and its crystal structure determined by the X-ray method. The triclinic crystals obtained from water or aqueous ethanol solution are twinned and contain 2 mol of lattice water. The unit cell contains four formula units and the structure was analyzed on the assumption that the space group is P\bar1. The positional and thermal parameters were refined to R=0.115. The vanadium atom has a distorted octahedral coordination and deviates by 0.39 Å from the equatorial plane, which is composed of two cis carboxylate oxygens, a water molecule and the pyridine nitrogen. Vanadyl oxygen and tertiary nitrogen occupy the axial sites. Absorption spectra indicated that the structure is maintained in an aqueous solution of pH 3.0 to 4.9. This geometrical isomer seems to be formed selectively in an aqueous medium.

The title compound was prepared, and its structure then determined by X-ray structure analysis. The crystal is trigonal with the space group P3221, a=8.450(3), c=42.00(6)Å, and Z=3. The crystal structure has been determined from the diffractometer data and refined by a least-squares method to an Rvalue of 0.103 for 1349 independent reflections with I>3σ(I). The cyclo-l-histidyl-l-histidyl is coordinated to the Cu atom viathe N atoms of the respective imidazolyl groups. The coordination of Cu is not planar but distorted toward the tetrahedral configuration, the interplanar angle betweent (Remark: Graphics omitted.) planes being 29°. The complex has virtually D2symmetry: there are two pseudo two-fold axes and one crystallographically imposed two-fold axis which relates two chelate rings. The chelate rings assume the δ conformation, and the ligating cyclo-l-histidyl-l-histidyl is of a folded form with a bowsprit-boat 2,5-piperazinedione ring. The electronic and circular dichroism spectra in the visible region are presented.

The optical resolution of [Pt(NH3)2(N1-Me-(S)-pn)]Cl2is effected by using silver di-µ-(+)-tartrato(4-)-bis(antimonate(III)) (Ag2[Sb2(+)-tart2]) as the resolving agent. X-Ray structure analysis of the less soluble diastereoisomeric salt, (+)350-[Pt(NH3)2(N1-Me-(S)-pn)][Sb2(+)-tart2]·H2O, revealed that the asymmetric secondary nitrogen is of the Rconfiguration. The crystal is orthorhombic, with a P212121space group, a=19.302(7) Å, b=14.791(4) Å, c=7.925(2) Å, and Z=4. The structure was determined from counter intensity data and refined to R0.049 using the least-squares method for 1955 independent non-zero reflections. The Pt atom has a square-planar coordination with 4 N atoms and both the N–CH3and C–CH3groups are equatorial with respect to the chelate ring. The circular dichroism spectrum of R-[Pt(NH3)2(N1-Me-(S)-pn)](ClO4)2, which was obtained from the less soluble di-µ-(+)-tartrato(4-)-bis(antimonate(III)) salt, is presented and discussed on the basis of the distribution of the possible conformers, the relative abundances of which were infered from 13C NMR data.

The crystal of the title compound is monoclinic, with a=9.415(3), b=15.767(7), c=8.786(3) Å, ß=94.25(4)°, the space group of P21and Z=2. The structure was determined from the counter intensity data by heavy-atom techniques and was refined by the block-diagonal least-squares calculations to R0.050 for 2604 non-zero reflections. The Pt atom has a square-planar coordination by 4N atoms, the secondary N atoms of which are of the Sabsolute configuration.

The µ-oxo-µ-sulfido-(oxalato)molybdate(V) complex has been prepared and characterized by X-ray analysis. The potassium salt crystallizes in monoclinic system, space group C2/c, with cell dimensions a=13.640(3), b=20.296(3), c=15.213(4) Å, ß=106.42(2)°, and Z=4. The structure was solved by the heavy-atom technique and refined by the block-diagonal least-squares method to R=0.048 for 3552 independent reflections. The complex anion is tetrameric, two dimeric Mo2O3S(ox)2moieties being bridged by one oxalato ligand. Both the molybdenum atoms in the dimer are bridged by one sulfur and one oxygen atoms. Each molybdenum atom has distorted octahedral environment; two oxygen atoms of a bidentate oxalato ligand, bridging sulfur and oxygen atoms in the equatorial plane, a terminal oxygen and one of the bridging quadridentate oxalato ligand oxygens. The complex can be denoted as K6[{Mo2O3S(ox)2}2(ox)]·10H2O and has an approximate C2hsymmetry, with a crystallographic center of symmetry. The Mo–O (quadridentate bridging oxalato) bonds (2.304(4), 2.302(4) Å) are evidently longer than the Mo–O (bidentate oxalato) bonds (2.112(4), 2.102(4), 2.093(4), 2.120(4) Å). The influence of the bridging oxalato ligand on the geometry of Mo2O3S core will be discussed.

The aquation rate of trans(NO2,O2)-[(NO2)(en)2CoO2Co(en)2(NO2)]2+has been measured in acidic aqueous solution at [H+]=0.003–0.25 M and I=0.50 M (LiClO4), the final products being trans-[Co(NO2)(OH2)(en)2]2+and H2O2in marked contrast to the acid decomposition of [(NH3)5CoO2Co(NH3)5]4+where the final products are Co(II) and O2. The reaction consists of two stages, each of which has preequilibrium of protonation. The observed rate constants for the first and second stages are consistent with the formula, k1obsd=k1K1[H+]/(1+K1[H+]) (i=1, 2), indicating the existence of protonated reactive forms in both stages. The rate constants, activation parameters and equilibrium constants are k1=7.46 s-1(25 °C), ?H1\eweq=66.9±1.3 k J mol-1, ?S1\eweq=-2.9±4.2 J K-1mol-1, and K1=3.44 M-1(25 °C) for the first stage and k2=0.400 s-1(25 °C), ?H2\eweq=85.4±2.1 kJ mol-1, ?S2\eweq=33.5±7.1 J K-1mol-1, and K2=2.98 M-1(25 °C) for the second stage. The solution of the reaction intermediate [Co(NO2)(O2H)(en)2]+has been obtained by ion exchange technique and characterized by the UV and visible spectra. The factors which decide the reaction path are discussed.

The structure of bis(cis-1,3-diaminocyclohexane) palladium(II) chloride has been determined from X-ray diffraction data collected by the counter method. The crystal is orthorhombic with space group Pnnm, a=17.728(5), b=6.418(4), c=6.914(2) Å, and Z=2. The crystal structure has been determined by Patterson and Fourier techniques and refined by a least-squares method to R=0.026 for 1151 independent reflections for which Fo2>3s(Fo2). The Pd atom has a planar coordination of 4N atoms and the complex cation has a crystallographically imposed C2hsymmetry, the two cis-1,3-diaminocyclohexane ligands being related to each other by a two fold axis. The six-membered chelate ring (Remark: Graphics omitted.) is of the envelope conformation. The structural features of the ligating cis-1,3-diaminocyclohexane have been described. The crystal of bis(cis-1,3-diaminocyclohexane)platinum(II) (orthorhombic, a=17.727(8), b=6.371(3), c=6.965(2) Å) was found to be isomorphous with that of the palladium analogue.

The crystal structure of trinitrotriamminecobalt (III) prepared accoding to the method of Jörgensen has been studied by X-rays, using rotation methods (Fe Kα, λ=1.937 A.). This structure belongs to the orthorhombic system and the dimensions of the unit cell which contains four molecules of [Co(NH3)3(NO2)3] are a=10.20 A., b=11.77 A., and c=6.99 A. The space group is D24−P212121. The cobalt atom is surrounded by six nitrogen atoms approximately in octahedral coordination. The shape and size of the nitro-groups are like those in Ag[Co(NH3)2(NO2)4]. Two of the nitrogroups are found to be (coordinated to) the cobalt atom in the trans-positions with respect to each other in conformity with the conclusion drawn from spectroscopic investigations.

The crystal structure of trans-dichlorodiethylenediamine-cobalt (III) chloride hydrochloride has been determined using the rotation method (Fe Kαλ=1.937 a.). The substance crystallizes in a monoclinic lattice with two formula units in the unit cell, the dimensions of which are a= 10.68 a., b=7.89 a., c=9.09 a. with β=110°26.The determined structure seems most easily described as consisting of layers of [Coen2Cl2]+ions parallel to the plane (100) and those of Cl−, H2O and H+. Two chlorine atoms are co-ordinated to a cobalt atom in trans-positions. The line joining them is perpendicular to the plane in which four nitrogen atoms are found to lie. The dimensions of a complex ion are given. The water molecules probably form a group [H2O···H···H2O]+together with a proton, O···O distance being 2.66 a. These groups are located between them. The dichroism of the crystal is, discussed on the basis of the determined structure.

An X-ray diffraction study of crystals of dichloro-aquo-triammine-cobalt (III) chloride eads to a hexagonal unit of structure with a=7.37 a. and c=8.75 a., containing two formula units in it. The most probable space group is D6h4−C6/mmc. For an accurate determination of the structure, the method of three dimensional Fourier series was used. The determined structure is most easily described as NiAs type, consisting of [Co(NH3)3H2OCl2]+and Cl−ions. Two chlorine atoms are coordinated to a cobalt atom in trans-positions with respect to each other, each being 2.33 A. from the cobalt atom. The Cl-Co-Cl direction being parallel to the c-axis, the octahedral complex ions seem to have statistical azimuthal orientations in the crystal and the apparent, symmetry of the complex ion is D3h− 6m2. Such an arrangement of the complex ions in the crystal may well account for the marked red-blue dichroism of the crystals.

The crystal structure of [Co (NH3)3(NO2)2Cl] is tetragonal, with eight formula units in a cell of dimensions a=9.87 Å and c=16.51 Å.The space group is C4n6-I4/a. The determination of atomic parameters was made by three dimensional Fourier syntheses. The configuration of the complex molecule is described.Two nitro-groups are found to be in transpositions with respect to each other. The main forces acting between these molecules in the crystal seem to be O … H-N bonds between the oxygen atoms of the nitro-group and the ammonia of the other. Molecules are linked together by these hydrogen bonds, forming a compact three-dimensional network in the crystal.

The crystal structure of cis-(+)589-[CoCl2en2]Cl·H2O has been determined by the X-ray-diffraction method. The crystal is monoclinic with the cell constants: a=12.07, b=11.52, c=8.33 Å, and β=96.9°. The space group is P21and Z=4. There are two crystallographically-independent complexes in the unit cell, but they have the same configuration and almost identical molecular dimensions. The absolute configuration of the complex cation is consistent with that proposed by McCaffery, Mason and Norman and should be denoted as Λ(δδ).

The absolute configuration of (−)589-[Co ox en2]+has been determined by the X-ray diffraction method. The crystals of (−)589-[Co ox en2]Br·H2O are orthorhombic, with the space group P212121, and the unit cell dimensions are: a=16.67(1)Å, b=12.40(1)Å, c=6.183(7)Å, and Z=4. The crystal structure was solved by the conventional Patterson and Fourier methods, and refined by the least-squares procedure to an Rfactor of 9.97%. The cobalt atom has an octahedral coordination, being chelated by an oxalate anion and two ethylenediamine molecules which are of the ob-lelconformation. The absolute configuration of the complex cation can be denoted as Δ(δλ).

The crystal structure of [Co(NH3)5Cl]Cl2has been determined by the two-dimensional Fourier method. The orthorhombic unit cell has dimensions of a=13.34, b=10.33 and c=6.73 Å, and it contains four formula units.The space group is Pnma-D2h16.The shape and the size of a complex ion were found to be approximately similar to those of the crystal of the corresponding rhodium(III) compound.One NH3group is co-ordinated to the central cobalt atom in the trans position to the chlorine atom; the Co-N(1) distance is 1.91Å, rather shorter than the four other Co-N distances, 1.97Å.

The crystal structure of trans-[Co en2Cl2]·NO3has been determined by means of X-ray analysis. The space group is P21/c with two formula units in a cell of the dimensions of a=6.33Å, b=9.25Å, c=10.62Å, and β=114.5°. The crystal is composed of [Co en2Cl2]+and NO3−. The geometry of the complex ion herein determined is not significantly different from those reported before. It has been proposed that the nitrate ion is in a disordered arrangement.

The absolute configuration of an optically active complex ion [Co en3]3+has been determined by means of X-ray absorption edge technique. Cu Kα radiation was used to excite the cobalt atoms in the crystals of d- and l-2[Co en3]Cl3·NaCl·6H2O. The effects of the anomalous dispersion were observed by single crystal oscillation photographs as well as Laue photographs. A brief description of the principle of the method and the experimental procedure is included.

The preparation of two mixed salts, 2d-[Co en3]Cl3·NaCl·6H2O and 2l-[Co en3] Cl3·NaCl·6H2O is described. The space group is P3, with one formula unit in a cell of dimensions: a=11.47±0.03 Å, c=8.06±0.02 Å. However, the structure has the pseudo space group P63. By evaluating the functions ρ(XY) and ρ(YZ), projections of the structure on two crystal-lographic planes were obtained. A kind of twinned structure was proposed to get a better agreement between the observed and calculated intensities. The structure shows very close resemblance to that of d,l-[Co en3]Cl3·3H2O. A sodium ion is octahedrally surrounded by six water molecules, with Na ···O distances of 2.62 Å. The whole structure is ionic consisting of the ions [Co en3]3+,[Na(H2O)6] and Cl−.

The crystal structure of [Co en3]Cl3·3H2O has been determined by X-ray methods. It is trigonal D3d4–P\bar3c1 with four formula units in a cell of dimensions: a=11.50±0.02, c=15.52±0.04 Å. The configuration of the two stereoisomeric complex ions [Co en3]3+is described. The three ethylenediamine molecules in a complex ion assume “ gauche ” forms; their nitrogen atoms form a slightly distorted octahedron around a central cobalt atom. It is shown that ionic bonds essentially link the complex ions in the structure. The watermolecules are weakly associated to chlorine it is found that a single crystal can be completely dehydrated by gently heating at 120°C, without bringing about any remarkable change in its appearance, except a loss. of transparency. A single crystal oscillation photograph was obtained even after complete dehydration.

The crystal structure of (−)589-[Co(NO2)2en2] (+)589-[Co mal2en] has been investigated by the X-ray method. Crystal data: triclinic, space group P1; a=10.58(2)Å, b=7.98(1)Å, c=7.99(1)Å, α=122.8(2)°, β=105.3(2)°, γ=74.6(2)°; Z=1. The crystal structure was determined by the Fourier technique and was refined by the leastsquares method to an Rfactor of 0.101. The Δconfiguration has been assigned to both the complex cation and anion, (−)589-[Co(NO2)2en2]+and (+)589-[Co mal2en]−. The two Co-mal chelate rings are nearly planar. The O–Co–O angle in this ring is 96°, slightly larger than the N–Co–N angle observed in the cobalt(III)-trimethylenediamine chelate ring. All the ethylenediamine ligands in the two complex ions have the ob-conformation.

1. Absorption spectra of a number of ethylenediamine cobaltic complex salts have been observed. Generally speaking, their absorption bands, especially the second, are more hypsochromic than those of the corresponding ammine salts.2. The results have proved that the author’s hypothesis on the absorption spectra holds good for the ethylenediamine complex salts.3. Examples of the third absorption bands have been found in the diethylenediamine cobaltic complexes of known configurations.4. A new method of separating [Co en3]3+and [Co en2Cl2(6)(1)]+has been devised.

The crystal structure of (−)589-[Co acac tn2][As-(+)-tart]2·H2O has been determined by the X-ray diffraction method. The crystals are monoclinic, with lattice constants of a=12.02(1) Å, b=13.73(2) Å, c=9.02(1) Å, and β=107.4(3)°, and with the space group of P21, containing two formula units in a cell. The structure was determined by the application of Patterson and Fourier techniques and was refined by the least-squares method to an Rfactor of 10.4%. The absolute configuration of (−)589-[Co acac tn2]2+can be denoted as Δ. The two Co-tn chelate rings assume the chair form, and the Co-acac chelate ring is almost planar. The geometry of [As-(+)-tart]22−is identical with that of [Sb-(+)-tart]22−.

The crystal structure of (+)589-[Co(CN)2en2]Cl·H2O has been determined from three-dimensional X-ray photographic data. The crystals are monoclinic, with the lattice constants of a=8.15(1), b=11.69(2), c=6.61(1) Å, and β=107.1(2)°, and with the space group of P21containing two formula units in the cell. The structure was solved by a conventional Fourier technique and was refined by the least-squares method to an Rfactor of 0.114. The absolute configuration of the complex ion can be denoted as Λ(λλ); this is in accordance with the assignment made by Mason et al.The complex ion has an approximately two-fold axis, and both of the ethylenediamine chelate rings are of the ob-conformation.

The crystal structure of 2,2′-bipyridinium tetrabromocobaltate(II) has been established by successive Fourier analyses. The atomic parameters were refined by least-squares techniques, using the three-dimensional X-ray data, to an Rfactor of 0.127 for 1461 non-zero reflections. The complex crystallizes in the space group P21/cwith four formula units in the unit cell with dimensions of a=8.42, b=14.00, c=12.88 Å, and β=98.7°. The crystal consists of slightly distorted tetrahedral [CoBr4]2−anions and 2,2′-bipyridinium cations, in which two pyridinium ring planes are inclined toward one another at an angle of 39°. The two N+–H groups in the cation participate in N+–H···Br−type hydrogen bonds (N···Br=3.23 Å and 3.31 Å). The mean value of the four Co–Br bond lengths is 2.42 Å.

The structure of trans-dibromo-bisethylenediamine cobalt(III) bromide hydrobromide dihydrate has been determined by X-ray analysis. [Co en2Br2]Br·HBr·2H2O is monoclinic, a=10.98, b=8.18, c=9.46 Å, and β=113.2°, space group P21⁄c, two formula units in the cell. The structure consists of [Co en2Br2]+, [H2O···H···H2O]+and Br−, and is isotype with [Co en2Cl2]Cl·HCl·2H2O. The complex ion has a center of symmetry. Two enantiomorphous ethylenediamine molecules, taking “gauche” configration, are coordinated to a cobalt atom. A cobalt atom is surrounded in a square coplanar configuration by four nitrogen atoms at distances 2.0 Å, and on a line approximately perpendicular to the plane of nitrogen atoms are two bromine atoms at distances 2.44 Å. The marked dichroism of the crystal is explainable in terms of the characteristic features in the arrangement of the complex ions in the crystal.