Transition Metal Bis Research Articles

Effect of the Keggin anions on assembly of CuI-bis(tetrazole) thioether complexes containing multinuclear CuI-cluster

In order to investigate the effect of polyoxometalate (POM) on the assembly of transition metal-bis(tetrazole) thioether complexes, three new complexes based on different Keggin anions and multinuclear CuI-cluster [CuI12(bmtr)9(HSiMo12O40)4] (1), [CuI3(bmtr)3(PM12O40)] (M=W for 2; Mo for 3) (bmtr=1,3-bis(1-methyl-5-mercapto-1,2,3,4-tetrazole)propane), have been hydrothermally synthesized and characterized by routine physical methods and single crystal X-ray diffraction. In compound 1, two kinds of nanometer-scale tetranuclear subunits linked by [SiMo12O40]4− polyanions assemble a (3, 4)-connected three-dimensional (3D) self-penetrating framework. Compounds 2 and 3 are isostructural, exhibiting a 1D chain with [PW12O40]3−/[PMo12O40]3− polyanions and trinuclear clusters arranging alternately. The distinct structural differences between these POM-based CuI-bmtr complexes of 1 and 2/3 maybe rest on the contrast of Keggin-type polyoxometalate with different central heteroatoms, which have been discussed in detail. In addition, the electrochemical properties of the title complexes have been investigated.

Structural, Electronic, and Magnetic Properties of Neutral and Charged Transition Metal–Bis(dicarbollide) Sandwich Clusters

Structural, electronic, and magnetic properties of transition metal (TM)–bis(dicarbollide) (TM(Dcb)2; TM = Sc–Mn, Dcb = dicarbollide) sandwich clusters and their charged counterparts (TM(Dcb)2+, TM(Dcb)2–) are systematically investigated by using all electron density functional theory approach. All TM(Dcb)2 sandwich clusters are highly stable because of the formation of ionic–covalent bonding. The Ti(Dcb)2 is the most stable, the Sc- and V(Dcb)2 are intermediate, and the Cr- and Mn(Dcb)2 are the least stable. The magnetic moment of TM(Dcb)2 exhibits a clear element-dependent variation with 1 μB for Sc(Dcb)2 and 0 μB for Ti(Dcb)2 and with a linear increased trend by 1 μB from Ti(Dcb)2 to Mn(Dcb)2. This element-dependent magnetic behavior can be well understood by electron transfer as well as spin density distribution. We further reveal that charging can induce the rotation of the ligands in the Sc-, V-, Cr-, and Mn(Dcb)2 clusters, which makes them promising candidates for molecular motors.

Mononuclear bis(pentalene) sandwich compounds of the first-row transition metals: variable hapticity of the pentalene rings and intramolecular coupling reactions

Neutral bis(pentalene)metal sandwich compounds have been synthesized for the first row transition metals titanium and iron. In this connection, the complete series of first row transition metal bis(pentalene)metal complexes (C8H6)2M (M = Ti, V, Cr, Mn, Fe, Co, Ni) has now been investigated by density functional theory in order to evaluate the effect of the metal electronic requirements on the hapticity of the pentalene ligands. The lowest energy structure for the titanium complex is the 18-electron complex (η8-C8H6)(η6-C8H6)Ti with one octahapto and one hexahapto pentalene ligand rather than the previously suggested 20-electron complex (η8-C8H6)2Ti with two octahapto pentalene ligands. The experimental NMR observations on (C8H6)2Ti can then be reinterpreted as interchange of octahapto and hexahapto bonding of the pentalene units through a low energy bis(octahapto) (η8-C8H6)2Ti transition state. The lowest energy structure for (C8H6)2V has two fulvene-like hexahapto pentalene ligands and a local vanadium environment similar to the well-known dibenzenevanadium. The lowest energy structures of the later first row transition metals have two pentahapto pentalene ligands with local metal environments similar to those in the corresponding metallocenes. In the manganese and iron structures of this type, the remaining unpaired electrons on one of the uncomplexed carbon atoms in each η5-C8H6 system form a C–C single bond to couple the two pentalene ligands. This coupling of the two pentalene systems through a C–C single bond is similar to that found experimentally by X-ray crystallography in bis(pentalene)iron, (η5-C8H6)2Fe.

ChemInform Abstract: The Use of Silylethers and Silylthioethers in Syntheses of Oxohalide and Thiohalide Compounds of Molybdenum and Tungsten.

Abstract Convenient procedures for the preparation of molybdenum and tungsten oxo- and thiohalides are described which exploit reactions between transition metal halides and bis(silyl)ether and -thioether reagents, according to the general equation: MCI x +(Me 3 Si) 2 Y (Y = O,S)→M(Y)Cl x−2 +2Me 3 SiCl. W(O)Cl 4 ( 1 ) and Mo(O)Cl 3 ( 5 ) are formed in high yield by room temperature treatment of WCl 6 and MoCl 5 with (Me 3 Si) 2 O in CH 2 Cl 2 solvent. Mo(O) 2 Cl 2 ( 6 ) may be obtained from Mo(O)Cl 4 by an analogous room temperature procedure; efficient generation of W(O) 2 Cl 2 ( 2 ) requires warming of W(O)Cl 4 with (Me 3 Si) 2 O at 80°C in octane. In acetonitrile solvent, W(O)Cl 4 reacts with one equivalent of (Me 3 Si) 2 O to give W(O) 2 Cl 2 (CH 3 CN) 2 ( 3 ) in 70% yield. Treatment of W(O)Cl 4 with two equivalents of (Me 3 Si) 2 O in CH 2 Cl 2 leads to blue crystalline W(O) 2 Cl(OSiMe 3 ) ( 4 ), which is stable to elimination of Me 3 SiCl to 1OO°C. W(S)Cl 4 ( 7 ), W(S) 2 Cl 2 ( 8 ) and Mo(S)Cl 3 ( 9 ) are obtained by low temperature treatment of WCl 6 , W(S)Cl 4 and MoCl 5 , respectively, with one equivalent of (Me 3 Si) 2 S in CH 2 Cl 2 solvent. The mixed oxothiohalide compounds W(O)(S)Cl 2 ( 10 ) and Mo(O)(S)Cl 2 ( 11 ) may be isolated in good yield through the reaction of W(O)Cl 4 or Mo(O)Cl 4 with (Me 3 Si) 2 S in CH 2 Cl 2 at low temperature.

Syntheses, structures and magnetic properties of three new ion-pair complexes containing transition metal bis(malconitriledithiolate) anion and radical cations

Abstract Three new ion-pair complexes ( m -MPYNN) 2 Ni(mnt) 2 ( 1 ), ( p -MPYNN) 2 Ni(mnt) 2 ( 2 ) and ( p -MPYNN) 2 Cu(mnt) 2 ( 3 ) ( m - or p -MPYNNI = [3- or4- (4,4,5,5-tetramethyl-1-oxido-3-oxyl-4,5-dihydro-3H-imidazol-2′-yl)-1-methylpyridinium] iodide, mnt = maleonitriledithiolate) have been prepared and characterized by elemental analyses, IR, single crystal X-ray diffraction and magnetic susceptibility. In complex 1 , the m -MPYNN cations form a centrosymmetric dimer, and the [Ni(mnt) 2 ] 2− anion lies on a center of inversion. Complexes 2 and 3 show layered packing, and the p -MPYNN cations lie between the layers of the anions. Magnetic susceptibility measurements in the temperature range 2–300 K show that the three complexes exhibit weak antiferromagnetic behaviors. The behavior of complex 1 was explained with the singlet-triplet model.

Evidence for the Involvement of 5f Orbitals in the Bonding and Reactivity of Organometallic Actinide Compounds: Thorium(IV) and Uranium(IV) Bis(hydrazonato) Complexes

Migratory insertion of diphenyldiazomethane into both metal-carbon bonds of the bis(alkyl) and bis(aryl) complexes (C(5)Me(5))(2)AnR(2) yields the first f-element bis(hydrazonato) complexes (C(5)Me(5))(2)An[eta(2)-(N,N')-R-N-N=CPh(2)](2) [An = Th, R = CH(3) (18), PhCH(2) (15), Ph (16); An = U, R = CH(3) (17), PhCH(2) (14)], which have been characterized by a combination of spectroscopy, electrochemistry, and X-ray crystallography. The two hydrazonato ligands adopt an eta(2)-coordination mode leading to 20-electron (for Th) and 22-electron (for U) complexes that have no transition-metal analogues. In fact, reaction of (C(5)H(5))(2)Zr(CH(3))(2) or (C(5)Me(5))(2)Hf(CH(3))(2) with diphenyldiazomethane is limited to the formation of the corresponding mono(hydrazonato) complex (C(5)R(5))(2)M[eta(2)-(N,N')-CH(3)-N-N=CPh(2)](CH(3)) (M = Zr, R = H or M = Hf, R = CH(3)). The difference in the reactivities of the group 4 metal complexes and the actinides was used as a unique platform for investigating in depth the role of 5f orbitals on the reactivity and bonding in actinide organometallic complexes. The electronic structure of the (C(5)H(5))(2)M[eta(2)-(N,N')-CH(3)-N-N=CH(2)](2) (M = Zr, Th, U) model complexes was studied using density functional theory (DFT) calculations and compared to experimental structural, electrochemical, and spectroscopic results. Whereas transition-metal bis(cyclopentadienyl) complexes are known to stabilize three ligands in the metallocene girdle to form saturated (C(5)H(5))(2)ML(3) species, in a bis(hydrazonato) system, a fourth ligand is coordinated to the metal center to give (C(5)H(5))(2)ML(4). DFT calculations have shown that 5f orbitals in the actinide complexes play a crucial role in stabilizing this fourth ligand by stabilizing both the sigma and pi electrons of the two eta(2)-coordinated hydrazonato ligands. In contrast, the stabilization of the hydrazonato ligands was found to be significantly less effective for the putative bis(hydrazonato) zirconium(IV) complex, yielding a higher energy structure. However, the difference in the reactivities of the group 4 metal and actinide complexes does not arise on thermodynamic grounds but is primarily of kinetic origin. Unfavorable steric factors have been ruled out as the sole influence to explain these different behaviors, and electronic factors were shown to govern the reactivity. For the actinides, both the C(5)H(5) and more realistic C(5)Me(5) ligands have been taken into account in computing the energy surface. The reaction profile for the C(5)Me(5) system differs from that with the C(5)H(5) ligand by a uniform shift of approximately 5 kcal/mol in the relative energies of the transition state and products. The insertion of a second diazoalkane molecule into the sole metal-carbon bond in the mono(hydrazonato) complexes involves a high energy barrier (approximately 20 kcal/mol) for the zirconium(IV) system, whereas the actinides can facilitate the approach of the diazoalkane by coordination (formation of an adduct) and its insertion into the An-C bond with a very low barrier on the potential energy surface.

Preparation of spinel ferrites from citrate precursor route—A comparative study

Spinel ferrites MFe 2O 4 (M = Mn, Co, Ni, Cu) have been prepared from the thermolysis of transition metal bis(citrato)ferrates(III), M 3[Fe(C 6H 5O 7) 2] 2· xH 2O. Various physico-chemical studies, i.e. TG–DTG–DSC, XRD and Mössbauer spectroscopy have been employed for the investigation of the mode of decomposition and characterization of intermediates/products formed. After dehydration the anhydrous precursor undergoes an oxidative decomposition to yield α-Fe 2O 3 and respective metal oxide. Finally spinel ferrites, MFe 2O 4, are formed as a result of a solid-state reaction between the oxides at a much lower temperature (310–440 °C) and in less time as compared to that of the conventional ceramic method. SEM studies show these ferrites to be of nanosized. Ferrites obtained from the thermolysis of transition metal ferricitrate precursors show higher values of saturation magnetization than those got from respective ferrimalonate precursors, thus designating the former as novel materials to operate at high frequencies.

オレフィン重合新触媒による高分子材料の創製

This contribution reports on the unique olefin polymerization catalysis of the new catalysts developed at Mitsui Chemicals and the associated synthesis of value-added olefin-based materials. Research based on a ligand oriented catalyst design concept has resulted in the discovery of a series of high-performance imine-based group 4 transition metal complex catalysts, represented by bis (phenoxy-imine) early transition metal catalysts (FI catalysts) and bis (pyrrolide-imine) group 4 transition metal catalysts (PI catalysts). These imine-based catalysts possess distinctive features that result in characteristic polymerization catalysis and unique polymer synthesis. The features include presence of structural isomers, fluxional character regarding the interconversion of the structural isomers, high electrophilicity of a catalytically active species, susceptibility to reduction at the imine functionality, and versatility vis-a-vis activator selection. With these fea-tures, the catalysts can form a wide variety of unique olefin-based materials, which include vinyl-terminated polyethylenes (PEs), well-defined and multimodal PEs, ultra-high molecular weight ethylene/a-olefin copolymers, highly isotactic and syndiotactic PPs (iPPs and sPPs), regio- and stereoirregular high molecular weight poly(higher a-olefin)s, and ultra-fine particle PEs. Additionally, we have found that these catalysts are capable of mediating highly controlled living olefin (co) polymerizations to produce a wide array of block copolymers from ethylene, propylene, higher a-olefins and norbornene. Moreover, we have successfully synthesized well-defined functionalized PEs, PE/polar polymer hybrid materials (from vinyl-terminated PEs) and functionalized ultra-fine particle PEs (from ultra-fine particle PEs). Many of the olefin-based materials described above were unavailable prior to our work.

Catalytic Asymmetric Fluorination of α-Chloro-β-ketoesters in the Presence of Chiral Palladium Complexes

The chemistry of organic fluorine compounds is a rapidly developing area of research because of their importance in biochemical and medicinal applications and material science. Introduction of fluorine atom into biologically active compounds often leads to improvement of chemical and physical properties of the parent compounds due to unique properties of the fluorine atom. Chiral organofluorine compounds containing a fluorine atom bonded directly to a stereogenic center have been utilized in studies of enzyme mechanisms and as intermediates in asymmetric syntheses. The development of effective methodologies for the preparation of stereoselectively fluorinated compounds having a fluorine atom at a stereogenic carbon center is critical in order to further advances of fluorine chemistry. Until now, a number of enantioselective fluorinations have been achieved by reagent-controlled and catalytic enantioseletive fluorination. Recently, several groups have been reported the catalytic enantioselective fluorination of active methine derivatives using chiral Lewis acids such as Binap-Pd(II) and transition metal-bis(oxazoline) complexes and organocatalysts such as cinchonine-derived quaternary ammonium salt, imidazolidinone, and proline derivatives. A few synthetic methods for the preparation of α-chloroα-fluoro-β-ketoesters have been reported. In general, αchloro-α-fluoro-β-ketoesters were prepared by the electrophilic fluorination of α-chloro-β-ketoesters using NFSI or F2 in the presence of formic acid. Togni has recently reported the first catalytic enantioselective synthesis of α-chloro-αfluoro-β-ketoesters using chiral titanium complexes with up to 65% selectivity. As part of research program related to the development of synthetic methods for the enantioselective construction of stereogenic carbon centers, we reported the catalytic enantioselective α-fluorination and α-amination of β-ketoesters with excellent enantioselectivity which promoted by chiral ammonium salts and chiral palladium complexes. In this letter, we wish to report the catalytic enantioseletive electrophilic α-fluorination of α-chloro-β-ketoesters using chiral palladium complexes 3 which are airand moisturestable. To determine suitable reaction condition for the catalytic enantioselcetive fluorination of α-chloro-β-ketoesters 1, we first examined electrophilic fluorination of 1-chloro benzoylacetate 1a with N-fluorobenzenesulfonimide (NFSI) in the presence of 5 mol% of 3a in MeOH at room temperature (Table 1). As can be seen from Table 1, the fluorinated

Electronic states of neutral and cationic bis(benzene) titanium and vanadium sandwich complexes studied by pulsed field ionization electron spectroscopy

Ti- and V-bz2 (bz=C6H6) sandwich complexes have been prepared in a laser-ablation cluster beam source and studied by pulsed field ionization-zero electron kinetic energy photoelectron spectroscopy and theoretical calculations. The ground electronic states of the neutral Ti- and V-bz2 complexes are determined to be 1A1g and 2A1g, and their ionization energies are measured to be 5.732+/-0.001 and 5.784+/-0.002 eV, respectively. These neutral complexes have eta6 binding and are in an eclipsed D6h configuration with flat benzene rings. Ionization of the 1A1g and 2A1g neutral states of Ti- and V-bz2 yields the 2B1g and 3B1g ion states, respectively, in a D2h point group with slightly puckered benzene rings. In addition, the binding and structures of these two complexes are compared with other first-row transition metal bis(benzene) sandwiches.

Photoelectron Spectroscopy of the Bis(dithiolene) Anions [M(mnt)2]n-(M = Fe − Zn;n= 1, 2): Changes in Electronic Structure with Variation of Metal Center and with Oxidation

A detailed understanding of the electronic structures of transition metal bis(dithiolene) centers is important in the context of their interesting redox, magnetic, and optical properties. The electronic structures of the series [M(mnt)2]n- (M = Fe - Zn; mnt = 1,2-S2C2(CN)2; n = 1, 2) were examined by a combination of photodetachment photoelectron spectroscopy and density functional theory calculations, providing insights into changes in electronic structure with variation of the metal center and with oxidation. Significant changes were observed for the dianions [M(mnt)2]2- due to stabilization of the metal 3d levels from Fe to Zn and the transition from square-planar to tetrahedral coordination about the metal center (Fe-Ni, D(2h) --> Cu D2 --> Zn, D(2d). Changes with oxidation from [M(mnt)2]2- to [M(mnt)2]1- were largely dependent on the nature of the redox-active orbital in the couple [M(mnt)2](2-/1-). In particular, the first detachment feature for [Fe(mnt)2]2- originated from a metal-based orbital (Fe(II) --> Fe(III)) while that for [Fe(mnt)2]1- originated from a ligand-based orbital, a consequence of stabilization of Fe 3d levels in the latter. In contrast, the first detachment feature for both of [Ni(mnt)2]2- and [Ni(mnt)2]1- originated from the same ligand-based orbital in both cases, a result of occupied Ni 3d levels being stabilized relative those of Fe 3d and occurring below the highest energy occupied ligand-based orbital for both of [Ni(mnt)2]2- and [Ni(mnt)2]1- . The combined data illustrate the subtle interplay between metal- and ligand-based redox chemistry in these species and demonstrate changes in their electronic structures with variation of metal center, oxidation, and coordination geometry.

Probing the Intrinsic Electronic Structure of the Bis(dithiolene) Anions [M(mnt)2]2-and [M(mnt)2]1-(M = Ni, Pd, Pt; mnt = 1,2-S2C2(CN)2) in the Gas Phase by Photoelectron Spectroscopy

A detailed understanding of the electronic structure of transition metal bis(dithiolene) complexes is important because of their interesting redox, magnetic, optical, and conducting properties and their relevance to enzymes containing molybdenum and tungsten bis(dithiolene) centers. The electronic structures of the bis(dithiolene) anions [M(mnt)(2)](n-) (M = Ni, Pd, Pt; mnt = 1,2-S(2)C(2)(CN)(2); n = 0-2) were examined by a combination of photodetachment photoelectron spectroscopy (PES) and density functional theory calculations. The combined experimental and theoretical data provide insight into the molecular orbital energy levels of [M(mnt)(2)](2-) and the ground and excited states of [M(mnt)(2)](1-) and [M(mnt)(2)]. Detachment features from ligand-based orbitals of [M(mnt)(2)](2-) occur at similar energies for each species, independent of the metal center, while those arising from metal-based orbitals occur at higher energies for the heavier congeners. Electronic excitation energies inferred for [M(mnt)(2)](1-) from the PES experiments agree well with those obtained in optical absorption experiments in solution, with the PES experiments providing additional insight into the changes in energy of these transitions as a function of metal. The singly charged anions [M(mnt)(2)](1-) were also prepared and studied independently. Electron detachment from the ground states of these doublet anions accessed the lowest singlet and triplet states of neutral [M(mnt)(2)], thereby providing a direct experimental measure of their singlet-triplet splitting.

Bonding studies of dinuclear transition metal bis(μ-η 2-silane) complexes [L nM(μ-η 2-HSiR 2)] 2 by density functional theory

The bonding and structural features of a series of dinuclear transition metal bis(μ-η 2-silane) complexes [L n M(μ-η 2-HSiR 2)] 2 were studied using density functional theory calculations. These dinuclear complexes consist of two metal fragments doubly bridged by two (μ-η 2-HSi) units with a formal metalmetal bond. Each metal fragment conforms to either the 16- or 18-electron rule dependent on the spatial arrangement of ligands around each metal coordination sphere. These dinuclear silane complexes display noticeably shorter Si⋯H distances in the [M(μ-η 2-HSi)] 2 units when compared with mononuclear η 2-silane complexes. The shorter Si⋯H distances in the metal–(η 2-silane) interactions suggest that these dinuclear complexes are more non-classical than mononuclear ones. The more non-classical feature is a result of weaker metal(d) to SiH(σ*) back-donation interactions due to the presence of a metal substituent at silicon.

Catalysis of the silica sol-gel process by divalent transition metal bis(acetylacetonate) complexes.

Transition metal bis(acetylacetonate) complexes of Co(II), Ni(II), Cu(II), and Zn(II) have been found to be active catalysts for the sol-gel process. The catalytic activity of these complexes decreases in going from Co(II) to Zn(II) and is highest for the acetylacetonate ligand system. 29Si NMR studies show that the complexes act primarily as condensation catalysts and are, in that regard, similar to Brønsted bases such as hydroxide. Mechanistically, however, they appear to differ significantly from hydroxide in how they induce condensation. This is revealed in the catalyst concentration dependence, which is 1/2 order for the metal complexes and 1st order in hydroxide. Differences are also apparent in the thermochemical parameters that indicate that the metal complexes act to increase the entropy of the transition state leading to condensation. The catalytic activity is proportional to the degree of ligand dissociation of the metal complex, and experiments suggest that the active catalytic species is specifically the first dissociation product, MII(acac)+.

Polythiophene Hybrids of Transition-Metal Bis(salicylidenimine)s: Correlation between Structure and Electronic Properties

The synthesis, electrochemistry, and spectroscopic behavior of tetradentate bis(salicylidenimine) transition metal complexes 5−9 are reported. Appending these complexes with 3,4-ethylenedioxythiophene (EDOT) moieties allows for electrochemical polymerization at much lower potentials than the parent salen complexes. The resulting polymers display well-defined organic-based electrochemistry at potentials <0.5 V vs Fc/Fc+. The EDOT-modified N,N‘-ethylene bis(salicylidene), N,N‘-o-phenylene bis(salicylidene), and N,N‘-trans-cyclohexylene bis(salicylidene) complexes 5a−b, 6a−b, and 8a−b display cyclic voltammograms with four organic-based redox waves. Increasing the interchain separation through the use of nonplanar bis(salicylidene) ligands results in only two redox waves. The conductivity of the copper-based polymers decreases with increasing interchain spacing, with the maximum conductivity being 92 S cm-1 for poly(5a) and 16 S cm-1 for poly(7a). The nickel complexes were less sensitive to increased interchain separation and showed conductivities greater than 48 S cm-1 regardless of the interchain spacing and near 100 S cm-1 in the case of poly(6b). In situ spectroelectrochemistry was consistent with the segmented electronic nature of these polymers. Cyclic voltammetry of an analogous uranyl complex, 5c, revealed that two electrons per repeat unit were removed during oxidation. Consideration of our collective investigations, which also included in situ EPR spectroscopic studies, led to a postulation that π-aggregation processes are occurring in those polymers which are allowed to have close interchain spacing.

AGGREGATION BEHAVIOR OF COBALT(II), NICKEL(II), AND COPPER(II) BIS(2-ETHYLHEXYL) PHOSPHATE COMPLEXES IN n-HEPTANE

ABSTRACT The solution behavior of divalent transition metal-bis(2-ethylhexyl) phosphate (M(DEHP)2, M = cobalt, nickel or copper) complexes in n-heptane have been investigated by vapor pressure osmometry, viscometry and dynamic light scattering. Co(DEHP)2 complexes tend to form large macromolecular species with a mean aggregation number Nagg as large as 225, and the size of the macromolecular species decreases with increasing Co(DEHP)2 concentration. In contrast, Cu(DEHP)2 complexes tend to form small macromolecular species Nagg = 4-8 which increase in size with increasing Cu(DEHP)2 concentration. On the other hand, Ni(DEHP)2 complexes (and Ni(DEHP)2-2H2O complexes when the molar ratio of H2O

The photoelectron spectroscopy and electronic structure of metal β-diketonates and their analogs

He(I) photoelectron spectra of transition and non-transition metal bis- and tris-β-diketonate complexes were studied. Spectra have been interpreted based on the study of regularities in spectra of compound rows and results of quantum chemical calculations of ground and ionized states by X α-DV and ab initio methods. In group III d-metal complexes, the bond covalency changes in the sequenceYL 3 < LuL 3 < ScL 3, whereas for complexes of final elements in the transition row, the bond covalency is directly proportional to the period row. Ionization energy changes for O to NR group substitution, γ-H to Cl and CH 3 group, β-CH 3 groups to H, C(CH 3) and C 6H 5, are discussed. It was shown that for high-spin complexes, despite the closeness of the final state energies, ψ-function symmetry prohibits the interaction between states caused by d- and L-electrons removal.

Bis(η-heteroarene) titanium complexes derived from 2,4,6-tri-tert-butylpyridine and 2,4,6-tri-tert-butylphosphorin: Conformational preference in solution and redox activity

The complexes (Ti(NC5H2tBu3-2,4,6)2] 1, and [Ti(PC5H2tBu3-2,4,6)2] 2, have been synthesised in moderate yields via the co-condensation reaction between titanium vapour and [NC5H2tBu3-2,4,6] 3, or [PC5H2tBu3-2,4,6] 4 respectively. The conformation adopted by the molecules in solution has been investigated by NMR and is discussed in comparison with other first row transition metal bis(heteroarene) complexes. Both 1 and 2 are found to exist entirely in the synclinal conformation. The reaction of 1 and 2 with potassium results in formation of the potassium salts K+[Ti(NC5H2tBu3)2−] 5, and K+[Ti(PC5H2tBu3)2−] 6 respectively.

Syntheses and single-crystal X-ray structures of [(ButNP)2(ButN)2]MCl2 (M = Zr, Hf): the first transition-metal bis(alkylamido)cyclodiphosphazane complexes

L. Grocholl, L. Stahl and R. J. Staples, Chem. Commun., 1997, 1465 DOI: 10.1039/A702606D

Synthesis and Characterization of Complexes of Diamines with Transition Metal bis(Chlorosulphates), M(SO3Cl)2[M = Cr, Mn, Fe, Co, Ni, Cu

Abstract The reaction of transition metal bis(chlorosulphates) with diamines such as 1,3-propylenediamine (Pndn) and o-phenylenediamine (Opdn) resulted in the formation of complexes of the type [M (SO3Cl)2(Pndn)2] and [M(SO3Cl)2 (Opdn)2] (M = Cr, Mn, Fe, Co, Ni, Cu]. These complexes are hygroscopic in nature and soluble in most non-polar solvents. The covalent nature of the bonding of the SO3Cl− group has been ascertained on the basis of a shift to higher frequency in the ν1(A) vibration, the splitting of doubly degenerate (E) modes and low molar conductivity values. The magnetic susceptibility measurements and the electronic spectral studies are consistent with an octahedral geometry for all these complexes (except for the Ni(II) complex where tetragonal distortion is observed) such that each SO3Cl− group is coordinated in a monodentate manner.