Transition Metal Derivatives Research Articles

Bis(heptalene) “submarine” metal dimer sandwich compounds (C12H10)2M2 (M = Ti, V, Cr, Mn, Fe, Co, Ni)

The bis(heptalene)dimetal complexes (C12H10)2M2 of the first row transition metals from Ti to Ni are predicted by density functional theory to exhibit "submarine" sandwich structures with a pair of metal atoms sandwiched between the two heptalene rings. For the early transition metal derivatives (C12H10)2M2 (M = V, Cr) there are two types of such structures. In one structural type the metals are sandwiched between two heptahapto heptalene rings with metal-metal distances (3.5-3.8 Å) too long for direct metal-metal bonding. The other type of (C12H10)2M2 (M = V, Cr, Mn) structure has a pair of bonded metal atoms sandwiched between a fully bonded heptalene ligand and a heptalene ligand bonded to the metals only through an eight-carbon heptafulvene subunit, leaving an uncomplexed cis-1,3-diene unit. The formal metal-metal bond orders in these latter structures are 3, 2, and 1 for M = V, Cr, and Mn with predicted bond lengths of 2.5, 2.7, and 2.8 Å, respectively. For (C12H10)2Fe2 a singlet structure with each iron atom sandwiched between a hexahapto and a tetrahapto heptalene ring is energetically preferred over an alternate structure with ferrocene-like iron atoms sandwiched between two pentahapto heptalene rings. Partial bonding of each heptalene ring to the metal atoms occurs in the late transition metal derivatives (C12H10)2M2 (M = Co, Ni). This leads to an unsymmetrical structure for the cobalt derivative and a structure for the nickel derivative with each nickel atom sandwiched between a trihapto ligand and a tetrahapto ligand.

17O NMR Gives Unprecedented Insights into the Structure of Supported Catalysts and Their Interaction with the Silica Carrier

Flame silica was surface-labeled with (17)O, through isotopic enrichment of both siloxanes and silanols. After heat treatment at 200 and 700 °C under vacuum, the resulting partially dehydroxylated silica materials were investigated by high-field solid-state (1)H and (17)O NMR. More specifically, MQ MAS and HMQC sequences were used to probe the (17)O local environment. In a further step, these (17)O-tagged supports were used for the preparation of supported catalysts by reaction with perhydrocarbyl transition metal derivatives (zirconium tetraalkyl, tantalum trisalkyl-alkylidene, and tungsten trisalkyl-alkylidyne complexes). Detailed (17)O 1D and 2D MQ and HMQC MAS NMR studies demonstrate that signals in the Si-OH, Si-O-Si, and Si-O-metal regions are highly sensitive to local structural modifications, thanks to (17)O wide chemical shift and quadrupolar constant ranges. Experimental results were supported by DFT calculations. From the selective surface labeling, unprecedented information on interactions between supported catalysts and their inorganic carrier has been extracted.

Groups 5 and 6 Terminal Hydrazido(2−) Complexes: Nβ Substituent Effects on Ligand-to-Metal Charge-Transfer Energies and Oxidation States

Brightly colored terminal hydrazido(2-) (dme)MCl(3)(NNR(2)) (dme = 1,2-dimethoxyethane; M = Nb, Ta; R = alkyl, aryl) or (MeCN)WCl(4)(NNR(2)) complexes have been synthesized and characterized. Perturbing the electronic environment of the β (NR(2)) nitrogen affects the energy of the lowest-energy charge-transfer (CT) transition in these complexes. For group 5 complexes, increasing the energy of the N(β) lone pair decreases the ligand-to-metal CT (LMCT) energy, except for electron-rich niobium dialkylhydrazides, which pyramidalize N(β) in order to reduce the overlap between the Nb═N(α) π bond and the N(β) lone pair. For W complexes, increasing the energy of N(β) eventually leads to reduction from formally [W(VI)≡N-NR(2)] with a hydrazido(2-) ligand to [W(IV)═N═NR(2)] with a neutral 1,1-diazene ligand. The photophysical properties of these complexes highlight the potential redox noninnocence of hydrazido ligands, which could lead to ligand- and/or metal-based redox chemistry in early transition metal derivatives.

A 2-D Organic–Inorganic Hybrid Copper-Yttrium Heterometallic Monovacant Keggin Phosphotungstate Derivative: [Cu(dap)2]5.5[Y(α-PW11O39)2]·4H2O

A novel 2-D organic–inorganic hybrid copper-yttrium heterometallic monovacant Keggin phosphotungstate derivative [Cu(dap)2]5.5[Y(α-PW11O39)2]·4H2O (1) (dap = 1,2-diaminopropane) has been hydrothermally synthesized by reaction of Na9[A-α-PW9O34]·7H2O, CuCl2·2H2O, YCl3 and dap and structurally characterized by elemental analysis, IR spectrum, UV spectrum, powder X-ray diffraction (PXRD), and X-ray single-crystal diffraction. 1 illustrates an interesting 2-D copper-yttrium heterometallic sheet architecture with a 5-connected topology built by 1:2-type [Y(α-PW11O39)2]11− subunits and [Cu(dap)2]2+ bridges. To our knowledge, 1 represents a rare 2-D organic–inorganic hybrid Keggin phosphotungstate-based transition metal and rare-earth heterometallic derivative. The photocatalytic measurements show that 1 can inhibit the photodegradation of rhodamine-B.

Structural changes upon replacing carbonyl groups with thiocarbonyl groups in first row transition metal derivatives: new insights

The chemistry of metal thiocarbonyls is much more limited than that of metal carbonyls because of the instability of CS as a synthetic reagent. In view of the many gaps remaining in experimentally realized metal thiocarbonyl chemistry, theoretical studies using density functional methods have been used to explore the possible future scope of metal thiocarbonyl chemistry. This paper reviews such theoretical studies on binuclear metal carbonyl derivatives of the types M(2)(CS)(2)(CO)(n) and Cp(2)M(2)(CS)(2)(CO)(n) (Cp = η(5)-C(5)H(5); M = V through Ni) as well as the trinuclear and tetranuclear iron carbonyls Fe(3)(CS)(3)(CO)(n) (n = 9, 8, 7, 6) and Fe(4)(CS)(4)(CO)(n) (n = 12, 11, 10, 9). The substitution of one or two CO groups with CS groups to give less symmetrical structures leads to many more isomers. Structures in which a four-electron donor thiocarbonyl group uses its sulfur atom to bridge a metal-metal bond as a η(2)-μ-CS ligand are more favorable in binuclear metal thiocarbonyl chemistry than corresponding structures in metal carbonyl chemistry owing to the basicity of the sulfur atom. Six-electron donor thiocarbonyl groups bridging clusters of three or four iron atoms are also found in low-energy structures including a particularly favorable Fe(4)(CS)(4)(CO)(10) structure suggested as a possible target for future synthetic chemistry. In thiocarbonyl substitution products of simple binuclear metal carbonyls such as Fe(2)(CO)(9) [= Fe(2)(CO)(6)(μ-CO)(3)], Co(2)(CO)(8) [= Co(2)(CO)(6)(μ-CO)(2)], and Cp(2)Fe(2)(CO)(4) [= Cp(2)Fe(2)(CO)(2)(μ-CO)(2)], structures with bridging CS groups are invariably lower energy structures than isomeric structures with bridging CO groups.

In vitro Activities of Transition Metal Derivatives of Ketoconazole and Clotrimazole against a Wild Type Strain of Saccharomyces cerevisiae in Absence or Presence of Human Neutrophils

In vitro activities of a series of gold, copper and ruthenium clotrimazole (CTZ, CAS 23593-75-1) and ketoconazole (KTZ, CAS 65277-42-1) derivatives were investigated individually and in combination with human neutrophils (PMNs) against a wild type strain of Saccharomyces cerevisiae. For 11 out of 12 tested metal complexes, the minimal inhibitory concentrations (MICs) at which 100 % of yeast growth was inhibited ranged from 0.75 to 3.0 micromol/L. The complex RuCl3(CTZ)3 x 2CH3OH (1f) (MIC = 0.75 micromol/L) was, although modestly, the only one able to increase the fungistatic activity of the parental drug (MIC = 1 micromol/L). On the other hand, at a sub-MIC concentration (0.5 micromol/L), the complexes [Cu(KTZ)Cl2]2 x 2H2O (2c) and RuCl2(KTZ)2 (2e) displayed synergistic fungicidal effects with PMNs whereas phagocytic capacity was enhanced by complexes [Cu(KTZ)3Cl2] (2b) and RuCl2(KTZ)2 (2e). The findings suggest that the metal-based agents may give rise to drugs with improved antifungal properties.

Triple-Decker-Sandwich versus Rice-Ball Structures for Tris(benzene)dimetal Derivatives of the First-Row Transition Metals

Compounds of the type M(2)Bz(3) (Bz = benzene, C(6)H(6)) have been of interest since the related triple-decker mesitylenechromium sandwich (1,3,5-Me(3)C(6)H(3))(3)Cr(2) has been synthesized and characterized structurally by X-ray crystallography. Theoretical studies predict the lowest-energy M(2)Bz(3) structures of the early transition metals Ti, V, and Cr to be the triple-decker sandwiches trans-Bz(2)M(2)(η(6),η(6)-μ-C(6)H(6)) having quintet, triplet, and singlet spin states, respectively. In these structures, the central benzene ring functions as a hexahapto ligand to each metal atom. The singlet rice-ball cis-Bz(2)M(2)(μ-C(6)H(6)) structures with a 2.64-Å Mn═Mn double bond or a 2.81-Å Fe-Fe single bond are preferred for the central transition metals Mn and Fe. Singlet triple-decker-sandwich structures trans-Bz(2)M(2)(μ-C(6)H(6)) return as the lowest-energy structures for the late transition metals Co and Ni but with the central benzene ring only partially bonded to each metal atom. Thus, the lowest-energy cobalt derivative has a trans-Bz(2)Co(2)(η(3),η(3)-μ-C(6)H(6)) structure in which the central benzene ring acts as a trihapto ligand to each metal atom. Similarly, the lowest-energy nickel derivative has a trans-Bz(2)Ni(2)(η(2),η(2)-μ-C(6)H(6)) structure in which the central benzene ring acts as a dihapto ligand to each metal atom, leaving an uncomplexed C═C double bond. The metal-metal bond orders in the singlet "rice-ball" structures cis-Bz(2)M(2)(μ-C(6)H(6)) (M = Mn, Fe) and the hapticities of the central benzene rings in the singlet late-transition-metal triple-decker-sandwich structures trans-Bz(2)M(2)(μ-C(6)H(6)) (M = Co, Ni) are governed by the desirability for the metal atoms to attain the favored 18-electron configuration.

Structural and thermodynamic aspects of the dissociation of cyclopentadienyl rings from homoleptic cyclopentadienyl early transition metal, cerium, and thorium derivatives

Homoleptic cyclopentadienyl derivatives of the early transition metals and lanthanides that have been synthesized include Cp 4M (M = Ti, Zr, Ce, Hf, Th), Cp 3M (M = Sc, Y, most lanthanides, Ti, Zr, Hf, Th), and Cp 2M (M = Ti, V). Density functional theory shows that the Cp 4M structures with unusual S 4 symmetry are saddle points for the d-block metals Ti, Zr, Hf but genuine minima for the f-block metals Ce and Th. The true equilibrium Cp 4M geometries have C 1 symmetry with two η 5-Cp rings and two η 1-Cp rings for M = Ti and Hf but three η 5-Cp rings and one η 1-Cp ring for M = Zr. The dissociation energies for Cp 4M → Cp 3M + Cp are substantial and in the order Ti < Ce < Zr ∼ Hf < Th, roughly consistent with the observed relative stabilities of the +4 and +3 oxidation states of these metals. The C 3 h structures with all η 5-Cp rings are genuine minima for most of the Cp 3M compounds except for Cp 3Ti, which has a C s symmetry minimum with two η 5-Cp rings and one η 2-Cp ring, and Cp 3V, which has two η 5-Cp rings and one η 1-Cp ring. The dissociation energies for Cp 3M → Cp 2M + Cp are in the order V < Ti < Sc < Y < La, consistent with the relative stabilities of the +2 and +3 oxidation states of these metals.

Binuclear Cyclopentadienylmetal Cyclooctatetraene Derivatives of the First Row Transition Metals: Effects of Ring Conformation on the Bonding of an Eight-Membered Carbocyclic Ring to a Pair of Metal Atoms

Binuclear Cp(2)M(2)(μ-C(8)H(8)) derivatives have been synthesized for M = V, Cr, Co, and Ni and have now been studied theoretically for the entire first row of transition metals from Ti to Ni. The early transition metal derivatives Cp(2)M(2)(μ-C(8)H(8)) (M = Ti, V, Cr. Mn) are predicted to form low-energy cis-Cp(2)M(2)(μ-C(8)H(8)) structures with a folded C(8)H(8) ring (dihedral angle ∼130°) and short metal-metal distances suggesting multiple bonding. These predicted structures are close to the experimental structures for M = V, Cr with V≡V and Cr≡Cr bond lengths of ∼2.48 and ∼2.36 Å, respectively. The middle to late transition metals form trans-Cp(2)M(2)(μ-C(8)H(8)) structures (M = Mn, Fe, Co, Ni) with a twisted μ-C(8)H(8) ring and no metal-metal bonding. The hapticity of the central μ-C(8)H(8) ring in such structures ranges from five for Mn and Fe to four for Co and three for Ni and thus depend on the electronic requirements of the central metal atom. This leads to the favored 18-electron configuration for both metal atoms in the singlet Fe, Co, and Ni structures but only 17-electron metal configurations in the triplet Mn structure. In addition, the late transition metals form trans-Cp(2)M(2)(μ-C(8)H(8)) structures (M = Fe, Co, Ni), with the tub conformation of the μ-C(8)H(8) ring functioning as a tetrahapto (M = Fe, Co) or trihapto (M = Ni) ligand to each CpM group. A μ-C(8)H(8) ring in the tub conformation also bonds to two CpFe units as a bis(tetrahapto) ligand in both singlet and triplet cis-Cp(2)Fe(2)(μ-C(8)H(8)) structures.

ChemInform Abstract: Alkyliron- and Alkylcobalt Reagents. Part 5. Anticheleselective Cyanoalkylation with Cyanoalkyl Derivatives of Iron(II), Titanium(IV) and Further Transition Metals.

ChemInform Abstract: Alkyliron- and Alkylcobalt Reagents. Part 5. Anticheleselective Cyanoalkylation with Cyanoalkyl Derivatives of Iron(II), Titanium(IV) and Further Transition Metals.

ChemInform Abstract: Alkyliron and Alkylcobalt Reagents. Part 4. Aldehyde-Selective Cyanoalkylation with Cyanoalkyl Derivatives of Iron(II) and Other Transition Metals.

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Variable hapticity of the cyclooctatetraene ring in sandwich compounds of the first row transition metals

Density functional theory methods (B3LYP and BP86) indicate that the preferred structures for such early transition metal derivatives are (η 8-C 8H 8)M(η 4-C 8H 8) (M = Ti, V, Cr) with one octahapto η 8-C 8H 8 ring and one tetrahapto η 4-C 8H 8 ring. In such structures only 12 of the 16 carbon atoms of the two C 8H 8 rings are bonded to the metal, leading to 16-, 17-, and 18-electron complexes, respectively, in accord with the experimentally known structures for the Ti and V derivatives. The preferred structures for the Mn and Fe derivatives are (η 6-C 8H 8)M(η 4-C 8H 8) (M = Mn, Fe) with one hexahapto and one tetrahapto C 8H 8 ring and thus having 17- and 18-electron configurations, respectively, in accord with experimental data on the iron complex. The lowest energy structure for the cobalt complex is (η 4-C 8H 8)Co(η 2,2-C 8H 8) with two different types of tetrahapto C 8H 8 rings and a 17-electron metal configuration. The nickel complex (C 8H 8) 2Ni appears to prefer a structure with a 16-electron configuration and two trihapto C 8H 8 rings, similar to the known (η 3-C 3H 5) 2Ni rather than a bis(tetrahapto) structure with the favored 18-electron configuration. These theoretical studies indicate that in (C 8H 8) 2M derivatives of the first row transition metals, the number of carbon atoms in the pair of C 8H 8 rings involved in the bonding to the central metal atom gives the metal atoms 16-, 17-, or 18-electron configurations.

Thiazolo[5,4-d]thiazole-2,5-dicarboxylic acid, C 6H 2N 2O 4S 2, and its coordination polymers

Thiazolo[5,4-d]thiazole-2,5-dicarboxylic acid, C 6H 2N 2O 4S 2, was isolated as a polycrystalline material, and its crystal structure was determined by ab-initio X-ray powder diffraction (XRPD) methods. This species, upon deprotonation, was subsequently used in preparing the new coordination polymers Ag 2(C 6N 2O 4S 2), Mn(C 6N 2O 4S 2)(H 2O) 2, Co(C 6N 2O 4S 2)(H 2O) 2, Cu(C 6N 2O 4S 2)(H 2O) and Zn(C 6N 2O 4S 2)(H 2O) 2, fully characterized by analytical, thermal and XRPD structural methods – including in situ thermodiffractometry and simultaneous TGA and DSC. In the first-row transition metal derivatives, the [C 6N 2O 4S 2] 2− anion systematically prefers the N, O-chelating, vs. the expected O, O′-bridging, coordination mode, not allowing the formation of porous 3D frameworks. Indeed, these species are dense 1D coordination polymers. At variance, the silver derivative possesses a complex, dense 3D framework, due to the presence of μ 6-[C 6N 2O 4S 2] 2− ligands showing two μ 2-bridging carboxylates and two monohapto N-donor sites. When dehydration is viable, materials of E n (C 6N 2O 4S 2) formulation are irreversibly recovered ( n = 1 for E = Mn, Co, Zn, Cu; n = 2, for E = H).

Synthesis, Characterization, and Magnetism of Divalent Aryl Transition-Metal Complexes of the Simplest Dialkylamide, NMe2: Rare T-Shaped Coordination at Chromium

The synthesis and characterization of a series of first-row aryl transition metal derivatives of the simplest dialkylamido ligand NMe(2) are reported. The complexes Cr{Ar'Cr(mu-NMe(2))(2)}(2) (1) and {Ar'M(mu-NMe(2))}(2) (M = Mn (2), Fe (3); Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)) were obtained by reaction of the aryl metal halides {Ar'M(mu-X)}(2) (M = Cr, X = Cl; M = Fe, X = Br) or {Li(THF)Ar'MnI(2)}(2) with LiNMe(2) in a 1:2 ratio. A similar reaction of {Ar(#)Co(mu-I)}(2) (Ar(#) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2)) and LiNMe(2) in hexanes gave the unusual complex {Ar(#)Co(mu-I)(eta(1)-CH(2) horizontal lineNCH(3))}(2) (4), in which the NMe(2) ligand is dehydrogenated to afford a complexed imine. Complexes 1-4 were characterized by X-ray crystallography, UV-vis spectroscopy, and magnetic measurements. In the unique trinuclear complex 1, the central chromium(II) ion is bound to four NMe(2) groups in a square planar fashion. The NMe(2) groups also bridge to the two outer chromium(II) ions, which are bound to a terminal Ar' group to yield a rare example of three-coordinate T-shaped geometry at these atoms. In the dimers 2 and 3, each metal center is coordinated to a terminal terphenyl ligand and two bridging NMe(2) groups to give a distorted trigonal planar geometry. In contrast, the reaction of LiNMe(2) with {Ar(#)Co(mu-I)}(2) in a 2:1 ratio did not yield an amido product; instead, the NMe(2) ligand underwent hydrogen elimination. As a result, in the dimeric structure of 4, each cobalt ion is coordinated to a terphenyl ligand, two bridging iodides, and a neutral methylimine ligand, CH(2) horizontal lineNCH(3), to yield a very distorted tetrahedral cobalt(II) coordination environment. The magnetic properties of 1-4 revealed antiferromagnetic exchange coupling between the metal ions with J = -47(1) cm(-1) and J(13) = -25(1) cm(-1) for 1, J = -38(1) cm(-1) for 2, J = -75(3) cm(-1) for 3, and J = -32(4) cm(-1) for 4; the latter compound exhibited an unusually large temperature independent contribution to its molar magnetic susceptibility.

Dimetallocene Carbonyls of the Third-Row Transition Metals: The Quest for High-Order Metal−Metal Multiple Bonds

Theoretical studies of the third-row transition-metal derivatives Cp(2)M(2)(CO) (Cp = eta(5)-C(5)H(5); M = Os, Re, W, Ta) indicate that the lowest-energy structures have lower spin states and similar or higher metal-metal bond multiplicities than the corresponding first-row transtion-metal derivatives. Therefore, Cp(2)Os(2)(CO) is predicted to be a singlet with an Os-Os formal quadruple bond, whereas Cp(2)Fe(2)(CO) is a triplet. Similarly, Cp(2)Re(2)(CO) is predicted to be a singlet with a very short rhenium-rhenium distance, which is consistent with the formal quintuple bond required to give both rhenium-rhenium atoms the favored 18-electron configuration. This contrasts with the manganese analogue Cp(2)Mn(2)(CO) for which the lowest-energy structure is a septet with a formal Mn-Mn single bond. The tungsten derivative Cp(2)W(2)(CO) is predicted to be triplet with a four-electron donor bridging carbonyl group. This contrasts with Cp(2)Cr(2)(CO) predicted to be a septet (S = 3) with a two-electron donor carbonyl group. For Cp(2)Ta(2)(CO), the lowest-energy structure is predicted to be a triplet with a formal Ta identical withTa triple bond and a four-electron donor carbonyl group. However, Cp(2)V(2)(CO) is predicted to be a quintet with a formal V horizontal lineV double bond. In addition to these Cp(2)M(2)(CO) structures with one Cp ring bonded to each metal atom, higher-energy Cp(2)M-MCO structures are found with both Cp rings bonded to the same metal atom. The lowest-energy Cp(2)M-MCO structures are triplets (M = Os, W) or quintets (M = Re) with agostic hydrogen atoms for M = Os and Re. In these structures, the spin density is concentrated on the metal atom of the MCO group. These results suggest that lower spin states clearly become more viable for highly unsaturated metal complexes upon descending the periodic table.

Early transition metal derivatives stabilised by the phenylenediamido 1,2-C 6H 4(NCH 2tBu) 2 ligand: Synthesis, characterisation and reactivity studies: Crystal structures of [Ta{1,2-C 6H 4(NCH 2tBu) 2} 2Cl] and [Zr{(1,2-C 6H 4(NCH 2tBu) 2}(NMe 2)(μ-NMe 2)] 2

Li 2[1,2-C 6H 4(NCH 2 tBu) 2] reacts with one equiv of [TiCl 4(THF) 2] in refluxing toluene to give the chelate compound [Ti{1,2-C 6H 4(NCH 2 tBu) 2}Cl 2(THF)] ( 1), isolated as a black product, while the reaction of the dilithio diamido salt with one equiv of [ZrCl 4(THF) 2] in refluxing toluene affords the dinuclear zirconium derivative [Zr{1,2-C 6H 4(NCH 2 tBu) 2}Cl(THF)(μ-Cl)] 2 ( 2), obtained as an orange solid. Treatment of the dilithio diamido salt with TaCl 5 in a 2:1 molar ratio in toluene yields [Ta{1,2-C 6H 4(NCH 2 tBu) 2} 2Cl] ( 3) as a red product. The reaction of 1,2-C 6H 4(NHCH 2 tBu) 2 with [Zr(NMe 2) 4] in toluene at room temperature affords the dinuclear zirconium complex [Zr{1,2-C 6H 4(NCH 2 tBu) 2}(NMe 2)(μ-NMe 2)] 2 ( 4). The dibenzyl derivative [Ti{1,2-C 6H 4(NCH 2 tBu) 2}(CH 2Ph) 2] ( 5) is obtained by the reaction of 1 with 2 equiv of Mg(CH 2Ph)Cl at −78 °C. Compound 1 reacts with the lithium amide reagent LiN(SiMe 3) 2 to afford [Ti{1,2-C 6H 4(NCH 2 tBu) 2}Cl{N(SiMe 3)}] ( 6). The μ-oxo titanium derivative [(Ti{1,2-C 6H 4(NCH 2 tBu) 2}{CH 2Ph}) 2(μ-O)] 7 is precipitated when compound 5 is maintained in solution. The tendency of these compounds to coordinate donor ligands and their reactivity with Lewis acid reagents are described. All compounds were analytically and spectroscopically characterised and the molecular structures of the diamine 1,2-C 6H 4(NHCH 2 tBu) 2 and the complexes 3 and 4 were established by single-crystal X-ray diffraction studies. The lack of correlation between the degree of metallacycle folding and phenylene ring distortion is observed in the solid state structures. The performance of precursors 1, 3 and 5 were evaluated in ethylene polymerisation upon activation with B(C 6F 5) 3, methylaluminoxane (MAO) and sMAO as cocatalysts, with very modest activities.

Crystal structure of bis[aqua(dipyrido[3,2-a:2′,3′-c]phenazine)- cobalt(II)-4,4′-oxybis(benzoato)] – N,N′-dimethylformamide (1:1), [Co(H2O)(C14H8O5)(C18H10N4)]2 · C3H7NO

C67H47Co2N9O13, monoclinic, P121/c1 (no. 14), a = 23.219(5) A, b = 18.342(4) A, c = 14.511(3) A, . = 100.45(3)°, V = 6077.5 A, Z = 4, Rgt(F) = 0.080, wRref(F ) = 0.207, T = 293 K. Source of material A mixture of 4,4'-oxybis(benzoic acid) (H2oba, 1 mmol), dipyrido[3,2-a:2',3'-c]phenazine (dppz, 0.5 mmol), and CoCl2·6H2O (1 mmol) was suspended in a mixture of deionized water (4 ml) and DMF (10 ml) and sealed in a 20 ml Teflon-lined autoclave.Upon heating at 180 °C for twodays, the autoclavewas slowly cooled to room temperature. The crystals were collected, washed with deionized water and dried. Experimental details H atoms on C atoms were generated geometrically and refined as riding atoms with d(C—H) = 0.93 A and Uiso(H) = 1.2 Ueq(C). The H atoms of the water molecules were not located in a difference Fourier map. Discussion The 4,4'-oxybis(benzoate) dianion (oba) is an example of a flexible dianion because of the presence of an ether linkage between the two rigid phenylene rings, and its transition metal(II) derivatives readily furnish complexes with N-donor chelating ligands [1]. The coordination polymers based on a N-donor chelating ligand, such as 1,10-phenanthroline (phen), have been widely studied. However, far less attention has been given to the derivatives of phen. Dipyrido[3,2-a:2',3'-c]phenazine (dppz) as an important phen derivative possesses aromatic systems and may be a good candidate for the construction of metal-organic supramolecular architectures [2]. Further, the complexes constructed by dicarboxylate ligand and dppz ligand have rarely been documented. In the title crystal structure, each Co(II) atom is six-coordinated with a distorted octahedral environment formed by three carboxylate oxygen atoms from two different oba anions, onewater molecule and two nitrogen atoms from two distinct dppz ligands. The average Co—O and Co—N distances are comparable to those observed in literature independent. Neighboring Co(II) atoms are linked by the oba ligands using their carboxylate oxygen atoms, resulting in two chains. Interestingly, the dppz ligands are arranged in a parallel fashion at one side of the chains, leading to aromatic $-$ intercalation. Slipped $-stack arrangements between dppz ligands of two neighboring chains were observed (centroid-to-centroid distance of 3.73(3) A, vertical face-to-face distance of 3.46(4), and dihedral angle of 2.01(3)°), which form a supramolecular double-chain structure. 280 Z. Kristallogr. NCS 224 (2009) 280-282 / DOI 10.1524/ncrs.2009.0123 © by Oldenbourg Wissenschaftsverlag, Munchen Crystal: pink block, size 0.21 × 0.24 × 0.27 mm Wavelength: Mo K0 radiation (0.71073 A) &: 6.20 cm−1 Diffractometer, scan mode: Rigaku RAXIS-RAPID, 1 2max: 54.96° N(hkl)measured, N(hkl)unique: 57601, 1370 Criterion for Iobs, N(hkl)gt: Iobs > 2 !(Iobs), 7025 N(param)refined: 750 Programs: SHELXS-97 [3], SHELXl-97 [4], SHELXTL [5] Table 1. Data collection and handling.

1,10-Phenanthroline-5,6-dione complexes of middle transition elements: Mono- and dinuclear derivatives

The synthesis and the characterization of several mono- and dinuclear middle transition metal derivatives of 1,10-phenanthroline-5,6-dione, 1, are presented. The reaction of 1 with CrCl 2(THF) 2 gives CrCl 2( O, O′-C 12H 6N 2O 2)(THF) 2, 2, while the halides of iron(II), cobalt(II) and nickel(II) afford adducts of general formula MX 2( N, N′-C 12H 6N 2O 2), M = Fe, 4, Co, 5, X = Cl; M = Ni, 6, X = Br. DFT calculations on CrCl 2(L)(THF) 2 with L = O, O′-C 12H 6N 2O 2 or O, O′-C 14H 8O 2 allowed a direct comparison of the coordination properties of 9,10-phenanthrenequinone and 1,10-phenanthroline-5,6-dione to be made. Dinuclear compounds of general formula CrCl 2(THF) 2( O, O′-C 12H 6N 2O 2- N, N′)MX n L m , M = Zr, 7, X = Cl, n = 4, m = 0; M = Cr, 8, X = Cl, n = 2, L = THF, m = 2; M = Fe, 9, Co, 10, X = Cl, n = 2, m = 0; M = Ni, 11, X = Br, n = 2, m = 0, are prepared from 2 and the corresponding metal halide, while VCp 2( O, O′-C 12H 6N 2O 2- N, N′)FeCl 2, 12, is synthesized by reacting 4 with VCp 2. The electronic properties of the different complexes are investigated by magnetic moment measurements and EPR spectroscopy.

Synthesis and structural characterization of mixed transition metal derivatives of maleic acid: (M2+0.5Fe2+0.5)(C4H3O4)-2• 4H2O (with M2+=Mn, Co, Ni, and Zn) using powder diffraction data

Synthesis and structural characterization of mixed transition metal derivatives of maleic acid: (M²⁺_0.5Fe²⁺_0.5)(C₄H₃O₄)^-₂• 4H₂O (with M²⁺=Mn, Co, Ni, and Zn) using powder diffraction data

Synthesis and structural characterization of mixed transition metal derivatives of maleic acid: (M2+0.5Fe2+0.5)(C4H3O4)-2• 4H2O (with M2+=Mn, Co, Ni, and Zn) using powder diffraction data

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