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International audience; Phosphorus dendrimers are highly branched macromolecules, built with one phosphorus atom at each branching point. These dendrimers can be functionalized at will on the terminal functions. Grafting as terminal functions ligands suitable for the complexation of copper has been carried out several times, in particular with the aim of using the corresponding complexes as catalysts in a range of reactions, from O-and N-arylations and-vinylations, to the asymmetric benzoylation of linear or cyclic diols. A sequel of this work concerns the study of anticancer activity of analogous dendritic copper complexes.

The synthesis and characterization of complex [Cu(dppo)2] (dppo = 1,3-diphenylpropane-1,3-dione) is reported. The complex has been fully characterized by FT-IR, UV–vis, elemental analysis and Cyclic Voltammetry. The paramagnetic nature of the complex was confirmed by magnetic measurement and the square planar geometry was ascertained by single crystal X-ray determination. The complex has been found to be a good homogeneous catalyst for the synthesis of 1,2,3-triazole derivatives via one-pot reaction of arylboronic acids, sodium azide and alkynes in DMF.

Bis-acyl-/aroyl-hydrazones can be divided into two basic structural categories: those that are derived from a dihydrazide and those that are derived from a dialdehyde (or diketone). They form various types of complexes that are herein reviewed.

The synthesis and diastereoisomeric resolution of 2,6-diethyl-4,8-dimethyl-1,5-dioxo-s-hydrindacene allowed the determination of the structure of the meso compound by X-ray diffractometry. The diastereoisomers were inactive towards radical germylation but reacted with acidic hydrogermanes or germylithium yielding α-germylated alcohols. By contrast, they were poorly reactive towards germylamines or SET reactions. This diketone acts as an efficient spin trap in radical hydrogermylation of alkenes.

X-ray structures are presented of three new cobalt complexes prepared from Co(III) and N,N'-1,10-phenanthroline-5,6-dione. The cis-aqua-chloro-bis(N,N'-1,10-phenanthroline-5,6-dione)cobalt(II) nitrate trihydrate (3) and the cis-aqua-bromobis(N,N'-1,10-phenanthroline-5,6-dione)cobalt(II) trifluoro-methanesulfonate tetrahydrate (4), crystalize in the same space group with a similar arrangement of the complex ions. However, on the molecular scale there are important differences. The cobalt complex in 3 has a typical high-spin geometry whereas in 4 the cobalt complex displays a Jahn-Teller distortion characteristic for low-spin compounds. The third structure is di(N,N'-1,10-phenanthroline-5,6-diol)(N,N'-1,10-phenanthroline-5,6-dione )cobalt(III) bromide hexahydrate (5). NMR studies of the hydration of the Co(III)(1,10-phenanthroline-5,6-dione)(3)(3+) ion in water and DMSO are also presented. The various possible transformations of the N,N'-1,10-phenanthroline-5,6-dione ligand are discussed. (C) 2003 Elsevier B.V. All rights reserved.

The opening of carbon nanotubes by the addition of oxygen to form C n O 6 has been modelled using the AM1 Hamiltonian and the program mopac 6.0. Three series of nanotubes based on C 60 were considered. The first series was based on pulling two hemispherical halves of C 60 apart along a fivefold axis and inserting additional carbon atoms between the hemispheres to form C 70 , C 80 , C 90 and C 100 . The second series was obtained similarly by pulling C 60 apart along a threefold axis to form the D 3 h and D 3 isomers of C 78 and the D 3 d and D 3 isomers of C 96 . The third series was based on the extension of C 60 along a twofold axis to form C 76 and C 92 . There is a wide diversity in the bonding patterns in these nanotubes. In general, the hemispherical ends resemble C 60 with single bonds on pent–hex edges and double bonds on hex–hex edges, with the exception of C 80 in which there is significant double bond character on the pent–hex edges. The six-membered rings on the hemispherical ends have the normal Kekule pattern of single and double bonds. In general, the distinction between single and double bonds is continued into the tube part of the structure but again there are some exceptions. For example, in C 70 , D 3 -C 78 and C 76 there are some six-membered rings with delocalised bonding. In C 90 , D 3 h -C 78 and D 3 d -C 96 there are six-membered rings composed of six single bonds with six double bonds radiating out from the ring and these rings show significantly different chemical properties. Addition of oxygen occurs as near as possible to the end of the nanotube with the opening of a large hole leading into the interior of the structure. In the most favourable structures, a pair of oxygen atoms adds onto a hex–hex edge replacing the CC double bond by two CO ketone groups and the coalescence of two six-membered rings. Multiple additions may be of the same type leading to tris(diketone) structures with the coalescence of four six-membered rings into two different types of 18-membered rings. Alternatively, additional oxygen atoms may add onto pent–hex edges replacing the CC single bond with a COC ether linkage forming the mixed ether/ketones or the mixed ether/lactones which are generally the most stable types of structure.

The structures and stabilities of C 60 O n , where n =1–6, 9, have been calculated using the AM1 Hamiltonian and the program mopac 6.0, and by the density functional technique B3LYP/6-31G* at the AM1 geometry using Gaussian 98. Modes of oxygen addition considered were ethers, epoxides, ketones and ketenes. It is confirmed that in C 60 O a carbon–carbon bond on a pent–hex edge is replaced by an ether linkage. For higher levels of oxygen addition the replacement of a carbon–carbon bond by two ketone groups becomes important. Particularly stable structures are formed if the additions are on the same, or adjacent, C 6 rings of the C 60 structure where the oxygen atoms cooperate in opening up large holes in the molecule. Molecules of greatest stability have a mixture of ether oxygen atoms on pent–hex edges and diketone additions on hex–hex edges. A particularly important stable structure is the mixed ether/ketone isomer of C 60 O 6 in which a hinged C 5 O 2 hatch lid containing two ketone oxygen atoms is opened revealing a hatch 4–5 A in diameter. An even larger hole of approximately 6 A in diameter is opened up in a particularly stable isomer of C 60 O 9 which contains three ether and six ketone groups. Removal of the oxygen atoms from these structures and reoptimisation leads to hatch closing and C 60 is reformed.

Organocobalt(III) complexes with Schiff bases derived from a β -diketone bearing both an alkyl and an aryl group have been prepared. The template syntheses using benzoylacetone and ethylenediamine as complexing agents provide a route to alkylcobalt chelates with the corresponding tri- and tetradentate Schiff bases. However, if a β -diketone with two aryl groups, e.g. dibenzoylmethane, was employed as the starting ketoenol component, no organometallic products were detected; a new mixed-ligand ‘inorganic’ chelate of cobalt(II), [Co{O=C(Ph)CH=C(Ph)O} 2 (en)], was isolated instead. Its structure as well as that of one of the alkylcobalt complexes with a tridentate Schiff base composed of benzoylacetone and ethylenediamine have been established by X-ray techniques. The current scope of the template synthesis of alkylcobalt complexes with Schiff bases is summarized.

Cyclic voltammetry at a micro electrode of Co(II) salen, Fe(II) salen, electrode generated Fe(II)(acac)2, Fe(II) (salicylaldehyde)2, Fe(II) (salicylaldoxime)2, Fe(II) (bipy)3, Fe(II) (bipy)2, Co(II) (bipy)3, Co(II) (benzacac)2, and electrode generated Co(acac)2 in oxygen saturated aprotic solvents show positive shift of the O2 sigmoidal wave, as well as enhancement of the limiting current in the case of the first five compounds. In the case of Co(II) (bipy)3 the slope of the sigmoidal wave due to O2 becomes more positive, while for the other two Co(II) complexes there is no change except a small decrease in the wave height. The data are used to correlate and predict the O2 binding properties of the chelates in solution. The data for the diketone complexes of Co(II) indicate absence of any direct association, which is in line with the interpretation offered in the literature on the mechanism of their catalytic role in the O2 oxidation of substrates. The mechanism of the autoxidation of dimethylformamide in the presence of Fe(III) (bipy)3 and Cu(II) (bipy)2 is elucidated by the observation that these higher valent compounds are reduced to their next lower oxidation state by DMF.

Polyphenylene polymer preparation involves the cyclic trimerization polymerization of acetylated methyl benzoate with diacetyl benzene. Since the methyl benzoate groups do not take part in the polymerization they are present in high concentration. The s-diketone ligands were placed on the surface by reaction of the methylbenzoate group with base and a methyl ketone and the triketone by reaction with base to give the s-triketone. The s-triketones can bind two metal ions in a known geometry that is suitable for bimetallic catalysis of the rapid polyelectron oxidation of catechols. The final catalytic surfaces were prepared by treating the chemically modified polymer with copper(II), iron(II) and palladium(II) acetonitrile complexes with non-coordinating BF4− as the anion. Since the metal ions contain no strongly coordinating ligand, they are very reactive species. These surfaces catalyzed the rapid air oxidation of 3,5-di-tert-butylcatechol (DTBC). The diketone surfaces gave only 3,5-di-tert-butyl-o-quinone (DTBQ) while the triketone surfaces gave ring-cleaved products, confirming the special catalytic effect of the triketone surface. Also, only the triketone catalysts showed any activity for ring cleavage oxidation of DTBQ. These catalysts were much more reactive than previous ones using the same polyphenylene polymer but without the methyl benzoate groups. With these polymers the di- and triketone groups were placed on the surface by chemical modification of the unpolymerized acetyl groups.

This paper is devoted to a particular reaction able to give singly condesed Schiff base derivatives of s-diketones (called ‘half-units’) in an easy way. Indeed, 1,2-diamino-2-methylpropane, which possesses an amine function sterically hindered by two methyl groups, reacts with a diketone such as 2,4-pentanedione or 2-hydroxyacetophenone only by its non-hindered amine function, yielding a ‘half-unit’. In a following step, this terdentate ligand can react with an aldehyde function to give a non-symmetrical tetradentate Schiff base. Such a reaction can be performed on the free ‘half-unit’ or on its ‘complexed form’. Some examples of nickel and copper complexes are given. A particular interest has been given to the use of imidazole-2-carboxaldehyde which yields non-symmetrical Schiff base complexes with a free nitrogen atom not included in the N 3 O coordination site. According to the procedure of ‘complexes as ligands’, it is possible to isolate bimetallic complexes with imidazole bridges. Their genuine identity has been confirmed by NMR (nickel) and also by thermal variation of the magnetic susceptibility (copper).

Reaction of the dichloride dimer [{Ru(η3:η3-C10H16)Cl(μ-Cl)}2] (3) with β-diketones or their sodium salts results in the formation of the neutral chelate complexes [Ru(η3:η3-C10H16)Cl(R·CO·CH·CO·R′)] (R=R′=CH3 (7); R=CH3, R′=CF3 (8)). The equatorial (most abundant) isomer of 8 (8a) has been characterised by X-ray crystallography. Attempts to remove the chloride ligand in compounds such as 7 (via Ag+) to form cationic aqua species were unsuccessful. However, analogous reactions with the cationic chelate complexes [Ru(η3:η3-C10)Cl(L- L)][BF4] (LL=2,2′-bipyridyl (4); 1,10-phenanthroline (5)) resulted in the isolation of the aqua compounds [Ru(η3:η3-C10H16)(LL)(OH2)][BF4]2 (10 and 11) in good yields. Attempts to generate oxo species derived from 10 and 11 by both electrochemical and chemical means were unsuccessful.

The reaction of Tl(C 6 F 5 ) 2 Cl or Tl(C 6 F 5 ) 3 (diox) (diox=1,4 dioxane) with bidentate ligands (L=PPh 2 CH 2 PPh 2 , (O)PPh 2 CH 2 PPh 2 (O) or (S)PPh 2 CH 2 PPh 2 (S)) gives Tl(C 6 F 5 ) 2 ClL or Tl(C 6 F 5 ) 3 L, respectively. Displacement of chloride gives new cationic or neutral complexes, [Tl(C 6 F 5 ) 2 {(O)PPh 2 CH 2 PPh 2 (O)}] + BF 4 − or [Tl(C 6 F 5 ) 2 (acac){(O)PPh 2 CH 2 PPh 2 (O)}] (acac=acetylacetonate), respectively. The structure of the latter was determined by single-crystal X-ray diffraction at 143 K. Crystals are monoclinic, space group P 2 1 / n , a =12.733(3), b =23.717(8), c =14.981(4) A, β=110.37(3)°, Z =4 and R ( F )=0.046. The structure forms a chain polymer.

The crystal structure of bis(2,2,6,6-tetramethyl-3,5-heptanedionato) copper, Cu(thd) 2 , has been determined at 130, 250 and 293 K (monoclinic, space group P 2 1 / c , a = 10.200(3), b = 10.957(3), c = 11.491(4) A, β = 112.05(2)° at 130 K). At 130 K the structure shows no disorder. One of the t-Bu groups is involved in an unusually short intermolecular contact. At higher temperatures this same group is disordered. The number of configurations increases with the temperature. The room temperature crystal structures of bis(3-chloro-2,4-pentanedionato)copper, Cu(Clacac) 2 (monoclinic, space group P 2 1 / n , a = 4.815(2), b = 17.107(3), c = 8.013(2) A, β = 106.92(2)°), and (2,2,6,6- tetramethyl-3,5-heptanedionato)(3-chloro-2,4-pentanedionato) copper, Cu(thd)(Clacac) (orthorhombic, space group Pnma , a = 19.213(4), b = 6.453(4), c = 15.725(4) A) are also described. Two kinds of molecular stacking are observed depending on whether the complex is homo- or heteroleptic.

The kinetics of the ligand exchange reaction between tetrakis(acetylacetonato)hafnium(IV), Hf(acac) 4 , and free acetylacetone (Hacac) in C 6 D 6 have been studied by the 1 H NMR line-broadening method. The observed first- order rate constant k obs is expressed as a function of [Hacac] enol : k obs = ( k 2 + k 3, HA ,) K 1, HA [Hacac] enol / (1 + K 1,HA [Hacac] enol ), where [Hacac] enol signifies the concentration of Hacac in the enol form and K 1, HA is the equilibrium constant for the formation of a nine-coordinate adduct complex Hf(acac) 4 , Hacac. The rate constants k 2 and k 3, HA correspond to those of proton transfer from coordinated Hacac to leaving acac and the ring opening of acac in the adduct complex, respectively. The existence of the k 3, HA path was evidenced by the deuterium isotope effect on the rate. Activation parameters for the ( k 2 + k 3, HA ) path were obtained from the temperature dependence of the ( k 2 + k 3, HA ) value: Δ H ≠=41±2 kJ mol −1 and Δ S ≠=−81±5 J K −1 mol −1 The exchange reaction was accelerated by addition of H 2 O to the sample solution. These results are discussed in connection with those of the acac exchange in analogous quadrivalent metal complexes.

Y(thd)3(H2O) (I) has been prepared from yttrium nitrate via the aqueous method; its drying yielded Y(thd)3 (III). The sublimation of compound II, resulting from the reaction of yttrium isopropoxide with thdH, also yielded Y(thd)3. Compounds II and IlI have been characterized by elemental analysis, IR, 1H 13C{1H} and 89Y NMR spectroscopies and mass spectrometry. The thermal behaviour of each compound has been studied by TG and DT analyses. Compounds I and III crystallize in the triclinic (P 1 and orthorhombic (Pmn21) systems, respectively. The crystal structure determinations reveal centrosymmetric dimeric associations arising from hydrogen bonding between the water molecules and ketonic oxygen atoms for I whereas monomeric Y(thd)3 units with all thd rings in a chelating position are observed for III. The relationship between the crystal structures of I and III has been studied.

The reaction of metal(II) hexafluoroacetylacetonates (metal= Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)) with tetramethylpyrazine is reported. The X-ray crystal structures of [Mn(hfac) 2 ] 2 (tmp) 3 ·4H 2 O and Co(hfac) 2 (tmp)·4H 2 O are reported and reveal the formation of chain polymers through second sphere cis - and trans -derived stacking, respectively.

Complex formation between gadolinium(III) tetraphenylporphyrin, GdTPP(acac), and some amines has been investigated in toluene solution. GdTPP(acac) gives 1:1 complexes with morpholine, pyrimidine, imidazole and 1-methylpyrrolidine. 1:2 complexes are formed with the chain aliphatic amines like triethyl-, tributyl-, tripentyl- and trioctylamine. Spectrophotometric studies of the formation equilibria yield the values of the stability constants. An analysis of the experimental data strongly suggests that in the amine solutions of GdTPP(acac) additional coordination of the gadolinium ion takes place. CN increases from 6 to 8. GdTPP(acac)-amine adducts are very stable in solution, and prevent demetallation of the gadolinium porphyrin complex, which is usual in common solvents.

Twelve title complexes are prepared as perchlorate salts. These are Co(hfac)L 2+ with L= (MeNH 2 ) 4 , (n-AmNH 2 ) 4 , cis -(NH 3 ) 2 (en), ( R -pn)( S -pn), cyclen, cyclam, cis -(NH 3 ) 2 (bpy), (en)(bpy), (en)(phen), (tn)(bpy), (tn)(phen) and (bpy)(phen) where Hhfac=hexafluoro-2,4-pentanedione, MeNH2=methylamine, n-AmNH 2 =n-amylamine, en = ethylenediamine, pn=propylenediamine, cyclen=1,4,7,10-tetraazacyclododecane cyclam=1,4,8,11-tetmazacyclotetradecane, bpy 2,2′-dipyridyl, phen=1,10-phenanthroline and tn=1,3-propanediamine. The thermodynamic covalent hydration equilibrium constants K OH in water and K OMe in methanol are estimated for these complexes and for previously obtained Co(hfac)L 2+ by UV spectrophotometry. The values critically depend on the involvement as L ligand of a bpy or a phen ligand. p K OH ≈ −6.6 and p K OMe ≈ −8.7 when L involves neither bpy nor phen ligand. p K OH ≈−8.7 and p K OMe ≈−11.0 when L involves either a bpy or a phen ligand. p K OH ≈−11.5 and p K OMe ≈−14.6 when L involves two bpy or phen ligands. The isomeric structure of the complex is also discussed on the basis of the fluorine NMR spectra.

The X-ray structure determination is reported for the complex [Ni(bpdpn)Ni(hfacac)2]·CCl4 (H2bpdpn=N,N′- bis(3′-pyridazinecarboxamide)-1,3-propane, Hhfacac=hexafluoroacetylacetone. The complex is monoclinic, P2/c, a=22.147(12), b=10.611(2), c=32.061(18) A, β=105.50(3)°. The deprotonated bis-pyridazinecarboxamide complex Ni(bpdpn) acts as an N,N donor, via the 1-pyridazine nitrogens, to the Ni(hfacac)2 species, resulting in cis-N2O4 coordination to the β-diketonate species. The magnetic properties of the complex (μeff=3.22 BM (304 K), 3.19 BM (89 K)) are consistent with the Ni(bpdpn) entity being diamagnetic, as in the patent complex, and the Ni(hfacac)2 species being paramagnetic. Magnetic and electronic spectral properties indicate that analogous complexes involving the β-diketonate ligands trifluoroacetylacetonate and benzoylacetonate have structures similar to that of [Ni(bpdpn)Ni(hfacac)2]·CCl4.

1-Methyl-1-phenylhydrazine reacts with [MoO2(acac)2] in ROH (R = Me, Et, n-Pr) at room temperature, to yield [MoO(NNMePh)(acac)2] (I). In refluxing ROH under argon, complex I transforms into [{MoO(NNMePh)(acac)(μ-OR)}2] (R = Me(II), Et(III), n-Pr(IV)). The crystal structures of I and IV are reported. Crystals of I are monoclinic, space group P21/c, with unit cell dimensions a = 8.442(1), b = 16.090(1), c = 13.875(1) A, β = 94,86(1)° and Z = 4. The structure was solved using 2529 unique observed reflections. The refinement of 226 variables gave R and Rw values of 0.024 and 0.026, respectively. The lattice is made of discrete mononuclear molecules. Crystals of IV are monoclinic, space group P21/n, with a = 8.917(2), b = 21.728(3), c = 9.351(1) A, β = 107.83(2)° and Z = 2. The final refinement of 200 variables gave R = 0.036 and Rw = 0.039 for 2700 observed reflections. The lattice is made of discrete centrosymmetric dinuclear molecules. The geometries of the cis-[MoO(NNMePh)]2+ cores in I and IV are similar and indicative of multiple bonding. In I, MoO = 1.701(2), MoN = 1.789(3), NN = 1.281(4) A, MoNN = 175.6(2), OMoN = 102.8(1)°; in IV, MoO = 1.693(3), MoN = 1.780(4), NN = 1.292(6) A, OMoN = 101.8(2)°.

2 H NMR chemical (isotropic contact) shifts of various kinds of mixed ligand paramagnetic chromium(III) complexes with deuteriated malonato and/of acetylacetonato ligands were measured and discussed in relation to the relative positions of the deuterons in ligands with respect to the remaining coordination atoms. The contact shifts of methylene deuterons of the malonato ligands were found to be remarkably sensitive to ligating atoms located at the coordination site perpendicular to the malonato chelate plane, depending on the kind of ligating atoms, i.e. oxygen or nitrogen, and moreover on subtle differences of identical ligating atoms, e.g. primary or secondary amines. On the other hand, the contact shifts of the methyl deuterons of the acetylacetonato ligand are susceptible to the change of the ligating atoms at the coordination site coplanar with the acetylacetonato chelate plane.

Doubly cyclopalladated mixed chelates of the type [Pd2L(-2H)(β-diket)2] derived from N,N′-diethylbenzene-l,3- dicarbaldimine (L) and the unsymmetrical β-diketones (Hβ-diket) benzoyltrifluoroacetone (HBTA), benzoylacetone (HBA) and thenoyltrifluoroacetone (HTTA) have been synthesized and characterized. The crystal structure of [Pd2L(−2H)(BTA)2] is reported. The complex C32H26N2O4F6Pd2 crystallizes in the triclinic space group P with a=10.872(1), b=11.915(1), c=13.525(1) A, α= 101.74(1), β=112.78(1), γ=97.77(1)°, V=1537.5(7) A3 and Z=2. The structure was solved by direct methods and refined by block-diagonal least-squares method to R=0.034 and Rw=0.037 based on 3535 observed reflections with I>3σ(I).

The synthesis, EPR, magnetic and Mossbauer properties of two iron(III) complexes are reported. The heterodinuclear iron(III)-copper(II) complex Cu(salen)Fe(acac)2NO3 is obtained as an adduct from the reaction of the two mononuclear moieties, the Cu(salen) molecule and the mononuclear iron(III) molecule Fe(acac)2NO3 acting as a precursor of the dinuclear unit. The latter molecule itself has been prepared by ligand substitution from the tris-acetylacetonate Fe(acac)3. The dinuclear complex is characterized by comparing the properties of the mono- and the dinuclear complex. Fe(acac)2NO3 is identified from its typical IR spectrum with the main nitrate vibrations at 1380, 1250 and 1010 cm−1 and an axial S=5/2 EPR spectrum in the solid state. Ligand rearrangement occurs in solution as indicated by the presence of only ionic nitrate and a rhombic EPR spectrum. The dinuclear molecule presents a very modified IR spectrum, where the copper(salen) phenolic oxygen vibration and the bound-nitrate vibrations have disappeared; additionally no EPR spectrum can be recorded at X-band frequency. The magnetic data have been interpreted using spin-Hamiltonian formalism. From magnetic susceptibility measurements, in the solid state, the following set of parameters has been determined: g=1.99, D=4.15 cm−1 for the mononuclear complex, and J=−3 cm−1, g=2.05, D=−0.1 cm−1 for the dinuclear complex, indicating an effective antiferromagnetic interaction between the two metal ions. The Mossbauer studies yield: D=0.45 cm−1 for the mononuclear complex, and J=−1.5 cm−1, D=−0.20 cm−1 for the dinuclear complex.

Catalytic properties of dimeric molybdenum(VI) triketonates were compared to those of MoO 2 (acac) 2 in the epoxidation reaction of cyclooctene and 1,5-cyclooctadiene with tertiary butyl hydroperoxide. Studies of the reaction at a molar ratio of olefin:TBHP:catalyst= 1:1:0.001 for the monoolefin and 1:2:0.001 for the diolefin at 40 and 80 °C in dichloroethane were carried out. The dimeric Mo(VI) complexes preferentially catalyzed the production of a monoepoxide.

Complexes of the type M(hfac)2·polyether, bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)M·polyether (MBa, St, polyether = tetraglyme; MBa, polyether = hexaglyme; MCa, polyether = triglyme), are obtained in high yield upon reaction of M(hfac)2 with one equivalent of polyether. The complexes thus obtained appear to be sublimable, non-hygroscopic, thermally stable solids. They have been characterized by elemental analysis, molecular weight determinations, NMR spectroscopy, mass spectrometry, IR and TG-DTA analysis. The complex Ba(hfac)2·tetraglyme has been characterized by an X-ray structure determination. The barium atom is found to be coordinated by all nine oxygen atoms, with the polyether ligand wrapped around barium in a plane, with one hfac ligand on top of this plane and another below. The absence of short intermolecular interactions explains why the compound sublimes easily without decomposition.

The reaction of iron(III) acetylacetonate with zirconium(IV) n-propanolate in n-propanol leads to a tetranuclear species Zr3FeO(OC3H7)10(acac)3. This compound crystallizes in the triclinic system (space group P 1 ): a = 12.426(2), b = 12.977(2), c = 20.129(4) A, α = 91.55(1), β = 97.90(1), γ = 100.53(1)°. The structure consists of discrete tetranuclear molecules. The metal atoms design an almost perfect tetrahedron around a four-fold coordinated oxygen atom. The zirconium atoms are in a seven-fold coordination and the iron atom in a five-fold coordination.

The reaction of cis-[Pd(C6F3H2)2(PhCN)2] with 20% aqueous QOH (Q = NBu4) in acetone leads to the formation of the hydroxo complex Q2[{Pd(C6F3H2)2(μ-OH)}2] (1). Complex 1 reacts with weak acids H(LL) in a 1:2 molar ratio to give Q2[{Pd(C6F3H2)2(μ-LL)}2] (LL=pyrazolate (pz) (2); 3-methylpyrazolate (mpz) (3); 3,5-dimethylpyrazolate (dmpz) (4); indazolate (indz) (5)) or Q[Pd(C6F3H2)2(LL)] (LL=acetylacetonate (acac) (6); benzoylacetonate (bzac) (7); 8-hydroxyquinoline (oxin) (8)). Q2[{Pd(C6F3H2)2}2(μ-OH)(μ-dmpz)] (9) has been obtained by treatment of Q2[{Pd(C6F3H2)2(μ-Cl)}2] with QOH and Hdmpz (1:2:1 molar ratio) in methanol. Partial elemental analyses, conductance measurements and spectroscopic (IR, 1H and 19F NMR) methods have been used to study the new compounds.

The synthesis of a series of BaX 2 ·18-crown-6 complexes (X=hfac, tclac, tfac, thd, acac, O 2 CCF 3 , O 3 SCF 3 , O 2 CCH 3 , Cl, Br, I, NO3, OH and SCN) and BaX 2 compounds (X=tclac, tfac, O 2 CCF 3 and O 3 SCF 3 ) is described. The BaX 2 ·18-crown-6 complexes have been characterized by melting point determinations, elemental analysis and NMR spectroscopy. Their thermal stability and volatility at reduced pressure have been investigated. Barium bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)·18- crown-6, Ba(hfac) 2 ·18-crown-6, appears to be a non-hygroscopic, thermally stable, sublimable solid. This compound has also been characterized by mass spectrometry. The 18-crown-6 complexes of BaI 2 , Ba(SCN) 2 , Ba(O 2 CCF 3 ) 2 and Ba(O 3 SCF 3 ) 2 are involatile and thermally stable up to 200 °C. The 18- crown-6 complexes of BaX 2 with X=Cl, Br, OH, NO 3 , O 2 CCH 3 , acac, tclac, tfac and thd dissociate upon heating between 80 and 200 °C. In the complexes, with X=Cl, Br, NO 3 , OH and tfac, loss of 18-crown-6 is accompanied by some co-evaporation of the barium compound.

Tris(chelate) 2 (diene)ruthenium(II) complexes have been synthesized. All three possible diastereoisomers of Ru(bzac) 2 (cod) (where cod=1,5-cyclooctadiene and bzac=benzoylacetonato) have been isolated and diastereoisomerization processes were observed at elevated temperature. The energy barriers were found to be in the range of 35–36 kcal/mol. The DNMR behaviour of Ru(S 2 CNMe 2 ) 2 (cod) and Ru(S 2 PMe 2 ) 2 (L) complexes is also discussed. We synthesized a new Ru( N -isopropylsalicylaldiminato) 2 (cod) tris-chelate which was found to clathrate some solvents.

1,1-Diphenylhydrazine reacts with [MoO 2 (acac) 2 ] in methanol to yield either the mononuclear complex [MoO(NNPh 2 )(acac) 2 ] ( I ) or the binuclear complex [{MoO(NNPh 2 )(acac)(μ-OMe)} 2 ] (II) depending on the temperature. In refluxing ROH, complex I transforms into [{MoO(NNPh 2 )(acac)(μ-OR)}]. (R=Me: II ; R=Et: III ; R=n-Pr: IV .) The crystal structure of III is reported. Crystals are triclinic, space group P 1 , with unit cell dimensions a =9.211(1), b =10.375(2), c =12.107(3) A, α=72.98(2), β=64.55(1), γ=70.10(1)° and Z =1. The structure was solved using 5034 unique observed reflections; the refinement of 304 variables gave R and R w values of 0.024 and 0.026, respectively. The lattice is made of discrete centrosymmetrical dinuclear molecules. The geometry of the hydrazido(2−) ligand (MoN = 1.784(1), NN = 1.298(2) A, MoNN = 169.5(1)°) indicates extensive delocalization through the MoNN unit. II , III and IV are representative members of a new family of dinuclear complexes which display the [(Ph 2 NN)OMo(μ-OR) 2 MoO(NNPh 2 )] 2+ core.

The synthesis and properties of the mononuclear [Co(L)(hfacac) 2 ], [Co(L)(tfacac) 2 ] and of the dinuclear complexes [Co2(L)(acac)4], where L is 2,3-bis( 2− pyridyl)pyrazine (DPP), 2,3-bis( 2− pyridyl)quinoxaline (DPQ), 6-methyl-2,3-bis( 2− pyridyl)quinoxaline (MeDPQ), 6,7-dimethyl-2,3-bis( 2− pyridyl)quinoxaline (DMeDPQ), 6-chloro-2,3-bis( 2− pyridyl)quinoxaline (ClDPQ), 2,3-bis( 2− pyridyl)benzoquinoxaline (BDPQ); hfacac, tfacac and acac being hexafluoroacetylacetonate, trifluoroacetylacetonate and acetylacetonate, respectively, are described. The structures of [Co(L)(hfacac) 2 ] where L=BDPQ and DMeDPQ were solved. The [Co(BDPQ)(hfacac) 2 ] complex crystallizes in the Pi space group with cell parameters a =14.382( 4 ), b =12.853(3), c =9.094(3) A, α=92.55( 3 ), β=100.80(3), γ=94.54(3)° and Z =2. The [Co(DMeDPQ)(hfacac) 2 ] complex crystallizses in the P 2 1 / a space group with cell parameters a =19.130(5), b =9.248( 3 ), c =18.198(4) A,β=95.18( 3 ) and Z =4. Magnetic properties of the dinuclear complexes and a study of the coordination possibilities of this kind of ligands are presented.

The title compound crystallizes in the triclinic system (space group P 1 ) with parameters: a=1206.9(2), b=1304.7(3), c=1335.0(3) pm, α=106.32(2), β=113.74(1). γ=102.66(1)°. The crystal structure determination reveals discrete hexanuclear molecules. The Zr2Co4O19 inorganic core adopts a cubic close packing of oxygens, the metal atoms occupying octahedral holes. A μ6 oxygen atom is located at the center of the metal octahedron.

Neutral monomeric target bis(acetylacetonato)copper(II), (Cu(acac) 2 , C ), reacts reversibly with transmetalators Co(NS) 2 ( A 3 ) and Zn(NS) 2 ( A 4 ) (NS is monoanionic S -methyl isopropylidenehydrazinecarbodithioate) in methylene chloride to give products Co(acac) 2 ( D ) and Zn(acac) 2 ( E ), respectively, and co-product Cu(NS) 2 ( A 2 ). The reaction of excess C with A 3 proceeds in two kinetically resolvable steps, the rates of which are both independent of [ C ]. This indicates metal exchange through an especially stable precursor P to give a successor complex S , as found in the corresponding complex formation reaction of C with Cu(NS) 2 ( A 2 ). By contrast, the reactions of excess C with Ni(NS) 2 ( A 1 ) and Zn(NS) 2 ( A 4 ) proceed through precursors with measurable thermodynamic parameters to give different forms of successor complexes S . The kinetic and thermodynamic data for metal exchange in C are compared with those for irreversible transmetalation of heteropolymetallic targets with M(NS) 2 reagents.

An unusual β-diketone coordination mode is reported here for the first time. A dinuclear Mn(III) compound is obtained by reaction, in open atmosphere and basic medium, of a mononuclear, β- diketone like complex of the trinucleating ligand 1,3-bis(2-hydroxyphenyl)-1,3-propanedione with a Mn(II) salt. The aforementioned molecule is a potentially trinucleating ligand with three coordination sites: the most reactive is the central β-diketone moiety, while the outer are the less reactive. In the Mn(III) complex both metal ions are occupying the two outer sites. The compound bis(1,3-bis(2- hydroxyphenyl)-1,3-propanedione)tetrakispyridine dimanganese(III), C50H38N4O8Mn2, is monoclinic, space group P21/n, a=16.093(5), b=17.062(4), c=31.449(6) A, β=93.09(2)°, V=8622.7 A3, Z=8, Dx=1.44 Mg m−3, μ(Mo Kα)=6.20 cm−1 4516 final data for 259 refined parameters. R=0.076, Rw= 0.081. MnMn distance in the dinuclear compound is 5.295(2) A.

Excess neutral monomeric target bis-(acetylacetonato)copper(II), (Cu(acac) 2 , C), reacts reversibly with transmetalator Ni(NS) 2 ( A 1 : NS is monoanionic S -methyl isopropylidenehydrazinecarbodithioate) in methylene chloride to give two temperature-dependent forms of the successor complex Ni(acac) 2 · Cu(NS) 2 , ( D · A 2 ), S Ni ′and S Ni ′. The overall metal exchange reaction proceeds via two tempcrature-dependent forms of the 1:1 precursor C · A 1 , P Ni and P Ni ′, whose formation constants are β 4 = 490 M− 1 andβ 4 ′= 110 M− 1 at 23 °C, respectively. Excess C reacts irreversibly at a much higher first-order rate with Cu(NS) 2 ( A 2 ) in methylene chloride to form a complex C · A 2 . The data are compared with those for reactions of polynuclear halo(amine)copper targets with M(NS) 2 reagents.

2-Thenoyltrifluoroacetone complexes with U(VI), Fe(III), V(V) and Ca(II) have been synthesized and investigated. Characterization was by elemental analysis, UV-Vis, IR (4000–200 cm−1), 1H, 13C and 19F NMR spectral analyses. The complexes were shown to be neutral with molecular formula M(TTA)nX where n is the oxidation state of metal M. X is an adduct: H2O for Ca(II), CH3CH2OH for U(VI) and HTTA for V(V). UV-Vis, IR (4000–200 cm−1), 1H, 13C and 19F NMR spectral data with assignments are presented and discussed.

The reaction of SnCl4 with squaric acid in methanol yields colorless crystals of [(n- C4H9)4N]2[Sn2Cl4(OCH3)2(C4O4)2]. The compound crystallizes in the monoclinic space group P21/c with a = 13.914(2), b = 10.858(3), c = 19.305(4) A, β = 112.49(1)°, V = 2694.8(12) A3, Z = 2, Dcalc = 1.42 g cm−3. Structure solution and refinement based on 2120 reflections with F0⩾6σ(F0) (Mo Kα radiation, λ = 0.71073 A, 3529 reflections collected) converged at a conventional discrepancy value of 0.069. The structure consists of discrete (n-C4H9)4N+ cations and [Sn2Cl4(OCH3)2(C4O4)2]2− anions. The methoxy groups and the squarate ligands adopt bridging coordination to the hexacoordinate Sn(IV) centers.

The kinetics and mechanisms of the reactions of copper(II) and oxovanadium(IV), [VO] 2+ with heptane-3,5-dione to form the 1:1 complex have been investigated in aqueous solution at 25 °C and ionic strength 0.5 mol dm −2 NaClO 4 using the stopped- flow technique. In the case of copper(II), two separate reactions were observed, while only one reaction was observed when oxovanadium(IV) was the metal species. A detailed mechanism is proposed to account for the kinetic data. Cu 2+ reacts with the enol and keto tautomers of the ligand with rate constants of 1.14 × 10 4 and 8.9 dm 3 mol −1 s −1 , respectively. [VO] 2+ reacts with the enol and keto tautomers with rate constants of 5.33 and 0.986 dm 3 mol −1 s −1 , respectively, while [VO(OH)] + reacts with the keto tautomer with a rate constant of 7.64 dm 3 mol −1 s −1 . The results are discussed in the light of previous investigations.

A novel non-symmetrical tetradentate Schiff base, AE-ImH, resulting from the condensation of 7-amino- 4-methyl-5-aza-3-hepten-2-one (AEH) with imidazole- 2-carboxaldehyde, has been prepared and characterized. This ligand can react with copper and nickel ions to yield neutral M i AE-Im entities. When M i is Cu, the mononuclear units are associated in the solid state to yield a chain structure. Subsequent reaction of the mononuclear units with M o AE entities (M i for inner, M o for outer metal coordination site relating to the AE-ImH ligand) or Zn(hfa) 2 ·2H 2 O (hfa=anion of hexafluoroacetylacetone) gave homo- (CuCu; NiNi) and heterobinuclear (CuNi; CuZn; NiZn) imidazolate-bridged complexes [M i AE-ImM o AE] + or M i AE-ImZn(hfa) 2 . A significant antiferromagnetic interaction is operative in the copper-copper complex (2 J =−48 cm −1 ; g =2.08). NMR, ESR and electronic spectra confirm the existence of the dinuclear structure in solution. From the entire set of results we may assume that in the dinuclear complexes, the imidazolate ligand has a rather localized structure with two markedly different nitrogen atoms, viz. a pyrrolic nitrogen at the inner site and a pyridinic nitrogen at the outer site.

We report two new (Cu-M) heterobinuclear complexes containing an endogenous benzimidazolate bridge. In the reaction of Cu(hfac)2 and the neutral cadmium complex to prepare the heterobinuclear complex, a metal exchange reaction has occurred. Both complexes contain the copper(II) ion in an N2SO environment.

[Co(en) 2 (hfacOCH 3 )]ClO 4 was synthesized by means of the reaction between Co(en) 2 (hfac) 2+ and OCH 3 − in a methanolic medium. It crystallized in the monoclinic space group P 2 1 / c with a = 7.918(1), b = 14.971(2), c = 15.980(2) A, β = 98.422(8)° and Z = 4. The structure was determined from 3357 observed reflections. The final R value converged to 0.067. Hhfac = hexafluoroacetylacetone.

A novel trinuclear nickel(II) complex, [Ni 3 (3,5-Me 2 pz) 4 (acac) 2 ] (3,5-Me 2 pz=3,5-dimethylpyrazolate, acac=acetylacetone), has been prepared and characterized crystallographically. The terminal and center nickel atoms are bridged by two 3,5-Me 2 pz, providing a trinuclear structure. The geometry of each nickel atom is square planar (SqPl) and these planes provide the zigzag mode. This is the first crystal structure of a trinuclear nickel(II) complex having a (SqPl)-(SqPl)-(SqPl) coordination arrangement. The Ni(1)···Ni(2) separation is 3.1972(5) A and the Ni(II) complex has no attractive Ni(II)···Ni(II) interaction. The averaged Ni-N distance of 3,5-Me 2 pz and Ni-O distance of acac are 1.876 and 1.850 A, respectively.

The two geometrical isomers of Pd(tod)2 have been separated by normal phase liquid chromatography. The major (cis) isomer has been characterized by X-ray crystallography. C22H38PdO4, monoclinic, space group P21/n, a = 11.585(4), b = 10.567(5), c = 20.262(5) A, β = 90.41(3)°, Z = 4, Dc = 1.27 g cm−1, R = 0.056, Rw = 0.079 for 2152 ‘observed’ reflections.

The Cr(II) reduction of [Co(bipy)2(ptdn)2+ (bipy = 2,2t-bipyridine and ptdn = pentane-2,4-dione) proceeded too rapidly to be detected by the stopped-flow method and a lower limit of 3 × 104 M−1 s−1 (μ = 0.10 M (LiClO4)) and [H+] = 0.030 M was calculated for this reaction. Product studies established that both [Cr(bipy)(OH2)4]3+ and [Cr(bipy)(ptdn)(OH2)2]2+ were formed. The ration of products obtained was strongly dependent on the mixing technique used. Under conditions of excess chromium(II), more than the stoichiometric amount of Cr(III) products were isolated, indicating that some degree of substitution was occurring. Blank experiments established that the products obtained could have arisen from an outer-sphere reaction followed by capture of the free ligands by Cr(II). A synergistic effect between the acac and bipy ligands appears to be operating. Two reactions were observed on the stopped-flow instrument. Both are ascribed to ring-closure of bipy on Cr(III). The reaction to give [Cr(bipy)(OH2)4]3+ was characterised by k25 °C = 5.06 × 10−1 s−1 with activation parameters ΔH≠ = 9.9 ± 0.3 kcal/mol, and ΔS≠ = −26.8 ± 0.9 e.u. The second reaction was ascribed to the formation of [Cr(bipy)(ptdn)(OH2)2]2+ from [Cr(bipy)(ptdn)(OH2)3]2+ and had k25 °C = 5.83 × 10−2 s−2; ΔH≠ = 4.93 ± 0.06 kcal/mol, ΔS≠ = 47.6 ± 0.2 e.u. The final reaction was attributed to breakdown of the Cr(III) products. It occured very slowly with k25 °C = 4.6 × 10−6 s−1 (all values quoted at μ = 0.10 M (LiClO4) and [H+] = 0.030 M).

The [Co(acac) 2 ( N -phenylethylenediamine)] + (acac= 2,4-pentanedionate ion)and[Co(acac) 2 ( N,N′ -diphenylethylenediamine)] + complexes were separated into two and three racemic pairs of the diastereomers, respectively, by means of column chromatography and the diastereomers were resolved by the chemical method. The diastereomers are stable in acidic water pH (2.5), but easily epimerize in neutral or basic water. The isomer distributions at equilibrium were determined and the results compared with those of the corresponding N -methyl-substituted ethylenediamine complexes.

The title compound [Cr2(bhppH2)4(OH)2]·2C7H8 has been synthesized and isolated by chromatographic techniques from the reaction between 1,3-bis(2- hydroxyphenyl)-l,3-propanedione (bhppH3) and Cr(NO3)3·9H2O. Well formed single crystals were grown from toluene solutions and characterized by X-ray diffraction methods being triclinic, space group P 1 , with a = 12.692(2), b = 13.423(2), c = 21.983(4) A, α= 102.24(1), β = 92.04(1), γ = 115.72(1)°, V= 3.262(6) A3, Z = 2, Dx = 1.370 g cm−3 and μ = 3.9 cm−1, F(000) = 1.396. Magnetic susceptibilities were measured from 50 down to 4.2 K and fitted using the simplest Hamiltonian for exchange coupled systems = −2JS1S2. The best results were obtained with J=−4.1 cm−1 and g= 1.85. These values are compared with the Glerup, Hodgson and Pedersen (GHP) model.

Reaction mechanism of the dihalobis(acetylacetonato)technetium(IV) complexes [TcX2(acac)2, X = Cl and Br] was investigated by means of solvent extraction and spectrophotometric methods. TcX2(acac)2 is resistant to the attack of acid. In an alkaline solution, however, it liberates first halide ions and then acetylacetonate ions. As a final product, pertechnetate was recognized. The rate equation is expressed as R = k1[OH−][TcX2(acac)2] in a higher concentration of hydroxide ion, whereas it becomes complicated with a decrease in the concentration of hydroxide ion. The respective decomposition rate constants were determined.