Thiofunctional vanadium complexes

The neutral tetradentate ligand 1,6-bis(2'-pyridyl)-2,5-dithiahexane (N(2)S(2)), containing two thioether functions, reacts with [VX(2)L(4)] (X = Br, L(4) = 2 tmeda (tmeda = Me(2)NCH(2)CH(2)NMe(2)); X = I, L = tetrahydrofuran (THF)) and [VX(3)(THF)(3)] (X = Br, I) to form the complexes [VX(2)(N(2)S(2))] (1) and [VX(2)(N(2)S(2))]X (2), respectively. [V(2)(mu-Cl)(3)(THF)(6)]I and N(2)S(2) yield the V(IV) complex [VOCl(N(2)S(2)]I (3). The pentadentate, dianionic ligand 2,6-bis(2'-mercaptophenylthio)dimethylpyridine, NS(2)S'(2)(2-), which contains two thioether (S) and two thiophenolate (S') functions, reacts with [VBr(3)(THF)(3)] to afford [VBr(NS(2)S'(2))] (4). The complex [VO(Cl)S'NS'] (5; H(2)S'NS' is the Schiff base formed between o-mercaptoaniline and o-mercaptobenzaldehyde) is obtained by redox interaction between [VCl(3)(THF)(3)] and 2,2'-dithiodibenzaldehyde in the presence of o-mercaptoaniline. The crystal and molecular structures have been obtained for 3. THF, 4. THF, and 5. n-C(5)H(12). The relevance of these compounds and their formation for the interaction between vanadium and thiofunctional biomolecules is addressed.     

Ligand effects on the structures and magnetic properties of tricyanomethanide-containing copper(II) complexes

The preparation, crystal structure and magnetic properties of four heteroleptic copper(II) complexes with the tricyanomethanide (tcm(-)) and the heterocyclic nitrogen donors 3,6-bis(2-pyridyl)pyridazine (dppn), 2,5-bis(2-pyridyl)pyrazine (2,5-dpp), 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) and 2,3-bis(2-pyridyl)quinoxaline (2,3-dpq) are reported, {[Cu(2)(dppn)(OH)(tcm)(2)] x tcm}(n) (1), {[Cu(2,5-dpp)(tcm)] x tcm}(n) (2), {[Cu(2)(2,3-dpp)(2)(tcm)(3)(H(2)O)(0.5)] x tcm x 0.5H(2)O}(n) (3) and [Cu(2,3-dpq)(tcm)(2)](n) (4). 1 has a ladder-like structure with single mu-1,5-tcm ligands forming the sides and a bis-bidentate dppn and a single mu-hydroxo providing the rung. Each copper atom in 1 exhibits a distorted square pyramidal CuN(4)O surrounding: the basal plane is built by the hydroxo-oxygen, a nitrile-nitrogen atom from a tcm group and one pyrazine and a pyridyl nitrogen atoms from the dppn whereas the apical position is filled by a nitrile-nitrogen atom from a symmetry-related tcm ligand. The structures of 2-4 consists of zig-zag (2 and 3)/linear (4) chains of copper(II) ions which are bridged by either bis-bidentate 2,5-dpp (2) and 2,3-dpp (3) molecules or single mu-1,5-tcm (4) groups. The copper atoms in 2 and 4 are five coordinated with distorted trigonal bipyramidal (2) and square pyramidal (4) CuN(5) surroundings. The axial positions in 2 are occupied by two pyridyl-nitrogen atoms from two 2,5-dpp ligands whereas the trigonal plane is built by a nitrile-nitrogen from a terminally bound tcm group and two pyrazine nitrogen atoms from two 2,5-dpp molecules. The basal plane in 4 is defined by a pyridyl and a pyrazine nitrogen atoms from the bidentate 2,3-dpq ligand and two nitrile nitrogen atoms from two tcm groups (one terminal and the other bridging) whereas the apical position is filled by a nitrile nitrogen from another tcm ligand. The crystallographically independent copper atoms in 3 [Cu(1) and Cu(2)] exhibit elongated octahedral geometries being defined by four nitrogen atoms from two 2,3-dpp groups [Cu(1) and Cu(2)] either two terminally bound tcm ligands [Cu(1)] or a water molecule and a monodentate tcm ligand [Cu(2)] in cis positions. Magnetic susceptibility measurements for 1-4 in the temperature range 1.9-295 K reveal the occurrence of strong [J ca.-1000 cm(-1) (1); H = -JS(A) x S(B)] and weak [J = -0.13 (2), -0.67 (3) and -0.18 cm(-1) (4); H = -J Sigma(I)S(i) x S(i+1)] antiferromagnetic interactions in agreement with the different nature of the exchange pathways involved, diazine and single mu-hydroxo (1) and the extended 2,5-dpp (2), 2,3-dpp (3) and single mu-1,5-tcm (4) bridges with copper-copper separations of 3.363(8) (1), 7.111(1) (2), 6.823(1) and 7.056(1) (3) and 7.446(1) A (4).     

Square planar vs tetrahedral coordination in diamagnetic complexes of nickel(II) containing two bidentate pi-radical monoanions

The reaction of three different 1-phenyl and 1,4-diphenyl substituted S-methylisothiosemicarbazides, H(2)[L(1-6)], with Ni(OAc)(2).4H(2)O in ethanol in the presence of air yields six four-coordinate species [Ni(L(1-6)(*))(2)] (1-6) where (L(1-6)(*))(1-) represent the monoanionic pi-radical forms. The crystal structures of the nickel complexes with 1-phenyl derivatives as in 1 reveal a square planar structure trans-[Ni(L(1)(-3)(*))(2)], whereas the corresponding 1,4-diphenyl derivatives are distorted tetrahedral as is demonstrated by X-ray crystallography of [Ni(L(5)(*))(2)] (5) and [Ni(L(6)(*))(2)] (6). Both series of mononuclear complexes possess a diamagnetic ground state. The electronic structures of both series have been elucidated experimentally (electronic spectra magnetization data). The square planar complexes 1-3 consist of a diamagnetic central Ni(II) ion and two strongly antiferromagnetically coupled ligand pi-radicals as has been deduced from correlated ab initio calculations; they are singlet diradicals. The tetrahedral complexes 4-6 consist of a paramagnetic high-spin Ni(II) ion (S(Ni) = 1), which is strongly antiferromagnetically coupled to two ligand pi-radicals. This is clearly revealed by DFT and correlated ab initio calculations. Electrochemically, complexes 1-6 can be reduced to form stable, paramagnetic monoanions [1-6](-) (S = (1)/(2)). The anions [1-3](-) are square planar Ni(II) (d,(8) S(Ni) = 0) species where the excess electron is delocalized over both ligands (class III, ligand mixed valency). In contrast, one-electron reduction of 4, 5, and 6 yields paramagnetic tetrahedral monoanions (S = (1)/(2)). X-band EPR spectroscopy shows that there are two different isomers A and B of each monoanion present in solution. In these anions, the excess electron is localized on one ligand [Ni(II)(L(4-6)(*))(L(4-6))](-) where (L(4-6))(2-) is the closed shell dianion of the ligands H(2)[L(4-6)] as was deduced from their electronic spectra and broken symmetry DFT calculations. Oxidation of 1 and 5 with excess iodine yields octahedral complexes [Ni(II)(L(1,ox))(2)I(2)] (7), [Ni(II)(L(1,ox))(3)](I(3))(2) (8), and trans-[Ni(II)(L(5,ox))(2)(I(3))(2)] (9), which have been characterized by X-ray crystallography; (L(1-)(6,ox)) represent the neutral, two-electron oxidized forms of the corresponding dianions (L(1-6))(2-). The room-temperature structures of complexes 1, 5, and 7 have been described previously in refs 1-5.     

Photoluminescent copper(I) complexes with amido-triazolato ligands

A series of heteroleptic copper(I) complexes incorporating amido-triazole and diphosphine ligands, [Cu(I)(N-phenyl-2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline)(dppb)] (1), [Cu(I)(N-(4-methylphenyl)-2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline)(dppb)] (2), [Cu(I)(N-(4-methoxyphenyl)-2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline)(dppb)] (3), [Cu(I)(N-(4-chlorophenyl)-2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline)(dppb)] (4), [Cu(I)(2,6-dimethyl-N-[2-(1-phenyl-1H-1,2,3-triazol-4-yl)phenyl]aniline)(dppb)] (5), [Cu(I)(2,6-dimethyl-N-[2-(1-benzyl-1H-1,2,3-triazol-4-yl)phenyl]aniline)(dppb)] (6), (dppb = 1,2-bis(diphenylphosphino)benzene), have been prepared. The complexes adopt a distorted tetrahedral geometry in the solid state with the amido-triazole ligand forming a six-member ring with the Cu(I) ion. The complexes exhibit long-lived photoluminescence with colors ranging from yellow to red-orange in the solid state, in frozen glass at 77 K, and in fluid solution with modest quantum yields of up to 0.022. Electrochemically, complexes 1-4 show irreversible oxidation waves while 5 and 6 are characterized by quasi-reversible oxidations as determined by cyclic voltammetry. For 1-4, the emission energy and oxidation potential are found to vary linearly with the Hammett parameter σ(p) of the substituent in the para position of the amido ligand, while in 5 and 6, large differences in emission are observed because of the nature of N3 substitution in the triazole ring. Density functional theory calculations have been performed on the singlet ground states (S(o)) of all complexes at the BP86/6-31G(d) level to assist in assignment of the excited states. On the basis of both experimental and computational results, we have assigned the excited states as intraligand + metal-to-ligand charge transfer (3)(ILCT+MLCT) or ligand-to-ligand charge transfer mixed with MLCT (3)(MLCT +LLCT) in these complexes.     

Further insight into the coordination of 2,5-dicarbothioamidopyrroles: the case of Cu and Co complexes

The coordination chemistry of 2,5-dicarbothioamidopyrrole ligands, namely N2,N5-dibutyl-3,4-diphenyl-1H-pyrrole-2,5-bis(carbothioamide) and N2,N5,3,4-tetraphenyl-1H-pyrrole-2,5-bis(carbothioamide), has been investigated with Cu(II) metal centres by means of X-ray crystallography. This resulted in the formation of the expected planar S,N,S' coordinated complex for the former ligand and unexpected ring-closure reactions, with formation of benzothiazole sidearms, for the latter. Both Cu(II) and Cu(I), used in large excess, were found to favour the ring-closure reaction, although the structural characterisation of the resulting complexes contained only Cu(II) cations, with varying coordination geometries ranging from square planar and square-based pyramidal to tetrahedral. By repeating the reaction using a slight excess of Cu(II) (2?:?1) two more different structures were obtained where the metal was coordinated to the original ligand, N2,N5,3,4-tetraphenyl-1H-pyrrole-2,5-bis(carbothioamide), or to the mixed ligand where only one of the thioamide substituents had converted to a benzothiazole. The essential role of Cu for the ring closure reaction was also established by comparing its complex with structural features of the analogous Co(II) complex, the latter revealing no ring closure to give benzothiazole substituents and co-crystallisation of a mixed Co(II)/Co(III) complex. Finally, the structure and photophysical properties of the corresponding 3,4-diphenyl-2,5-bis(benzothiozol-5-yl)-pyrrole ligand, obtained via treatment of the thioamide with K(3)[Fe(CN)(6)], were also investigated revealing a blue-centered emission.     

Structure and properties of bivalent nickel and copper complexes with pyrazine-amide-thioether coordination: stabilization of trivalent nickel

Acyclic pyrazine-2-carboxamide and thioether containing hexadentate ligand 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpzctb), in its deprotonated form, has afforded light brown [Ni(II)(bpzctb)](1)(S=1) and green [Cu(II)(bpzctb)](2)(S=1/2) complexes. The crystal structures of 1.CH(3)OH and 2.CH(2)Cl(2) revealed that in these complexes the ligand coordinates in a hexadentate mode, affording examples of distorted octahedral M(II)N(2)(pyrazine)N'(2)(amide)S(2)(thioether) coordination. Each complex exhibits in CH(2)Cl(2) a reversible to quasireversible cyclic voltammetric response, corresponding to the Ni(III)/Ni(II)(1) and Cu(II)/Cu(I)(2) redox process. The E(1/2) values reveal that the complexes of bpzctb(2-) are uniformly more anodic by approximately 0.2 V than those of the corresponding complexes with the analogous pyridine ligand, 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpctb), attesting that compared to pyridine, pyrazine is a better stabilizer of the Ni(ii) or Cu(i) state. Coulometric oxidation of the previously reported complex [Ni(II)(bpctb)] and 1 generates [Ni(III)(bpctb)](+) and [Ni(III)(bpzctb)](+) species, which exhibit a LMCT transition in the 470--480 nm region and axial EPR spectra corresponding to a tetragonally elongated octahedral geometry. Complex 2 exhibits EPR spectra characteristic of the d(z(2)) ground state.     

A series of metal complexes with the non-innocent N,N'-bis(pentafluorophenyl)-o-phenylenediamido ligand: twisted geometry for tuning the electronic structure

A series of homoleptic complexes with non-innocent ligands derived from N,N'-bis(pentafluorophenyl)-o-phenylenediamine (H(2)(F)pda) are reported. [Ni(II)((F)sbqdi)(2)] (1), [Pd(II)((F)sbqdi)(2)] (2), [Co(II)((F)sbqdi)(2)] (3), and [Cu(II)((F)sbqdi)(2)] (4) were synthesized, where ((F)sbqdi)(1-) represents a radical anion formed by one-electron oxidation of the doubly deprotonated H2(F)pda. The oxidation states of ligands and metals in complexes 1-4 were assigned by single crystal X-ray crystallography performed at low temperatures. Complex 4 is the first Cu(II) complex where both o-phenylenediamine derived ligands are monoanionic radicals. The bulky N-C6F5 substituents force the complexes 1, 3, and 4 to adopt a twisted geometry (intermediate between square-planar and tetrahedral). The electronic structures of the neutral compounds 1-4 and of some of their cationic and/or anionic neighboring redox states were probed using EPR and UV-VIS-NIR spectroelectrochemistry. The twisted geometry of the complexes results in considerable changes in their electronic structures compared to the well known square-planar complexes while the strongly electron withdrawing N-C6F5 groups have a great influence on redox properties.     

Nine non-symmetric pyrazine-pyridine imide-based complexes: reversible redox and isolation of [M(II/III)(pypzca)2](0/+) when M = Co, Fe

The non-symmetric imide ligand Hpypzca (N-(2-pyrazylcarbonyl)-2-pyridinecarboxamide) has been deliberately synthesised and used to produce nine first row transition metal complexes: [M(II)(pypzca)(2)], M = Zn, Cu, Ni, Co, Fe; [M(III)(pypzca)(2)]Y, M = Co and Y = BF(4), M = Fe and Y = ClO(4); [Cu(II)(pypzca)(H(2)O)(2)]BF(4), [Mn(II)(pypzca)(Cl)(2)]HNEt(3). These are the first deliberately prepared complexes of a non-symmetric imide ligand. X-ray crystal structures of [Cu(II)(pypzca)(2)]·H(2)O, [Co(II)(pypzca)(2)], [Co(III)(pypzca)(2)]BF(4), [Cu(II)(pypzca)(H(2)O)(2)]BF(4)·H(2)O and [Mn(II)(pypzca)Cl(2)]HNEt(3) show that each of the (pypzca)(-) ligands binds in a meridional fashion via the N(3) donors. In the first three complexes, two such ligands are bound such that the 'spare' pyrazine nitrogen atoms are positioned approximately orthogonally to one another and also to the imide oxygen atoms. In MeCN the [M(II/III)(pypzca)(2)](0/+) complexes, where M = Ni, Co or Fe, exhibit one reversible metal based M(II/III) process and two distinct, quasi-reversible ligand based reduction processes, the latter also observed for M(II) = Zn. [Mn(II)(pypzca)Cl(2)]HNEt(3) displays a quasi-reversible oxidation process in MeCN, along with several irreversible processes. Both copper(II) complexes show only irreversible processes. Variable temperature magnetic measurements show that [Fe(III)(pypzca)(2)]ClO(4) undergoes a gradual spin crossover from partially high spin at 298 K (3.00 BM) to fully low spin at 2 K (1.96 BM), and that [Co(II)(pypzca)(2)] remains high spin from 298 to 4 K. All of the complexes are weakly coloured, other than [Fe(II)(pypzca)(2)] which is dark purple and absorbs strongly in the visible region.     

Trigonal planar copper(I) complex: synthesis, structure, and spectra of a redox pair of novel copper(II/I) complexes of tridentate bis(benzimidazol-2'-yl) ligand framework as models for electron-transfer copper proteins

The copper(II) and copper(I) complexes of the chelating ligands 2,6-bis(benzimidazol-2'-ylthiomethyl)pyridine (bbtmp) and N,N-bis(benzimidazol-2'-ylthioethyl)methylamine (bbtma) have been isolated and characterized by electronic and EPR spectra. The molecular structures of a redox pair of Cu(II/I) complexes, viz., [Cu(bbtmp)(NO(3))]NO(3), 1, and [Cu(bbtmp)]NO(3), 2, and of [Cu(bbtmp)Cl], 3, have been determined by single-crystal X-ray crystallography. The cation of the green complex [Cu(bbtmp)(NO(3))]NO(3) possesses an almost perfectly square planar coordination geometry in which the corners are occupied by the pyridine and two benzimidazole nitrogen atoms of the bbtmp ligand and an oxygen atom of the nitrate ion. The light-yellow complex [Cu(bbtmp)]NO(3) contains copper(I) with trigonal planar coordination geometry constituted by the pyridine and two benzimidazole nitrogen atoms of the bbtmp ligand. In the yellow chloride complex [Cu(bbtmp)Cl] the asymmetric unit consists of two complex molecules that are crystallographically independent. The coordination geometry of copper(I) in these molecules, in contrast to the nitrate, is tetrahedral, with pyridine and two benzimidazole nitrogen atoms of bbtmp ligand and the chloride ion occupying the apexes. The above coordination structures are unusual in that the thioether sulfurs are not engaged in coordination and the presence of two seven-membered chelate rings facilitates strong coordination of the benzimidazole nitrogens and discourage any distortion in Cu(II) coordination geometry. The solid-state coordination geometries are retained even in solution, as revealed by electronic, EPR, and (1)H NMR spectra. The electrochemical behavior of the present and other similar CuN(3) complexes has been examined, and the thermodynamic aspects of the electrode process are correlated to the stereochemical reorganizations accompanying the redox changes. The influence of coordinated pyridine and amine nitrogen atoms on the spectral and electrochemical properties has been discussed.     

Galactose oxidase models: solution chemistry, and phenoxyl radical generation mediated by the copper status

Galactose oxidase (GO) is an enzyme that catalyzes two-electron oxidations. Its active site contains a copper atom coordinated to a tyrosyl radical, the biogenesis of which requires copper and dioxygen. We have recently studied the properties of electrochemically generated mononuclear Cu(II)-phenoxyl radical systems as model compounds of GO. We present here the solution chemistry of these ligands under various copper and dioxygen statuses: N(3)O ligands first chelate Cu(II), leading, in the presence of base, to [Cu(II)(ligand)(CH(3)CN)](+) complexes (ortho-tert-butylated ligands) or [(Cu(II))(2)(ligand)(2)](2+) complexes (ortho-methoxylated ligands). Excess copper(II) then oxidizes the complex to the corresponding mononuclear Cu(II)-phenoxyl radical species. N(2)O(2) tripodal ligands, in the presence of copper(II), afford directly a copper(II)-phenoxyl radical species. Addition of more than two molar equivalents of copper(II) affords a Cu(II)-bis(phenoxyl) diradical species. The donor set of the ligand directs the reaction towards comproportionation for ligands possessing an N(3)O donor set, while disproportionation is observed for ligands possessing an N(2)O(2) donor set. These results are discussed in the light of recent results concerning the self-processing of GO. A path involving copper(II) disproportionation is proposed for oxidation of the cross-linked tyrosinate of GO, supporting the fact that both copper(I) and copper(II) activate the enzyme.     

Chiral monomeric and homochiral dimeric copper(II) complexes of a new chiral ligand, N-(1,2-bis(2-pyridyl)ethyl)pyridine-2-carboxamide: an example of molecular self-recognition

Reaction of Cu(ClO(4))(2) x 6H(2)O with a racemic mixture of the novel chiral ligand N-(1,2-bis(2-pyridyl)ethyl)pyridine-2-carboxamide (PEAH) affords only the homochiral dimeric copper(II) complexes [Cu(2)((R)()PEA)(2)](ClO(4))(2) and [Cu(2)((S)()PEA)(2)](ClO(4))(2) in a 1:1 ratio. The phenomenon of molecular self-recognition is also observed when a racemic mixture of the monomeric copper(II) complex [Cu((R(S))()PEA)(Cl)(H(2)O)] is converted into the homochiral dimeric species [Cu(2)((R(S))()PEA)(2)](ClO(4))(2) via reaction with Ag(+) ion. This is the first report of direct conversion of a racemic mixture of a chiral monomeric copper(II) complex to a mixture of the homochiral dimers.     

Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index, tau4

Four Cu(I) complexes were synthesized with a family of pyridylmethylamide ligands, HL(R) [HL(R) = N-(2-pyridylmethyl)acetamide, R = null; 2,2-dimethyl-N-(2-pyridylmethyl)propionamide, R = Me(3); 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide, R = Ph(3))]. Complexes 1-3 were synthesized from the respective ligand and [Cu(CH(3)CN)(4)]PF(6) in a 2 : 1 molar ratio: [Cu(HL)(2)]PF(6) (1), [Cu(2)(HL(Me3))(4)](PF(6))(2) (2), [Cu(HL(Ph3))(2)]PF(6) (3). Complex 4, [Cu(HL)(CH(3)CN)(PPh(3))]PF(6), was synthesized from the reaction of HL with [Cu(CH(3)CN)(4)]PF(6) and PPh(3) in a 1 : 1 : 1 molar ratio. X-Ray crystal structures reveal that complexes 1, 3 and 4 are mononuclear Cu(I) species, while complex 2 is a Cu(I) dimer. The copper ions are four-coordinate with geometries ranging from distorted tetrahedral to seesaw in 1, 2, and 4. Complexes 1 and 2 are very air sensitive and they display similar electrochemical properties. The coordination geometry of complex 3 is nearly linear, two-coordinate. Complex 3 is exceptionally stable with respect to oxidation in the air, and its cyclic voltammetry shows no oxidation wave in the range of 0-1.5 V. The unusual inertness of complex 3 towards oxidation is attributed to the protection from bulky triphenyl substituent of the HL(Ph3) ligand. A new geometric parameter for four-coordinate compounds, tau(4), is proposed as an improved, simple metric for quantitatively evaluating the geometry of four-coordinate complexes and compounds.     

Formation of dinuclear,macrocyclic, and chain structures from HgI(2) and a semirigid benzimidazole-based bridging ligand: an example of ring-opening supramolecular isomerism

The reactions of HgI(2) with the semirigid ditopic ligand 1,3-bis(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (bbimms) afforded three new complexes, [Hg(2)(mu-I)(2)I(2)(bbimms)] (1), [Hg(2)I(4)(bbimms)(2)] (2), and catena-poly[HgI(2)(bbimms)] (3). The ligand and all complexes have been structurally characterized by single-crystal X-ray diffraction. 1 is a triply bridged dinuclear complex comprised of two Hg(II) ions, one bridging ligand, two bridging I(-) anions, and two terminal I(-) anions. 2 is a dinuclear metallamacrocycle comprised of two Hg(II) ions, two bridging ligands, and four terminal I(-) anions, while 3 is a helical chain with the repeating unit of HgI(2)(bbimms). 2 and 3 can be classified as supramolecular isomers, and both are related to the triply bridged precursor 1 via the addition of one more ligand in a ring-opening process.     

Fluorous biphasic catalysis: synthesis and characterization of copper(I) and copper(II) fluoroponytailed 1,4,7-Rf-TACN and 2,2'-Rf-bipyridine complexes--their catalytic activity in the oxidation of hydrocarbons,olefins, and alcohols,including mechanistic implications

In this contribution on fluorous biphasic catalysis (FBC), we present the synthesis and characterization of new copper complexes, and define their role, as precatalysts, in the FBC oxidation of hydrocarbons, olefins, and alcohols. Thus the previously reported, but poorly characterized, fluoroponytailed ligand, 2,2'-R(f)-bipyridine (R(f)=-(CH(2))(3)C(8)F(17)) 2, as well as the new Cu(II) fluoroponytailed carboxylate synthon complex [Cu(C(8)F(17)(CH(2))(2)CO(2))(2)] 3, will be addressed. Moreover, the reaction of previously described ligands, 1,4,7-R(f)-TACN 1, or 2,2'-R(f)-bipyridine 2 with 3 afforded new perfluoroheptane-soluble Cu(II) complexes, [Cu(C(8)F(17)(CH(2))(2)CO(2))(2)(R(f)-tacn)] 4 and [Cu(C(8)F(17)(CH(2))(2)CO(2))(2)(R(f)-bpy)] 5, respectively. The reaction of 1 with [Cu(CH(3)CN)(4)]PF(6) or [CuCl] provided new Cu(I) complexes, which could be isolated and fully characterized as [Cu(R(f)-tacn)X']X, in which X=PF(6) (6) or X'=Cl (7) (soluble in perfluoroheptane). The Cu(II) and Cu(I) complexes, 4-7, were characterized by elemental analysis, mass spectrometry, and IR, diffuse reflectance UV/Vis, and EPR spectroscopies; complex 7 was also characterized by (1)H and (19)F[(1)H] NMR spectroscopy. Complexes 4 and 5, as well as 6 and 7 generated in situ, were evaluated as precatalysts for hydrocarbon and olefin functionalization. The oxidation reactions of these substrates in the presence of the necessary oxidants, tert-butyl hydroperoxide (TBHP) and oxygen gas, proceeded under FBC conditions for 5, 7, and Cu(I) salts with 2. However, the complexes with ligand 2 could not be recycled, owing to significant ligand dissociation. The Cu(II) complex 4, with the ligand 1, provide the oxidation of 4-nitrobenzyl alcohol to 4-nitrobenzaldehyde under single-phase FBC conditions at 90 degrees C with TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy) and O(2); the precatalyst 4, can be utilized for an additional four catalytic cycles without loss of activity. Plausible mechanisms concerning these FBC oxidation reactions will be discussed.     

Syntheses and structures of copper(I) complexes based on Cu(n)X(n) (X = Br and I; n = 1, 2 and 4) units and bis(pyridyl) ligands with longer flexible spacer

Self-assembly of four bis(pyridyl) ligands with longer flexible spacer: 1,4-bis(3-pyridylaminomethyl)benzene (L1), 1,4-bis(2-pyridylaminomethyl)benzene (L2), 1,3-bis(3-pyridylaminomethyl)benzene (L3) and 1,3-bis(2-pyridylaminomethyl)benzene (L4), and CuX (X = Br and I) leads to the formation of eight [Cu(n)X(n)]-based (X = Br and I; n = 1, 2, and 4) complexes, [Cu(2)I(2)L1(PPh(3))(4)] (1), [Cu(4)Cl(2)Br(2)(L4)(2)(PPh(3))(6)]·(CH(3)CN)(2) (2), [Cu(2)I(2)(L3)(2)] (3), {[Cu(2)Br(2)L2(PPh(3))(2)]·(CH(2)Cl(2))(2)}(n) (4), [CuIL1](n)·nCH(2)Cl(2) (5), [CuIL1](n) (6), [CuIL4](n) (7) and [Cu(2)I(2)L4](n) (8), which have been synthesized and characterized by elemental analysis, IR, TG, powder and single-crystal X-ray diffraction. Structural analyses show that the eight complexes possess an increasing dimensionality from 0D (1-3) to 1D (4) to 2D (5-8), in which 1 and 2 contain a CuX unit, 2-7 contain a Cu(2)X(2) unit and 8 contains a Cu(4)X(4) unit. Such evolvement indicates that the conformation of flexible bis(pyridyl) ligands and the participation of triphenylphosphine (PPh(3)) as a second ligand take an essential role in the framework formation of the Cu(i) complexes. Moreover, a pair of symmetry-related L3 ligands in complex 3 coordinate to the rhomboid Cu(2)I(2) dimer to form "handcuff-shaped" dinuclear structures, which are further joined together through intermolecular N-HI hydrogen bonds to furnish a 2D (4,4) layer. Although complexes 5 and 6 exhibit a similar 2D (4,4) layer constructed from L1 ligand bridging [Cu(2)I(2)](n) units, the different packing fashion of the layers leads to the formation of 3D porous frameworks of 5 and dense 3D frameworks of 6. The "twisted-boat" conformation of the Cu(4)I(4) tetramer unit in complex 8 has not been reported so far.     

The first stereochemically nonrigid monomeric two-coordinate copper(I) complexes with homoleptic and heteroleptic "N2" donor set

A novel set of stereochemically nonrigid monomeric two-coordinate copper(I) complexes, [Cu(eta(1)-H(2)CPz'(2))(2)]ClO(4) 1, [Cu(HPz')(2)]ClO(4) 2, and [Cu(HPz')(eta(1)-H(2)CPz'(2))]ClO(4) 3, where Pz' = 3,5-di-tert-butylpyrazolyl, has been synthesized and characterized by X-ray diffraction and variable-temperature (1)H NMR spectroscopy. Based on the (1)H NMR line shape analysis of complexes 1 and 2, the intramolecular fluxional process was proposed for these two-coordinate copper(I) complexes. Also, the mixed ligand complex 3 shows that these two different dynamic binding modes of the coordinated HPz' and H(2)CPz'(2) ligands can proceed simultaneously on a single copper(I) ion.     

Tri- and tetracoordinate copper(I) complexes bearing bidentate soft/hard SN and SeN ligands based on 2-aminopyridine

The coordination properties of the EN ligands N-(2-pyridinyl)amino-diphenylphosphine sulfide, N-(2-pyridinyl)amino-diisopropylphosphine sulfide, N-(2-pyridinyl)amino-diphenylphosphine selenide, N-(2-pyridinyl)amino-diisopropylphosphine selenide towards copper(I) precursors CuX (X = Br, I), [Cu(IPr)Cl] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), and [Cu(CH(3)CN)(4)]PF(6) were studied. Treatment of CuX with EN ligands resulted in the formation of tricoordinate complexes of the type [Cu(κ(2)(E,N)-EN)X]. The reaction of [Cu(IPr)Cl] with EN ligands, followed by halide abstraction with AgSbF(6), afforded cationic tricoordinate complexes [Cu(κ(2)(S,N)-EN)(IPr)](+), while the reaction of [Cu(CH(3)CN)(4)](+) with two equivalents of EN ligands yielded tetrahedral complexes [Cu(κ(2)(E,N)-EN)(2)](+). Halide removal from [Cu(κ(2)(S,N)-SN)I] with silver salts in the presence of L = CH(3)CN and CNtBu afforded dinuclear complexes of the type [Cu(κ(2)(S,N),μ(S)-SN)(L)](2)(2+) containing bridging SN ligands. With the terminal alkynes HC≡CC(6)H(4)Me and HC≡CC(6)H(4)OMe, complexes of the formula [Cu(κ(2)(S,N)-SN-iPr)(η(2)-HC≡CC(6)H(4)Me)](+) and [Cu(κ(2)(S,N)-SN-iPr)(η(2)-HC≡CC(6)H(4)OMe)](+) were obtained. The mononuclear nature of these compounds was supported by DFT calculations. Most complexes were also characterized by X-ray crystallography.     

A 3D Cu(II) coordination framework with μ4-/μ2-oxalato anions and a bent dipyridyl coligand: unique zeolite-type NiP2 topological network and magnetic properties

The reaction of copper(II) nitrate, oxamide, and an angular bridging ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) under hydrothermal conditions affords a 3D pillared-layer coordination framework {[Cu(2)(4-bpo)(ox)(2)](H(2)O)(4)}(n) (1) (ox = oxalate), featuring the unique zeolite-type NiP(2) network and interesting properties.     

Metal-ligand charge-transfer-promoted photoelectronic Bergman cyclization of copper metalloenediynes: photochemical DNA cleavage via C-4' H-atom abstraction

Metal-to-ligand charge-transfer (MLCT) photolyses (lambda > or = 395 nm) of copper complexes of cis-1,8-bis(pyridin-3-oxy)oct-4-ene-2,6-diyne (bpod, 1), [Cu(bpod)(2)]PF(6) (2), and [Cu(bpod)(2)](NO(3))(2) (3) yield Bergman cyclization of the bound ligands. In contrast, the uncomplexed ligand 1 and Zn(bpod)(2)(CH(3)COO)(2) compound (4) are photochemically inert under the same conditions. In the case of 4, sensitized photochemical generation of the lowest energy (3)pi-pi state, which is localized on the enediyne unit, leads to production of the trans-bpod ligand bound to the Zn(II) cation by photoisomerization. Electrochemical studies show that 1, both the uncomplexed and complexed, exhibits two irreversible waves between E(p) values of -1.75 and -1.93 V (vs SCE), corresponding to reductions of the alkyne units. Irreversible, ligand-based one-electron oxidation waves are also observed at +1.94 and +2.15 V (vs SCE) for 1 and 3. Copper-centered oxidation of 2 and reduction of 3 occur at E(1/2) = +0.15 and +0.38 V, respectively. Combined with the observed Cu(I)-to-pyridine(pi) MLCT and pyridine(pi)-to-Cu(II) ligand-to-metal charge transfer (LMCT) absorption centered near approximately 315 nm, the results suggest a mechanism for photo-Bergman cyclization that is derived from energy transfer to the enediyne unit upon charge-transfer excitation. The intermediates produced upon photolysis degrade both pUC19 bacterial plasmid DNA, as well as a 25-base-pair, double-stranded oligonucleotide. Detailed analyses of the cleavage reactions reveal 5'-phosphate and 3'-phosphoglycolate termini that are derived from H-atom abstraction from the 4'-position of the deoxyribose ring rather than redox-induced base oxidation.