Aziridination of styrene: comparison of [N-(p-tolylsulfonyl)imino]phenyliodinane and chloramine-T as nitrene donors

Chloramine-T and [N-(p-tolylsulfonyl)imino]phenyliodinane (PhI=NTs) are contrasted as nitrene donors for the aziridination of styrene using copper(II) triflate, and copper-exchanged zeolite Y (CuHY) as catalysts. For both catalysts, PhI=NTs is found to give significantly higher yields of the aziridine both in the presence and absence of a chiral bis(oxazoline) modifier. In addition, chloramine-T is found to induce leaching of most of the Cu from CuHY, and with this nitrene donor CuHY does not function as a heterogeneous catalyst. In contrast, PhI=NTs causes negligible leaching of Cu from CuHY and, consequently, for the heterogeneous CuHY catalyst, PhI=NTs is the preferred nitrene donor. With chloramine-T, the beneficial effects observed on addition of copper powder are shown to be due to the copper powder acting as a reservoir for Cu²⁺ in solution, since Cu²⁺ in solution is rapidly deactivated by toluenesulfonamide, a degradation product of the nitrene donor.     

Cu(I) beta-diketiminates for alkene aziridination: reversible Cu-arene binding and catalytic nitrene transfer from PhI=NTs

beta-Diketiminato Cu(I)-lutidine complexes [RMeNN]Cu(2,4-lutidine) (R = Me (4a), (i)Pr (4b)) were prepared in high yield from Tl[RMeNN] and [CuBr(2,4-lutidine)(2)](2). Both 4a and 4b reversibly dissociate lutidine base in toluene to give [RMeNN]Cu(toluene) solvento complexes. A related base-free dicopper species [[Me(2)NN]Cu](2) (6) bridged via eta(2)-binding of opposing N-aryl rings could be isolated by the addition of Tl[Me(2)NN] to CuBr. The lutidine precursors serve as precatalysts for the aziridination of alkenes with PhI=NTs. Styrene, beta-methylstyrene, and cyclooctene gave the highest yields (59-96%) with a low olefin to PhI=NTs ratio (3:1) and 5 mol % catalyst loading.     

Isolation of a pentadentate ligand and stepwise synthesis, structures, and magnetic properties of a new family of homo- and heterotrinuclear complexes

A neutral pentadentate ligand, di(pyrazolecarbimido)amine (Hdcadpz), and its adduct with HClO4, [H2dcadpz]+[ClO4]-, were for the first time isolated from our previously reported [Cu3(dcadpz)2(Hpz)2(ClO4)2](ClO4)2.H2O by the use of (NH4)2S to remove the CuII ions and characterized by IR, EA, UV, NMR, MS, and X-ray crystallography. Reactions of copper(II) or nickel(II) nitrate with Hdcadpz in a 1:2 molar ratio generated two mononuclear precursors of [Cu(dcadpz)2] (1) and [Ni(dcadpz)2].2/3DMF (2). Furthermore, three new linear homo- and heterotrinuclear complexes of the same motif [M{M'(dcadpz)2}M] (M=CoII, NiII, M'=CuII, NiII), [{Co(pdm)}2{Cu(dcadpz)2}](NO3)4 (3), [{Ni(pdm)}2{Cu(dcadpz)2}](NO3)4 (4), and [{Ni(MeOH)(H2O)2}2{Ni(dcadpz)2}](NO3)4 (5), were synthesized from these two precursors (pdm=2,6-pyridinedimethanol) and characterized by X-ray crystallography. Magnetic studies show that the central Cu(dcadpz)2 motif is antiferromagnetically coupled with both the terminal Co(II) atoms via the dcadpz- ligand in 3 with a J value of -5.27 cm(-1) and ferromagnetically coupled with both the terminal Ni(II) atoms in 4 with a J value of 2.50 cm(-1), while 5 behaves only as a Curie paramagnet between 2 and 300 K due to the diamagnetic character of the central square-planar Ni(II) atom.     

195Pt NMR of heteropolymetallic complexes containing secondary dithiooxamides as binucleating ligands

Monometallic [Pt{S-S2C2(NR)2H}2] (S-S2C2(NR)2H = kappa2-S,S-S2C2(NR)2H = bis-dialkyl-dithioxamidate, R = methyl, isoamyl, benzyl) and binuclear and trinuclear heterobimetallic complexes [Pt{S-S2C2(NR)2H}{mu-S2C2(NR)2}MLn] (mu-S2C2(NR)2 = kappa2-S,S(Pt)-kappa2-N,N(M)-S2C2(NR)2) and [Pt{{mu-S2C2(NR)2}MLn}2] (MLn+ = [(eta3-allyl)palladium]+, [bis-(2-phenylpyridine)rhodium]+, [(eta6-p-cymene)(chloro)ruthenium]+, [(1,4-cyclooctadiene)rhodium]+, [(pentamethylcyclopentadienyl)(chloro)rhodium]+) have been prepared and characterized. The progressive substitution of the residual amidic hydrogen in the [Pt{S-S2C2(NR)2H}2] complexes with a MLn+ metal fragment results in the deshielding of platinum nuclei, a red shift of the MLCT absorption maximum, and a decrease in the oxidation potential. Such behavior has been interpreted as a progressive electron shift from platinum to the binucleating ligands, the extent of which depends on the nature of MLn+ metal fragment.     

Facile amine formation by intermolecular catalytic amidation of carbon-hydrogen bonds

A simple copper-based catalytic system has been developed for the carbon-hydrogen amidation reaction. The copper-homoscorpionate complex Tp(Br3)Cu(NCMe) catalyzes the transfer of the nitrene unit NTs (Ts = p-toluenesulfonyl) and its subsequent insertion into the sp(3) C-H bonds of alkyl aromatic and cyclic ethers or the sp(2) C-H bonds of benzene using PhI=NTs as the nitrene source, affording the corresponding trisubstitued NR(1)HTs amines in moderate to high yields. The use of the environmentally friendly chloramine-T has also proven effective, with the advantage that sodium chloride is formed as the only byproduct. A tandem, one-pot consecutive nitrene-carbene insertion system has been developed to yield amino acid derivatives.     

Structural and magnetic diversity in cyano-bridged bi- and trimetallic complexes assembled from cyanometalates and [M(rac-CTH)]n+ building blocks (CTH = d,l-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)

Seven new cyano-bridged heterometallic systems have been prepared by assembling [M'(rac-CTH)]n+ complexes (M' = CrIII, NiII, CuII), which have two cis available coordination positions, and [M(CN)6]3- (M = FeIII, CrIII) and [Fe(CN)2(bpy)2]+ cyanometalate building blocks. The assembled systems, which have been characterized by X-ray crystallography and magnetic investigations, are the molecular squares (meso-CTH-H2)[{Ni(rac-CTH)}2{Fe(CN)6)}2].5H2O (2) and [{Ni(rac-CTH)}2{Fe(CN)2(bpy)2}2](ClO4)4.H2O (5), the bimetallic chain [{Ni(rac-CTH)}2{Cr(CN)6)}2Ni(meso-CTH)].4H2O (3), the trimetallic chain [{Ni(rac-CTH)}2{Fe(CN)6)}2Cu(cyclam)]6H2O (4), the pentanuclear complexes [{Cu(rac-CTH}3{Fe(CN)6}2].2H2O (6) and [{Cu(rac-CTH)}3{Cr(CN)6)}2].2H2O (7), and the dinuclear complex [Cr(rac-CTH)(H2O)Fe(CN)6].2H2O (8). With the exception of 5, all compounds exhibit ferromagnetic interaction between the metal ions (JFeNi = 12.8(2) cm-1 for 2; J1FeCu= 13.8(2) cm-1 and J2FeCu= 3.9(4) cm-1 for 6; J1CrCu= 6.95(3) cm-1 and J2CrCu= 1.9(2)cm-1 for 7; JCrFe = 28.87(3) cm-1 for 8). Compound 5 exhibits the end of a transition from the high-spin to the low-spin state of the octahedral FeII ions. The bimetallic chain 3 behaves as a metamagnet with a critical field Hc = 300 G, which is associated with the occurrence of week antiferromagnetic interactions between the chains. Although the trimetallic chain 4 shows some degree of spin correlation along the chain, magnetic ordering does not occur. The sign and magnitude of the magnetic exchange interaction between CrIII and FeIII in compound 8 have been justified by DFT type calculations.     

Ferromagnetic coupling promoted by kappa3N:kappa2N bridging system

Syntheses, structures, and magnetic properties of novel trinuclear complexes of the same motif [M{Cu(pz2bg)2}M]4+ (M = CuII, NiII, CoII, MnII), catena-[Cu2{Cu(pz2bg)2}(Hpz)2(PhSO3)2](PhSO3)2.4H2O (2.4H2O), [Ni2{Cu(pz2bg)2}(MeOH)2(H2O)4](NO3)4 (3), [Co2{Cu(pz2bg)2}(NO3)2(EtOH)2](NO3)2 (4), and [Mn2{Cu(pz2bg)2}(NO3)4(MeCN)2] (5), which include the complex ligand [Cu(pz2bg)2] (1), are reported (Hpz = pyrazole, pz2bg- = di(pyrazolecarbimido)aminate; bispyrazolyl derivative of biguanidate). The reaction of Cu(ClO4)2.6H2O, sodium dicyanamide, Hpz, and PhSO3H.H2O (1:2:4:4) in MeOH yielded blue crystals of [Cu2(1)(Hpz)2(PhSO3)2](PhSO3)2.4H2O (2.4H2O). In 2, the tricopper(II) units, which consist of two Cu(II) ions bridged by 1, are linked by benzenesulfonate anions to form a ladder structure. Complex 1 was isolated by removing the terminal Cu(II) ions from 2 with use of Na(4)edta. Complexes 3-5 were obtained by the reaction of 1 with an excess of each M(II) ion. In 2-5, the adjoining metal ions are ferromagnetically coupled via the pz2bg- ligand with J values of +7.2(1), +7.5(1), +2.7(1), and +0.3(1) cm(-1), respectively, using a spin Hamiltonian H = -2J(S(M1)S(Cu) + S(Cu)S(M2)). The ferromagnetic interaction was attributed to the strict orthogonality of magnetic dsigma orbitals, which are controlled by the kappa3N:kappa2N bridging geometry of the pz2bg- ligands.     

Group 11 complexes with unsymmetrical P,S and P,Se disubstituted ferrocene ligands

The reaction of the unsymmetrical ligands 1-diphenylphosphino-1'-(phenylsulfanyl)ferrocene and 1-diphenylphosphino-1'-(phenylselenyl)ferrocene, Fc(EPh)PPh2(E = S, Se), with several group 11 metal derivatives leads to the synthesis of complexes of the type [MX{Fc(EPh)PPh2}](M = Au, X = Cl, C6F5; M = Ag, X = OTf), (OTf = trifluoromethanesulfonate), [M{Fc(EPh)PPh2}2]X (M = Au, X = ClO4; M = Ag, X = OTf), [M(PPh3){Fc(EPh)PPh2}]OTf (M = Au, Ag), [Au2{Fc(SPh)PPh2}2](ClO4)2, [Au(C6F5)2{Fc(SePh)PPh2}]ClO4, [Au(C6F5)3{Fc(EPh)PPh2}], [Au2(C6F5)6{Fc(SePh)PPh2}] or [Cu{Fc(EPh)PPh2}2]PF6(E = S, Se). In these complexes coordination depends upon the metal centre; with gold it takes place predominantly to the phosphorus atom and with silver and copper to both phosphorus and chalcogen atoms. The treatment of some of the gold complexes with other metal centres affords heterometallic derivatives that in some cases are in equilibrium with the homometallic derivatives. Several compounds have been characterized by X-ray diffraction, four pairs of homologous compounds, yet not a single pair is isotypic. In many of them a three dimensional network is formed through secondary bonds such as hydrogen bonds, Au...Cl or Au...Se interactions. The complex [Ag(OTf){Fc(SePh)PPh2}] forms one-dimensional chains through trifluoromethanesulfonate bridging ligands.     

Alkoxo-bridged copperII complexes as nodes in designing solid-state architectures. The interplay of coordinative and d10-d10 metal-metal interactions in sustaining supramolecular solid-state architectures

Four novel polymeric coordination networks have been obtained through self-assembly processes involving alkoxo-bridged copperII species as nodes, and anionic cyano-complexes as linkers: infinity2[{Cu2(pa)2}{M(CN)2}2](M=Ag, 1; Au, 2), (infinity)3[{Cu4(mea)4}{Au(CN)2}4.H2O]3, and (infinity)3[{Cu2(pa)2}{Ni(CN)4}](pa = deprotonated propanolamine; mea = deprotonated monoethanolamine). The supramolecular architectures of compounds 1, and 2 are sustained by argentophilic or strong aurophilic interactions. The solid-state architectures of 1 and 2, which are isomorphous, consist of infinite layers, constructed from binuclear alkoxo-bridged nodes and [M(CN)2]- spacers. The layers are stacked in an offset parallel mode, and are further interconnected through Ag...Ag or Au...Au contacts (1: Ag...Ag 3.015 A; 2: Au....Au 3.069 A). Compound 3 consists of unique fourfold interpenetrating diamondoid nets. The diamondoid topology is built of heterocubane {Cu4O4} nodes, which are connected by [Au(CN)2]- rods. The Cu-O distances within the {Cu4O4} node vary between 1.927(2) and 2.679(1) A, showing unsymmetric bridging of the copper atoms. Aurophilic interactions are established between the bridging and terminal [Au(CN)2]- metalloligands, and connect the interpenetrating nets, resulting in infinite chains of gold atoms (the Au...Au distances vary between 3.253 and 3.305 [Angstrom]). Compound 4 exhibits a 3-D network constructed from {Cu2(pa)2]2+ nodes connected by square-planar [Ni(CN)4]2- ions. Compounds 1, 2 and 4 are weakly paramagnetic. The cryomagnetic investigation of reveals a gradual increase, followed by a decrease of the chiMT product, as the temperature is lowered. A superposition of ferro- (J1=+20.8 cm(-1)) and antiferromagnetic (J2=-6.4) interactions within the tetranuclear node was found. Antiferromagnetic interactions are established between the tetranuclear nodes (theta=-2.99 K).     

Dinitrogen chemistry from trigonally coordinated iron and cobalt platforms

This report establishes that trigonally coordinated "[PhBPiPr3]M" platforms (M = Fe, Co) will support both pi-acidic (N2) and pi-basic (NR) ligands at a fourth binding site. The N2 complexes of iron that are described are the first thoroughly characterized examples to exhibit a 4-coordinate geometry. Methylation of monomeric {Fe0(N2)-} and {Co0(N2)-} species successfully derivatizes the beta-N atom of the coordinated N2 ligand and affords the diazenido products {FeII(N2Me)} and {CoII(N2Me)}, respectively. One-electron oxidation of the mononuclear M0(N2)- species produces dinuclear and synthetically versatile MI(N2)MI complexes. These latter species provide clean access to the chemistry of the "[PhBPiPr3]MI" subunit. For example, addition of RN3 to MI(N2)MI results in oxidative nitrene transfer to generate [PhBPiPr3]MNR with concomitant N2 release.     

Chelate complexes of some NNO tridentate Schiff bases with iron(II), cobalt(II), nickel(II) and copper(II)

Summary The Schiff bases a-(C₅H₄N)CMe=NNHCOR (R = Ph, 2-thienyl or Me), prepared by condensation of 2-acetylpyridine with the acylhydrazines RCONHNH₂, coordinate in the deprotonated iminol form to yield the octahedral complexes, M[NNO]₂ M = Co or Ni; [NNOH] = Schiff base and the square-planar complexes, Pd[NNO]Cl. The Schiff bases also coordinate in the neutral keto form yielding the octahedral complexes (M[NNOH]2)Z2 (M = Ni, Co or Fe; Z = C104, BF₄ or N03) and complexes of the type M[NNOH]X2 (M = Ni, Co, Fe or Cu; X = Cl, Br or NCS). Spectral and x-ray diffraction data indicate that the complexes M[NNOH]X2 (M = Ni or Fe) are polymeric octahedral, as are the corresponding cobalt complexes having R = 2-thienyl. However, the cobalt complexes Co[NNOH]X2 (X = CI or Br; R = Ph or Me) and the copper complexes Cu[NNOH]CI₂ (R = Ph, 2-thienyl or Me) are five-coordinate, while the thiocyanato complex Co[NNOH](NCS)₂ (R = 2-thienyl) is tetrahedral.     

Transient terminal Cu-nitrene intermediates from discrete dicopper nitrenes

Reaction of the copper(I) beta-diketiminate {[Me3NN]Cu}2(mu-toluene) with the aryl azide N3Ar (Ar = 3,5-Me2C6H3) in toluene results in immediate effervescence and formation of the dicopper nitrene {[Me3NN]Cu}2(mu-NAr) (2) in 77% yield. The X-ray structure of 2 shows nearly symmetric bonding of the nitrene to two Cu centers separated by 2.911(1) A with Cu-N distances of 1.794(5) and 1.808(5) A along with a Cu-N-Cu angle of 107.8(2) degrees . This structure is conceptually related to the dicopper carbenes {[MexNN]Cu}2(mu-CPh2) (x = 2 or 3) (Dai, X.; Warren J. Am. Chem. Soc. 2004, 126, 10085. Badiei, Y. M.; Warren J. Organomet. Chem. 2005, 690, 5989.) which exhibit shorter Cu-Cu distances (2.4635(7) or 2.485(1) A) and acute Cu-C-Cu angles (79.51(14) or 80.1(2) degrees ). Addition of the Cu(I) anilidoimine {[Me2AI]Cu}2 (prepared from CuOtBu and the aniline-imine H[Me2AI] in 77% yield) to a benzene-d6 solution of 2 results in the formation of two new anilidoimine complexes {[Me2AI]Cu(mu- NAr)Cu[Me3NN] (5) and {[Me2AI]Cu}2(mu-NAr) (6) as well as [Me3NN]Cu(benzene) over 3 h. These observations are consistent with the slow dissociation of a [Me3NN]Cu fragment from 2 to generate the transient terminal nitrenes [Me3NN]Cu=NAr and [Me2AI]Cu=NAr quickly trapped by the [Me2AI]Cu fragment to form the new unsymmetrical and symmetrical dicopper nitrenes 5 and 6. Preliminary reactivity studies indicate electrophilic reactivity at the nitrene moiety. Dicopper nitrene 2 reacts with 10 equiv PMe3 and CNtBu to give ArN=PMe3 and ArN=C=NtBu in 94% and 92% yields, respectively, with concomitant formation of [Me3NN]Cu(L) (L = PMe3 and CNtBu). Reaction between 2 and 2 equiv PMe3 allows for observation of the structurally characterized Cu(I) phosphaimide [Me3NN]Cu(ArN=PMe3) (7).     

Tetranuclear copper(II) complexes bridged by alpha-D-glucose-1-phosphate and incorporation of sugar acids through the Cu4 core structural changes

Tetranuclear copper(II) complexes containing alpha-D-glucose-1-phosphate (alpha-D-Glc-1P), [Cu4(mu-OH){mu-(alpha-D-Glc-1P)}2(bpy)4(H2O)2]X3 [X = NO3 (1a), Cl (1b), Br (1c)], and [Cu4(mu-OH){mu-(alpha-D-Glc-1P)}2(phen)4(H2O)2](NO3)3 (2) were prepared by reacting the copper(II) salt with Na2[alpha-D-Glc-1P] in the presence of diimine ancillary ligands, and the structure of 2 was characterized by X-ray crystallography to comprise four {Cu(phen)}2+ fragments connected by the two sugar phosphate dianions in 1,3-O,O' and 1,1-O mu4-bridging fashion as well as a mu-hydroxo anion. The crystal structure of 2 involves two chemically independent complex cations in which the C2 enantiomeric structure for the trapezoidal tetracopper(II) framework is switched according to the orientation of the alpha-D-glucopyranosyl moieties. Temperature-dependent magnetic susceptibility data of 1a indicated that antiferromagnetic spin coupling is operative between the two metal ions joined by the hydroxo bridge (J = -52 cm(-1)) while antiferromagnetic interaction through the Cu-O-Cu sugar phosphate bridges is weak (J = -13 cm(-1)). Complex 1a readily reacted with carboxylic acids to afford the tetranuclear copper(II) complexes, [Cu4{mu-(alpha-D-Glc-1P)}2(mu-CA)2(bpy)4](NO3)2 [CA = CH3COO (3), o-C6H4(COO)(COOH) (4)]. Reactions with m-phenylenediacetic acid [m-C6H4(CH2COOH)2] also gave the discrete tetracopper(II) cationic complex [Cu4{mu-(alpha-D-Glc-1P)}2(mu-m-C6H4(CH2COO)(CH2COOH))2(bpy)4](NO3)2 (5a) as well as the cluster polymer formulated as {[Cu4{mu-(alpha-D-Glc-1P)}2(mu-m-C6H4(CH2COO)2)(bpy)4](NO3)2}n (5b). The tetracopper structure of 1a is converted into a symmetrical rectangular core in complexes 3, 4, and 5b, where the hydroxo bridge is dissociated and, instead, two carboxylate anions bridge another pair of Cu(II) ions in a 1,1-O monodentate fashion. The similar reactions were applied to incorporate sugar acids onto the tetranuclear copper(II) centers. Reactions of 1a with delta-D-gluconolactone, D-glucuronic acid, or D-glucaric acid in dimethylformamide resulted in the formation of discrete tetracopper complexes with sugar acids, [Cu4{mu-(alpha-D-Glc-1P)}2(mu-SA)2(bpy)4](NO3)2 [SA = D-gluconate (6), D-glucuronate (7), D-glucarateH (8a)]. The structures of 6 and 7 were determined by X-ray crystallography to be almost identical with that of 3 with additional chelating coordination of the C-2 hydroxyl group of D-gluconate moieties (6) or the C-5 cyclic O atom of D-glucuronate units (7). Those with D-glucaric acid and D-lactobionic acid afforded chiral one-dimensional polymers, {[Cu4{mu-(alpha-D-Glc-1P)}2(mu-D-glucarate)(bpy)4](NO3)2}n (8b) and {[Cu4{mu-(alpha-D-Glc-1P)}2(mu-D-lactobionate)(bpy)4(H2O)2](NO3)3}n (9), respectively, in which the D-Glc-1P-bridged tetracopper(II) units are connected by sugar acid moieties through the C-1 and C-6 carboxylate O atoms in 8b and the C-1 carboxylate and C-6 alkoxy O atoms of the gluconate chain in 9. When complex 7 containing d-glucuronate moieties was heated in water, the mononuclear copper(II) complex with 2-dihydroxy malonate, [Cu(mu-O2CC(OH)2CO2)(bpy)] (10), and the dicopper(II) complex with oxalate, [Cu2(mu-C2O4)(bpy)2(H2O)2](NO3)2 (11), were obtained as a result of oxidative degradation of the carbohydrates through C-C bond cleavage reactions.     

Synthesis and coordination chemistry of an alkyne functionalised bis(pyrazolyl)methane ligand

The alkyne functionalised bidentate N-donor ligand (2-propargyloxyphenyl)bis(pyrazolyl)methane was prepared in high yield from the reaction of (2-hydroxyphenyl)bis(pyrazolyl)methane with propargyl bromide in the presence of base. A series of transition-metal complexes including [MCl2] (M=Cu, Co, Ni, Zn, Pt), [M2](NO3)2 (M=Cu, Co, Ni, Zn), [Ag]NO3 and [Pd(dppe)](OTf)2 were prepared and characterised by spectroscopic techniques. In addition, ligand as well as the Co(II) and Zn(II) complexes [CoCl2]2, [ZnCl2] were structurally characterized by single-crystal X-ray diffraction. The organometallic gold(I) and platinum(II) acetylide complexes [Pz2CH(C6H(4)-2-OCH2C[triple bond, length as m-dash]CAuPPh3)] and trans-[{Pz2CHC6H(4)-2-OCH2C[triple bond, length as m-dash]C}2Pt(PPh3)2] were prepared from and [AuCl(PPh3)] and trans-[PtCl2(PPh3)2], respectively. Treatment of these complexes with [Pd(OTf)2(dppe)] or [Cu(MeCN)4]PF6 results in formation of the cationic, mixed-metal complexes, which were isolated (Pt/Pd, Au/Pt) or detected by electrospray mass spectrometry (Au/Cu, Pt/Cu).     

Linking two distinct layered networks of nanosized {Ln18} and {Cu24} wheels through isonicotinate ligands

A new series of heterolanthanide(III)-copper(I) wheel-cluster complexes [Ln6(micro3-O)2](IN)18-[Cu8(micro4-I)2(micro2-I)3].H3O (IN=isonicotinate; Ln=Y 1, Nd 2, Dy 3, Gd 4, Sm 5, Eu 6, Tb 7) were prepared by hydrothermal reaction at low pH. X-ray crystallographic studies reveal that two unusual trinuclear [Ln3(micro3-O)] and tetranuclear [Cu4(micro4-I)] cores are successfully used as secondary building units to make two different nanosized wheels [Ln18(micro3-O)6(CO2)48](6-), {Ln18}, and [Cu24(micro4-I)6(micro2-I)12]6+, {Cu24}, with 12-rings and a diameter of 26.7 and 26.4 A, respectively. The wheels are further assembled into two-dimensional (2D) {Ln18} and {Cu24} networks, the linkages between two distinct layered networks of {Ln18} and {Cu24} wheels by IN pillars along the c axis giving a series of unprecedented three-dimensional (3D) sandwich frameworks. To our knowledge, compounds 1-7 are the first examples containing two different layered networks of nanosized Ln and transition metal (TM) wheels in wheel-cluster chemistry. The IR, UV/Vis, thermogravimetric analysis (TGA), luminescent, and magnetic properties of these complexes were also studied.     

Copper-complex-linked polytungsto-bismuthate (-antimonite) chain containing sandwich Cu(II) ions partially modified with imidazole ligand

Two sandwich-type complexes Na9n(Cu(im)4(H2O)2)1.5n(Cu(im)4(H2O))n[{Cu(im)4}{Na(H2O)2}3{Cu3(im)2(H2O)}(XW9O33)2]2n .(xH2O)n (im=imidazole, X=Bi (1), Sb(2), x=42.5 (1), 40 (2)) have been synthesized and structurally characterized. Basic frameworks of 1 and 2 are built from sandwich-type [{Na(H2O) 2} 3{Cu3(im)2(H2O)}(XW9O33)2](9-) (X=Bi or Sb) anions and [Cu(im) 4](2+) cations. The Cu(2+) and Na(+) ions in the central belt are coordinated by alpha-[XW9O33](9-) units, im, and water molecules to form {CuO4(im)}, {CuO4(H2O)}, and {NaO4(H2O)2} groups in which Cu (2+) ions are partially modified with im ligands. These groups connect alternately forming a six-membered ring including six alpha-[XW9O 33](9-) units. Neighboring anions are further linked by [Cu(im) 4](2+) cations to display an unprecedented anionic chain, which is first observed in sandwich-type tungsto-bismuthate (-antimonite) system. Two kinds of isolated copper complexes and sodium ions are located as counterions, which cause three-dimensional packings of 1 and 2 to present interesting cage structures. The magnetic properties for 1 and 2 both indicate dominant antiferromagnetic interactions among trinuclear Cu(II) clusters.     

Stereoselectivity in the formation of tris-diimine complexes of Fe(II), Ru(II), and Os(II) with a C2-symmetric chiral derivative of 2,2'-bipyridine

A C2-symmetric enantiopure 4,5-bis(pinene)-2,2'-bipyridine ligand (-)-L was used to investigate the diastereoselectivity in the formation of [ML3]2+ coordination species (M = Fe(II), Ru(II), Os(II), Zn(II), Cd(II), Cu(II), Ni(II)), and [ML2Cl2] (M = Ru(II), Os(II)). The X-ray structures of the [ML3]2+ complexes were determined for Delta-[FeL3](PF6)2, Delta-[RuL3](PF6)2, Lambda-[RuL3](PF6)2, Delta-[OsL3](PF6)2, and Lambda-[OsL3](TfO)2. All of these compounds were also characterized by NMR, CD and UV/VIS absorption spectroscopy. The [FeL3]2+ diastereoisomers were studied in equilibrated solutions at various temperatures and in several solvents. The [RuL3]2+ complexes, which are thermally stable up to 200 degrees C, were photochemically equilibrated.     

Dinuclear nickel and palladium complexes with bridging 2,5-diamino-1,4-benzoquinonediimines: synthesis, structures, and catalytic oligomerization of ethylene

Dinuclear, divalent acetylacetonato (acac) complexes of the type [M(acac){mu-C6H2(--NR)4}M(acac)] (M = Ni, Pd) have been prepared by the reaction of the corresponding bis(acac) metal precursor with 2,5-diamino-1,4-benzoquinonediimines C6H2(NHR)2(=NR)2 (4a, R = CH2-t-Bu; 4b, R = CH2Ph; 4c, R = Ph), which are metalated and become bridging ligands, also like in the complex [(C8H11)Pt{mu-C6H2(--NCH2-t-Bu)4}Pt(C8H11)] (6) obtained by the reaction of 4a with [PtCl2(COD)]. The complexes were fully characterized, including by X-ray diffraction for [Ni(acac){mu-C6H2(--NCH2Ph)4}Ni(acac)] (9b) and [Pd(acac){mu-C6H2(--NCH2-t-Bu)4}Pd(acac)] (10a). The coordination geometry around the metal ions is square-planar, and a complete electronic delocalization of the quinonoid pi system occurs between the metal centers over the two N--C--C--C--N halves of the ligand. The nature of the N substituent explains the differences between the supramolecular stacking arrangements found for [Ni(acac){mu-C6H2(--NR)4}Ni(acac)] (9a; R = CH2-t-Bu; 9b, R = CH2Ph). The Ni complexes were evaluated as catalyst precursors for ethylene oligomerization in the presence of AlEtCl(2) or MAO as the cocatalyst, in particular in order to study possible cooperative effects resulting from electronic communication between the metal centers and to examine the influence of the N substituent on the activity and selectivity. These catalysts afforded mostly ethylene dimers and trimers.     

Synthesis, characterisation and speciation studies of heterobimetallic pyridinehydroxamate-bridged Pt(II)/M(II) complexes (M = Cu, Ni, Zn). Crystal structure of a novel heterobimetallic 3-pyridinehydroxamate-bridged Pt(II)/Cu(II) wave-like coordination polymer

The reaction of cis-[Pt(NH3)2(3-pyhaH)2]2+ (3-pyhaH = 3-pyridinehydroxamic acid) and cis-[Pt(NH3)2(4-pyhaH)2]2+ (4-pyhaH = 4-pyridinehydroxamic acid) with Cu(II), Ni(II) or Zn(II) in aqueous solution affords novel heterobimetallic pyridinehydroxamate-bridged complexes, {cis-[Pt(NH3)2(mu-3-pyha)M(mu-3-pyha)].SO4.xH2O}n and {cis-[Pt(NH3)2(mu-4-pyha)M(mu-4-pyha)].SO4.xH2O}n respectively. The crystal and molecular structure of one of these, {cis-[Pt(NH3)2(mu-3-pyha)Cu(mu-3-pyha)]SO4.8H2O}n 3a, has been determined and was found to be a novel heterobimetallic wave-like coordination polymer, the structure of which contains interlinked pyridinehydroxamate-bridged repeating units of Pt(II) and Cu(II) ions in slightly distorted square-planar N4 and O4 coordination environments respectively and extensive hydrogen-bonding through the Pt ammines and the deprotonated hydroxamate O and via the O of the SO4(2-) counterions and the H(N) of the hydroxamate moiety. Spectrophotometric and speciation studies on the other heterobimetallic systems confirm that very similar species are being formed in solution and based on elemental analysis and spectroscopic results analogous complexes are formed in the solid-state. In this paper, we report the first examples of coordination polymers incorporating both Pt(II)/Cu(II), Pt(II)/Ni(II) and Pt(II)/Zn(II) and containing pyridinehydroxamic acids as bridging scaffolds.     

Influence of the terminal ligands on the redox properties of the {Pt2(mu-S)2} core in [Pt2(Ph2X(CH2)2XPh2)2(mu-S)2] (X = P or As) complexes and on their reactivity towards metal centres, protic acids and organic electrophiles

In order to explore possible ways for modulating the unusually rich chemistry shown by complexes of formula [L2Pt(mu-S)2PtL2] we have studied the influence of the nature of the terminal ligand L on the chemical properties of the {Pt2(mu-S)2} core. The systematic study we now report allows comparison of the behaviour of [Pt2(dpae)2(mu-S)2](dpae = Ph2As(CH2)2AsPh2) (1) with the already reported analogue [Pt2(dppe)2(mu-S)2](dppe = Ph2P(CH2)2PPh2). Complex 1 as well as the corresponding multimetallic derivatives [Pt(dpae){Pt2(dpae)2(mu-S)2}](BPh4)2 2, [M{Pt2(dpae)2(mu-S)2}2]X2 (M = Cu(II), X = BF4 3; M = Zn(II), X = BPh4 4; M = Cd(II), X = ClO4 5; M = Hg(II), X = Cl 6 or X2 = Cl(1.5)[HCl2](0.5) 6') have been characterized in the solid phase and in solution. Comparison of structural parameters of 1 and 3-6' with those of the corresponding phosphine analogues, together with the results of the electrochemical study for 1, allow us to conclude that replacement of dppe by dpae causes a decrease in basicity of the {Pt2(mu-S)2} core. The study of the reactivity of 1 towards CH2Cl2 and protic acids has led to the structural characterization of [Pt(dpae)(S2CH2)] 9 and [PtCl2(dpae)] 10. Moreover, comparison with the reactivity of [Pt2(dppe)2(mu-S)2] indicates that the stability of the intermediate species as well as the nature of the final products in both multistep reactions are sensitive to the nature of the terminal ligand.