X-ray Structures Of 3a Research Articles

Metal complexes of ‘Heena’ (2-hydroxy-1,4-naphthoquinone): Synthesis, Characterization and anticancer activity

The Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of Henna; 2-hydroxy-1,4-naphthoquinone (Lw) are synthesized at 0 °C (Mn2+; 1, Co2+; 2, Ni2+; 3, Cu2+; 4 and Zn2+; 5), 26 °C (Mn2+; 1A, Co2+; 2A, Ni2+; 3A, Cu2+; 4A and Zn2+; 5A) and characterized. The compositions of all complexes are of the type [M(Lw)2(H2O)2]. The geometry of the complexes synthesized at 26 °C is trans, whereas cis for complex 4 at 0 °C. The pyridine adduct (4Apy) of copper complexes 4A and methanol (4MeOH) adduct of complex 4 is characterized by single crystal X-ray diffraction studies. The molecular interactions are revealed from the X-ray structures of 2A, 5A, 4Apy, and 4MeOH. Anticancer activity of all complexes was evaluated against two cancer cell lines, MCF-7 (breast cancer cell line) and A-549 (lung cancer cell line). The complexes synthesized at 0 °C show enhanced activity against the A549 cell line. Cell cycle analysis, effect on mitochondrial potential, estimation of Reactive Oxygen Species (ROS), effect on peripheral blood mononuclear cells (PBMCs), Tunnel assay, etc., experiments were performed on complex 1A.

Triazene as the Directing Group Achieving Highly Ortho-Selective Diborylation and Sequential Functionalization.

This study describes a regioselective ortho,ortho'-diborylation of aromatic triazenes catalyzed by [Ir(OMe)(cod)]2 in near-quantitative yields without an additional ligand. Aromatic triazenes act as both substrates and ligands. The X-ray structures of 2a and 2p indicate that the monoborylation products could promote the occurrence of diborylation. The synthesized triazene-substituted diboronate esters could undergo a variety of transformations including directing group removal. One-pot sequential modification provides a short entry to densely functionalized arenes.

Square-planar aminonitronate transition metal complexes (M = CuII, NiII, PdII, and PtII)

Treatment of the aromatic aminonitrones p-RC6H4C(NH2)N+(Me)O− (R=NMe2, Cl) with CuCl2·2H2O, NiCl2·2H2O, β-PdCl2, or cis-[PtCl2(Me2SO)2] in the presence of a base leads to the [M{p-RC6H4C(NH)N+(Me)O−}2] (M=Cu,Ni,Pd) (72–95%) or [Pt{p-RC6H4C(NH)N+(Me)O–}Cl(Me2SO)] (ca. 80%) complexes, respectively. These compounds were characterized by elemental analyses (C, H, N), HRESI+-MS, FTIR, 1H and 13C{1H} NMR, and for the CuII and NiII complexes EPR and magnetic susceptibility. In addition, eight species were studied by single-crystal X-ray diffraction. In the X-ray structures of 2a–d, the hydrogen bonds are responsible for the formation of 1D polymeric chains. These bonds were evaluated by DFT calculations (M06/DZP-DKH level of theory) and topological analysis of the electron density distribution within the formalism of Bader’s theory (QTAIM method). Estimated strengths of these non-covalent interactions are 2.7–4.4kcal/mol.

Synthesis, characterization and thermal studies of 1,3-bis(4-pyridyl)propane bridged dicobaloximes

Twelve different 1,3 bis(4-pyridyl)propane (dpyp)-bridged dicobaloximes of the type [RCo(dmgH)2]2-μ-1,3-bis(4-pyridyl)propane where R = Me – octyl (1a–8a), decyl (9a), dodecyl (10a), tetradecyl (11a), 1-chlorohexyl (12a) have been synthesized from their corresponding aqua complexes. All the synthesized cobaloximes have been characterized by 1H, and 13C Nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, UV–visible (UV–Vis) and FT-IR spectroscopy. The X-ray structures of 2a and 8a are reported. Thermal stability of these complexes has been studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Differential scanning calorimetry (DSC) study reveals that there is a mesophase in these ligand-bridged dicobaloximes with higher alkyl chains. These dpyp-bridged complexes are significant due to the flexible spacer of dpyp in between two cobaltmetallobicycles which influence extensive intermolecular CH⋯O interactions in the crystal packing diagram of the structures 2a and 8a. The mesophase formation for these complexes strongly depends on the length of the alkyl chain (axial R group).

Bis-cyclometalated complexes of Pd(II) and Pd(IV) from iminophosphoranes: Synthesis, structure and reactivity

The mononuclear bis-orthopalladated complexes [Pd(CˆN){C6H4(PPh2NPh)-2}] [CˆN = (2-(pyridin-2-yl)phenyl) 3a, (2-((dimethylamino)methyl)phenyl) 3b, (S)-(2-(1-(dimethylamino)ethyl)phenyl) 3c, (quinolin-8-ylmethyl) 3d, (4-methoxy-2-((triphenyl-λ5-phosphanylidene)carbamoyl)phenyl) 3e] have been synthesized as single isomers by reaction of the corresponding chloride dimers [Pd(μ-Cl)(CˆN)]2 (1a–1e) with the lithium derivative [Li{C6H4(PPh2NPh)-2}] (2) in Et2O. Spectroscopic data show that the two palladated C atoms are in cis disposition, which is confirmed by the X-ray structure of 3a. Oxidation of 3a with PhI(OAc)2 affords the corresponding Pd(IV) derivative (OC-6-32)[Pd(OAc)2{C6H4(PPh2NPh)-2}{C6H4-(2′-NC5H4)-2}] 4a also as a single isomer. 4a undergoes reductive elimination through C–O coupling to give the dimer [Pd(μ-OAc){C6H4(PPh2NPh)-2}]25 and the ortho-acetoxylated phenylpyridine 6. The reactivity of 3b–3e towards oxidants is also discussed.

Reactions of molybdenum pentachloride with oxygen and nitrogen donor ligands

The interactions of molybdenum pentachloride (1) with a variety of organic compounds were studied in dichloromethane and the metal products were isolated in the solid state. The 3:1molar reactions of 1 with OCRR′ (R=R′=Ph; R=H, R′=2-C6H4Me) afforded the complexes Mo(O)Cl3(OCRR′)2 (R=R′=Ph, 2a; R=H, R′=2-C6H4Me, 2b) in high yields. Compound ▪, 3, was isolated in 35% yield from 1 and 2-acetylfuran. The 1:1 reaction of 1 with phenazine (C12H8N2) 1 resulted in the formation of MoCl5(C12H8N2), 4; the oxydo-chloride derivative Mo(O)Cl3[κ1(N)-C12H8N2], 5, was prepared straightforwardly by addition of phenazine to Mo(O)Cl3, formed in situ upon treatment of 1 with tetrahydrofuran. The addition of a twofold excess of Me2NCH2CH2CO2Me to 1 afforded MoCl4[κ1(N)-Me2NCH2CH2CO2Me]2, 6, in 72% yield. The reaction of 1 with MeO2CCCCO2Me led to a mixture of inseparable products: MoOCl3(κ1-MeO2CCCCO2Me)2, 7a, MoCl5(κ1-MeO2CCCCO2Me), 7b, and MoCl4(κ1-MeO2CCCCO2Me)2, 7c, were recognized by combined EPR/DFT investigation. Analogous DFT/EPR studies were performed on 2b and 4. The X-ray structures of 2a, 3 and 5 were determined; the X-ray structure of 5 represents a rare example of crystallographically-characterized pentacoordinated Mo(V) neutral complex.

Zirconium and hafnium complexes containing N-alkyl substituted amine biphenolate ligands: coordination chemistry and living ring-opening polymerization catalysis

The coordination chemistry of zirconium and hafnium complexes containing the tridentate amine biphenolate ligands [RN(CH2-2-O-3,5-C6H2(tBu)2)2](2-) ([R-ONO](2-); R = tBu (1a), iPr (1b), nPr (1c)) featuring distinct N-alkyl substituents is described. Alcoholysis of Zr(OiPr)4(HOiPr) or Hf(OiPr)4(HOiPr) with H2[1a] in diethyl ether solutions at -35 °C generates the corresponding five-coordinate [1a]M(OiPr)2 (M = Zr (2a), Hf (3a)) in high isolated yield. Similar reactions employing H2[1b] produce six-coordinate [1b]M(OiPr)2(HOiPr) (M = Zr (2b·HOiPr), Hf (3b·HOiPr)) as an isopropanol adduct. Repetitive trituration of 2b·HOiPr and 3b·HOiPr with diethyl ether gives five-coordinate 2b and 3b, respectively. Treatment of M(OiPr)4(HOiPr) with H2[1c] under similar conditions affords six-coordinate [1c]M(OiPr)2(HOiPr) (M = Zr (2c·HOiPr), Hf (3c·HOiPr)), subsequent recrystallization of which from acetonitrile-diethyl ether solutions leads to acetonitrile adducts 2c·MeCN and 3c·MeCN. Reactivity studies of these zirconium and hafnium complexes revealed that they are all active catalysts for ring-opening polymerization of ε-caprolactone. Among them, the N-isopropyl derived complexes are most reactive. Polymerizations catalyzed by 2b, 3b and 3c·MeCN were proved to be living. The X-ray structures of 2a·HOiPr, 2a·MeCN, 2c·HOiPr, 2c·MeCN, and 3c·MeCN are presented.

Reactivity of the bridged-sulfide complex Pd2Cl2(μ-S)(μ-dmpm)2toward electrophiles

The dipalladium(I) complex Pd(2)Cl(2)(dmpm)(2) (1a) [dmpm = bis(dimethylphosphino)methane] is known to react with elemental sulfur (S(8)) to give the bridged-sulfide complex Pd(2)Cl(2)(μ-S)(dmpm)(2) (2a) but, in the presence of excess S(8), PdCl(2)[P,S-dmpm(S)] (4a) and dmpm(S)(2) are generated. Treatment of 1a with elemental selenium (Se(8)), however, gives only Pd(2)Cl(2)(μ-Se)(dmpm)(2) (3a). Complex 4a is best made by reaction of trans-PdCl(2)(PhCN)(2) with dmpm(S). Complex 2a reacts with MeI to yield initially Pd(2)I(2)(μ-S)(dmpm)(2) and MeCl, and then Pd(2)I(2)(μ-I)(2)(dmpm)(2) and Me(2)S, whereas alkylation of 2a with MeOTf generates the cationic, bridged-methanethiolato complex [Pd(2)Cl(2)(μ-SMe)(dmpm)(2)]OTf (5). Oxidation of 2a with m-CPBA forms a mixture of Pd(2)Cl(2)(μ-SO)(dmpm)(2) and Pd(2)Cl(2)(μ-SO(2))(dmpm)(2), whereas Pd(2)Br(2)(μ-S)(dmpm)(2) reacts selectively to give Pd(2)Br(2)(μ-SO)(dmpm)(2) (6b). Treatment of the Pd(2)X(2)(μ-S)(dmpm)(2) complexes with X(2) (X = halogen) removes the bridged-sulfide as S(8), with co-production of Pd(II)(dmpm)-halide species. X-ray structures of 3a, 5 and 6b are presented. Reactions of dmpm with S(8) and Se(8) are clarified. Differences in the chemistry of the dmpm systems with that of the corresponding dppm systems [dppm = bis(diphenylphosphino)methane] are discussed.

Metal(II) template assisted syntheses of two P―C―O―P chelating ligands incorporating a bulky 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phosphaadamantyl cage

Abstract Facile condensation of one equiv. of the caged hydroxymethylphosphine Ad`PCH2OH (Ad` = C10H16O3) with ClPR2 (R = Ph, iPr), in the presence of one equiv. of MCl2(cod) (M = Pt, Pd; cod = cycloocta-1,5-diene), afforded the five-membered chelate complexes cis-MCl2(Ad`PCH2OPR2) (1a, M = Pt, R = Ph; 1b, M = Pd, R = Ph; 2a, M = Pt, R = iPr) in reasonable to excellent yields. The X-ray structures of 1a and 2a have been determined, the latter using diffraction data collected at a synchrotron source. The M―P―C―O―P metallacycle remains intact even after stirring in CD3OD for 24 h at room temperature.

Synthesis and Reactivity of Coordinatively Unsaturated Dinuclear Ruthenium Bridging Imido Complexes

[Cp*Ru(μ-NHPh)]2 (Cp* = η5-C5Me5) reacted with CO, t-BuNC, Ph2S═CH2, or Me3SiC≡CH to give the dinuclear ruthenium bridging imido complexes [(Cp*Ru)2(μ-NPh)(μ-L)] (2a, L = CO; 2b, L = t-BuNC; 2c, L = CH2; 2d, L = CCHSiMe3). Protonolysis of 2d with t-BuOH produced the parent vinylidene complex [(Cp*Ru)2(μ-NPh)(μ-CCH2)] (2e). Treatment of 2e with HOTf or MeOTf afforded the cationic alkylidyne complexes [(Cp*Ru)2(μ-NPh)(μ-CR)]OTf (2f, R = Me; 2g, R = Et). Hydride abstraction from 2c with Ph3CBF4 gave the methylidyne complex [(Cp*Ru)2(μ-NPh)(μ-CH)]BF4 (2h). X-ray structures of 2a−c and 2f revealed short Ru−N distances (1.876−1.894 Å) consistent with Ru−N multiple bonds, and the μ-alkylidyne 2f also featured short Ru−C bonds (1.929(7) and 1.914(7) Å). In addition to giving simple Lewis base adducts such as [(Cp*Ru)2(μ-NPh)(μ-CO)(PMe3)] and [(Cp*Ru)2(μ-NPh)(μ-CH2)(t-BuNC)2], these imido complexes provided an array of novel ligand coupling reactions. Thus, 2b underwent a tandem imido−isocyanide coupling and C−H activation reaction to give an amidinate complex. Complexes 2c and 2e mediated imido−CO−methylene and imido−CO−vinylidene coupling to give [{Cp*Ru(CO)2}2(μ-PhNCOCH2)] (6) and [{Cp*Ru(CO)}2(μ-PhNCOC═CH2)] (7), respectively. Complex 2c also underwent a selective coupling reaction with 2 equiv of Me3SiC≡CH to give the μ-allenylimine complex [(Cp*Ru)2{μ-Me3SiCH═C═C(SiMe3)C(Me)═NPh}] (8). The imido methylidyne complex coupled with 2 equiv of alkynes to give [(Cp*Ru)2{μ-HC(R1CCR2)(R2CCR1)NPh}]OTf (9a−c), a product of double alkyne cycloaddition to the Ru−N and Ru−C multiple bonds and C−C coupling of the resulting ruthena- and azaruthenacyclobutene moieties.

Sulfur Donor Atom Effects on Copper(I)/O2 Chemistry with Thioanisole Containing Tetradentate N3S Ligand Leading to μ-1,2-Peroxo-Dicopper(II) Species

To better understand the effect of thioether coordination in copper-O(2) chemistry, the tetradentate N(3)S ligand L(ASM) (2-(methylthio)-N,N-bis((pyridin-2-yl)methyl)benzenamine) and related alkylether ligand L(EOE) (2-ethoxy-N,N-bis((pyridin-2-yl)methyl)ethanamine) have been studied. The corresponding copper(I) complexes, [(L(ASM))Cu(I)](+) (1a) and [(L(EOE))Cu(I)](+) (3a), were studied as were the related compound [(L(ESE))Cu(I)](+) (2a, L(ESE) = (2-ethylthio-N,N-bis((pyridin-2-yl)methyl)ethanamine). The X-ray structure of 1a and its solution conductivity reveal a monomeric molecular structure possessing thioether coordination which persists in solution. In contrast, the C-O stretching frequencies of the derivative Cu(I)-CO complexes reveal that for these complexes, the modulated ligand arms, whether arylthioether, alkylthioether, or ether, are not coordinated to the cuprous ion. Electrochemical data for 1a and 2a in CH(3)CN and N,N-dimethylformamide (DMF) show the thioanisole moiety to be a poor electron donor compared to alkylthioether (1a is ∼200 mV more positive than 2a). The structures of [(L(ASM))Cu(II)(CH(3)OH)](2+) (1c) and [(L(ESE))Cu(II)(CH(3)OH)](2+) (2c) have also been obtained and indicate nearly identical copper coordination environments. Oxygenation of 1a at reduced temperature gives a characteristic deep blue intermediate [{(L(ASM))Cu(II)}(2)(O(2)(2-))](2+) (1b(P)) with absorption features at 442 (1,500 M(-1) cm(-1)), 530 (8,600 M(-1) cm(-1)), and 605 nm (10,400 M(-1) cm(-1)); these values compare well to the ligand-to-metal charge-transfer (LMCT) transitions previously reported for [{(L(ESE))Cu(II)}(2)(O(2)(2-))](2+) (2b(P)). Resonance Raman data for [{(L(ASM))Cu(II)}(2)(O(2)(2-))](2+) (1b(P)) support the formation of μ-1,2-peroxo species ν(O-O) = 828 cm(-1)(Δ((18)O(2)) = 48), ν(sym)(Cu-O) = 547 cm(-1) (Δ((18)O(2)) = 23), and ν(asym)(Cu-O) = 497 cm(-1) (Δ((18)O(2)) = 22) and suggest the L(ASM) ligand is a poorer electron donor to copper than is L(ESE). In contrast, the oxygenation of [(L(EOE))Cu(I)](+) (3a), possessing an ether donor as an analogue of the thioether in L(ESE), led to the formation of a bis(μ-oxo) species [{(L(EOE))Cu(III)}(2)(O(2-))(2)](2+) (3b(O); 380 nm, ε ∼ 10,000 M(-1) cm(-1)). This result provides further support for the sulfur influence in 1b(P) and 2b(P), in particular coordination of the sulfur to the Cu. Thermal decomposition of 1b(P) is accompanied by ligand sulfoxidation. The structure of [{(L(EOE))Cu(II)(Cl)}(2)](+) (3c) generated from the reductive dehalogenation of organic chlorides suggests that the ether moiety is weakly bound to the cupric ion. A detailed discussion of the spectroscopic and structural characteristics of 1b(P), 2b(P), and 3b(O) is presented.

Synthesis, X-ray structures, electrochemical properties and cytotoxic effects of Co(II) complexes

1-Benzothiazol-2-yl-3,5-dimethyl-1 H-pyrazole ( 1a) and 1-benzothiazol-2-yl-5-(2-hydroxyphenyl)-3-methyl-1 H-pyrazole-4-carboxylic acid methyl ester ( 1b) were reacted with the hexahydrates of cobalt(II) chloride, cobalt(II) nitrate and cobalt(II) perchlorate to give the corresponding complexes 2a– 4a and 2b– 5b, respectively. Obtained compounds differ in coordination spheres of central atoms. The complex 2a includes a fivefold coordinated cobalt(II) ion, whereas 3a shows a distorted octahedral configuration around the cobalt(II) ion. All complexes were characterised by FTIR spectroscopy, MS and elemental analysis. The X-ray structures of 2a, 3a and 5b complexes were also solved. The cytotoxic properties of the ligand 1a and both series of Co(II) complexes were examined on human leukemia NALM-6 and HL-60 cells and melanoma WM-115 cells. The ligands, were found to have very low cytotoxicity. Complex 3b exhibited the highest cytotoxic activity with IC 50 values in the range of 6.9–17.1 μM for three examined cell lines.

Syntheses and structures of new alkali-metal boraamidinates and ferrocenyl aminoboranes

The ferrocenyl bis(amino)boranes FcB[N(H)R]2 (Fc = ferrocenyl; 1a, R = tBu, 1b, R = Dipp) and 1,1′-Fc{B[N(H)tBu]2}2 (2) are obtained by the reactions of [Li][N(H)R] with the corresponding ferrocenyl dibromoboranes FcBBr2 and 1,1′-Fc(BBr2)2. In a similar manner 1,4-[N(H)tBu]2BC6H4B[N(H)tBu]2 (3) is prepared in good yield by treatment of 1,4-Br2BC6H4BBr2 with five equivalents of [Li][N(H)tBu] in toluene. Compound 3 is converted to the highly air-sensitive tetralithio derivative [Li4][1,4-(NtBu)2BC6H4B(NtBu)2] (4), by deprotonation with nBuLi in hexanes. Alkali-metal derivatives of a monoanionic boraamidinate [M][PhB(NDipp){N(H)Dipp}] [M = Li (5), K (6)] are produced by reactions of PhB[N(H)Dipp]2 with one equivalent of nBuLi in hexanes or [K][CH2Ph] in THF, respectively. The use of two equivalents of [K][CH2Ph] generates the dipotassium reagent [K2][PhB(NDipp)2] (7) in excellent yield. The X-ray structures of 1a, 1b, 2, 4·6THF, 5·2THF and 7·3THF were determined. The complex 4·6THF incorporates one terminal and one bridging THF molecule for each Li+ cation. The boraamidinate ligand in 5·2THF is connected in an N-monodentate fashion to the Li+ cation, which is solvated by two THF molecules. In the solid state 7·3THF forms an extended structure as a result of η1-amide–η6-arene coordination to the two K+ cations, which are coordinated by one or two THF molecules, respectively.

Syntheses and structures of [Me 2Si{As(P tBu) 3} 2] and [(CyP) 3SiMe 2] (Cy = cyclohexyl, C 6H 11)

The reaction of the anion [( t BuP) 3As] − ( 1) with Me 2SiCl 2 results in nucleophilic substitution of the Cl − anions, giving the di- and mono-substituted products [Me 2Si{As(P t Bu) 3} 2] ( 3a) and [Me 2Si(Cl){As(P t Bu) 3}] ( 3b). Analogous reactions of the pre-isolated [(CyP) 4As] − anion ( 2) (Cy = cyclohexyl) with Me 2SiCl 2 produced mixtures of products, from which no pure materials could be isolated. However, reaction of 2 [generated in situ from CyPHLi and As(NMe 2) 3] gives the heterocycle [(CyP) 3SiMe 2] ( 4). The X-ray structures of 3a and 4 are reported.

Synthesis, structure and spectroelectrochemical property of (2,2′-bipyridine)–metal (M = Pt, Pd) dichloride with 4,4′-bis(fluorous-ponytail) on bipyridine

The 4,4′-bis(R fCH 2OCH 2)-2,2′-bpy ligands [R f = n-C 3F 7 ( 1a), HCF 2(CF 2) 3 ( 1b)] were prepared and then treated with [MCl 2(CH 3CN) 2] (M = Pt or Pd) to result in the corresponding metal complexes, [MCl 2(4,4′-bis(R fCH 2OCH 2)-2,2′-bpy)] (M = Pt 2a–b; Pd 3a–b). Both ligands and metal complexes were fully characterized by multi-nuclei NMR ( 1H, 19F and 13C), FTIR, and mass (GC/MS or HR-FAB) methods. The X-ray structures of 2a–b and 3a–b were studied. With terminal CF 3, the structures of 2a and 3a exhibit disordered polyfluorinated regions in solid state. With terminal HCF 2, the structures of 2b and 3b show a π–π stacking of the bpy planes, five-membered C–H···O hydrogen bond and an unusual intramolecular blue-shifting C–H···F–C hydrogen bond system, whereas without terminal HCF 2, the structures of 2a and 3a show the similar π–π stacking, five-membered C–H···O hydrogen bond and typical orientation of polyfluorinated ponytails, but not the C–H···F–C hydrogen bond system. The CV and UV/Vis studies were also carried out.

Nitric Oxide Oxidatively Nitrosylates Ni(I) and Cu(I) C-Organonitroso Adducts

Monovalent nickel and copper beta-diketiminato complexes react with ArN=O (Ar = 3,5-Me(2)C(6)H(3), Ph) to give C-nitroso adducts that exhibit three different modes of bonding with varying degrees of N-O bond activation. The addition of ArNO to 2 equiv of [Me(2)NN]Ni(2,4-lutidine) {[Me(2)NN](-) = 2,4-bis(2,6-dimethylphenylimido)pentyl} gives {[Me(2)NN]Ni}(2)(mu-eta(2):eta(2)-ONAr) (1a and 1b), which exhibit symmetrical bonding of the ArN=O moiety between two [Me(2)NN]Ni fragments, with a N-O bond distance of 1.440(4) A in 1a that is significantly longer than those in free C-organonitroso compounds (1.13-1.29 A). [Me(2)NN]Cu(NCMe) reacts with 0.5 equiv of ArNO in ether to give the dinuclear adducts {[Me(2)NN]Cu}(2)(mu-eta(2):eta(1)-ONAr) (2a and 2b), which exhibit eta(2) and eta(1) bonding of the ArN=O moiety with separate [Me(2)NN]Cu fragments possessing N-O distances of 1.375(6) A (2a) and 1.368(2) A (2b). In arene solvents, one beta-diketiminatocopper(I) fragment dissociates from 2 to give [Me(2)NN]Cu(eta(2)-ONAr) (3a and 3b), which may be isolated by the addition of 1 equiv of ArNO to [Me(2)NN]Cu(NCMe). The X-ray structures of 3a and 3b are similar to those of related Cu(I) alkene adducts, with N-O distances in the narrow range 1.333(4)-1.338(5) A. IR spectra of the nitrosobenzene adducts 1b, 2b, and 3b exhibit nu(NO) stretching frequencies at 915, 1040, and 1113 cm(-1), respectively, following the decreasing degree of N=O activation observed in the X-ray structures of species 1, 2, and 3. Both 1a and 3a react with anaerobic NO(g) to give the corresponding N-aryl-N-nitrosohydroxylaminato complexes [Me(2)NN]M(kappa(2)-O(2)N(2)Ar) [M = Ni (4), Cu (5)]. In the reaction of dinuclear 1a with NO, one [Me(2)NN]Ni fragment is trapped as the nickel nitrosyl [Me(2)NN]Ni(NO). Reaction of the monovalent complex [Me(2)NN]Cu(eta(2)-ONAr) with NO(g) to give divalent [Me(2)NN]Cu(kappa(2)-O(2)N(2)Ar) represents an example of oxidative nitrosylation.

Formation and Reactivity of [(tacn)-N-CO-ReIIIBr(CO)2]+in Water: a Theoretical and Experimental Study

The chemistry of [(tacn)-N-CO-Re(III)(CO)(2)Br]X (X = Cl or Br), obtained in good yield from the reaction of fac-[(tacn)Re(I)(CO)(3)]Br (1, tacn = 1,4,7-triazacyclononane) with X(2) in water, is described. The [(tacn)-N-CO-Re(III)(CO)(2)Br]X complex (2 with X = Br(-); 2a with X = BrCl(2)(-)), which we have previously communicated, is characterized by an unusual three-membered ring acyl amide bond. Complex 2 is stable as a solid but is reactive in aqueous solution. Under basic conditions (1 M NaOH), reductive decarbonylation was observed, and the bis-carbonyl complex [(tacn)Re(I)(CO)(2)Br] (3) was obtained in quantitative yield. The Br(-) ligand in 3 could be replaced by CN(-), giving the neutral complex [(tacn)Re(I)(CO)(2)(CN)] (4). In acidic media (1 M HBr), complex 2 partially converted to the monocarbonyl mu-oxo bridged dinuclear complex {[(tacn)Re(III)(CO)Br](2)O}(2+) (5 as [PF(6)](-) salt). Under mild oxidative conditions the trioxo [(tacn)Re(VII)O(3)](ReO(4)(-)) (6) was formed almost quantitatively, and small amounts of the uncommon Re(VI) complex [(tacn)Re(VI)O(2)Br](ReO(4)(-)) (7) were identified. Mechanistic investigations at the density functional level of theory (DFT) showed that the elementary steps in the formation of 2 from 1 and 3 from 2 involved reactions of the complexes with hydroxide. The calculated pathway is strongly exothermic (ca. -137 kcal/mol), confirming the energetically and kinetically highly favored formation of 3. The X-ray structures of 2a and 3-5 are reported and discussed.

Copper coordination to the aldehyde and hemiacetal form of 4-bromo-2-[(2-diethylaminoethyl)ethylaminomethyl]-6-formylphenol: Synthesis and structure of [Cu(H 2L) 2(X) 2] X 2 · nH 2O ( [formula omitted]) and [Cu(L′)] 2 · 2CH 3OH

The coordination behaviour of Cu 2+ towards 4-bromo-2-[(2-diethylaminoethyl)ethyl-aminomethyl]-6-formylphenol (HL) having phenolate, amine and aldehyde donor sites has been studied. In aqueous, weakly acidic solution Cu 2+ coordinates to the phenolate and aldehyde oxygen giving rise to the complexes [Cu(H 2L) 2X 2]X 2 ( X = NO 3 − ( 1a) and CIO 4 − ( 1b)), while in alkaline solution a complex of composition [CuL 2] ( 2) is formed. In methanol, the aldehyde groups in 1 and 2 suffer nucleophilic attack from the solvent resulting in the formation of the hemiacetal form of the ligand and in the isolation of [Cu(L′)] 2 · 2CH 3OH ( 3). X-ray structures of 1a, 1b and 3 are reported, the latter featuring a rare example of a coordinated methyl-hemiacetal.

Template synthesis of N 2S and N 3S chelates via alkylation of bis(2-aminoethanethiolato)Ni: sulfur- and nitrogen-centered alkylations

Alkylation of bis(2-aminoethanethiolato)nickel(II) ( 1) with alkylating agents containing pendant donor groups has been investigated. Reaction with 2-bromoethylamine is strictly sulfur-centered yielding (2-[(2-aminoethyl)thio]ethaneamine)nickel(II)bromide, [(DAES) 2Ni]Br 2 ( 2), which was isolated as a lilac solid. Addition of chloroacetamide yields the sulfur- and nitrogen-alkylated product (2-[(2-aminoethyl)thio]acetamide)nickel(II)chloride, (AETA)NiCl 2 ( 3a), as a green solid. Recrystallization from water/acetone yields 3a as single crystals along with single crystals of [(AETA)NiCl(OH 2)]Cl ( 3b). The strictly S-alkylated product (2-[(2-amino-2-oxoethyl)thio]acetamide)nickel(II)iodide, [(AOTA) 2Ni]I 2 ( 4), is obtained upon reaction of 1 with iodoacetamide. A pathway is proposed consistent with the observed leaving group effect on the site of alkylation. The X-ray structures of 3a, 3b, and 4 are reported and the hydrogen-bonding network is described.

Flexible N,N,N-chelates as supports for iron and cobalt chloride complexes; synthesis, structures, DFT calculations and ethylene oligomerisation studies.

The aryl-substituted N-picolylethylenediamine and diethylenetriamine ligands, (ArNHCH(2)CH(2))[(2-C(5)H(4)N)CH(2)]NH and (ArNHCH(2)CH(2))(2)NH (Ar = 2,6-Me(2)C(6)H(3), 2,4,6-Me(3)C(6)H(2)), have been prepared by employing palladium-catalysed N-C(aryl) coupling reactions of the corresponding primary amines with aryl bromide. Treatment of MCl(2) with (ArNHCH(2)CH(2))[(2-C(5)H(4)N)CH(2)]NH affords [[(ArNHCH(2)CH(2))((2-C(5)H(4)N)CH(2))NH]CoCl(2)](Ar = 2,6-Me(2)C(6)H(3) 1a; 2,4,6-Me(3)C(6)H(2)) 1b and [[(ArNHCH(2)CH(2))((2-C(5)H(4)N)CH(2))NH]FeCl(2)](n)(n= 1, Ar = 2,6-Me(2)C(6)H(3) 2a; n= 2, 2,4,6-Me(3)C(6)H(2) 2b) in high yield. The X-ray structures of 1a and 1b are isostructural and reveal the metal centres to adopt distorted trigonal bipyramidal geometries with the N,N,N-chelates adopting fac-structures. A facial coordination mode of the ligand is also observed in bimetallic 2b, however, in 2a the N,N,N-chelate adopts a mer-configuration with the metal centre adopting a geometry best described as square pyramidal. Solution studies indicate that mer-fac isomerisation is a facile process for these systems at room temperature. Quantum mechanical calculations (DFT) have been performed on 1a and 2a, in which the ligands employed are identical, and show the fac- to be marginally more stable than the mer-configuration for cobalt (1a) while for iron (2a) the converse is evident. Reaction of (ArNHCH(2)CH(2))(2)NH with CoCl(2) gave the five-coordinate complexes [[(ArNHCH(2)CH(2))(2)NH]CoCl(2)](Ar = 2,6-Me(2)C(6)H(3) 3a, 2,4,6-Me(3)C(6)H(2) 3b), in which the ligand adopts a mer-configuration; no reaction occurred with FeCl(2). All complexes 1-3 act as modest ethylene oligomerisation catalysts on activation with excess methylaluminoxane (MAO); the iron systems giving linear alpha-olefins while the cobalt systems give mixtures of linear and branched products.