Reactivity study of arene(azido)ruthenium N∩O-base complexes with activated alkynes

Substitution reaction of chloro η⁶-arene ruthenium N∩O-base complexes [(η⁶-arene)Ru(N∩O)Cl] [N∩O = pyrazine-2-carboxylic acid (pca-H), 8-hydroxyquinoline (hq-H); arene = p-ⁱPrC₆H₄Me, N∩O = hq (1); arene = C₆Me₆, N∩O = hq (2)] with NaN₃ yield the neutral arene ruthenium azido complexes of the general formula [(η⁶-arene)Ru(N∩O)N₃] [N∩O = pca, arene = p-ⁱPrC₆H₄Me (3), arene = C₆Me₆ (4); N∩O = hq, arene = p-ⁱPrC₆H₄Me (5), arene = C₆Me₆ (6)]. These complexes undergo [3 + 2] dipolar cycloaddition reaction with activated alkynes dimethyl and diethyl acetylenedicarboxylates to yield the arene triazole complexes [(η⁶-arene)Ru(N∩O){N₃C₂(CO₂R)₂}] [N∩O = pca, R = Me, arene = p-ⁱPrC₆H₄Me (7), C₆Me₆ (8); R = Et, arene = p-ⁱPrC₆H₄Me (9), C₆Me₆ (10); N∩O = hq, R = Me, arene = p-ⁱPrC₆H₄Me (11) C₆Me₆ (12); R = Et, arene = p-ⁱPrC₆H₄Me (13), C₆Me₆ (14)]. On the bases of proton NMR study, in the above triazole complexes N(2) isomers are assigned with dimethylacetylenedicarboxylate whereas N(1) isomers with diethylacetylenedicarboxylate. All complexes have been characterized by IR and NMR spectroscopy as well as by elemental analysis. The molecular structures of the azido complexes [(η⁶-p-ⁱPrC₆H₄Me)Ru(pca)N₃] (3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(hq)N₃] (5) and [(η⁶-C₆Me₆)Ru(hq)N₃] (6) have been established by single crystal X-ray diffraction studies.     

Calix[4]arene supported group 5 imido complexes

The reaction of imidoyl chlorides [V(NR)Cl₃] (R = Ph 1, Tol 2, tBu 3) and calix[4]arene methyl ether H₃Mecalix unexpectedly leads to the formation of the structurally characterized vanadium (IV) complex [VCl(Mecalix)] (4). Calix[4]arene methyl ether stabilized imido complexes of the type [V(NR)(Mecalix)] (R = Ph 7, Tol 8, tBu 9) were afforded from the reaction of [V(NR)Cl₃] (R = Ph 1, Tol 2, tBu 3) and the tris(lithium) or tris(sodium) salt of the calix[4]arene ether. The lithium salt [{Li₃(Mecalix)}₂] (5) is a dimer in the solid state, in which two monomeric trianions are bridged by lithium cations. Imido complexes [M(NR)(Mecalix)] (M = Nb: R = tBu, 12, R = Tol 13, R = Mes 14, R = Dipp 15; M = Ta: R = tBu 16, R = Tol 17) (Tol = 4-C₆H₄Me, Mes = 2,6-C₆H₃Me₂; Dipp = 2,6-C₆H₃iPr₂) have been prepared from structurally characterized [NbCl₂(Mecalix)] (10) and previously known [TaCl₂(Mecalix)] (11) via reaction with two equivalents of the appropriately metallated (Li, K) primary amine. The molecular structures of 13 and 15 confirm the mononuclear nature of these complexes.     

Synthesis and characterization of nickel(II) complexes bearing 2-(imidazol-2-yl)pyridines or 2-(pyridin-2-yl)phenanthroimidazoles/oxazoles and their polymerization of norbornene

Series of 2-R₁-6-(1-R₂-4,5-diphenyl-1H-imidazol-2-yl)pyridine (R₁ = R₂ = H, L1; R₁ = Me, R₂ = H, L2; R₁ = H, R₂ = Me, L3; R₁ = R₂ = Me, L4), 2-(6-R₁-pyridin-2-yl)-1H-phenanthro[9,10-d]imidazole (R₁ = H, L5; R₁ = Me, L6) and 2-(pyridin-2-yl)phenanthro[9,10-d]oxazole (L7) were synthesized and used to prepare their corresponding dihalonickel complexes (C1-C9). All organic compounds and nickel complexes were characterized by elemental and spectroscopic analyses. Molecular structures of C1, C4, C5 and C8 were confirmed by the single-crystal X-ray diffraction analysis. The single-crystal X-ray analysis revealed complex C1 as a distorted octahedral geometry, complex C4 as a distorted square pyramidal geometry, complex C5 as a distorted trigonal bipyramidal configuration, and complex C8 as a tetrahedral geometry. Upon activation with methylaluminoxane (MAO), the nickel complexes showed good activity towards norbornene polymerization through main additional and minor ring-opening metathesis. The reaction parameters such as norbornene concentration, reaction temperature and different coordinate environments caused by the ligands affected their catalytic performances.     

Synthesis and characterization of ether-derivatized aminophosphines and their application in C-C coupling reactions

Four new bis(phosphino)amine ligands (Ph₂P)₂N-C₆H₃-R, where R = 3,5-OMe (1), 2,5-OMe (2), 2,4-OMe (3) or 3,4-OMe (4), were prepared via aminolysis of the corresponding dimethoxyanilines with 2 equiv. of diphenylphosphine chloride in the presence of triethyl amine. Oxidation of these ligands with aqueous H₂O₂, elemental S₈ or Se powder afforded the corresponding chalcogen oxides 1a-4a, sulfides 1b-4b and selenides 1c-4c in good yields. Reaction of 1-4 with [MCl₂(cod)] (M = Pt, Pd; cod = cycloocta-1,5-diene) in equimolar ratios afforded cis-[MCl₂{(Ph₂P)₂N-C₆H₃-R}] (M = Pt; R = 3,5-OMe 1d, R = 2,5-OMe 2d, R = 2,4-OMe 3d, and R = 3,4-OMe 4d. M = Pd; R = 3,5-OMe 1e, R = 2,5-OMe 2e, R = 2,4-OMe 3e, and R = 3,4-OMe 4e). Similarly, reaction of [Cu(CH₃CN)₄]PF₆ with the 1-4 in 1:2 ratio gave [Cu{(Ph₂P)₂N-C₆H₃-R}₂]PF₆ (R = 3,5-OMe 1f, 2,5-OMe 2f, 2,4-OMe 3f and 3,4-OMe 4f). All new compounds were fully characterized by spectroscopy and elemental analysis and the molecular structures of seven representative compounds were determined by single-crystal X-ray crystallography. In addition, the palladium complexes were investigated as pre-catalysts in C-C coupling reactions.     

Four novel Co(II) and Mn(II) coordination polymers with triazolyl derivate: Syntheses, crystal structures and magnetic properties

Four novel coordination polymers, one-dimensional chains [M(PTE)₂(N₃)₂]_n (M = Mn for 1 and Co for 2), and two-dimensional layers [M(PTE)₂(dca)₂]_n (M = Mn for 3 and Co for 4) (PTE = 1-(2,4-difluorophenyl-2-(1H-1,2,4-triazol-1-yl)ethanone, dca = dicyanamide anion, N(CN)₂⁻), have been synthesized under mild ambient conditions and structurally characterized by single crystal X-ray diffraction. In all four crystal structures, the metal atoms adopt octahedral coordination geometry with six nitrogen atoms from two monodentate PTE ligands and four azido (or dca) bridging ligands. The crystal structures of 1 and 2 are isostructural 1-D polymeric chains, alternatively linked by double end-on and double end-to-end azido bridges. However, the bent dca ligands as bidentate μ₂-1,5 bridging ligands interlink the octahedral metal units to lead to 2-D (4,4) grid networks in 3 and 4. Temperature-dependent magnetic measurements in 2-300 K have been performed for these four polymers, and suggest alternative ferro- and antiferromagnetic couplings for end-on and end-to-end azido bridges in 1, and the dominant ferromagnetic coupling in 2, respectively. Both polymers 3 and 4 show weak antiferromagnetic exchanges through the μ₂-1,5-dca bridges. The effects of auxiliary coligands on the structure and the nature of these magnetic exchanges are discussed in the light of the crystal structures in detail.     

Photolysis of arene chromium tricarbonyl complexes in presence of amine-boranes: Observation of σ-borane complexes in solution

Activation of the B-H σ-bond of amine-boranes on the chromium(0) center of arene chromium tricarbonyl complexes (η⁶-arene)Cr(CO)₃ (arene = fluorobenzene, 1a; benzene, 1b and mesitylene, 1c) has been studied. Photolysis of 1b in presence of ammonia-borane (H₃N·BH₃, AB) and tert-butylamine-borane (^tBuH₂N·BH₃, TBAB) resulted in H₂ evolution and precipitation of a BNH_x polymer. On the other hand, photolysis in the presence of trimethylamine-borane (Me₃N·BH₃, TMAB) resulted in the formation of a σ-borane complex (2) along with Cr(CO)₅(η¹-HBH₂·NMe₃) (3). The σ-borane complexes (η⁶-arene)Cr(CO)₂(η¹-HBH₂·NMe₃) (arene = fluorobenzene, 2a; benzene, 2b and mesitylene, 2c) were characterized in solution by ¹H, ¹¹B, and ¹³C NMR spectroscopy. Electron withdrawing substituents on the arene ring provide the more stable σ-borane moiety in this series of complexes.     

Influence of the phosphine arrangement on the reactivity of palladium(II) and platinum(II) polyphosphine complexes with copper(I) chloride

The distorted square-planar complexes [Pd(PNHP)Cl]Cl (1) (PNHP = bis[2-(diphenylphosphino)ethyl]amine), [M(P₃)Cl]Cl [P₃ = bis[2-(diphenylphosphino)ethyl]phenylphosphine; M = Pd (2), Pt (3)] and [Pt(NP₃)Cl]Cl (5) (NP₃ = tris[2-(diphenylphosphino)ethyl]amine), coexisting in the later case with a square-pyramidal arrangement, react with one equivalent of CuCl to give the mononuclear heteroionic systems [M(L)Cl](CuCl₂) [L = PNHP, M = Pd (1a); L = P₃, M = Pd (2a), Pt (3a); L = NP₃, M = Pt (5a)]. The crystal structure of 3a confirms that Pt(II) retains the distorted square-planar geometry of 3 in the cation with P₃ acting as tridentate chelating ligand, the central P atom being trans to one chloride. The counter anion is a nearly linear dichlorocuprate(I) ion. However, the five-coordinate complexes [Pd(NP₃)Cl]Cl (4), [M(PP₃)Cl]Cl (M = Pd (6), Pt (7); PP₃ = tris[2-(diphenylphosphino)ethyl] phosphine) containing three fused five-membered chelate rings undergo a ring-opening by interaction with one (4, 6, 7) and two (6, 7) equivalents of CuCl with formation of neutral MCu(L)Cl₃ [L = NP₃, M = Pd (4a); L = PP₃, M = Pd (6a), Pt (7a)] and ionic [MCu(PP₃)Cl₂](CuCl₂) [M = Pd (6b), Pt (7b)] compounds, respectively. The heteronuclear systems were shown by ³¹P NMR to have structures where the phosphines are acting as tridentate chelating ligands to M(II) and monodentate bridging to Cu(I). Further additions of CuCl to the neutral species 6a and 7a in a 1:1 ratio resulted in the achievement of the ionic complexes 6b and 7b with ions as counter anions. It was demonstrated that the formation of heterobimetallic or just mononuclear mixed salt complexes was clearly influenced by the polyphosphine arrangement with the tripodal ligands giving the former compounds. However, complexes [M(NP₃)Cl]Cl constitute one exception and the type of reaction undergone versus CuCl is a function of the d⁸ metal centre.     

Triorganotin(IV) complexes of Schiff base derived from 6-amino-2-mercaptobenzothiazole: Synthesis, characterization and X-ray crystal structures

Nine triorganotin(IV) complexes of the type R₃SnL (L = L1 R = Me 1, Ph 2, PhCH₂3; L = L2 R = Me 4, Ph 5, PhCH₂6; L = L2 R = Me 7, Ph 8, PhCH₂9) have been obtained by reaction of new Schiff base HL1, HL2 or HL3 with triorganotin(IV) chloride in the presence of sodium ethoxide. All the complexes 1-9 were characterized by elemental, IR and NMR spectra analyses. Except for complexes 3, 4, 6, 9, the others were also characterized by X-ray crystallography diffraction analyses, which revealed that complexes 1, 2, 5, 7, 8 were four coordinated and displayed a capped tetrahedron.     

Palladium(II), platinum(II), ruthenium(II) and mercury(II) complexes of potentially tridentate Schiff base ligands of (E, N, O) type (E = S, Se, Te): Synthesis, crystal structures and applications in Heck and Suzuki coupling reactions

Schiff bases of 2-hydroxybenzophenone (HBP) (C₆H₅)(2-HOC₆H₄)CN(CH₂)_nEAr (L1/L2: E = S, Ar = Ph, n = 2/3; L3/L4: E = Se, Ar = Ph, n = 2/3; L5/L6: E = Te, Ar = 4-MeOC₆H₄, n = 2/3) and their complexes [PdCl(L-H)] (L = L1−L6; 1, 2, 3, 5, 7, 11), [PtCl(L3-H/L5-H)] (4/8), [PtCl₂(L4/L6)₂] (6/12), [(p-cymene)RuCl(L5/L6)]Cl (9/13) and [HgBr₂(L5/L6)₂] (10/14) have been synthesized and characterized by proton, carbon-13, selenium-77 and tellurium-125 NMR, IR and mass spectra. Single crystal structures of L1, 1, 3, 4, 5 and 7 were solved. The Pd-E bond distances (Å): 2.2563(6) (E = S), 2.3575(6)−2.392(2) (E = Se); 2.5117(5)−2.5198(5) (E = Te) are near the lower end of the bond length range known for them. The Pt-Se bond length, 2.3470(8) Å, is also closer to the short values reported so far. The Heck and Suzuki reaction were carried out using complexes 1, 3, 5 and 7 as catalysts under aerobic condition. The percentage yields for trans product in Heck reaction were found upto 85%.     

Palladium complexes based on tridentate pyrazolyl-ligands: Synthesis, structures and use in Suzuki cross-coupling reactions

The reaction of [PdCl(Me)(cod)] (cod = 1,5-cyclooctadiene) with tridentate bis(pyrazolyl) ligands affords the alkyl-palladium(II) complexes [Pd(CH₃)(NZN)][BF₄] (1, NZN = 1,1′-(2,2′-oxybis(ethane-2,1-diyl)bis(3,5-dimethyl-1H-pyrazole); 2, NZN = bis[2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]sulfane) in good yield. Compounds 1-2 were characterized by elemental analysis, multinuclear NMR spectroscopy, and X-ray structural analysis. Single crystal X-ray structural analyses indicate that the complexes are monomeric and the palladium center resides in a slightly distorted square planar environment. Furthermore, despite their intrinsic similarity, the NON and NSN ligands adopt different coordination modes around the palladium metal center. Additionally, the [PdCl₂(NON)] (3) was shown to be an efficient catalyst precursor for the coupling of aryl bromides and iodides with arylboronic acids, esters and borate salts.     

Bis(pyrazolyl) palladium(II), platinum(II) and gold(III) complexes: Syntheses, molecular structures and substitution reactions with l-cysteine

A series of pyrazolyl palladium(II), platinum(II) and gold(III) complexes, [PdCl₂(3,5-R₂bpza)] {R = H (1), R = Me (2), bpza = bis-pyrazolyl acetic acid}, [PtCl₂(3,5-R₂bpza)] {R = H (3a), R = Me (4)}, [AuCl₂(3,5-R₂bpza)]Cl {R = H (5a), R = Me (6a)} and [PdCl₂(3,5-R₂bpzate)] {R = Me (7)} have been synthesised and structurally characterised. Single crystal X-ray crystallography showed that the pyrazolyl ligands exhibit N^N-coordination with the metals. Anticancer activities of six complexes 1-6a were investigated against CHO cells and were found to have low activities. Substitution reactions of selected complexes 1, 2, 3a and 5a with l-cysteine show that the low anticancer activities compounds and that the rate of substitution with sulfur-containing compounds is not the cause of the low anticancer activities.     

Mimicking the reduced, oxidized and azide inhibited form of manganese superoxide dismutase by mononuclear Mn compounds utilizing tridentate ligands

The manganese complexes [Mn^II(Hbmimpm)₂(NO₃)](NO₃) · Et₂O (1), [Mn^III(bmimpm)₂(OAc)] · 2CH₂Cl₂(2), and [Mn^III(bmiapm)₂(OAc)] · MeOH · H₂O · CH₂Cl₂(3) containing the new ligands Bis(1-methylimidazol-2-yl)-(4-methoxyphen-1-yl)methanol (Hbmimpm) and Bis[(1-methylimidazol-2-yl)](2-aminophenyl)methanol (Hbmiapm) were synthesized. They are good structural models for the reduced (1) and oxidized (2, 3) form of manganese superoxide dismutase. All complexes were characterized by spectroscopic methods and X-ray structure analysis. Compounds 1 and 2 crystallize in the monoclinic space group P2₁/c whereas complex 3 crystallizes in the monoclinic space group P2₁/n. The coordination sphere around the manganese cores is distorted octahedral with two corresponding tridentate ligands representing the protein ligands and one nitrate (1) or acetate (2, 3) ion occupying two cis positions. Similar to the enzyme the Mn(III) complex 2 reacts with sodium azide. The obtained microcrystalline azide adduct was characterized by UV-Vis and IR spectroscopy.     

Synthesis and structural studies of mixed-ligand rhenium(V) complexes anchored by tridentate pyrazole-based ligands

The novel oxorhenium dichlorides mer-[ReO(L1)Cl₂] (1) and fac-[ReO(L2)Cl₂] (2) (L1 = 2-[2-(pyrazol-1-yl)ethyliminomethyl]phenolate; L2 = 2-[2-(pyrazol-1-yl)ethylaminomethyl]phenolate) were synthesized by reacting [NBu₄][ReOCl₄] with L1H and L2H, respectively. X-ray structural analysis of 1 and 2 has shown that L1 and L2 act as (N,N,O)-tridentate chelators coordinating to the Re(V) centre in a meridional and in a facial fashion, respectively. The reactivity of 2 towards potential bidentate/dianionic substrates is strongly dependent on the donor atom set, being observed that the presence of sulphur favours the displacement of the ancillary ligand (L2). By contrast, complex 2 reacted with (O,O)-bidentate substrates (1,2-ethanediol and oxalic acid) providing the mixed-ligand complexes fac-[ReO(L2)(OCH₂CH₂O)] (3) and fac-[ReO(L2)(C₂O₄)] (4). Complexes 3 and 4 are air and water-stable and have been characterized by the common spectroscopic techniques (IR, ¹H and ¹³C NMR) and by X-ray diffraction analysis.     

Transition metal halide salts of 8-methylquinolinium: Synthesis and structures of (8-methylquinolinium)2 MX4·nH2O (M = Cu, Co, Zn; X = Cl, Br; n = 0, 1)

The reactions of metal(II) chlorides and bromides with 8-methylquinoline (8-mequin) in neutral and acidic solutions were investigated. The reaction with ZnCl₂, ZnBr₂, CoCl₂, CoBr₂, CuCl₂ or CuBr₂ with the appropriate HX in water or aqueous ethanol gave complexes of the formula (8-mequin)₂MX₄ (1, M = Cu, X = Cl; 2, M = Cu, X = Br; 3, M = Co, X = Cl; 4, M = Co, X = Br) or (8-mequin)₂ZnX₄·nH₂O (5, X = Cl, n = 0; 6, X = Br, n = 0; 7, X = Cl, n = 1; 8, X = Br, n = 1). Crystals of 1, 2 and 4-8 suitable for single crystal X-ray diffraction were obtained and the structures reported. Compounds 1 and 2 crystallize in the monoclinic space group C2/c, while 4-8 crystallize in the triclinic space group, . Variable temperature magnetic susceptibility data indicate very weak interactions for the copper compounds 1 and 2, while the magnetic behavior of 3 and 4 is dominated by single ion anisotropy, with weaker antiferromagnetic interactions.     

Construction of carbon chains on ruthenium and osmium carbonyl clusters

We have used the elimination of AuX(PR₃) (X = halide, R = Ph, tol) that occurs in reactions of alkynylgold(I)-phosphine complexes with M₃(μ-H)₃ (μ₃-CBr) (CO)₉ (M = Ru, Os) to prepare the complexes M₃(μ-H)₃(μ₃-CCCR)(CO)₉ [M = Ru, R = Ph 2, CCSiMe₃3, Fc 4, CCFc 6-Ru, CC[Ru(PPh₃)₂Cp] 8; M = Os, R = CCFc 6-Os, CCCCFc 7], Fc′{(μ₃-CCC)Ru₃(μ-H)₃(CO)₉}₂5, and bis-cluster-capped carbon chain complexes {M₃(μ-H)₃(CO)₉}₂{μ₃:μ₃-C(CC)_nC} (M = Ru, n = 2 9, 3 10-Ru; M = Os, n = 3 10-Os) and {(L)(OC)₈(μ-H)₃M₃}C(CC)_nC{Co₃(μ-dppm)(CO)₇} (n = 1, M = Ru, L = CO 11, PPh₃12-Ru/P; n = 2, L = CO 12-Ru, PPh₃13; M = Os, L = CO 12-Os) in good to excellent yields. X-ray structural determinations of 2-5, 6-Ru, 6-Os, 7, 9, 11, 12-Ru, 12-Os and 12-Ru/P are reported.     

Synthesis and structure of dichloropalladium(II) complexes of heteroleptic N,S- and N,Se-donor ligands based on the 2-organochalcogenomethylpyridine motif, and Mizoroki-Heck catalysis mediated by complexes of N,S-donor ligands

Ligands containing the 2-organochalcogenomethylpyridine motif with substituents in the 4- or 6-position of the pyridyl ring, R⁴,R⁶-pyCH₂ER¹ [R⁴ = R⁶ = H, ER¹ = SMe (1), SeMe (2), SPh (6), SePh (7); R⁴ = Me, R⁶ = H, ER¹ = SMe (3), SPh (8), SePh (9); R⁴ = H, R⁶ = Me, ER¹ = SMe (4), SPh (10), SePh (11); R⁴ = H, R⁶ = Ph, ER¹ = SMe (5), SPh (12), SePh (13)] are obtained on the reaction of R⁴,R⁶-pyMe with LiBuⁿ followed by R¹EER¹. On reaction with PdCl₂(NCMe)₂, the ligands with a 6-phenyl substituent form cyclopalladated species PdCl{6-(o-C₆H₄)pyCH₂ER¹-C,N,E} (5a, 12a, 13a) with the structure of 13a (ER¹ = SePh) confirmed by X-ray crystallography; other ligands form complexes of stoichiometry PdCl₂(R⁴,R⁶-pyCH₂ER¹). Complexes with R⁶ = H are monomeric with N,E-bidentate configurations, confirmed by structural analysis for 3a (R⁴ = Me, ER¹ = SMe), 7a (R⁴ = H, ER¹ = SePh) and 9a (R⁴ = Me, ER¹ = SePh). Two of the 6-methyl substituted complexes examined by X-ray crystallography are oligomeric with trans-PdCl₂(N,E) motifs and bridging ligands, trimeric [PdCl₂(μ-6-MepyCH₂SPh-N,S)]₃ (10a) and dimeric [PdCl₂(μ-6-MepyCH₂SePh-N,Se)]₂ (11a). This behaviour is attributed to avoidance of the Me···Cl interaction that would occur in the cis-bidentate configuration if the pyridyl plane had the same orientation with respect to the coordination plane as observed for 3a, 7a and 9a [dihedral angles 8.0(2)-16.8(2)°]. When examined as precatalysts for the Mizoroki-Heck reaction of n-butyl acrylate with aryl halides in N,N-dimethylacetamide at 120 °C, the complexes exhibit the anticipated trends in yield (ArI > ArBr > ArCl, higher yield for electron withdrawing substituents in 4-RC₆H₄Br and 4-RC₆H₄Cl). The most active precatalysts are PdCl₂(R⁴-pyCH₂SMe-N,S) (R = H (1a), Me (3a)); complexes of the selenium containing ligands exhibit very low activity. For closely related ligands, the changes SMe to SPh, 6-H to 6-Me, and 6-H to 6-Ph lead to lower activity, consistent with involvement of both the pyridyl and chalcogen donors in reactions involving aryl bromides. The precatalyst PdCl₂(pyCH₂SMe-N,S) (1a) exhibits higher activity for the reaction of aryl chlorides in Buⁿ₄NCl at 120 °C as a solvent under non-aqueous ionic liquid (NAIL) conditions.     

Different coordination modes of 5,5-diethylbarbiturate in the copper(II) complexes with some aliphatic amines: Synthesis, spectroscopic, thermal and structural studies

Three new copper(II) complexes of 5,5-diethlybarbiturate (barb), [Cu(barb)₂(dmen)]·0.5H₂O (dmen = N,N-dimethylethylenediamine) 1, [Cu(barb)₂(bapa)] (bapa = bis(3-aminopropyl)amine) 2, and [Cu(barb)(apen)](barb)·2H₂O (apen = N,N′-bis(3-aminopropyl)ethylenediamine) 3, have been synthesized and characterized by chemical, spectroscopic and thermal methods. Single crystal X-ray diffraction studies revealed that all complexes are mononuclear. The copper(II) ion exhibits a square-pyramidal coordination geometry in 1 and 3, but a trigonal-bipyramidal geometry in 2. The barb ligand shows different coordination modes. 1 presents the unequal coordination of the barb ligands: one is monodentate (N) and the other one is bidentate (N, O). In 2, both barb ligands are N-coordinated, whereas in 3, one barb ligand is N-coordinated, while the second barb ligand behaves as a counter-ion. The dmen, bapa and apen ligands act as bi-, tri- and tetradentate ligands, respectively. All complexes display a hydrogen-bonded network structure. The IR spectroscopic analysis shows that the ν(CO) stretching frequencies do not correlate predictably with the coordination mode of the barb ligand in 1. Thermal analysis data for 1-3 are in agreement with the crystal structures.     

Hydrothermal synthesis, structural determination, and thermal properties of 2-D cobalt- and nickel-based coordination polymers incorporating pendant-arm 3-pyridinecarboxylate ligands

Hydrothermal synthesis has afforded a family of four coordination polymers containing divalent nickel or cobalt and pendant-arm pyridylcarboxylate ligands. Utilizing 3-pyridylacetic acid and appropriate metal precursors produced [M(3-pyrac)₂(H₂O)₂] phases (M = Co (1); M = Ni (2)), while 3-pyridylpropionic acid generated [M(3-pyrprop)₂(H₂O)₂] coordination polymers (M = Co (3); M = Ni (4)). Single crystal X-ray diffraction revealed that 1-4 all display discrete 2-D layers with (4,4)-topology, anchored via bridging 3-pyridylcarboxylate ligands bearing monodentate carboxylate termini. Intralamellar hydrogen bonding between the aquo ligands and unligated carboxylate oxygen atoms is observed within 1-4. The pseudo 3-D structures of 1-4 are further assembled via stacking of individual neutral layers by interlayer hydrogen bonding. Thermal properties are also discussed.     

Lewis-base copper(I) formates: Synthesis, reaction chemistry, structural characterization and their use as spin-coating precursors for copper deposition

Consecutive synthesis methodologies for the preparation of a series of copper(I) formates [L_mCuO₂CH] (L = ⁿBu₃P: 4a, m = 1; 4b, m = 2; 5, L = [Ti](CCSiMe₃)₂, m = 1, [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) and [L_mCuO₂CH·HO₂CR] (L = ⁿBu₃P: 7a, m = 1, R = H; 7b, m = 2, R = H; 7c, m = 2, R = Me; 7d, m = 2, R = CF₃; 7e, m = 2, R = Ph. L = (^cC₆H₁₁)₃P, R = H: 8a, m = 2; 8b, m = 3. L = (CF₃CH₂O)₃P, R = H: 9a, m = 2; 9b, m = 3. L = (CH₃CH₂O)₃P, R = H: 10a, m = 2; 10b, m = 3. L = [Ti](CCSiMe₃)₂; m = 1: 11a, R = H; 11b, R = Ph) is reported using [CuO₂CH] (1) and L (2a, L = ⁿBu₃P; 2b, L (^cC₆H₁₁)₃P; 2c, L = (CF₃CH₂O)₃P; 2d, L = (CH₃CH₂O)₃P; 3, L = [Ti](CCSiMe₃)₂) as key starting materials. Addition of formic acid (6a) or carboxylic acid HO₂CR (6b, R = Me; 6c, R = CF₃; 6d, R = Ph) to the afore itemized copper(I) formates 4 and 5 gave metal-organic or organometallic 7-11. The molecular structures of 8a and 11a in the solid state are reported showing a threefold coordinated copper(I) ion, setup by either two coordinatively-bonded phosphorus atoms and one formate oxygen atom (8a) or two π-bonded alkyne ligands and one oxygen atom (11a). A formic acid molecule is additionally hydrogen-bonded to the CuO₂CH moiety. The use of 7b as suitable precursor for the deposition of copper onto TiN-coated oxidized silicon wafers by the spin-coating process below 300 °C is described. Complex 7b offers an appropriate transformation behavior into metal phase by an elimination-decarboxylation mechanism. The morphology of the copper films strongly depends on the annealing conditions. A closed grain network densified by a post-treatment is obtained (8 °C min⁻¹, N₂/H₂ carrier gas). Hydrogen post-anneal to 420 °C after film deposition gave a copper film showing resistivities from 2.5 to 3.7 μΩ cm. This precursor was also used for gap-filling processes.     

Three zinc(II) complexes constructed from aromatic dicarboxylate and 1,4-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene: Syntheses, crystal structures and luminescent properties

To investigate the effect of organic anions on the coordination frameworks, we synthesized three new complexes, namely, Zn(DPA)(bpimb)_0.5(H₂O) (1), Zn(BDC)(bpimb)_0.5 (2) and Zn₂(SDBA)₂(bpimb)·H₂O (3) (H₂DPA = diphenic acid; H₂BDC = isophthalic acid; H₂SDBA = 4,4′-dicarboxybiphenylsulfone), which were obtained by the reactions of 1,4-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene (bpimb) as main ligand, and several aromatic polycarboxylate as organic anions with Zn(NO₃)₂·6H₂O. Single-crystal structure analysis shows that complex 1 is a one-dimensional chain structure, which is further interlinked into a higher-dimensional supramolecular framework by hydrogen-bonding interactions. In 2, BDC bridge Zn(II) atoms to give dimeric units, which are further linked by bpimb ligands to form sql nets. In 3, SDBA ligands and bpimb ligands connect Zn(II) ions into catenane-like two-dimensional layers. These catenane-like two-dimensional layers stack in an ABAB fashion to form a 3D supramolecular network. The distinct structures indicate three kinds of carboxylic ligands with different lengths and angles play fundamental roles in the formation of the final products. In addition, the luminescence measurements reveal that three complexes exhibit strong fluorescent emissions in the solid state at room temperature.