Hexanuclear manganese(III) single-molecule magnets from derivatized salicylamidoximes

Four novel hexanuclear manganese(III) complexes based on derivatized salicylamidoximes, [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Me₂N-sao)₆(EtOH)₄] (1), [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Me₂N-sao)₆(ⁱPrOH)₄] (2), [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Et₂N-sao)₆(EtOH)₄] (3) and [Mn^III₆(μ₃-O)₂(O₂CPh)₂(Et₂N-sao)₆(ⁱPrOH)₄] (4) (Me₂N-Hsao = dimethylsalicylamidoxime; Et₂N-Hsao = diethylsalicylamidoxime), have been prepared and characterized. Single-crystal X-ray diffraction allows one to determine that 1·2CHCl₃ and 4 crystallize in the triclinic system with space group P(–1), whereas 3 crystallizes in the monoclinic system with space group P2₁/n. dc and ac magnetic susceptibility measurements of 1-4 reveal ferromagnetic coupling between Mn(III) metal ions and single-molecule magnet behaviour. The anisotropy barriers are 56, 52, 71 and 59 K for 1, 2, 3 and 4, respectively.     

Tin(IV) complexes obtained by reacting 2-benzoylpyridine-derived thiosemicarbazones with SnCl4 and Ph2SnCl2

Reaction of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH, HL1) and its N(4)-methyl (H2Bz4Me, HL2) and N(4)-phenyl (H2Bz4Ph, HL3) derivatives with SnCl₄ and diphenyltin dichloride (Ph₂SnCl₂) gave [Sn(L1)Cl₃] (1), [Sn(L1)PhCl₂] (2), [Sn(L2)Cl₃] (3), (4) [Sn(L3)PhCl₂] (5) and [Sn(L3)Ph₂Cl] (6). Infrared and ¹H, ¹³C and ¹¹⁹Sn NMR spectra of 1-3, 5 and 6 are compatible with the presence of an anionic ligand attached to the metal through the N_py-N-S chelating system and formation of hexacoordinated tin complexes. The crystal structures of 1-3, 5 and 6 show that the geometry around the metal is a distorted octahedron formed by the thiosemicarbazone and either chlorides or chlorides and phenyl groups. The crystal structure of 4 reveals the presence of and trans [Ph₂SnCl₄]²⁻.     

Synthesis and structure of isopropyldimethylsilyl-substituted octamethyltitanocene

Reduction of isopropyldimethylsilyl-substituted titanocene dichloride [TiCl₂(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (1) by excess magnesium in the presence of excess bis(trimethylsilyl)ethyne (btmse) in tetrahydrofuran at 60 °C yielded a mixture of products amongst them only the trinuclear Ti-Mg-Ti hydrido-bridged complex Mg[Ti(μ-H)₂(η⁵-C₅Me₄SiMe₂Prⁱ)]₂ (3) was isolated and characterized. The precursor of titanocene, [Ti(η⁵-C₅Me₄SiMe₂Prⁱ)₂(η²-btmse)] (6), was obtained from the identical system which, after initial formation of [TiCl(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (2), reacted at −18 °C overnight and then the solution was rapidly separated from the remaining magnesium. Titanocene [Ti(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (7) was obtained by thermolysis of 6 at 75 °C in vacuum. Crystal structures of 1, 2, 3, 6, and 7 were determined.     

Silyl stabilized azanes: Reactions of mono- and dilithium bis(trimethylsilyl)hydrazide with dichloro- and tetrachlorostannane

SnCl₄ acts primarily as an oxidant and oxidizes monolithium bis(trimethylsilyl) hydrazide 1 to mainly bis(trimethylsilyl)amine, BSA and tris(trimethylsilyl)hydrazine, TrSH and itself get reduced to SnCl₂. Similarly, reaction of SnCl₄ with dilithiumbis(trimethylsilyl) hydrazide 2, oxidizes it to lithium tris(trimethylsilyl)hydrazide, Li-TrSH. Reaction of dichlorostannane (reduction of oxidation state of tin from +4 to +2) with 1 gives a simple substitution reaction and give a pale yellow solid, 1,4-bis(trimethylsilyl)-1,2,4,5-tetraza-3,6-distannacyclohexane, 3b. Whereas, in reaction of 2 with SnCl₂ intermediate stannimine [(Me₃Si)₂N-NSn], tetramerizes and further loses tetrakis(trimethylsilyl)tetrazene, TST to give a cubane compound [(Me₃Si)N-Sn]₄, 4.     

An experimental and a DFT study on the synthesis, spectroscopic characterization, and reactivity of the adducts of dimethyl- and diphenyltin(IV) dichlorides with γ-pyrones [4H-pyran-4-one (PYR) and 2,6-dimethyl-4H-pyran-4-one (DMP)]: Crystal structure of Ph2SnCl2(PYR)

The Sn(IV) R₂SnCl₂(γ-pyrone)_n [R = Me or Ph; γ-pyrone = 4H-pyran-4-one (PYR) or 2,6-dimethyl-4H-pyran-4-one (DMP); n = 1 or 2] adducts have been synthesized and investigated. The adducts Ph₂SnCl₂(PYR) (1), Me₂SnCl₂(PYR)₂ (2), Ph₂SnCl₂(DMP) (3) and Me₂SnCl₂(PYR)(PNO) (4), (PNO = 4-methylpyridine N-oxide) have been prepared by the addition of the corresponding γ-pyrone to chloroform solution of R₂SnCl₂. The new compounds have been characterized by elemental analysis and spectroscopic (IR, ¹H, ¹³C NMR and Mössbauer) means. The single-crystal diffraction study of 1 shows the Sn(IV) to be five-coordinate, [Sn-O and Sn-Cl(1), Sn-Cl(2) distances of 2.3190(13) and 2.4312(6), 2.3653(7), respectively], and the Cl-Sn-Cl bond angle to be 91.17°. The reactivity of 2 towards bipy, Ph₃PO, QNO (Q = quinoline) resulted in complete displacement of PYR and formation of already known compounds whereas, the PNO displaced only one equivalent of PYR, causing the preparation of the new mixed complex 4, possibly through a S_N¹ formation mechanism. DFT/B3LYP molecular orbital calculations were carried out for the 1-4 complexes, their precursors, Ph₂SnCl₂, (5) and Me₂SnCl₂, (6) and the ligands, PYR, DMP and PNO in an attempt to explain the structures and reactivity of the complexes. Optimized resulting geometries, vibrational frequencies, and the electron-accepting ability of the complexes and the precursors towards nucleophiles are discussed.     

Aminobis(phenolate)s of imidomolybdenum(VI) and -tungsten(VI)

The reactions of trans-[MoO(ONO^Me)Cl₂] 1 (ONO^Me = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) dianion) and trans-[MoO(ONO^tBu)Cl₂] 2 (ONO^tBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) with PhNCO afforded new imido molybdenum complexes trans-[Mo(NPh)(ONO^Me)Cl₂] 3 and trans-[Mo(NPh)(ONO^tBu)Cl₂] 4, respectively. As analogous oxotungsten starting materials did not show similar reactivity, corresponding imido tungsten complexes were prepared by the reaction between [W(NPh)Cl₄] with aminobis(phenol)s. These reactions yielded cis- and trans-isomers of dichloro complexes [W(NPh)(ONO^Me)Cl₂] 5 and [W(NPh)(ONO^tBu)Cl₂] 6, respectively. The molecular structures of 4, cis-6 and trans-6 were verified by X-ray crystallography. Organosubstituted imido tungsten(VI) complex cis-[W(NPh)(ONO^tBu)Me₂] 7 was prepared by the transmetallation reaction of 6 (either cis or trans isomer) with methyl magnesium iodide.     

Anticancer activity of new organo-ruthenium, rhodium and iridium complexes containing the 2-(pyridine-2-yl)thiazole N,N-chelating ligand

The dinuclear dichloro complexes [(η⁶-arene)₂Ru₂(μ-Cl)₂Cl₂] and [(η⁵-C₅Me₅)₂M₂(μ-Cl)₂Cl₂] react with 2-(pyridine-2-yl)thiazole (pyTz) to afford the cationic complexes [(η⁶-arene)Ru(pyTz)Cl]⁺ (arene = C₆H₆1, p-ⁱPrC₆H₄Me 2 or C₆Me₆3) and [(η⁵-C₅Me₅)M(pyTz)Cl]⁺ (M = Rh 4 or Ir 5), isolated as the chloride salts. The reaction of 2 and 3 with SnCl₂ leads to the dinuclear heterometallic trichlorostannyl derivatives [(η⁶-p-ⁱPrC₆H₄Me)Ru(pyTz)(SnCl₃)]⁺ (6) and [(η⁶-C₆Me₆)Ru(pyTz)(SnCl₃)]⁺ (7), respectively, also isolated as the chloride salts. The molecular structures of 4, 5 and 7 have been established by single-crystal X-ray structure analyses of the corresponding hexafluorophosphate salts. The in vitro anticancer activities of the metal complexes on human ovarian cancer cell lines A2780 and A2780cisR (cisplatin-resistant), as well as their interactions with plasmid DNA and the model protein ubiquitin, have been investigated.     

Novel hydridotris(pyrazolyl)borate ruthenium(II) complexes containing the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane: Synthesis and evaluation of DNA binding properties

A series of half-sandwich ruthenium(II) complexes containing κ³(N,N,N)-hydridotris(pyrazolyl)borate (κ³(N,N,N)-Tp) and the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA) [RuX{κ³(N,N,N)-Tp}(PPh₃)_2−n(PTA)_n] (n = 2, X = Cl (1), n = 1, X = Cl (2), I (3), NCS (4), H (5)) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)L][PF₆] (L = NCMe (6), PTA (7)) have been synthesized. Complexes containing 1-methyl-3,5-diaza-1-azonia-7-phosphaadamantane(m-PTA) triflate [RuCl{κ³(N,N,N)-Tp}(m-PTA)₂][CF₃SO₃]₂ (8) and [RuX{κ³(N,N,N)-Tp}(PPh₃)(m-PTA)][CF₃SO₃] (X = Cl (9), H (10)) have been obtained by treatment, respectively, of complexes 1, 2 and 5 with methyl triflate. Single crystal X-ray diffraction analysis for complexes 1, 2 and 4 have been carried out. DNA binding properties by using a mobility shift assay and antimicrobial activity of selected complexes have been evaluated.     

The effect of titanium alkoxides in the synthesis of heterobimetallic complexes by titanocene(III) alkoxide-induced metal-metal bond cleavage of metal carbonyl dimers

A series of titanocene(III) alkoxides L₂Ti(III)OR where L = Cp, R = Et(1b), ^tBu(1a), 2,6-Me₂C₆H₃(1c), 2,6-^tBu₂-4-Me-C₆H₂(1d), or L = Cp*, R = Me(2e), ^tBu(2a), Ph(2f) was synthesized and subjected to reaction with [CpM(CO)₃]₂ [M = Mo, W], [CpRu(CO)₂]₂, and Co₂(CO)₈. The Ti(III) precursors 1a, 1c, 2a, 2e, and 2f reacted with [CpM(CO)₃]₂ [M = Mo, W] to form heterobimetallic complexes L₂Ti(OR)(μ-OC)(CO)₂MCp [M = Mo, W], of which Ti and M are linked by an isocarbonyl bridge. Reactions of these Ti(III) complexes with Co₂(CO)₈ resulted in formation of Ti-Co₁ heterobimetallic complexes, from 2a, 2e, or 2f, or Ti-Co₃ tetrametallic complexes, Cp₂Ti(O^tBu)(μ-OC)Co₃(CO)₉ from 1a, 1b, or 1c. The products were characterized by NMR, IR, and X-ray crystallography. Reaction mechanisms were proposed from these results, in particular, from steric/electronic effects of titanium alkoxides.     

Syntheses, crystal structures and properties of Co(II) complexes with N,N′-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine (bpb), and Cd(II), Hg(II) complexes with reduced bpb

Five novel coordination polymers, [Co(bpb)₂Cl₂] (1), [Co(bpb)₂(SCN)₂] (2), [Cd(H₄bpb)_0.5(dmf)(NO₃)₂] (3), [Cd₂(H₄bpb)Br₄] (4), and [Hg₂(H₄bpb)I₄] (5) [bpb=N,N′-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine, H₄bpb=N,N′-bis(3-pyridylmethyl)-1,4-benzenedimethylamine], were synthesized and their structures were determined by X-ray crystallography. In the solid state, complex 1 is a 1D hinged chain, while 2 has 2D network structure with the ligand bpb serving as a bridging ligand using its two pyridyl N atoms. The imine N atoms keep free of coordination and bpb acts as a bidentate ligand in both 1 and 2. Complexes 3, 4, and 5 with reduced bpb ligand, i.e. H₄bpb, show similar 2D network structure, in which ligand H₄bpb serves as a tetradentate ligand. Thermogravimetric analyses for complexes 1-5 were carried out and found that they have high thermal stability. The magnetic susceptibilities of compounds 1, 2 were measured over a temperature range of 75-300 K.     

Synthesis and ethylene polymerization behavior of {MeB(3-Ph-pyrazolyl)3}TiCl3

The new methyl-tris(pyrazolyl)borate reagents Li[MeTp^Ph] (1) [MeTp^Ph]⁻ = MeB(3-Ph-pyrazolyl)₃⁻) and Tl[MeTp^Ph] (2) react with TiCl₄ to afford (MeTp^Ph)TiCl₃ (3) in 77% and 81% yield respectively. 2 reacts with ZrCl₄ and HfCl₄ to yield mixtures of products. The reaction of 1 with TiCl₃(THF)₃ proceeds with B-N bond cleavage to afford TiCl₃(3-Ph-pyrazole)(THF)₂ as the major product (30%). The reaction of 3 with MeLi (3 equiv) yields 1 (60%) and reduced Ti species, via apparent displacement of [MeTp^Ph]⁻ and generation of unstable TiCl₄Me_4−x species. Under MAO activation conditions (MAO = methylalumoxane), 3 polymerizes ethylene to linear polyethylene. 3/MAO is significantly more active in ethylene polymerization than the hydrido-tris(pyrazolyl)borate analogue {HB(3-Ph-pyrazolyl)₃}TiCl₃/MAO.     

Synthesis and structural studies of rhenium(I) tricarbonyl complexes with thione containing chelators

Sodium dihydrobis(2-mercaptothiazolyl)borate, Na[H₂B(tiaz)₂], reacts with (NEt₄)₂[Re(CO)₃Br₃] in water to afford fac-[Re{κ³-H(μ-H)B(tiaz)₂}(CO)₃] (1). In a similar manner, treatment of the same Re(I) starting material with bis(2-mercaptoimidazolyl)methane, H₂C(tim^Me)₂, yields fac-[ReBr{κ²-H₂C(tim^Me)₂}(CO)₃] (2). The organometallic complexes 1 and 2 have been characterized by IR, ¹H and ¹³C NMR spectroscopy, and also by X-ray crystallographic analysis. X-ray diffraction analysis revealed the presence of a short B-H?Re interaction in the case of 1, and the absence of C-H?Re interactions in the crystal structure of 2. For both compounds the rhenium atom adopts a slightly distorted octahedral coordination with a facial arrangement of the carbonyl ligands. The three remaining coordination positions are occupied by the two thione sulfur atoms from the anchor ligands, and by an agostic hydride (1) or a bromide ligand (2). Compound 1 is highly stable either in the solid state or in solution. In particular, its B-H?Re interaction is retained in solution, even in coordinating solvents, namely acetonitrile, dimethylsulfoxide and tetrahydrofuran. Unlike 1, compound 2 is only moderately stable in acetonitrile, undergoing a slow release of the bis(2-mercaptoimidazolyl)methane.     

Trimethylstannyl (diphenylphosphino)acetate: a source of (diphenylphosphino)acetate ligand in the synthesis of coordination compounds

Trimethylstannyl (diphenylphosphino)acetate (1), which is readily accessible from potassium (diphenylphosphino)acetate and trimethylstannyl chloride, may serve as the source of (diphenylphosphino)acetate anion in the preparation of coordination compounds. Thus, the reactions between [M(cod)Cl₂] (M = Pd and Pt; cod = η²:η²-cycloocta-1,5-diene) and two equivalents of 1 give [M(Ph₂PCH₂CO₂-κ²O,P)₂] (2 and 3), while the reaction of [{Pd(μ-Cl)Cl(PFur₃)}₂] (4; Fur = 2-furyl) with one equivalent of 1 yields [SP-4-3]-[PdCl(Ph₂PCH₂CO₂-κ²O,P)(PFur₃)] (5). The reactions of 1 with the dimers [{Rh(η⁵-C₅Me₅)Cl(μ-Cl)}₂] and [{Ru(η⁶-1,4-MeC₆H₄(CHMe₂))Cl(μ-Cl)}₂] (at 1-to-metal ratio 1:1) produce O,P-chelated complexes as well, albeit as stable adducts with the liberated Me₃SnCl: [RhCl(η⁵-C₅Me₅)(Ph₂PCH₂CO₂-κ²O,P)] · Me₃SnCl (6) and[RuCl(η⁶-1,4-MeC₆H₄(CHMe₂))(Ph₂PCH₂CO₂-κ²O,P)] · Me₃SnCl (8). The related complexes with P-monodentate (diphenylphosphino)acetic acid, [RhCl₂(η⁵-C₅Me₅)(Ph₂PCH₂CO₂H-κ,P)] (7) and [RuCl₂(η⁶-1,4-MeC₆H₄(CHMe₂))(Ph₂PCH₂CO₂H-κP)] (9), were obtained by bridge splitting in the dimers with the phosphinocarboxylic ligand. All new compounds were characterized by spectral methods and combustion analyses, and the structures of 2 · 3CH₂Cl₂, 3, 4, 5, 6 and 8 were determined by X-ray crystallography.     

Synthesis and structural characterisation of rhodium hydride complexes bearing N-heterocyclic carbene ligands

Addition of excesses of N-heterocyclic carbenes (NHCs) IEt₂Me₂, IⁱPr₂Me₂ or ICy (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene; IⁱPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene; ICy = 1,3-dicyclohexylimidazol-2-ylidene) to [HRh(PPh₃)₄] (1) affords an isomeric mixture of [HRh(NHC)(PPh₃)₂] (NHC = IEt₂Me₂ (cis-/trans-2), IⁱPr₂Me₂ (cis-/trans-3), ICy (cis-/trans-4) and [HRh(NHC)₂(PPh₃)] (IEt₂Me₂(cis-/trans-5), IⁱPr₂Me₂ (cis-/trans-6), ICy (cis-/trans-7)). Thermolysis of 1 with the aryl substituted NHC, 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (IMesH₂), affords the bridging hydrido phosphido dimer, [{(PPh₃)₂Rh}₂(μ-H)(μ-PPh₂)] (8), which is also the reaction product formed in the absence of carbene. When the rhodium precursor was changed from 1 to [HRh(CO)(PPh₃)₃] (9) and treated with either IMes (=1,3-dimesitylimidazol-2-ylidene) or ICy, the bis-NHC complexes trans-[HRh(CO)(IMes)₂] (10) and trans-[HRh(CO)(ICy)₂] (11) were formed. In contrast, the reaction of 9 with IⁱPr₂Me₂ gave [HRh(CO)(IⁱPr₂Me₂)₂] (cis-/trans-12) and the unusual unsymmetrical dimer, [(PPh₃)₂Rh(μ-CO)₂Rh(IⁱPr₂Me₂)₂] (13). The complexes trans-3, 8, 10 and 13 have been structurally characterised.     

Synthesis of tridentate 2,6-bis(imino)pyridyl aminechlorohydro ruthenium(II) complexes: The convenient use of amine hydrochlorides to generate metal-hydride

The reaction of low-valent ruthenium complexes with 2,6-bis(imino)pyridine ligand, [η²-N₃]Ru(η⁶-Ar) (1) or {[N₃]Ru}₂(μ-N₂) (2) with amine hydrochlorides generates six-coordinate chlorohydro ruthenium (II) complexes with amine ligands, [N₃]Ru(H)(Cl)(amine) (4). Either complex 1 or 2 activates amine hydrochlorides 3, and the amines coordinate to the ruthenium center to give complex 4. This is a convenient and useful synthetic approach to form ruthenium complexes with amine and hydride ligands using amine hydrochloride.     

Diruthenium(I,I) saccharinate complexes: Synthesis, molecular structure, and evaluation as catalysts for carbenoid reactions of diazoacetates

The dinuclear ruthenium complexes [Ru₂(μ-sac)₂(CO)₆] (1), [Ru₂(μ-sac)₂(CH₃CN)₂(CO)₄] (3), [Ru₂(μ-sac)₂(CO)₅(PPh₃)] (4) and [Ru₂(μ-sac)₂(CO)₄(PPh₃)₂] (5) as well as the tetranuclear ruthenium complex [Ru₂(μ-sac)₂(CO)₅]₂ (2) (sac = saccharinate, C₇H₄NO₃S⁻) were synthesized starting from Ru₃(CO)₁₂ and saccharin. X-ray crystal structure analysis of 1, 3A × p-xylene, 4 × CH₂Cl₂ and 5 × 3CH₂Cl₂ showed that the core is bridged through the amidate moieties of the two saccharinate ligands, with a head-tail arrangement in complexes 1, 3A and 5, and a head-head arrangement in 4. For complex 3, an equilibrium mixture of the head-head regioisomer 3A and a second species 3b exists in solution. Complexes 1 and 2 are suitable catalysts for the cyclopropanation of nucleophilic alkenes (styrene, cyclohexene and 2-methyl-2-butene) with methyl diazoacetate.     

Synthesis and crystal structure characterization of iron(II), cobalt(II) and nickel(II) complexes with 1,3-bis(2-pyridylmethylthio)propane

Three new mononuclear complexes of nitrogen–sulfur donor sets, formulated as [Fe^II(L)Cl₂] (1), [Co^II(L)Cl₂] (2) and [Ni^II(L)Cl₂] (3) where L = 1,3-bis(2-pyridylmethylthio)propane, were synthesized and isolated in their pure form. All the complexes were characterized by physicochemical and spectroscopic methods. The solid state structures of complexes 1 and 3 have been established by single crystal X-ray crystallography. The structural analysis evidences isomorphous crystals with the metal ion in a distorted octahedral geometry that comprises NSSN ligand donors with trans located pyridine rings and chlorides in cis positions. In dimethylformamide solution, the complexes were found to exhibit Fe^II/Fe^III, Co^II/Co^III and Ni^II/Ni^III quasi-reversible redox couples in cyclic voltammograms with E_1/2 values (versus Ag/AgCl at 298 K) of +0.295, +0.795 and +0.745 V for 1, 2 and 3, respectively.     

Palladium complexes of multidentate pyrazolylmethyl pyridine ligands: Synthesis,structures and phenylacetylene polymerization

The compounds, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (_MeNˆNˆN) (L1) and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (_tBuNˆNˆN) (L2), react with either [Pd(NCMe)₂Cl₂] or [Pd(COD)ClMe] to form the mononuclear palladium complexes [Pd(_MeNˆNˆN)Cl₂] (1), [Pd(_MeNˆNˆN)ClMe] (2), [Pd(_tBuNˆNˆN)Cl₂] (3) and [Pd(_tBuNˆNˆN)ClMe] (4). Reactions of 1, 2 and 4 with the halide abstractor, NaBAr₄ (Ar = 3,5-(CF₃)₂C₆H₃), led to the formation of stable tridentate cationic species [Pd(_MeNˆNˆN)Cl]⁺(5), [Pd(_MeNˆNˆN)Me]⁺ (6) and [Pd(_tBuNˆNˆN)Cl]⁺ (7) respectively. The analogous carbonyl linker cationic species [Pd{(3,5-Me₂pz-CO)₂-py}Cl]⁺ (9) and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl]⁺ (10), prepared by halide abstraction of the neutral complexes [Pd{(3,5-Me₂pz-CO)₂-py}Cl₂] and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl₂] by NaBAr₄, were however less stable with t_1/2 of 14 and 2 days respectively. Attempts to crystallize 1 and 3 from the mother liquor resulted in the isolation of the salts [Pd(_MeNˆNˆN)Cl]₂[Pd₂Cl₆] (11) and [Pd(_tBuNˆNˆN)Cl]₂[Pd₂Cl₆] (12). Although when complexes 1–4 were reacted with modified methylaluminoxane (MMAO) or NaBAr₄, no active catalysts for ethylene oligomerization or polymerization were formed, activation with silver triflate (AgOTf) produced active catalysts that oligomerized and polymerized phenylacetylene to a mixture of cis-transoidal and trans-cisoidal polyphenylacetylene.     

Copper(II) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Crystal structure of a binuclear complex

Ten copper(II) complexes {[CuL¹Cl] (1), [CuL¹NO₃]₂ (2), [CuL¹N₃]₂ · 2/3H₂O (3), [CuL¹]₂(ClO₄)₂ · 2H₂O (4), [CuL²Cl]₂ (5), [CuL²N₃] (6), [Cu(HL²)SO₄]₂ · 4H₂O (7), [Cu(HL²)₂] (ClO₄)₂ · 1/2EtOH (8), [CuL³Cl]₂ (9), [CuL³NCS] · 1/2H₂O (10)} of three NNS donor thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL¹], pyridine-2-carbaldehyde-N(4)-2-phenethyl thiosemicarbazone [HL²] and pyridine-2-carbaldehyde N(4)-(methyl), N(4)-(phenyl) thiosemicarbazone [HL³]} were synthesized and physico-chemically characterized. The crystal structure of compound 9 has been determined by X-ray diffraction studies and is found that the dimer consists of two square pyramidal Cu(II) centers linked by two chlorine atoms.