Mononuclear Cationic Complexes Research Articles

New molybdenum(VI) complexes with thiazole-hydrazone ligand: Preparation, structural characterization, and catalytic applications in olefin epoxidation

The reaction of [MoO2(acac)2] with (E)-2-((2-(benzo[d]thiazol-2-yl)hydrazono)methyl)-6-methoxyphenol (H2L), in acetonitrile and ethanol resulted in the formation of {[MoO2(HL)(H2O)]2[Mo6O19]·2MeCN} (1) (mononuclear cationic complex with hexamolybdate anion) and [MoO2L(EtOH)] (2) (neutral mononuclear complex), depending on the reaction conditions. In these compounds, the ligand is coordinated to the cis-MO22+ core via phenolic-oxygen, thiazole and azomethine nitrogen atoms, while the remaining sixth coordination site is occupied by the oxygen atom from the solvent molecule. Crystal and molecular structures of the compounds 1 and 2 were determined by the single crystal X-ray diffraction method. All of the investigated compounds were further characterized by elemental analysis, FT-IR and NMR spectroscopy. The molybdenum(VI) species were used as catalyst for olefin oxidation in the presence of tert-butylhydroperoxide (TBHP) as an oxidant. Under similar experimental conditions with equal Mo loading, the presence of the {[MoO2(HL)(H2O)]2[Mo6O19]·2MeCN} (1) resulted in higher oxidation conversion than [MoO2L(EtOH)] (2). It seems 1 contains two potentially active parts, the [MoO2(HL)H2O]+ cation and the Mo6O19−2 anion.

Antibacterial, in vitro antitumor activity and structural studies of rhodium and iridium complexes featuring the two positional isomers of pyridine carbaldehyde picolinic hydrazone ligand

Half-sandwich organometallic rhodium and iridium complexes [1–6] have been synthesized with ligands L1 (L1=Pyridin-2-ylmethylene picolinichydrazine) and L2 (L2=Pyridin-3-ylmethylene picolinichydrazine). Treatment of [{Cp∗MCl2}2] (M=Rh/Ir) with L1 in methanol has yielded mononuclear cationic complexes such as [{Cp∗M(L1N∩N)Cl}]PF6 where {M=Rh (1) and Ir (2)} and dinuclear complexes such as [{(Cp∗MCl)2(L1N∩N, N∩N)}]PF6 where {M=Rh (3) and Ir (4)} in 1:2 and 1:1 metal dimer to ligand ratios respectively. Reactions of [{Cp∗MCl2}2] with L2 in both 1:2 and 1:1 metal dimer to ligand ratios have yielded two metalla-macrocyclic dinuclear and dicationic complexes such as [{Cp∗M(L2N∩NμN)}2](PF6)2 where {M=Rh (5) and Ir (6)}. Spectroscopic and crystallographic data were used to elucidate the structures of the synthesized complexes. The in vitro antitumor evaluation of the complexes 1 and 2 by fluorescence based apoptosis study revealed their antitumor activity against Dalton’s ascites lymphoma (DL) cells. The antibacterial evaluation of complexes 1, 2, 5 and 6 by agar well-diffusion method revealed their significant activity against the two species considered viz., Proteus vulgaris (MTCC 426) and Vibrio parahaemolyticus (MTCC 451) with zone of inhibition up to 43mm. The docking study with few key enzymes associated with cancer viz., ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase and topoisomerase II revealed their strong interactions with complexes under study. Complexes 1–6 exhibited a HOMO (highest occupied molecular orbital) – LUMO (lowest unoccupied molecular orbital) energy gap from 2.95eV to 3.59eV. TDDFT calculations explain the nature of electronic transitions and found well agreement with the experiments.

Mono, di and trinuclear photo-luminescent cadmium(II) complexes with N2O and N2O2 donor salicylidimine Schiff bases: Synthesis, structure and self assembly

Four new octahedral cadmium(II) complexes, [(Cd)(L1)(HL1)](ClO4) (1), [Cd2(L2)2(SCN)2(CH3OH)2] (2), [(CdL3)3(μ-1,1,1-OH)](ClO4)2 (3) and [Cd2(L4)2(SCN)(NO3)] (4) have been synthesized using four Schiff bases, HL1, HL2, HL3 and HL4, (where HL1=2-(2-(ethylamino)ethyliminomethyl)phenol, HL2=2-(2-(dimethylamino)ethyliminomethyl)-4-bromophenol, HL3=2-(2-(diethylamino)ethyliminomethyl)-6-methoxyphenol and HL4=2-(2-(ethylamino)ethyliminomethyl)-6-methoxyphenol). All four complexes have been characterized by elemental and spectral analysis and structures have been confirmed by single crystal X-ray diffraction studies. Complex 1 is a mononuclear cationic bis-ligand complex. Complex 2 features a double end-to-end thiocyanate bridged dinuclear cadmium(II) complex. Complex 3 has a partial cubane [Cd3O4] core in which three [CdL3] subunits are interconnected through two types of oxygen bridges afforded by phenoxo oxygen atoms of ligands and a central hydroxo group. Complex 4 has a double phenoxo bridged dinuclear structure. Supramolecular interactions in all four complexes were also explored. All four complexes show fluorescence.

Synthesis, characterization, and antileishmanial activities of gold(I) complexes involving quinoline functionalized N-heterocyclic carbenes

A series of new mononuclear cationic or neutral gold(I) complexes containing quinoline functionalized N-heterocyclic carbene(s) (NHC(s)) were synthesized and fully characterized by spectroscopic methods. The X-ray structures of two key compounds are presented. Proligands and their corresponding gold(I) complexes together with previously described silver(I) and gold(I) bis(NHC-quinoline) and gold(I) bis(NHC-methylbipyridine) complexes were evaluated in vitro towards Leishmania infantum. In parallel, the in vitro cytotoxicity of these molecules was assessed on the murine macrophages J774A.1. All gold(I) compounds show potent antileishmanial activity against L. infantum promastigotes and three of them are also efficient against L. infantum intracellular amastigotes. Structure-activity and toxicity relationships enables to evidence a lead-compound (6) displaying both a high activity and a good selectivity index.

Anion modulated structural variations in copper(II) complexes with a semicarbazone Schiff base: Synthesis, characterization and self assembly

Two copper(II) complexes, [Cu(L)N3]n (1) and [Cu(HL)2](I3)ClO4 (2), where HL=2-pyridylaldehydesemicarbazone, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Complex 1 crystallizes in monoclinic space group P21/a, whereas, complex 2 crystallizes in triclinic space group P-1. Complex 1 is a stair-like coordination polymer with square pyramidal geometry of copper(II), whereas, complex 2 is a mononuclear cationic bis-ligand complex of octahedral copper(II). Lower coordination ability of tri-iodide or perchlorate compared to azide may be related with variations of the structures of the complexes.

Structural and theoretical studies of mono and di-insertion of symmetric alkynes into the Pd–C σ bond of cyclopalladated secondary (tert-butyl and ethyl) benzylamines

The reactivity of the dinuclear cyclopalladated complexes derived from secondary benzylamines, [Pd2{(C,N)–C6H4CH2NH(R)}2(μ-X)2] [X = Br, R = t-Bu (1a); X = Cl, R = t-Bu (1b); X = Cl, R = Et (1c)] is reported. 1a reacted with dimethyl acetylenedicarboxylate (DMAD) to yield the mono-inserted complex [Pd2{(C,N)–C(CO2Me)C(CO2Me)C6H4CH2NH(t-Bu)}2(μ-Br)2] (2a). 1a, 1b and 1c reacted with (R′)CC(R′) (R′ = CO2Me, Ph) to give [Pd{(C,N) C(R′)C(R′)C(R′)C(R′)C6H4CH2NH(R)}X] [X = Br, R = t-Bu, R′ = CO2Me (3a); X = Cl, R = t-Bu, R′ = Ph (2b); X = Cl, R = Et, R′ = Ph (2c)] through a double insertion of the alkyne into the Pd–C σ bond. 2c also reacts with Ag(CF3SO3) and pyridine to give mononuclear cationic complex [Pd{(C,N)–C(Ph)C(Ph)C(Ph)C(Ph)}C6H4CH2NH(Et)(py)]CF3SO3 (3c). The crystal structures of di-inserted complexes 2b, 2c and 3c have been determined by X-ray diffraction studies. Their molecular structures showed that the conformation of the CC double bonds within the butadienyl group attached to the aromatic ring was trans–cis. Density functional theory (DFT) calculations also indicated that this arrangement is more stable than other possible conformations.

Metal Complexes of Enrofloxacin Part I: Preparation, Spectroscopic, Thermal Analyses Studies and Antimicrobial Evaluation

The interaction of titanium (IV), yttrium (III), zirconium (IV), palladium (II) and cerium (IV) with deproto- nated enrofloxacin leads to the formation of the neutral or cationic mononuclear complexes. The isolated solid complexes have been characterized with physicochemical and spectroscopic techniques and thermogravimeteric analyses. The spectro- scopic data indicate that the enrofloxacin ligand is on the deprotonated mode acting as bidentate ligand coordinated to the metal ions through the ketone oxygen and a carboxylato oxygen and the metal ions completed the coordination number with water molecules. The thermal decomposition mechanisms proposed for enrofloxacin and their metal complexes were discussed. The activation energies, E * , enthalpies, ∆H * , entropies, ∆S * and Gibbs free energies, ∆G * , of the thermal decomposition reactions have been derived from thermogravimetric (TG) and differential thermogravimetric (DTG) curves, using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. The antimicrobial activity has been evaluated against six different microorganisms.

Synthesis and Characterization of Cationic Rhodium Peroxo Complexes

Mononuclear cationic rhodium complexes of dioxygen have been synthesized and characterized. Crystallographic, spectroscopic, and computational results support the conclusion that these complexes are best described as RhIII{O22–} (rhodium(III) peroxo) complexes, in contrast to recently reported neutral analogues that are best described as RhI{1O2} adducts. The nature of the ligand trans to the O2 ligand is crucial in defining the electronic nature of the RhO2 bonding. It is determined that π-donor ligands such as the halides—in conjunction with sufficient steric bulk—can stabilize the formation of RhI{1O2} adducts, whereas stronger field ligands lead to the stabilization of asymmetric O2 binding that ultimately favors formation of higher coordinate RhIII peroxo species. The factors that control the relative stabilization of RhIII{O22–} versus RhI{1O2} species are related to the well-established Dewar–Chatt–Duncanson model that has been successfully used to describe the bonding in isoelectronic transition-metal alkene complexes. The specific factors that control the stabilization of one electromer (resonance structure) over another are explored and discussed in detail.

Structural Heterogeneity of AgI Complexes with a Flexible 1,2‐Bis[(imidazol‐2‐yl)thiomethyl]benzene Ligand and Issues Regarding the Phase Purity of the Bulk Material

AbstractA series of AgI coordination compounds with a new ligand, 1,2‐bis[(imidazol‐2‐yl)thiomethyl]benzene, and counterions such as PF6–, SbF6–, CF3SO3–, BF4– and NO3– was characterised by powder and single‐crystal XRD. Powder XRD revealed the presence of a mixture of crystallographic phases that were further identified by single‐crystal XRD. Despite conformational flexibility, 1,2‐bis[(imidazol‐2‐yl)thiomethyl]benzene has a tendency to form N,N‐chelated AgI mononuclear cationic complexes with a linear N–AgI–N unit. However, T‐shaped geometry (N2O) around the silver ion was also observed, which involved solvent molecules and/or counterions. The formation of a cationic 1D chain with the N,N′‐bridging ligand was revealed with the BF4– counterion. Coordination compounds that possess different nuclearity were formed with the NO3– counterion. In the dinuclear and trinuclear complexes, the ligand showed bischelating behaviour with N‐donor atoms that interact with one and S‐donor atoms with another metal centre. Furthermore, the crystal structure of the trinuclear complex revealed the presence of two crystallographically independent cationic moieties in the asymmetric unit, which only differ by a single O‐donor ligand (NO3– vs. H2O), where both of the moieties possess three different geometries around the constituent silver ions. Argentophilic interactions are present in the majority of the reported structures. Available amine N atoms facilitate hydrogen bond formation and promote the occurrence of solvates.

Cyclodiphosphazane appended with thioether functionality: Synthesis, transition metal chemistry and catalytic application in Suzuki–Miyaura cross-coupling reactions

The coordination chemistry of thioether functionalized cyclodiphosphazane ligand, cis-{ t BuNP(OCH 2CH 2SCH 3)} 2 ( 1) is described. The reactions of 1 with [Pd (COD)Cl 2] in 1:1, 1:2 and 2:1 M ratios afforded cis-[PdCl 2{ t BuNP(OCH 2CH 2SCH 3)} 2] ( 2), cis-[{PdCl 2} 2{ t BuNP(OCH 2CH 2SCH 3)} 2] ( 3) and trans-[PdCl 2{( t BuNP(OCH 2CH 2SCH 3)) 2} 2] ( 4), respectively. Treatment of 1 with [Pd(PEt 3)Cl 2] 2 or [PdCl( η 3-C 3H 5)] 2 in appropriate molar ratios produce the mono- and binuclear complexes [PdCl 2(PEt 3{ t BuNP(OCH 2CH 2SCH 3)} 2] ( 5) and [{PdCl( η 3-C 3H 5)} 2{ t BuNP(OCH 2CH 2SCH 3)} 2] ( 6) in good yield. The reaction of 1 with [{Ru( p-cymene)Cl 2} 2] afforded the mononuclear cationic complex, [{( p-cymene)RuCl{ t BuNP(OCH 2CH 2SCH 3)} 2]Cl ( 7), whereas the reactions of [Rh(COD)Cl] 2, [Pt(COD)Cl 2] and [Au(SMe 2)Cl] with 1 yielded the corresponding P-coordinated neutral complexes, [RhCl(COD){ t BuNP(OCH 2CH 2SCH 3)} 2] ( 8) cis-[PtCl 2{ t BuNP(OCH 2CH 2SCH 3)} 2] ( 9), respectively. The binuclear palladium(II) complex 3 was found to be an effective catalyst for the Suzuki–Miyaura cross-coupling reactions.

Novel mononuclear η 5-pentamethylcyclopentadienyl complexes of platinum group metals bearing pyrazolylpyridazine ligands: Syntheses and spectral studies

Condensation of 3,6-dichloropyridazine with 3,5-dimethylpyrazole in 1:1 ratio yielded one side substituted pyrazolylpyridazine ligand 3-chloro-6-(3,5-dimethylpyrazolyl)pyridazine ( L) while condensation of 3,6-dichloropyridazine with substituted pyrazoles in 1:2 ratio yielded both side substituted pyrazolylpyridazine ligands such as 3,6-bis(pyrazolyl)pyridazine ( L1), 3,6-bis(3-methylpyrazolyl)pyridazine ( L2) and 3,6-bis(3,5-dimethylpyrazolyl)pyridazine ( L3). A new series of cationic mononuclear complexes of the type [(η 5-Cp)M a(L)(PPh 3)]PF 6, [(η 5-Cp*)M b(L)Cl]PF 6, [(η 5-Cp*)Ru(L′)(PPh 3)]PF 6 and [(η 5-Cp*)M b(L′)Cl] + (where M a = Ru, Os; M b = Rh, Ir and L′ = L1, L2, L3) bearing pyrazolylpyridazine and η 5-cyclopentadienyl ligands are reported. The complexes have been completely characterized by spectral studies. The molecular structures of representative complexes have been determined by single crystal X-ray crystallography.

Tridentate Assembling Ligands Based on Oxazoline and Phosphorus Donors in Dinuclear Pd(I)−Pd(I) Complexes

To examine the bonding preferences of potentially tridentate phosphorus, nitrogen donor ligands on a dinuclear metal core, we have studied the coordination of the oxazoline-based ligands bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine (NPN) and bis(4,4-dimethyl-2-oxazolyl dimethylmethoxy)phenylphosphine (NOPON(Me2)) toward the dinuclear d(9)-d(9) Pd(I) complex [Pd(2)(NCMe)(6)][BF(4)](2). In the dinuclear product [Pd(2)(NPN-N,P,N)(2)](BF(4))(2) (1), in which the Pd-Pd bond length of 2.5489(7) A is rather short, the two interacting metal centers are P,N bridged by two molecules of the NPN ligand, forming two six-membered rings. The other oxazoline ring of each ligand further chelates a Pd center through its nitrogen atom, forming five-membered chelates, as in the mononuclear complex [PdCl(2)(NPN-N,P)] (5). In contrast, the reaction between [Pd(2)(NCMe)(6)](BF(4))(2) and NOPON(Me2) in the presence of LiCl afforded the mononuclear cationic complex [Pd(NOPON(Me2)-N,P,N)Cl](BF(4)) (3), which is also obtained by halide abstraction from [Pd(NOPON(Me2)-N,P)Cl(2)] with NaBF(4). When this reaction was performed in the presence of 1 equiv of t-BuNC, the new dinuclear Pd(I)-Pd(I) complex [Pd(2)Cl(2)(CNt-Bu)(NOPON(Me2)-N,P,N)] (4) was isolated, which can also be obtained from a comproportionation reaction between Pd(II) and Pd(0) complexes. The oxazoline in the P,N bridge is involved in a seven-membered ring moiety, a situation rarely encountered in Pd(I)-Pd(I) chemistry. Its nitrogen atom is coordinated trans to the isonitrile ligand whereas that of the P,N chelate at Pd(1) is trans to Pd(2). The fluxional processes involving the oxazoline moieties of the NPN and NOPON(Me2) ligands in 1 and 4, respectively, were examined by variable-temperature NMR spectroscopy. The crystal structures of 1, 3.0.5CH(3)CN, and 4 have been determined by X-ray diffraction. Prior to this work, relatively few complexes have been reported in the literature in which a potentially tridentate functional phosphorus ligand is simultaneously chelating and bridging a dinuclear Pd(I)-Pd(I) system.

Cationic Terminal Gallylene Complexes by Halide Abstraction: Coordination Chemistry of a Valence Isoelectronic Analogue of CO and N2

While N(2) and CO have played central roles in developing models of electronic structure, and their interactions with transition metals have been widely investigated, the valence isoelectronic diatomic molecules EX (E = group 13 element, X = group 17 element) have yet to be isolated under ambient conditions, either as the "free" molecule or as a ligand in a simple metal complex. As part of a program designed to address this deficiency, together with wider issues of the chemistry of cationic systems [L(n)M(ER)](+) (E = B, Al, Ga; R = aryl, amido, halide), we have targeted complexes of the type [L(n)M(GaX)](+). Halide abstraction is shown to be a viable method for the generation of mononuclear cationic complexes containing gallium donor ligands. The ability to isolate tractable two-coordinate products, however, is strongly dependent on the steric and electronic properties of the metal/ligand fragment. In the case of complexes containing ancillary pi-acceptor ligands such as CO, cationic complexes can only be isolated as base-trapped adducts, even with bulky aryl substituents at gallium. Base-free gallylene species such as [Cp*Fe(CO)(2)(GaMes)](+) can be identified only in the vapor phase by electrospray mass spectrometry experiments. With bis(phosphine) donor sets at the metal, the more favorable steric/electronic environment allows for the isolation of two-coordinate ligand systems, even with halide substituents at gallium. Thus, [Cp*Fe(dppe)(GaI)](+)[BAr(f)(4)](-) (9) can be synthesized and shown crystallographically to feature a terminally bound GaI ligand; 9 represents the first experimental realization of a complex containing a valence isoelectronic group 13/group 17 analogue of CO and N(2). DFT calculations reveal a relatively weakly bound GaI ligand, which is confirmed experimentally by the reaction of 9 with CO to give [Cp*Fe(dppe)(CO)](+)[BAr(f)(4)](-). In the absence of such reagents, 9 is stable for weeks in fluorobenzene solution, presumably reflecting (i) effective steric shielding of the gallium center by the ancillary phosphine and Cp* ligands; (ii) a net cationic charge which retards the tendency toward dimerization found for putative charge neutral systems; and (iii) (albeit relatively minor) population of the LUMOs of the GaI molecule through pi overlap with the HOMO and HOMO-2 of the [Cp*Fe(dppe)](+) fragment.

Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions

The new cationic mononuclear complexes [(η 6-arene)Ru(Ph-BIAN)Cl]BF 4 [η 6-arene = benzene ( 1), p-cymene ( 2)], [(η 5-C 5H 5)Ru(Ph-BIAN)PPh 3]BF 4 ( 3) and [(η 5-C 5Me 5)M(Ph-BIAN)Cl]BF 4 [M = Rh ( 4), Ir ( 5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η 5-C 5Me 5)Ir(Ph-BIAN)Cl]BF 4 has been determined crystallographically. Complexes 1– 5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH 3COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η 5-C 5Me 5)Rh(Ph-BIAN)Cl]BF 4 ( 4) displays the most effective catalytic activity.

Synthesis and structure of the monometallic cationic complex [Cp(CO) 2Fe{η 2-(CH 2CHCH 2CH 3)}]PF 6 (Cp = η 5-C 5H 5)

The bimetallic carbocation complex [{Cp(CO) 2Fe} 2(μ-C 4H 7)]PF 6 reacted with trifluoroacetic acid to give the mononuclear cationic complex [Cp(CO) 2Fe{η 2-(CH 2CHCH 2CH 3)}]PF 6, which formed yellow orthorhombic crystals in the space group P2 12 12 1 with a = 7.652(4), b = 13.422(7), c = 14.037(7); α = β = γ = 90.00 and Z = 4. The carbocation is coordinated to the metal in a η 2-fashion forming a chiral metallacyclopropane type structure. The β-CH carbon (C9) is disordered over two positions (C9A and C9B), each having about 50% occupancy. This is attributed to there being both the R and S enantioface isomers in equal amounts in the crystal sample. NMR data indicate that the metallacyclopropane structure observed in the solid state is preserved in solution.

Influence of synthesis conditions on the properties of 2-pyrimidinecarbonitrile in complexing reactions: Synthesis and structure of the coordination polymer [Ag(C4H3N2CN)NO3] and mononuclear complex [Ag(C4H3N2COOH)2]NO3·H2O

The coordination polymer [Ag(C4H3N2CN)NO3] (I) and mononuclear complex [Ag(C4H3N2COOH)2]NO3 · H2O (II) have been synthesized and characterized by X-ray crystallography. The crystals of I are monoclinic, space group Pm, a = 5.364(1) A, b = 6.631(1) A, c = 5.648(1) A, β = 105.68(3)°, V = 193.42(6) A3, d calcd = 2.361 g/cm3, Z = 1. The crystals II are triclinic, space group \(P\bar 1\), a = 6.859(1) A, b = 8.872(2) A, c = 12.825(3) A, α = 81.29(3)°, β = 86.33(3)°, γ = 69.66(3)°, V = 723.3(3) A3, d calcd = 2.002 g/cm3, Z = 2. The structure of I is built of polymeric chains [Ag(C4H3N2CN)] ∞ + linked through coordinated anions NO 3 − into layers (a 2D polymer) perpendicular to the [001] direction. The formation of II is a result of hydrolysis of the carbonitrile group to the carboxyl group (in the presence of metal ions in the solution) and coordination of the ligand to the metal. In II, mononuclear cationic complexes [Ag(N2H3C5OOH)2]+ are linked through H-bonds into supramolecular chains along direction [010]. Hydrogen bonds are also formed between free NO 3 − anions and water molecules.

Synthesis, X-ray structure and magnetic studies of Cu(II) complexes of tridentate SNS ligands (S-dbpt, N, N, N′, N′-tetraisobutylpyridine-2,6-dithiocarboxamide; S-dppt, N, N, N′, N′-tetraisopropylpyridine-2,6-dithiocarboxamide): Role of steric factors on the geometry around Cu(II)

The synthesis, structure and magnetic properties of two new tetranuclear copper(II) compounds [{Cu(S-dbpt)} 2(μ-Cl) 2][{CuCl 2} 2(μ-Cl) 2] (S-dbpt; N, N, N′, N′-tetraisobutylpyridine-2,6-dithiocarboxamide) 1 and [{CuCl(S-dppt)}] 2[{CuCl 2} 2(μ-Cl) 2] (S-dppt; N, N, N′, N′-tetraisopropylpyridine-2,6-dithiocarboxamide) 2 are reported. Both compounds contain a cationic complex with copper(II) coordinated to the ligand through both the thioamide S atoms and pyridilic N atom and one chlorine atom. The structure of the cationic dinuclear entity [{Cu(S-dbpt)} 2(μ-Cl) 2] 2+ in 1 consists of two square pyramids sharing a basal to apical edge. For compound 2, there are two cationic mononuclear complexes [{CuCl(S-dppt)}] +. Both compounds contain the same dinuclear chlorine bridged anion [{CuCl 2} 2(μ-Cl) 2] 2−, containing a planar [Cu 2(μ-Cl) 2] core. Magnetic susceptibility measurements show weak antiferromagnetic coupling between the Cu(II) ions in these anionic complexes ( J = −077 cm −1 for 1 and 0.88 cm −1 for 2). The cationic complex of 1 shows a ferromagnetic interaction with J = +3.2 cm −1.

Selective Oxidation and Reduction of Trinuclear Titanium(II) Hexaazatrinaphthylene ComplexesSynthesis, Structure, and Electrochemical Investigations

Titanocene complexes with chelating N-heterocyclic ligand bridges react with ferrocenium salts as selective oxidants to afford air-stable cationic complexes and allow the preparation of exceptional mixed valence hexaazatrinaphthylene complexes [(Cp2Ti)3(mu3-HATNMe6)]n+ (1n+) (n=1, 2, 3, 4). Cyclic voltammograms (CV) and differential pulse voltammograms (DPV) show that nine oxidation states of 1 are generated without decomposition. Comproportionation constants Kc have been calculated in order to determine the extent of electronic communication between the titanium centers. The Kc values of the mixed valence states are indicative of uncoupled (14+), moderately coupled (15+), and strongly coupled (1-, 1+, and 12+) systems. Small but significant structural changes occurring upon oxidation of neutral 1 are observed by X-ray structural analysis on 1+-14+. Anion-pi interactions between the electron-deficient central ring of the HATNMe6 moiety and PF6- and BF4- counterions, respectively, are found for 12+, 13+, and 14+. The short cation-anion contacts cause interesting molecular allignments in terms of molecular architecture. For 12+ the assembly of an one-dimensional (1D) polymer is observed. Electrochemical investigations on the mononuclear cationic titanocene complexes [(Cp2Ti)(L)]+ (L=2,2'-biquinoline (2+), 4,4'-dimethyl-2,2'-biquinoline (3+), and 5,8'-dimethyl-2,3'-biquinoxaline (4+)) showed similar oxidation and reduction characteristics among each other. Conversion to monoanionic, neutral, and dicationic states is enabled. As found for the trinuclear compounds 1n+, the molecular structures of 2+-4+ reveal significant differences compared to their neutral parents.

Cationic palladium(II)-allyl-complexes containing 2-pyridyldiphenylphosphine: X-ray crystal structure of the binuclear complex [Pd(η 3-2-Me-allyl)(μ-Ph 2PPy)] 2(BF 4) 2. Detection of an intramolecular C(allyl)–H⋯phenyl ring π-interaction

Reaction of [PdCl(η 3-2-Me-allyl)(Ph 2PPy)] ( 1) with AgBF 4 affords the new dinuclear cationic complex [Pd(η 3-2-Me-allyl)(μ-Ph 2PPy)] 2(BF 4) 2 ( 2). The X-ray structural analysis of 2 shows that the 2-pyridyldiphenylphosphine ligands adopt a binucleating role through the P and N atoms bridging two independent palladium centres to form an eight-membered metallocyclic ring. One of the anti hydrogen atoms of the allyl moiety was located very close to a phenyl ring of Ph 2PPy indicating the occurrence of a CH/π interaction. Addition of one equivalent of Ph 2PPy to complex ( 2) affords the mononuclear cationic complex [Pd(η 3-2-Me-allyl)(Ph 2PPy) 2](BF 4) ( 3).

Synthesis and Reactivity of Cationic Palladium Phosphine Carboxylate Complexes

Simple routes to two new types of mononuclear cationic palladium phosphine acetate complexes featuring κ1- or κ2-carboxylates have been developed, and the resulting materials have been characterized by single-crystal X-ray diffraction. In acetonitrile the complex [(iPr3P)2Pd(κ2O,O‘-OAc)]+ leads not to the independently prepared trans-[(iPr3P)2Pd(MeCN)(OAc)]+ but to reversible cyclometalation to form [(iPr3P)(MeCN)Pd(κ2C,P-C(Me)2PiPr2)]+.