Structural diversity of di and triorganotin complexes with 4-sulfanylbenzoic acid: Supramolecular structures involving intermolecular Sn?O, O-H?O or C-H?X (X = O or S) interactions

Twelve new organotin complexes with 4-sulfanylbenzoic acid of two types: R_nSn[S(C₆H₄COOH)]_4−n (I) (n = 3: R = Me 1, n-Bu 2, Ph 3; PhCH₂4; n = 2: R = Me 5; n-Bu 6, Ph 7, PhCH₂8) and R₃Sn(SC₆H₄COO)SnR₃ · mEtOH (II) (m = 0: R = Me 9, n-Bu 10, PhCH₂12; m = 2: R = Ph 11), along with the 4,4′-bipy adduct of 9, [Me₃Sn(SC₆H₄COO)SnMe₃]₂(4,4-bipy) 13, have been synthesized. The coordination behavior of 4-sulfanylbenzoic acid is monodentate in 1-8 by thiol S atom but not carboxylic oxygen atom. While, in 9-13 it behaves as multidenate by both thiol S atom and carboxylic oxygen atoms. The supramolecular structures of 6, 11 and 13 have been found to consist of 1D molecular chains built up by intermolecular O-H?O, C-H?O or C-H?S hydrogen bonds. The supramolecular aggregation of 7 is 2D network determined by two C-H?O hydrogen bonds. Extended intermolecular C-H?O interactions in the crystal lattice of 9 link the molecules into a 2D network.     

Syntheses, characterizations and crystal structures of new organoantimony(V) complexes with heterocyclic (S, N) ligand

Eight new organoantimony(V) complexes with 1-phenyl-1H-tetrazole-5-thiol [L¹H] and 2,5-dimercapto-4-phenyl-1,3,4-thiodiazole [L²H] of the type R_nSbL_5 − n (L = L¹: n = 4, R = n-Bu 1, Ph 2, n = 3, R = Me 3, Ph 4; L = L²: n = 4, R = n-Bu 5, Ph 6, n = 3, R = Me 7, Ph 8) have been synthesized. All the complexes 1-8 have been characterized by elemental, FT-IR, ¹H and ¹³C NMR analyses. Among them complexes 2, 6 and 8 have also been confirmed by X-ray crystallography. The structure analyses show that the antimony atoms in complexes 2 and 6 display a trigonal bipyramid geometry, while it displays a distorted capped trigonal prism in complex 8 with two intramolecular Sb?N weak interactions. Furthermore, the supramolecular structure of 2 has been found to consist of one-dimensional linear molecular chain built up by intermolecular C-H?N weak hydrogen bonds, while a macrocyclic dimer has been found in complex 6 linked by intermolecular C-H?S weak hydrogen bonds with head-to-tail arrangement. Interestingly, one-dimensional helical chain is recognized in complex 8, which is connected by intermolecular C-H?S weak hydrogen bonds.     

Syntheses,supramolecular structures and properties of six coordination complexes based on 5-sulfosalicylic acid and bipyridyl-like chelates

Six new complexes constructed by 5-sulfosalicylic acid and bipyridyl-like ligands (2,2′-bipy and 1,10-phen), namely [Cu₄(OH)₂(ssal)₂(phen)₄ · 7H₂O] (1), [Cu₄(OH)₂(ssal)₂(bipy)₄ · 2H₂O] (2), [Cd(Hssal)(bipy)] (3), [Cd(HL)₂(phen)₂] (4), [Cr(ssal)(bipy)(H₂O)₂ · 2H₂O] (5) and [Cr(ssal)(phen)₂] (6) (H₃ssal = 5-sulfosalicylic acid, H₂L = p-hydroxybenzenesulfonic acid, bipy = 2,2′-bipy, phen = 1,10-phen) were prepared under hydrothermal conditions and their structures were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are both tetranuclear copper complexes with a stepped topology. In complex 3, a new coordination mode of the Hssal²⁻ group is reported in this work. During the synthetic process of complex 4, in situ decarboxylation of 5-sulfosalicylic acid into p-hydroxybenzenesulfonic acid is involved. Two chromium 5-sulfosalicylates (5 and 6) are reported for the first time. These new complexes display different supramolecular structures by O–H?O, C–H?O hydrogen bonds as well as π?π, C–H?π and O?π interactions. The results of magnetic determination show that ferromagnetic interactions exist in complex 1, however, antiferromagnetic interactions exist in 2.     

4,5-Bis[(triorganotin)thiolato]-1,3-dithiole-2-thione, (R3Sn)2(dmit), 4,5-bis[(triorganotin)thiolato]-1,3-dithiole-2-one, (R3Sn)2(dmio), compounds: Crystal structures of (cyclohexyl3Sn)2(dmio), (Ph3Sn)2(dmit) and (Ph3Sn)2(dmio)

The synthesis and crystal structures of 4,5-bis[(triorganotin)thiolato]-1,3-dithiole-2-thione, (R₃Sn)₂(dmit), 1, and 4,5-bis[(triorganotin)thiolato]-1,3-dithiole-2-one, (R₃Sn)₂(dmio), 2, compounds are reported. Compounds, (1 or 2: R = Ph or cyclohexyl, Cy), have been obtained from reaction of R₃SnCl with Cs₂dmit or Na₂dmio. The presence of the two tin centres in (2: R = Ph) is shown in the ¹³C NMR spectrum by the couplings of both Sn atoms to the dmio olefinic carbons with J values of 29.4 and 24.7 Hz. The δ¹¹⁹ Sn values for (1: R = Ph) and (2: R = Ph) differ by about 30 ppm, values being −20.7 and −50.1 ppm, respectively, in CDCl₃ solution. X-ray structure determinations for (1: R = Ph) and (2: R = Ph or Cy) reveal the compounds to have 4-coordinate, distorted tetrahedral tin centres. The dithiolato ligands, dmit and dmio, act as bridging ligands, in contrast to their chelating roles in R₂Sn(dmit) and R₂Sn(dmio). A further difference between R₂Sn(dmit) and R₂Sn(dmio), on one hand, and 1 and 2 on the other, is that intermolecular Sn-S and Sn-O interactions are absent in 1 and 2. However, weak intermolecular hydrogen bonding interactions are found in (1: R = Ph) [C-H?π] and in (2: R = Ph) [C-H?π and C-H?O].     

Synthetic, spectral and structural studies of some homo and hetero binuclear arene ruthenium (II) polypyridyl complexes

Homo-hetero binuclear cationic complexes with the formulation [(η⁶-arene)RuCl(μ-dpp)(L)]⁺ (η⁶-arene = benzene; L = PdCl₂ (1a); PtCl₂ (1b), and η⁶-arene = p-cymene; L = PdCl₂ (2a); PtCl₂ (2b)), [(η⁶-arene)RuCl(μ-dpp)(L)]²⁺(η⁶-arene = p-cymene; L = [(η⁶-C₆H₆)RuCl] (2c), and [(η⁶-C₁₀H₁₄)RuCl] (2d)) were prepared. Molecular structure of the representative homo binuclear complex [{(η⁶-C₁₀H₁₄)RuCl}(μ-dpp){(η⁶-C₁₀H₁₄)RuCl}](PF₆)₂ (2d) was determined crystallographically. Weak interaction studies on the complex 2d revealed stabilisation of the crystal packing by weak inter and intra molecular C-H?X (X = F, Cl, π) and π-π interactions. The C-H?F interactions lead to parallel helical chains and encapsulation of counter anion in self-assembled cavity arising from C-H?π and π-π weak interactions.     

Palladium(II) and platinum(II) saccharinate complexes containing pyridine and 3-acetylpyridine: Synthesis, crystal structures, fluorescence and thermal properties

New palladium(II) and platinum(II) complexes of saccharinate (sac), trans-[Pd(py)₂(sac)₂] (1), cis-[Pt(py)₂(sac)₂] (2), trans-[Pd(3-acpy)₂(sac)₂] (3) and cis-[Pt(3-acpy)₂(sac)₂] (4) (py = pyridine and 3-acpy = 3-acetylpyridine) have been synthesized. Elemental analysis, UV-Vis, IR, NMR and TG/DTA characterizations have been carried out. The structures of 1-4 were determined by X-ray diffraction. The palladium(II) and platinum(II) ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of py or 3-acpy, forming a distorted square-planar geometry. The palladium(II) complexes (1 and 3) are trans isomers, while the platinum(II) complexes (2 and 4) are cis isomers. The mononuclear species in the solid state are connected by weak intermolecular C-H?O hydrogen bonds, C-H?π and π?π stacking interactions. The platinum(II) complexes show significant fluorescence at the room temperature.     

Crystal structures,theoretical calculations,spectroscopic and electrochemical properties of Cr(III) complexes with dipicolinic acid and 1,10-phenantroline

The crystal structures of compounds Na[Cr(dipic)₂] · 2H₂O (1) and [Cr(dipic)(phen)Cl] · 1/2H₂O (2), dipic = dipicolinate, phen = 1,10-phenantroline, were determined. In both complexes, Cr(III) is in a distorted octahedral environment. In complex (1), the metal is coordinated to two nearly perpendicular dipic anions acting as tridentate ligands through one oxygen of each carboxylate group and the pyridinic nitrogen atom. In complex (2), Cr(III) ion is similarly coordinated to a dipic anion, defining a ligand equatorial plane. The phen molecule bridges the remaining equatorial coordination site and one of the axial positions through its N-atoms. The other axial position is occupied by a chloride ion.     

Secondary bonding in functionalized organotellurium compounds: preparation and structural characterization of bis(acetamido)tellurium(IV) diiodide and bis(4-methylbenzoylmethyl)tellurium(II)

Elemental tellurium inserts, under mild conditions, between C-I bond of iodoacetamide to afford bis(acetamido)tellurium(IV) diiodide (NH₂COCH₂)₂TeI₂, 1. Heating of N-bromomethylphthalimide with activated tellurium powder however, resulted in the formation of bis(phthalimido)methane, 2, instead of the expected product bis(phthalimidomethyl)tellurium(IV) dibromide. The IR spectrum of 1 is indicative of intramolecular Te?OC interaction which is also substantiated by its single-crystal structure. The compound with planar small-bite chelating organic ligands acquires butterfly shape that imparts almost perfect C_2v molecular symmetry but unlike other organotellurium(IV) iodides, the solid state structure of 1 is devoid of any intermolecular Te?I or I?I secondary interactions owing to the presence of intramolecular Te?O secondary bonds as well as intermolecular N-H?O, N-H?I and C-H?I hydrogen bonds. Bis(4-methylbenzoylmethyl)telluride (4-MeC₆H₄COCH₂)₂Te, 3b, prepared by the reduction of the corresponding dibromide, is the first structurally characterized acyclic dialkyltelluride and interestingly, does not involve intramolecular Te?OC interaction invariably present in the parent dihalides (4-YC₆H₄COCH₂)₂TeX₂ (Y = H, X = I 4a; Y = H, X = Br 5a; Y = MeO, X = Br 5c). Weak intermolecular Te?Te and C-H?O hydrogen bonds appear to be the non covalent intermolecular associative forces that dominate its crystal packing in the solid state of this Te(II) derivative. The dialkyltellurides (4-YC₆H₄COCH₂)₂Te, (Y = H, 3a, Me, 3b) undergo oxidation in presence of (SCN)₂ to give the corresponding bis(isothiocyanato)tellurium(IV) derivatives and form 2:1 adducts with Pt(II) and Pd(II) chlorides.     

Helices of ruthenium complexes involving pyridyl-azine ligands: synthesis, spectral and structural aspects

New cationic complexes [Ru(η⁵-C₅H₅)(EPh₃)(L)]BF₄ [L = pyridine-2-carbaldehyde azine (paa); E = P, 1; E = As, 2; E = Sb, 3] and κ¹ bonded dppm complexes [Ru(η⁵-C₅H₅)(κ¹-dppm)(L)]BF₄ [L = paa 4; L = p-phenylene-bis(picoline)aldimine (pbp) 5] containing both group V donor and pyridyl-azine ligand are reported. The complexes were fully characterized by analytical and spectral studies. ³¹P NMR spectral studies suggested coordination of dppm in the complexes 4 and 5 in κ¹-manner, which was further, confirmed by structural studies on the representative complex 4. Weak interaction studies revealed that inter- and intramolecular C-H?X (X = O, F, Cl, π) and π-π interactions in the complexes 1 and 4 lead to helical structures.     

Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.     

Synthesis,structure, optical and magnetic properties of [CrL(X)3], {L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine; X = Cl,N3, NCS}

Three complexes of composition [CrL(X)₃], where L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine and X = Cl⁻, N₃⁻, NCS⁻ are synthesized. They are characterized by IR, UV–Vis, fluorescence, EPR spectroscopic, and X-ray crystallographic studies. Structural studies reveal that the Cr(III) ion is coordinated by three N atoms of L in a meridional fashion. The three anions occupy the other three coordination sites completing the mer-N₃Cl₃ (1) and mer-N₃N₃ (2 and 3), distorted octahedral geometry. The Cr–N2 has a shorter length than the Cr–N1 and Cr–N3 distances and the order Cr–N(NCS⁻) < Cr–N(N₃⁻) < Cr–Cl is observed. They exhibit some of the d–d transitions in the visible and intra-ligand transitions in the UV regions. The lowest energy d–d transition follows the trend [CrLCl₃] < [CrL(N₃)₃] < [CrL(NCS)₃] consistent with the spectrochemical series. In DMF, they exhibit fluorescence having π → π^∗ character. All the complexes show a rhombic splitting as well as zero-field splitting (zfs) in X-band EPR spectra at 77 K.     

The variability of hydrogen-bonded supramolecular assemblies in crystalline picrates prepared from ferrocenyl-substituted β-aminoalcohols

Ferrocene-based β-aminoalcohols FcCH₂NHCR₂CH₂OH (R = H, 1a; R = Me, 1b) and (S)-FcCH₂NHCH(CHMe₂)CH₂OH (1c; Fc = ferrocenyl) react with 2,4,6-trinitrophenol (Hpic) under proton transfer to afford the corresponding ammonium picrates 2a-c. In the crystal, these picrates associate predominantly via N-H?O and O-H?O bifurcated hydrogen bonds between the NH₂⁺ and OH groups in the aminoalcohol chain as the donors and the phenoxide and NO₂ oxygen atoms of the picrate anion as the acceptors. Compounds 2a and 2b form closed dimeric assemblies [1nH]₂[pic]₂ (n = a, b) around the crystallographic inversion centres. By contrast, their chiral analogue 2c gives rise to monomeric units [1cH][pic] (albeit through similar interactions), that further aggregate into infinite linear chains via N-H?O hydrogen bonds. The formed assemblies are interconnected by the soft C-H?O hydrogen bonds and via π?π stacking interactions of the picrate ions.     

Ethylene addition to group-6 transition metal oxo complexes - A theoretical study

Quantum chemical calculations using density functional theory (B3LYP) were carried out to elucidate the reaction pathways for ethylene addition to the chromium and molybdenum complexes CrO(CH₃)₂(CH₂) (Cr1) and MoO(CH₃)₂(CH₂) (Mo1). The results are compared with previously published results of the analogous tungsten system WO(CH₃)₂(CH₂) (W1). The comparison of the group-6 elements shows that the molybdenum and tungsten compounds Mo1 and W1 have a similar reactivity while the chromium compound has a more complex reactivity pattern. The kinetically most favorable reaction pathway for ethylene addition to Mo1 is the [2+2]_Mo,C addition across the MoCH₂ double bond which has an activation barrier of only 8.4 kcal/mol. The reaction is slightly exothermic with ΔE_R = −0.6 kcal/mol. The [2+2]_Mo,O addition across the MoO double bond and the [3+2]_C,O addition have much higher barriers and are strongly endothermic. The thermodynamically mostly favored reaction is the [1+2]_Mo addition of ethylene to the metal atom which takes place after prior rearrangement of the Mo(VI) compound Mo1 to the Mo(IV) isomer Mo1g. The reaction is −19.2 kcal/mol exothermic but it has a large barrier of 34.5 kcal/mol. The kinetically and thermodynamically most favorable reaction pathway for ethylene addition to the chromium homologue Cr1 is the multiple-step process with initial rearrangements Cr1 → Cr1c → Cr1g which are followed by a [1+2]_Cr addition yielding an ethylene π complex Cr1g + C₂H₄ → Cr1g-1. The highest barrier comes from the first step Cr1 → Cr1c which has an activation energy of 14.2 kcal/mol. The overall reaction is exothermic by −26.3 kcal/mol.     

Structural characterization of rare intramolecularly (1,4-Te?N) bonded diorganotellurides and their monomeric complexes with mercury(II) halides: Metal assisted C-H?X (Hg) interactions leading to supramolecular architecture

Monomeric tellurides 4-RC₆H₄(SB)Te [SB = 2-(4,4′-NO₂C₆H₄CHNC₆H₃-Me); R = H, 1a; Me, 1b; OMe, 1c], which incidentally represent the first example of a telluride with 1,4-Te?N intramolecular interaction, have been prepared and characterized by solution and solid-state ¹²⁵Te NMR, ¹³C NMR and X-ray crystallography. Interplay of weak C-H?O and C-H?π interactions in the crystal lattice of 1b and 1c are responsible for the formation of supramolecular motifs. These tellurides undergo expected oxidative addition reactions with halogens and interhalogens and also interact coordinatively with mercury(II) halides to give 1:2 complexes, HgX₂[4-RC₆H₄(SB)Te]₂ (X = Cl, R = H, 2a; Me, 2b; OMe, 2c and X = Br, R = H, 3a; Me, 3b; and OMe, 3c) with no sign of Te-C bond cleavage, as has been reported for some 1,5-Te?N(O) intramolecularly bonded tellurides. The complexes 2a and 3c are the first structurally characterized monomeric 1:2 adducts of mercury(II) halides with Te ligands. The 1,4-Te?N intramolecular interactions in the solid-state are retained in the complexes highlighting simultaneously the Lewis acid and base character of the Te(II) atom. Packing of molecules in the crystal lattice of 2a and 3c reveals that non-covalent C-H?Cl/Br interactions involving metal-bound halogen atoms possess significant directionality and in combination with coordinative covalent interactions may be of potential use in creating inorganic supramolecular synthons.     

Self-assembly of organooxotin(IV) clusters with Schiff-base-containing-triazole from hydrolysis or solvothermal synthesis: Crystal structures, hydrogen bonds, C-H?π stacking and S?S interaction

Eight new organostannoxane-based multiredox assemblies containing-Schiff-base-triazole ligand peripheries have been readily synthesized by hydrolysis or solvothermal synthetic routes. The reactions of the diorganotin dichloride with the Schiff-base-containing-triazole ligand afford the following types: [(Me₂Sn)₂O₂(Ln)]₂ (n = 1, for 1) [(Me₂Sn)₂O(RO)(Ln)]₂ (R = Et, n = 2, for 2; R = Me, n = 3, for 3), [(n-Bu₂Sn)₂O₂(Ln)]₂ (n = 1, for 4; n = 2, for 5; n = 3, for 6) and [(Me₂Sn)₂Ln₂O]₂ · L (n = 2; L = H₂O for 7, L = CH₃OH for 8). All the complexes were characterized by elemental analysis, IR, ¹H, ¹³C and ¹¹⁹Sn spectra analyses. Except for complexes 4 and 6, the other complexes are also characterized by X-ray crystallography diffraction analyses. Complexes 1-3 and 5 show similar structures containing a Sn₄O₄ ladder-shaped skeleton in which the N atom from a corresponding thione-form deprotonated Schiff base coordinated to the exo tin atoms in monodentate chelating agent. Complex 7 and 8 show a novel framework containing a Sn₂O₂ symmetrical core with two N atoms from triazole moiety coordinated to tin atoms. Weak but significant intermolecular hydrogen bondings, C-H?π stacking or non-bonded S?S interaction lead to aggregation and self-assembly of these complexes into 1D, 2D or 3D supramolecular frameworks.     

Self-assembly syntheses and crystal structures of triorganotin(IV) pyridinecarboxylate: 1D polymers and a 42-membered macrocycle

A series of new triorganotin(IV) pyridinecarboxylates with 6-hydroxynicotinic acid (6-OH-3-nicH), 5-hydroxynicotinic acid (5-OH-3-nicH) and 2-hydroxyisonicotinic acid (2-OH-4-isonicH) of the types: [R₃Sn (6-OH-3-nic)·L]_n (I) (R = Ph, L = Ph·EtOH, 1; R = Bn, L = H₂O·EtOH, 2; R = Me, L = 0, 3; R = n-Bu, L = 0, 4), [R₃Sn (5-OH-3-nic)]_n (II) (R = Ph, 5; R = Bn, 6; R = Me, 7; R = n-Bu, 8), [R₃Sn (2-OH-4-isonic·L)]_n (III) (R = Bn, 9, L = MeOH; R = Me, L = 0, 10; R = Ph, 11, L = 0.5EtOH) have been synthesized. All the complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy analyses. Among them, except for complexes 5 and 6, all complexes were also characterized by X-ray crystallography diffraction analysis. Crystal structures show that complexes 1-10 adopt 1D infinite chain structures which are generated by the bidentate O, O or N, O and the five-coordinated tin centers. Significant O-H?O, and N-H?O intermolecular hydrogen bonds stabilize these structures. Complex 11 is a 42-membered macrocycle containing six tin atoms, and forms a 2D network by intermolecular N-H?O hydrogen.     

Synthesis and spectral characterization of mercury(II) complexes with the bidentate Schiff base ligand N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane: The crystal structures of [Hg((23-MeO-ba)2en)I2] and [Hg((23-MeO-ba)2en)Br2]

Three mercury(II) complexes, [Hg((23-MeO-ba)₂en)X₂] (X = I (1), Br (2) and Cl(3)), and the ligand (23-MeO-ba)₂en ((23-MeO-ba)₂en = N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane) have been synthesized and characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy. The crystal and molecular structures of 1 and 2 were determined by X-ray crystallography from single-crystal data. The metal-to-ligand ratio was found to be 1:1. The mercury(II) center in 1 and 2 has a distorted tetrahedral geometry with HgN₂I₂ and HgN₂Br₂ chromophores, respectively. The Schiff base ligand (23-MeO-ba)₂en acts as a chelating ligand, coordinating via the two nitrogen atoms to the mercury(II) center, and it adopts an E,E conformation. The coordination sphere of the mercury(II) center in 1 and 2 is completed by the two I and Br atoms, respectively. In complex 1 an inter-molecular non-classical hydrogen bond of the type C-H?O was found, while in complex 2 inter- and intra-molecular non-classical hydrogen bonds of the type C-H?X (X = O and Br) were found. The ¹H NMR spectra of the complexes exhibit downfield as well as upfield shifts of the free ligand resonances, reflecting changes in the ligand’s geometry during its coordination.     

Transition-metal complexes of phenoxy-imine ligands modified with pendant imidazolium salts: Synthesis, characterisation and testing as ethylene polymerisation catalysts

Reaction between 3-((1R,2R)-2-{[1-(3,5-di-tert-butyl-2-hydroxy-phenyl)-meth-(E)-ylidene]-amino}-cyclohexyl)-1-isopropyl-4-phenyl-3H-imidazol-1-ium bromide (1a) or the derivative 3-((1R,2R)-2-{[1-(2-hydroxy-5-nitro-phenyl)-meth-(E)-ylidene]-amino}-cyclohexyl)-1-isopropyl-4-phenyl-3H-imidazol-1-ium bromide (1b) and metal halides MCl_x.yTHF (M = Zr, x = 4, y = 2; M = V, x = y = 3; M = Cr, x = y = 3), in THF, at −78 °C gives the metal complexes of general formula [MCl_x(κ²-N,O-OC₆H₂R¹R²C(H)N-C₆H₁₀-Im)₂][Br]₂ (where M = Zr, x = 2, R¹ = R² = ^tBu, 2; M = Zr, x = 2, R¹ = H, R² = NO₂, 3; M = V, x = 1, R¹ = R² = ^tBu, 4; M = Cr, x = 1, R¹ = R² = ^tBu, 5; M = Fe, x = 0, R¹ = R² = ^tBu, 6; Im = 1-isopropyl-4-phenyl-3H-imidazol-1-ium-3-yl). ¹H and ¹³C NMR spectroscopy of 2 and 3 indicate κ²-N,O-ligand coordination via the phenoxy-imine moiety with pendant imidazolium salt that is corroborated by a single crystal structure of 6. Compounds 2, 3, 4 and 5 were tested as precatalysts for ethylene polymerisation in the presence of methylaluminoxane (MAO) cocatalyst, showing low activity. Selected polymer samples were characterised by GPC showing multimodal molecular weight distributions.     

Synthesis and characterization of the first transition-metal fullerene complexes containing bis(η-benzene)chromium moieties

While photochemical reaction of C₆₀ with an equimolar amount of Mo(CO)₄(η⁶-Ph₂PC₆H₅)₂Cr (1) in toluene at room temperature produced bimetallic Mo/Cr fullerene complex fac/mer-(η²-C₆₀)Mo(CO)₃[(η⁶-Ph₂PC₆H₅)₂Cr] (2) in 87% yield, the thermal reaction of an equimolar mixture of C₆₀, M(dba)₂ (M = Pd, Pt; dba = dibenzylideneacetone) and (η⁶-Ph₂PC₆H₅)₂Cr (3) in toluene at room temperature afforded bimetallic M/Cr fullerene complexes (η²-C₆₀)M[(η⁶-Ph₂PC₆H₅)₂Cr] (4, M = Pd; 5, M = Pt) in 88% and 92% yields, respectively. Products 2, 4 and 5 are the first transition-metal fullerene complexes containing bis(η⁶-benzene)chromium moieties. While 2, 4 and 5 were characterized by elemental analysis and spectroscopy, the crystal molecular structures of 4 along with the starting materials 1 and 3 have been determined by X-ray diffraction techniques.     

Dinuclear and polynuclear silver(I) saccharinate complexes with 1,3-diaminopropane and N-methylethylenediamine constructed from Ag?C interactions

New dinuclear and polynuclear Ag(I) complexes with the formula of [Ag₂(sac)₂(pen)₂] (1) and [Ag₂(sac)₂(nmen)]_n (2), (sac = saccharinate, pen = 1,3-diaminopropane, nmen = N-methylethylenediamine) have been synthesized and characterized by IR spectroscopy and thermal (TG/DTG, DTA) analysis. In addition, their structures were determined by single crystal X-ray diffraction technique. In 1, Ag(I) ions are doubly bridged by two pen ligands, besides pen ligands exhibit an interesting coordination mode by binding bridging ligand. Sac ligands connect to silver atom through its imino N atom. Furthermore, each Ag(I) ion exhibits a T-shaped coordination geometry. In 2, Ag(I) coordination environment is again T-shaped, including weak Ag-Ag bonds. The sac exhibits bidentate bringing mode, involving its imino nitrogen and carbonyl oxygen atoms, besides, bridging of Ag(I) centres by sac ligands results in argentophilic contacts. The polymeric units are assembled into two-dimensional networks by hydrogen bonds, C-H?π stacking interactions, weak Ag?C_sac (η²) and Ag?O interactions.