Synthesis and application of novel ionic phosphine ligands with a cobaltocenium backbone

Six novel ionic phosphine ligands with a cobaltocenium backbone, 1,1′-bis(dicyclohexylphosphino) cobaltocenium hexafluorophosphate () (1a), 1,1′-bis(di-iso-propylphosphino) cobaltocenium hexafluorophosphate () (2a), 1,1′-bis(di-tert-butylphosphino) cobaltocenium hexafluorophosphate () (3a), and the monophosphine ligand (Cc⁺ = cobaltocenium; R = Cy, 1b; R = i-Pr, 2b; R = t-Bu, 3b) were synthesized and characterized by elemental analysis, spectroscopy, and X-ray diffraction techniques. These ligands are air-stable and useful for Suzuki coupling reactions in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (), enabling high catalytic activity.     

Ruthenium (II) complexes of the chelating phosphine borane H2ClB · dppm

Reaction of H₂ClB · PPh₂CH₂PPh₂ (H₂ClB · dppm) with results in displacement of all three acetonitrile ligands and the formation of (1), which has been characterised crystallographically. Reaction with carbon monoxide results in a change from η² to η¹ of the borane ligand to afford (2). Compound 1 undergoes H/D exchange under a D₂ atmosphere to afford , while 2 does not.     

Synthesis and characterization of new thorium and uranium phenolate complexes

The reaction between the chelating amino bisphenole ligand (ONOO)H₂ (1) and (ONNO)H₂ (2) with an excess of NaH gives the corresponding bis-sodium salts 3 and 4 quantitatively.The salts were reacted with thorium tetrachloride at room temperature to obtain the corresponding (ONOO)ThCl₂ (5) and (ONNO)ThCl₂ (6) complexes.However, ThCl₄ and UCl₄ react with (3) at higher temperatures to give the corresponding isomorphous homoleptic complexes (ONOO)₂Th (7) and (ONOO)₂U (8).We have also synthesized and characterized a thorium salicylaldiminato complex L₃ThCl (11) , in order to study the effect of the bridged ligand on the molecular structure.     

Crystal structures and spectroscopic properties of a new zinc phosphite cluster and an unexpected chainlike zinc phosphate obtained by hydrothermal reactions

A new zinc phosphite cluster, Zn₂(4,4′-dmbpy)₂(H₂PO₃)₄1, and a new chainlike zinc phosphate, Zn₂(5,5′-dmbpy)₂(HPO₄)(H₂PO₄)₂2, have been synthesized under hydrothermal conditions (4,4′-dmbpy=4,4′-dimethyl-2,2′-dipyridy, 5,5′-dmbpy=5,5′-dimethyl-2,2′-dipyridy). Compound 1 is a molecular zinc phosphite constructed from ZnO₃N₂ trigonal bipyramids, H₂PO₃ pseudo-pyramids and 4,4′-dmbpy ligands. Compound 2 possesses a 1D chainlike framework constructed from ZnO₃N₂ trigonal bipyramids, HPO₄ tetrahedra, H₂PO₄ tetrahedra and 5,5′-dmbpy ligands. Both compounds 1 and 2 exhibit intensive photoluminescence originated from the intraligand π-π* transitions. Crystal data: 1, monoclinic, P2₁/n, , , , β=110.857(3)°, , Z=2, R1=0.0297, wR₁=0.0801; 2, triclinic, P-1, , , , α=64.995(9)°, β=65.952(9)°, γ=65.296(8)°, , Z=2, R₁=0.0418, wR₁=0.1010.     

Synthesis, characterization, and the role of counterion in stabilizing trigonal pyramidal copper(I)/2,2′bipyridine complexes containing electron-poor methyl acrylate

Copper(I)/2,2′-bipyridine complexes, [Cu^I(bpy)(π-CH₂CHCOOCH₃)][A] have been synthesized and characterized. These complexes are used in copper(I) mediated cyclopropanation and aziridination reactions of methyl acrylate and represent the first class of trigonal pyramidal copper(I) complexes with π-coordinated electron poor olefins. In the case of 1 and 3, weak coordination of the counterion was observed. The counterion was noncoordinating in complex 2, which was dimeric in the solid state with the oxygen atoms of the carbonyl moieties in methyl acrylate bridging two copper(I) centers.     

Tris(trimethylsilyl)silyl versus tris(trimethylsilyl)germyl: Radical reactivity and oxidation ability

A comparison of the tris(trimethylsilyl)silyl I and tris(trimethylsilyl)germyl II radical reactivity is provided. Their formation as well as their reactivity encountered in a large variety of chemical processes (addition to double bond, halogen abstraction, peroxyl radical formation…) is examined by laser flash photolysis, quantum mechanical calculations and electron spin resonance (ESR) experiments. The starting compound (TMS)₃GeH is more reactive than (TMS)₃SiH toward the t-butoxyl, the t-butylperoxyl and the phosphinoyl radicals. A similar behavior is noted for an aromatic ketone triplet state. II exhibits a lower absolute electronegativity: accordingly, the addition to electron rich alkenes is less efficient than for I. Radical II is also found less reactive for both the peroxylation and the halogen abstraction reactions. The rearrangement of is slower than for ; this is related to the respective exothermicity of the processes.     

Ruthenium-tin complexes from the reaction of HSnPh3 with Ru3(CO)10(NCMe)2 and their reactions with bis(tri-t-butylphosphine)platinum

The compounds Ru₃(CO)₉(SnPh₃)₂(NCMe)(μ-H)₂ (1), Ru₃(CO)₁₀(SnPh₃)₂(μ-H)₂ (2), Ru(CO)₄(SnPh₃)₂ (3) and Ru(CO)₄(SnPh₃)(H) (4) were obtained from the reaction of Ru₃(CO)₁₀(NCMe)₂ with HSnPh₃ in hexane solvent. Compounds 1, 3 and the new compound Ru₃(CO)₇(SnPh₃)₃(NCMe)₂(μ-H)₃ (5) were obtained from reaction of Ru₃(CO)₁₀(NCMe)₂ with HSnPh₃ in a CH₂Cl₂ and MeCN solvent mixture. Compound 2 and the new compound Ru₃(CO)₉(SnPh₃)₃(μ-H)₃ (6) were obtained from reactions of 1 and 5 with CO, respectively. Compounds 2 and 6 eliminated benzene when heated to yield Ru₃(CO)₁₀(μ-SnPh₂)₂ (7) and Ru₃(CO)₉(μ-SnPh₂)₃ (8) which contain bridging SnPh₂ ligands. Compound 7 was found to react with to yield the adduct, (9) in 59% yield by the addition of groups to two of the Ru-Sn bonds to the bridging SnPh₂ ligands. Fenske-Hall molecular orbital calculations were performed to provide an understanding of the metal-metal bonding in the clusters of 7 and 9. Compounds 1, 2, 5, 6, 7 and 9 were characterized structurally by single crystal X-ray diffraction analysis.     

Synthesis and characterization of new, modified terphenyl ligands: Increasing the rotational barrier for flanking rings

The synthesis and characterization of some new terphenyl ligands, modified by meta alkyl substitution on the central ring are described. The new ligands were designed for potential applications in the stabilization of novel low valent main group species or transition metal heteronuclear multiply bonded compounds. Compounds (1), (3) (Mes = 2,4,6-trimethylphenyl), (5) (Trip = 2,4,6-triisopropylphenyl) and (6) (Dipp = 2,6-diisopropylphenyl) were obtained by addition of two equivalents of the corresponding aryl Grignard reagent to the benzyne intermediate generated by lithiation with BuⁿLi of the starting material 2,4-dichloro-5-isopropylcumene, followed by quenching with iodine. The lithium salts of 2 and 4 were obtained treatment of the parent terphenyl iodides with one equivalent of nBuLi. All compounds were isolated as either colorless crystals or as white powders. They were characterized by ¹H and ¹³C NMR spectroscopy and (in the case of 1 and 3) by X-ray crystallography. DFT calculations were performed on model terphenyl molecules in an attempt to estimate how much the rotation barriers of the flanking aryls can be influenced by substitution by alkyl groups of the two meta positions on central ring.     

Reactions of pyridyl donors with halogens and interhalogens: an X-ray diffraction and FT-Raman investigation

Three different N-donors L, namely N-ethyl-N′-3-pyridyl-imidazolidine-4,5-dione-2-thione (1), N,N′-bis(3-pyridylmethyl)-imidazolidine-4,5-dione-2-thione (2), and tetra-2-pyridyl-pyrazine (3), bearing one, two and four pyridyl substituents, respectively, have been reacted with halogens X₂ (X = Br, I) or interhalogens XY (X = I; Y = Cl, Br). CT σ-adducts L · nXY, bearing linear N?XY moieties (L = 3; X = I; Y = Br, I; n = 2), and salts containing the protonated cationic donors H_nLⁿ⁺ (L = 1 − 3; n = 1, 2, 4), counterbalanced by Cl⁻, Br⁻, , , , , I₂Br⁻, , or anions, have been isolated. Among the reactions products, (H1⁺)Cl⁻, (H1⁺)Br⁻, , , and 3 · 2IBr have been characterised by single-crystal X-ray diffraction. The nature of the products has been elucidated based on elemental analysis and FT-Raman spectroscopy supported by MP2 and DFT calculations.     

p-Cymene ruthenium thioether complexes

Thioethers PhC₂H₄SMe, PhC₃H₆SⁱPr and MeSAllyl form substitutionally labile monomeric adducts (p-cymene)RuCl₂(SRR′) (2a-c) upon treatment with the {(p-cymene)RuCl₂}₂ dimer (p-cymene = η⁶-MeC₆H₄ⁱPr-1,4). Pure adducts were obtained by crystallization from CH₂Cl₂/Et₂O, and 2a,c as well as the bis(thioether) complex (3) were studied by X-ray crystallography. The trichloro bridged diruthenium complex is formed as a byproduct in the preparation of 3 and was also crystallographically characterized. In solution, pure samples 2a-c equilibrate with free thioether and the dimeric starting complex 1. The amount of 1 present in these mixtures increases with increasing bulk of the thioether substituents. Attempts to thermally replace the cymene ligand by the dangling arene substituent of the thioether ligand of 2a,b failed. Complexes 2a-c as well as the dimethylsufide derivative 2d were studied by cyclic voltammetry and display a close to reversible (2a,c,d) or partially reversible (2b) oxidation near +0.85 V and an irreversible reduction at rather negative potential. New peaks observed after oxidation and reduction point to dissociation of the thioether ligand as the main decomposition pathway of the associated radical cations and anions.     

Cyclic voltammetry and theoretical calculations of silyl-substituted 1,4-benzoquinones

Cyclic voltammograms of 2,3,5,6-tetrakis(trimethylsilyl)-1,4-benzoquinone (1a), 2,3,5,6-tetrakis(dimethylvinylsilyl)-1,4-benzoquinone (1b), 2,3,5,6-tetrakis(dimethylsilyl)-1,4-benzoquinone (1c), 4,4,6,6,10,10,12,12-octamethyl-4,6,10,12-tetrasilatricyclo[7.3.0.0^3,7]dodeca-1(9),3(7)-diene-2,8-dione (1d), and 5-t-butyl-2-(pentamethyldisilanyl)-1,4-benzoquinone (5h) showed that the first reduction step was reversible and that the second step was irreversible. The first half-wave reduction potentials of 1a, 1b, 1c, and 1d shifted negatively relative to 1,4-benzoquinone by −0.31, −0.24, −0.03, and −0.18 V, respectively. These results demonstrated that the electron-accepting ability of the chair-form quinones 1a and 1b was lower than that of the planar quinones 1c and 1d. The of 5h (−0.93 V vs. Ag/Ag⁺) was quite similar to that of 5-t-butyl-2-trimethylsilyl-1,4-benzoquinone (5a, −0.94 V). A cyclic voltammogram of dimethylsilylene-bridged 1,4-benzoquinone dimer 7 showed two kinds of (−0.76 and −0.94 V). The electrochemical behavior of 7 would be interpreted in terms of near-neighbor interactions between reduced and non-reduced quinone units. Theoretical calculations of the silyl-1,4-benzoquinones reproduced well the solid state structures of the compounds. Also, the computed vibrational frequencies of the silyl-1,4-benzoquinones were in good agreement with the IR absorption frequencies of the CO units in the compounds. The LUMO energy levels of the silyl-1,4-benzoquinones were quantitatively proportional to the .     

Low-temperature flux syntheses and characterizations of two 1-D anhydrous borophosphates: Na3B6PO13 and Na3BP2O8

Two new anhydrous sodium borophosphates with one-dimensional structure, Na₃B₆PO₁₃(1) and Na₃BP₂O₈(2), were synthesized by low-temperature molten salts techniques using boric acid and sodium dihydrogen phosphate as flux, respectively. The crystal structures were solved by means of single-crystal X-ray diffraction (1, orthorhombic, Pnma (no. 62), , , , Z=4; 2 , monoclinic, C2/c (no. 15), , , , β=92.492(5)°, Z=8). Compound 1 is characterized by an infinite chain of containing eight-membered rings in which all vertexes of borate groups contribute to interconnection. Compound 2 reveals an infinite straight chain built of vertex-sharing four-membered rings, and chains in neighboring layers arranged along different orientations. The relations between structures and the synthetic conditions with only traced water are discussed.     

Self-assembly of silver polymers based on flexible isonicotinate ligand at different pH values: syntheses, structures and photoluminescent properties

Two interesting coordination polymers, [Ag₈(IN)₆(NO₃)₂] 1 and [Ag(IN)(HIN)]_1/2 [Ag(IN)] 2 (HIN=isonicotinic acid) have been synthesized hydrothermally at different pH values. 1 crystallizes in the triclinic space group P-1, with , , , α=75.87(3)°, β=80.87(3)°, γ=76.50(3)°, and Z=2. Compound 1 is the first example of a bilayer framework, in which both single layers are connected by the bond interactions (Ag-O) between Ag from two two-dimensional (2D) single layers generated by the A building block and O atoms from one-dimensional (1D) chain constructed by the B building block, in which coordination modes of IN were reported for the first time. 2 crystallizes in the monoclinic space group P2(1)/c, with , , , β=92.90(3)°, V=1185.0(4) and Z=4. Compound 2 exhibits a 2D plywood-like structure assembled by hydrogen bonds and weak Ag-O interactions.     

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⁻.     

Palladium complexes with meso-bioxazoline ligands for alternating styrene/CO copolymerisation: Counterion effect

Two sets of mono- and dicationic palladium complexes (8) and (10), having and as counterions, were synthesised. The interionic structure of the methyl-acetonitrile complexes [Pd((R,S)-Bn-Box)(CH₃)(NCCH₃)](X) (8) in solution, was investigated by pulsed-gradient spin-echo (PGSE) diffusion measurements and (¹H, ¹⁹F)-HOESY NMR spectroscopy. A high degree of ion-pairing was found in each complex. The HOESY spectra showed that the and anions take up selective positions, on the side of the complex remote from the benzyl groups, but close to the acetonitrile ligand, while the triflate is, partially, occupying a pseudo fifth coordination position on the side of the cation remote from the two benzyl-groups. The complexes 8 and 10 were used as catalyst precursors for the copolymerisation of styrene with carbon monoxide, producing syndiotactic copolymers, with the exception of complex 10a, that led to isotactic copolymers.     

Deprotonated diindolylmethanes as dianionic analogues of scorpionate bis(pyrazolyl)borate ligands: synthesis and structural characterization of representative titanocene and zirconocene complexes

Deprotonation of di(3-methylindol-2-yl)phenylmethane (L₂H₂) or with two equivalents of ⁿBuLi, followed by reactions with Cp₂TiCl₂ or Cp₂ZrCl₂ yielded complexes . Compounds 1-4 were characterized by NMR spectroscopy, and compounds 1, 3, and 4 were further analyzed by X-ray crystallography and elemental analysis. The molecular structures of 1, 3, and 4 illustrate that chelating di(3-methylindol-2-yl)methanes have a structural relationship to coordinated bis(pyrazolyl)borates.     

Design and synthesis of four coordination polymers generated from 2,2′-biquinoline-4,4′-dicarboxylate and aromatic bidentate ligands

Four coordination polymers [Zn(bqdc)(phen)]_n (1), [Zn(bqdc)(bpy)(H₂O)]_n (2), [Mn(bqdc)(bpy)(H₂O)₂]_n (3) and [Mn(bqdc)(phen)(H₂O)₂]_n (4) (H₂bqdc=2,2′-biquinoline-4,4′-dicarboxylic acid, phen=1,10-phenanthroline and bpy=2,2′-bipyridyl) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. Crystal data for 1: monoclinic system, C2/c, , , , β=103.78(3)°, , Z=4. Crystal data for 2: monoclinic system, p2₁/n, , , , β=107.13(7)°, , Z=4. Crystal data for 3: monoclinic system, C2/c, , , , β=116.8010(11)°, , Z=4. Crystal data for 4: monoclinic system, C2/c, , , , β=117.04(3)°, , Z=4. Single helix-like chains exist in 1. The supramolecular structure of 1 exhibits extended two-dimensional network while 2-4 display extended three-dimensional architectures based on interchain hydrogen bonding and π-π interactions. Compounds 1 and 2 show blue photoluminescence under UV light suggesting that they may be employed to develop luminescent materials. Compounds 3 and 4 show interesting magnetic behaviors.