Cobalt bis(dicarbollide) ions functionalized by CMPO-like groups attached to boron by short bonds; efficient extraction agents for separation of trivalent f-block elements from highly acidic nuclear waste

New boron substituted cobalta bis(dicarbollide)(1-) ion (1) derivatives of formula [(8,8′-(RPhP(O)(CH₂)nC(O)N) < (1,2-C₂B₉H₁₀)₂-3,3′-Co]⁻ (R = Ph or C₈H₁₇, n = 1, 3a, 3b; R = Ph, n = 2, 3c), [(8-(Ph₂P(O)CH₂C(O)NR)(1,2-C₂B₉H₁₀))(1′,2′-C₂B₉H₁₁)-3,3′-Co]⁻ (R = H, C₂H₅, CH₂C₆H₅, 5a-c) and [(8-(²RPhP(O)CH₂C(O)N(¹R)CH₂-1,2-C₂B₉H₁₀))(8′-CH₃O-1′,2′-C₂B₉H₁₀)-3,3′-Co]⁻ (¹R = Benzyl, ²R = Ph or C₈H₁₇, 7a,b) were prepared with the aim to develop a new class of efficient extraction agents for partitioning of polyvalent f-block elements, i.e. lanthanides and actinides from high-level activity nuclear waste. The anionic ligands were characterized by multinuclear NMR spectroscopy and MS, the structures of Cs3a and the calcium complex of 7a were determined by X-ray diffraction analysis. The crystallographic study of the Cs3a proved a formation of linear chains in the structure, where the metal cation is coordinated by oxygen atoms of the CMPO terminal groups. The X-ray structure of the Ca²⁺ complex of the ionic ligand 7a proved a 1:3 metal to ligand ratio. Presented also is the X-ray structure of the starting ammonium compound 6 used in the synthesis of 7a and 7b. With exception of 5c, these anionic ligands are of high extraction efficiency, the highest being found for 7a in low polar solvent mixture hexyl methyl ketone-dodecane 1:1. These properties qualify some of these derivatives for possible technological applications.     

Syntheses of C-substituted icosahedral dicarbaboranes bearing the 8-dioxane-cobalt bisdicarbollide moiety

The treatment of 1,2-, 1,7- and 1,12-carbaborane lithiated isomers with [3,3′-Co-8-(CH₂CH₂O)₂-(1,2-C₂B₉H₁₀)-(1′,2′-C₂B₉H₁₁)] (1) at molar ratios 1:1 or 1:2 at room temperature in THF leads generally to the formation of a series of orange double-cluster mono and dianions. These were characterized by NMR and MS methods as [1′′-X-1′′,2′′-closo-C₂B₁₀H₁₁]⁻, [2]⁻; [1′′-X-1′′,7′′-closo-C₂B₁₀H₁₁]⁻, [3]⁻ and [1′′-X-1′′,12′′-closo-C₂B₁₀H₁₁], [4]⁻ for the monoanions, whereas [1′′,2′′-X₂-1′′,2′′-closo-C₂B₁₀H₁₀]²⁻, [2]²⁻; [1′′,7′′-X₂-1′′,7′′-closo-C₂B₁₀H₁₀]²⁻, [3]²⁻; and [1′′,12′′-X₂-1′′,12′′-closo-C₂B₁₀H₁₀]²⁻, [4]²⁻ for the dianions (where X = 3,3′-Co-8-(CH₂CH₂O)₂-(1,2-C₂B₉H₁₀)-1′,2′-(C₂B₉H₁₁)). Moreover, these borane-cage subunits can be easily modified via attaching variable substituents onto cage carbon and boron vertices, which makes these compounds structurally flexible potential candidates for BNCT of cancer and HIV-PR inhibition.     

Syntheses and catalytic activities of Group 4 metal complexes derived from C(cage)-appended cyclohexyloxocarborane trianion

The reaction of Li[closo-1-Me-1,2-C₂B₁₀H₁₀] with cyclohexene oxide produced closo-1-Me-2-(2′-hydroxycyclohexyl)-1,2-C₂B₁₀H₁₀ (1) in 86% yield. Decapitation of (1) with potassium hydroxide in refluxing ethanol gave the corresponding cage-opened potassium salt of the carborane anion, [nido-1-Me-2-(2′-hydroxycyclohexyl)-1,2-C₂B₉H₁₀]⁻ (2) in 82% yield. Deprotonation of (2) with two equivalents of n-butyllithium in THF at −78 °C, followed by its further reaction with anhydrous MCl₄ · 2THF (M = Ti, Zr) produced the corresponding d⁰-half-sandwich metallacarboranes, closo-1-M(Cl)-2-Me-3-(2′-σ-O-cyclohexyl)-η⁵-2,3-C₂B₉H₉ (3 M = Zr; 4 M = Ti), in 59% and 51% yields, respectively. Reaction of Li[closo-1,2-C₂B₁₀H₁₁] with Merrifield’s peptide resin (1%) in refluxing THF gave the ortho-carborane-functionalized polymer (5) in 88% yield. The corresponding closo-1-polystyryl-2-(2′-hydroxycyclohexyl)-1,2-C₂B₁₀H₁₀ (6) was produced in 94% yield by refluxing a mixture of the lithium salt of (5) and cyclohexene oxide in THF for 2 days. Compound (6) was decapitated, deprotonated and then reacted with ZrCl₄ · 2THF to produce a polymer-supported d⁰-half-sandwich metallacarborane closo-1-Zr(Cl)-2-polystyryl-3-(2′-σ-O-cyclohexyl)-η⁵-2,3-C₂B₉H₉ (7) in 41% yield. Compounds (3) and (7), in the presence of MMAO-7 (13% ISOPAR-E), were found to catalyze the polymerization of ethylene and vinyl chloride in toluene to give high molecular weight PE (9.4 × 10³ (M_w/M_n = 1.8)) and PVC (2.1 × 10³ (M_w/M_n = 1.6)), respectively.     

Synthesis and characterization of isomeric 4- and 8-(σ-CHCHPh)-closo-ruthenacarboranes with η:η-phosphacarbocyclic ligand

Reactions of [3,3-(PPh₃)₂-3-Cl-3-H-3,1,2-closo-RuC₂B₉H₁₁] (1) and its exo-nido isomer [exo-5,6,10-{Ru(Ph₃P)₂Cl}-5,6,10-(μ-H)₃-10-H-7,8-nido-C₂B₉H₈] (2) with NH₄PF₆ in methanol or ethanol solution followed by heating in the presence of an excess of phenylacetylene (3) affords a mixture of two isomeric closo species [3,3-{(1′-3′-η³):(5′,6′-η²)-ortho-C₆H₄PPh₂CHC(Ph)CHCHPh}-8-(σ-CHCHPh)-3,1,2-closo-RuC₂B₉H₁₀] (4) and [3,3-{(1′-3′-η³):(5′,6′-η²)-ortho-C₆H₄PPh₂CHC(Ph)CHCHPh}-4-(σ-CHCHPh)-3,1,2-closo-RuC₂B₉H₁₀] (5) in which boron vertexes in β- and α-sites with respect to the cage carbons bear the (E)-CHCHPh group. The X-ray diffraction study of 4 together with the multinuclear NMR data for 4 and 5 revealed that such an unusual η³:η²-phosphacarbocyclic ligand in both isomeric complexes is formed by specific insertion of the initially metal-bound PPh₃ group into the chain of two alkyne molecules coupled in a “head-to-tail” fashion around the metal vertex.     

New fulvalenium salts of bis(dicarbollide) cobalt and iron: Synthesis, crystal structure and electrical conductivity

New radical cation salts (BEDT-TTF)₂[3,3′-Co(1,2-C₂B₉H₁₁)₂] (1), (BEDT-TTF)₂[8-I-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] (2), (BMDT-TTF)[3,3′-Co(1,2-C₂B₉H₁₁)₂] (3) and (TMTSF)₂[3,3′-Fe(1,2-C₂B₉H₁₁)₂] (4) were synthesized and their crystal structures and electrical conductivities were determined. Compound 4 is isostructural to the earlier reported Co analogue. All the radical cation salts synthesized are semiconductors.     

Reaction of nido-1,2-(CpRuH)2B3H7 with ethynylferrocene to yield new metallacarboranes

Addition of ethynylferrocene to nido-1,2-(Cp^∗RuH)₂B₃H₇ (1) at ambient temperature leads to nido-1,2-(Cp^∗Ru)₂(1,5-μ-C{Fc}Me)B₃H₇ (2, 3) and closo-4-Fc-1,2-(Cp^∗RuH)₂-4,6-C₂B₂H₃ (4). Compounds 2 and 3 represent a pair of geometric isomers, nido-species in which the regiochemistry of the alkyne reduction conforms to the Markovnikoff rule. Compound 4 is an octahedral structure in which the inserted alkyne is on an open face of the closo cluster.     

A boron-boron linked large metallacarborane cluster: Characterization and X-ray structure of 8,9′-[closo-{3-Co(η-C5H5)-1,2-C2B9H10}]2

The 8,9′-[closo-{3-Co(η⁵-C₅H₅)-1,2-C₂B₉H₁₀}]₂ (1) species, in which two large closo-CoC₂B₉ sub-clusters are connected by a B-B bond, is unexpectedly obtained from the reaction of closo-[3-Co(η⁵-C₅H₅)-1,2-C₂B₉H₁₁] with sulfur in the presence of aluminium chloride under reflux conditions. The solid state conformation of 1 seems to be the result of a pair of intramolecular C-H?H-B dihydrogen bonds between the protonic H atoms of the C₅H₅ fragment of a sub-cluster and the hydridic H atoms of the C₂B₉H₁₁ fragment in the other sub-cluster in 1.     

Protonation of palladium(II)-allyl and palladium(0)-olefin complexes containing 2-pyridyldiphenylphosphine

The pendant nitrogen atom of the Ph₂PPy ligand in the Pd(II)-allyl complexes [PdCl(η³-2-CH₃-C₃H₄)(Ph₂PPy)] (1) and [Pd(η³-2-CH₃-C₃H₄)(Ph₂PPy)₂]BF₄ (3) has been protonated with methanesulfonic acid to afford the corresponding pyridinium salts [PdCl(η³-2-CH₃-C₃H₄)(Ph₂PPyH)](CH₃SO₃) (1a) and [Pd(η³-2-CH₃-C₃H₄)(Ph₂PPyH)₂](CH₃SO₃)₂(BF₄) (3a).Protonation strongly influences the ¹H and ¹³C NMR spectral parameters of the allyl moieties of 1a and 3a whose signals resonate at lower fields with respect to the parent species indicating that upon protonation Ph₂PPy becomes a weaker σ-donor and a stronger Π-acceptor. The allyl moiety, which in 1 is static, becomes dynamic in 1a, the observed syn-syn and anti-anti exchange being due to deligation of the protonated phosphine from the metal centre. Treatment of complex 3 with diethylamine in the presence of fumaronitrile gives the new Pd(0)-olefin complex [Pd(η²-fumaronitrile)(PPh₂Py)₂] (4) which has been characterized by elemental analysis and NMR spectroscopy. Low temperature protonation of 4 with methanesulfonic acid leads to the bis-protonated species [Pd(η²-fumaronitrile)(Ph₂PPyH)₂](CH₃SO₃)₂ (4a) which is stable only at temperatures <0 °C.     

Intramolecularly coordinated organoantimony(III) carboxylates

The reactions of organoantimony chlorides L^1,2SbCl₂1 and 2 ([2,6-(ROCH₂)₂C₆H₃]⁻, R = Me; L¹ and R = t-Bu; L²) with silver salts of selected carboxylic acids resulted to corresponding organoantimony carboxylates L^1,2Sb(OOCR′)₂, 1a-c (for L¹) and 2a-c (for L²), where R′ = CH₃ for 1a, 2a; R′ = CHCH₂ for 1b, 2b and R′ = CF₃ for 1c, 2c. All compounds were characterized by the help of elemental analysis, ESI-MS, ¹H and ¹³C NMR spectroscopy. The solid state structure investigation using single crystal X-ray diffraction techniques (2a, c) and IR spectroscopy revealed significant differences in coordination mode of both O,C,O chelating ligand and carboxylic groups in this set of compounds. The structure of all compounds in solution of non-coordinating solvent (CDCl₃) was determined by means of variable temperature ¹H, ¹³C, ¹⁹F NMR spectroscopy and IR spectroscopy.     

Synthesis and crystal structure of four Pd(II) complexes containing nido or closo carborane diphosphine ligands

Three Pd(II) complexes [Pd₂(μ-Cl)₂{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] · 0.25CH₂Cl₂ (1), [Pd{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] · 4CHCl₃ (2) and [PdCl₂(1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀)] (3) have been synthesized by the reactions of 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ with PdCl₂ in acetonitrile, cyanophenyl and dichloromethane, respectively. A fourth complex, [PdI₂(1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀)] (4), was obtained by a ligand exchange reaction through the substitution of the Cl⁻ of complex 3 with I⁻. All four complexes have been characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal X-ray determination showed that the carborane cage, nido for 1, 2 and closo for 3, 4, was coordinated bidentately to the Pd atom through the two P atoms, and the geometry at the Pd atom was square-planar in all the complexes.     

Mono- and bis-(2-dimethylaminoethyl)tetramethylcyclopentadienyl zirconium(IV) complexes: synthesis and structural studies in crystalline state and in solutions

A novel half-sandwich Zr(IV) complex [η⁵:η¹-N-C₅(CH₃)₄CH₂CH₂N(CH₃)₂]ZrCl₃ (6) together with zirconocene dichlorides [η⁵-C₅(CH₃)₄CH₂CH₂N(CH₃)₂][η⁵-C₅(CH₃)₅]ZrCl₂ (4) and [η⁵-C₅(CH₃)₄CH₂CH₂N(CH₃)₂]₂ZrCl₂ (5) have been prepared. Complex 6 has been isolated and characterized in three different forms, namely, as an adduct with THF 6a, an adduct with tetrahydrothiophene 6b, and a solvent-free form 6c. Molecular structures of complexes 4, 6b, and 6c have been established by X-ray diffraction analysis. Complex 6c has been shown to be a monomeric solvent-free half sandwich Zr(IV) complex. The dynamic behavior of complex 6a in a non-solvating medium (an equilibrium between 6a and 6c along with a degenerate interconversion of the Zr-C_cp-CH₂-CH₂-N(CH₃)₂-(Zr) pseudo-five-member metallacycle) have been studied by the variable-temperature ¹H and ¹³C{¹H} NMR spectroscopy. The activation parameters for the degenerate five-member cycle interconversion have been elucidated.     

Synthesis, structure and electrical conductivity of fulvalenium salts of cobalt bis(dicarbollide) anion

New radical cation salts (TMTSF)₂[3,3′-Co(1,2-C₂B₉H₁₁)₂] (1), (TTF)[3,3′-Co(1,2-C₂B₉H₁₁)₂] (2) and (ET)[3,3′-Co(1,2-C₂B₉H₁₁)₂] (3) were synthesized and their crystal structures and electrical conductivities were determined. Compound 1 has layered structure with conducting stacks of the TMTSF cations, whereas compounds 2 and 3 contain separated pairs of fulvalenium cations. Conductivity of crystals 1 at room temperature was found to be 15 Ohm⁻¹ cm⁻¹, that is the maximum value found for fulvalenium metallacarborane salts.     

Synthesis and characterization of three nickel(ii) carborane complexes containing nido- or closo-carborane diphosphine ligand

Three nickel(II) carborane complexes, [Ni₂(μ-Cl)₂{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] (1), [Ni{7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀}{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] (2) and [NiBr₂{1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀}] · CH₂Cl₂ (3), have been synthesized by the reactions of 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodecaborane with NiCl₂ · 6H₂O or NiBr₂ · 6H₂O in ethanol under different conditions, respectively. For complex 1, it could also be obtained under the solvothermal condition. All the three complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal analysis shows that the molecular symmetry of complex 1 is centrosymmetric, containing two same structure units - Ni(7,8-(PPh₂)₂-7,8-C₂B₉H₁₀) linked by two bridged-Cl atoms. The central square plane formed by the [Ni₂Cl₂] unit is almost parallel to the two side NiPP planes. For complex 2, the coordination environment of the Ni atom is a seriously distorted square-planar, in which two positions come from the chelating diphosphine ligand [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]⁻ degraded from the closo species, while the other two are occupied by an unsymmetrical chelating phosphine oxide ligand [7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀]⁻. As for complex 3, the geometry at the Ni atom is a slightly distorted square-planar. The closo carborane diphosphine ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ was coordinated bidentately to the metal ion through the two phosphorus atoms, and the two Br atoms are at cis position which can fulfill the four coordination mode of the metal.     

Syntheses and characterization of η-cyclopentadienyl and η-indenyl ruthenium(II) complexes of arylazoimidazoles: The molecular structure of the complex [(η-C5H5)Ru(PPh3)(C6H5-NN-C3H3N2)]

The complex [(η⁵-C₅H₅)Ru(PPh₃)₂Cl] (1) reacts with several arylazoimidazole (RaaiR′) ligands, viz., 2-(phenylazo)imidazole (Phai-H), 1-methyl-2-(phenylazo)imidazole (Phai-Me), 1-ethyl-2-(phenylazo)imidazole (Phai-Et), 2-(tolylazo)imidazole (Tai-H), 1-methyl-2-(tolylazo)imidazole (Tai-Me) and 1-ethyl-2-(tolylazo)imidazole (Tai-Et), gave complexes of the type [(η⁵-C₅H₅)Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (2), R = H, R′ = CH₃ (3), R = H, R′ = C₂H₅ (4), R = CH₃, R′ = H (5), R, R′ = CH₃ (6), R = CH₃, R′ = C₂H₅ (7)}. The complex [(η⁵-C₉H₇)Ru(PPh₃)₂(CH₃CN)]⁺ (8) undergoes reactions with a series of N,N-donor azo ligands in methanol yielding complexes of the type [(η⁵-C₉H₇) Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (9), R = H, R′ = CH₃ (10), R = CH₃, R′ = H (11), R = CH₃, R′ = C₂H₅ (12)}, respectively. These complexes were characterized by FT IR and FT NMR spectroscopy as well as by analytical data. The molecular structure of the complex [(η⁵-C₅H₅)Ru(PPh₃)(C₆H₅-NN-C₃H₃N₂)]⁺ (2) was established by single crystal X-ray diffraction study.     

Factors affecting the lability of the σ(M-X) bond in cycloplatinated and cyclopalladated complexes containing [C(sp, ferrocene),N,X] or [C(sp, phenyl),N,X] (X = S, N) terdentate ligands

The reactions of the cyclometallated complexes [M{[(η⁵-C₅H₃)-CHN-(C₆H₄-2-SMe)]Fe(η⁵-C₅H₅)}Cl] [with M = Pt (5a) or Pd (5b)] with PPh₃ under different experimental conditions are reported. These studies have allowed the isolation of [M{[(η⁵-C₅H₃)-CHN-C₆H₄-2-SMe]Fe(η⁵-C₅H₅)}(PPh₃)]X [M = Pt and X⁻ = Cl⁻ (6a) or (7a) or M = Pd and X⁻ = Cl⁻ (6b) or (7b)] and the neutral complex [Pd{[(η⁵-C₅H₃)-CHN-(C₆H₄-2-SMe)]Fe(η⁵-C₅H₅)}Cl(PPh₃)] (8b). In 6-7a,b the ferrocenyl Schiff base behaves as a [C(sp², ferrocene),N,S]⁻ group while in 8b it acts as a [C(sp², ferrocene),N]⁻ ligand. The X-ray crystal structure of 7b confirms the mode of binding of the ferrocenyl ligand. The comparison of the results obtained and those reported for [M{(C₆H₄)-CHN-(CH₂-CH₂-2-SEt)}Cl] and [M{(C₆H₄)-CHN-(C₆H₄-2-SMe)}Cl] {with a [C(sp², phenyl),N,S]⁻ terdentate ligand} or [M{[(η⁵-C₅H₃)-CHN-(CH₂)₃-NMe₂]Fe(η⁵-C₅H₅)}Cl] {in which the ligand acts as a [C(sp², ferrocene),N,N′]⁻ group} have allowed the elucidation of the relative importance of the factors affecting the lability of the M-X (X = S or N′) and M-Cl bonds in cyclometallated compounds with [C,N,S]⁻ and [C(sp², ferrocene),N,X]⁻ ligands.     

New alkenyl-substituted group 4 C-ansa-metallocene complexes. Reactivity of the substituent at the carbon ansa bridge

The allyl-substituted group 4 metal complexes [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti, R = CH₂CHCH₂, (2); R = CH₂C(CH₃)CH₂ (3); M = Zr, R = CH₂CHCH₂ (4), R = CH₂C(CH₃)CH₂ (5)] have been synthesized by the reaction of allyl ansa-magnesocene derivatives and the tetrachloride salts of the corresponding transition metal. The dialkyl complexes ] [M = Ti, R = CH₂=CHCH₂, R′ = Me (6), R′ = CH₂Ph (7); R = CH₂C(CH₃)CH₂, R′ = Me (8), R′ = CH₂Ph (9); M = Zr, R = CH₂CHCH₂, R′ = Me (10), R′ = CH₂Ph (11); R = CH₂C(CH₃)CH₂, R′ = Me (12), R′ = CH₂Ph (13)] have been synthesized by the reaction of the corresponding ansa-metallocene dichloride complexes 2-5 and two molar equivalents of the alkyl Grignard reagent. Compounds 2-5 reacted with H₂ under catalytic conditions (Wilkinson’s catalyst or Pd/C) to give the hydrogenation products [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = CH₂CH₂CH₃ (14) or R = CH₂CH(CH₃)₂ (15); M = Zr and R = CH₂CH₂CH₃ (16) or R = CH₂CH(CH₃)₂ (17)]. The reactivity of 2-5 has also been tested in hydroboration and hydrosilylation reactions. The hydroboration reactions of 3, 4 and 5 with 9-borabicyclo[3.3.1]nonane (9-BBN) yielded the complexes [M{(9-BBN)CH₂CH(R)CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (18); M = Zr and R = H (19) or R = CH₃ (20)]. The reaction with the silane reagents HSiMe₂Cl gave the corresponding [M{ClMe₂SiCH₂CHRCH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (21); M = Zr and R = H (22) or R = CH₃ (23)]. The reaction of 22 with t-BuMe₂SiOH produced a new complex [Zr{t-BuMe₂SiOSi(Me₂)CH₂CH₂CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (24) through the formation of Si-O-Si bonds. On the other hand, reactivity studies of some zirconocene complexes were carried out, with the insertion reaction of phenyl isocyanate (PhNCO) into the zirconium-carbon σ-bond of [Zr{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}₂Me₂] (25) giving [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr{Me{κ²-O,N-OC(Me)NPh}] as a mixture of two isomers 26a-b. The reaction of [Zr{(n-Bu)(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}(CH₂Ph)₂] (27) with CO also provided a mixture of two isomers [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr(CH₂Ph){κ²-O,C-COCH₂Ph}] 28a-b. The molecular structures of 4, 11, 16 and 17 have been determined by single-crystal X-ray diffraction studies.     

Sulfur and oxygen functionalized cyclopentadienyl half-sandwich cobalt complexes with 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolato ligands

Sulfur and oxygen functionalized cyclopentandienyl half-sandwich cobalt dicarbonyl complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]Co(CO)₂ (3) and [η⁵-C₅H₄(CH₂)₂OCH₃]Co(CO)₂ (7) were prepared. Oxidation of 3 or 7 with I₂ led to formation of 18-electron complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]CoI₂ (4) and [η⁵-C₅H₄(CH₂)₂OCH₃]Co(CO)I₂ (8). The reactions of diiodide complex (4) with dilithium 1,2-dicarba-closo-dodecaborane(12)-1,2-dichalcogenolates [(THF)₃LiE₂C₂B₁₀H₁₀Li(THF)]₂ [E=S (1a), Se (1b)] afforded 18-electron mononuclear complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]Co(E₂C₂B₁₀H₁₀) [E=S (5a), Se (5b)] in which sulfur atoms of side-chain were attached via an intramolecular coordination. Complex 7 reacted with 1a and 1b to give the binuclear complexes {[η⁵-C₅H₄(CH₂)₂OCH₃]Co(E₂C₂B₁₀H₁₀)}₂ [E=S (10a), Se (10b)]. The molecular structures of 5a and 10b were determined by X-ray crystallographic analysis. According to the X-ray structure analyses, 10b contains two o-carborane diselenolate bridges, and each Cp^′Co fragment is attached to one terminal and two bridging selenolato ligands. The central Co₂Se₂ four-membered ring is planar, and the direct metal-metal interaction is absent.     

One ligand different metal complexes: Biological studies of titanium(IV), tin(IV) and gallium(III) derivatives with the 2,6-dimethoxypyridine-3-carboxylato ligand

The reaction of 2,6-dimethoxypyridine-3-carboxylic acid (DMPH) with different precursors [Ti(η⁵-C₅H₅)₂Cl₂], [Ti(η⁵-C₅H₄Me)₂Cl₂], [Ti(η⁵-C₅H₄SiMe₃)(η⁵-C₅H₅)Cl₂], [Ti(η⁵-C₅Me₅)Cl₃], SnMe₃Cl and Ga^tBu₃ yielded the complexes [Ti(η⁵-C₅H₅)₂(DMP-κO)₂] (1), [Ti(η⁵-C₅H₄Me)₂(DMP-κO)₂] (2), [Ti(η⁵-C₅H₄SiMe₃)(η⁵-C₅H₅)(DMP-κO)₂] (3), [Ti(η⁵-C₅Me₅)(DMP-κ²O,O′)₃] (4), [SnMe₃(μ-DMP-κO:κO′)]_∞ (5), and [Ga^tBu₂(μ-DMP-κO:κO′)]₂ (6). 1-6 have been characterized by spectroscopic methods and the molecular structure of the complexes 1, 2, 3, 5 and 6 have been determined by X-ray diffraction studies. The cytotoxic activity of 1-6 was tested against the tumour cell lines human adenocarcinoma HeLa, human myelogenous leukaemia K562, human malignant melanoma Fem-x and human breast carcinoma MDA-MB-361. The results of this study show a higher cytotoxicity of the tin(IV) and gallium(III) derivatives in comparison to their titanium(IV) counterparts. Furthermore, the different titanium compounds showed differences in their cytotoxicities with a higher activity of complex 4 (mono-(cyclopentadienyl) derivative) compared to that of 1-3 (bis-(cyclopentadienyl) complexes). A qualitative UV-vis study of the interactions of these complexes with DNA has also been carried out.     

1D and 2D supramolecular structures of silver carborane dicyclohexylphosphine complexes constructed by C-H?H-B dihydrogen bonding interactions

Five new carborane dicyclohexylphosphine complexes, [Ag₂(μ-I)₂{1,2-(P Cy₂)₂-1,2-C₂B₁₀H₁₀}₂] (1), [Ag₂(SCN)₂{1,2-(PCy₂)₂-1,2-C₂B₁₀H₁₀}₂]_n·CH₂Cl₂ (2), [Ag(ClO₄){1,2-(PCy₂)₂-1,2-C₂B₁₀H₁₀}]·CH₂Cl₂ (3), [Ag₂(μ-NO₃)₂{1,2-(PCy₂)₂-1,2-C₂B₁₀H₁₀}₂]·CH₂Cl₂ (4) and [Ag(SC₆H₄COOH){1,2-(PCy₂)₂-1,2-C₂B₁₀H₁₀}₂]·CH₂Cl₂ (5), have been synthesized by the reactions of 1,2-bis(dicyclohexylphosphino)-1,2-dicarba-closo-dodecaborane with AgX (X = I, SCN, ClO_4, NO₃ and SC₆H₄COOH) in CH₂Cl₂. The structures of the five complexes were characterized by elemental analysis, FT-IR, ¹H, ¹³C, ¹¹B and ³¹P NMR spectroscopy. X-ray structure analysis revealed that the structures of the complexes can be classified into three types. Complexes 1 and 4 are di-μ-X-bridged structures and complexes 3 and 5 are mononuclear structures, while complex 2 is a chain-like polymer. Complexes 1 and 2 form 2D supramolecular networks and complexes 3, 4 and 5 form 1D chains via C-H?H-B dihydrogen bonding interactions.     

Relationships between Fe NMR, Mössbauer parameters, electrochemical properties and the structures of ferrocenylketimines

A comparative study of the electrochemical properties, ⁵⁷Fe NMR and Mössbauer spectroscopic data of compounds [(η⁵-C₅H₅)Fe{(η⁵-C₅H₄)-C(R¹)N-R²}] {R¹ = H, R² = CH₂-CH₂OH (1a), CH(Me)-CH₂OH (1b), CH₂C₆H₅ (1c), C₆H₄-2Me (1d), C₆H₄-2SMe (1e) or C₆H₄-2OH (1f) and R¹ = C₆H₅, R² = C₆H₄-2Me (2d)} is reported. The X-ray crystal structure of [(η⁵-C₅H₅)Fe{(η⁵-C₅H₄)-CHN-C₆H₄-2OH}] (1f) is also described. Density functional theoretical (DFT) studies of these systems have allowed us to examine the effects induced by the substituents of the “-C(R¹)N-R²” moiety or the aryl rings (in 1d-1f) upon the electronic environment of the iron(II) centre.