Synthesis of new charge-compensated cobalt bis(1,2-dicarbollide) derivatives

New hetero-substituted charge-compensated cobalt bis(1,2-dicarbollide) derivatives were synthesized by the reaction of 8,8′-μ-iodo-3-commo-3-cobalta-bis(1,2-dicarba-closo-dodecaborane) [8,8′-μ-I-3,3′-Co(1,2-C₂B₉H₁₀)₂] with 1,4-thioxane, pyridine N-oxide, and tetrahydropyran. X-ray diffraction studies showed that the 8′-iodo-8-(pyridiniumoxy)eucosahydro-1,1′,2,2′-tetracarba-3-commo-cobalta-closo-tricosaborate molecule has the gauche-conformation (the substituents are turned with respect to each other by 69.2°). The positive charge is predominantly localized on the N(Py) atom.     

Bis(dicarbollide) Complexes of Transition Metals as a Platform for Molecular Switches. Study of Complexation of 8,8′-Bis(methylsulfanyl) Derivatives of Cobalt and Iron Bis(dicarbollides)

Complexation of the 8,8′-bis(methylsulfanyl) derivatives of cobalt and iron bis(dicarbollides) [8,8′-(MeS)₂-3,3′-M(1,2-C₂B₉H₁₀)₂]⁻ (M = Co, Fe) with copper, silver, palladium and rhodium leads to the formation of the corresponding chelate complexes, which is accompanied by a transition from the transoid to the cisoid conformation of the bis(dicarbollide) complex. This transition is reversible and can be used in design of coordination-driven molecular switches based on transition metal bis(dicarbollide) complexes. The solid-state structures of {(Ph₃P)ClPd[8,8′- (MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂-κ²-S,S′]} and {(COD)Rh[8,8′-(MeS)₂-3,3′-Co(1,2-C₂B₉H₁₀)₂-κ²-S,S′]} were determined by single crystal X-ray diffraction.     

Molecular conductors with 8,8′-diiodo cobalt bis(dicarbollide) anion

New molecular conductors on the base of 8,8′-diiodo cobalt bis(dicarbollide) anion (TTF)[8,8′-I₂-3,3′-Co(1,2-C₂B₉H₁₀)₂] (1), (BMDT-TTF)₄[8,8′-I₂-3,3′-Co(1,2-C₂B₉H₁₀)₂] (2) and (BEDT-TTF)₂[8,8′-I₂-3,3′-Co(1,2-C₂B₉H₁₀)₂] (3) were synthesized and their crystal structures and electrical conductivities were determined. All the radical cation salts prepared were found to be semiconductors. Some regularities in the crystal structures of the TTF-based radical cation salts with bis(dicarbollide) complexes of transition metals are discussed.     

Synthesis of Boronated Amidines by Addition of Amines to Nitrilium Derivative of Cobalt Bis(Dicarbollide)

A series of novel cobalt bis(dicarbollide) based amidines were synthesized by the nucleophilic addition of primary and secondary amines to highly activated B-N⁺≡C–R triple bond of the propionitrilium derivative [8-EtC≡N-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]. The reactions with primary amines result in the formation of mixtures of E and Z isomers of amidines, whereas the reactions with secondary amines lead selectively to the E-isomers. The crystal molecular structures of E-[8-EtC(NMe₂)=HN-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)], E-[8-EtC(NEt₂)=HN-3,3′-Co(1,2- C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] and E-[8-EtC(NC₅H₁₀)=HN-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] were determined by single crystal X-ray diffraction.     

Synthesis of functional derivatives of the [3,3′-Co(1,2-C2B9H11)2] anion

A series of various functional derivatives of the cobalt bis(1,2-dicarbollide) anion [8-XCH₂CH₂OCH₂CH₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ (X=OH, NH₂, and CH(NH₂)COOH) were prepared by the ring-opening reactions of [8-O(CH₂CH₂)₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] with different nucleophiles followed by functional group interconversion reactions. Acidic hydrolysis of [8-NCCH₂CH₂OCH₂CH₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻ resulted in the shorter-chain alcohol [8-HOCH₂CH₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)]⁻. Structures of (Bu₄N)[8-AcNHC(COOEt)₂CH₂CH₂OCH₂CH₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] and [8-(1-C₅H₅N)CH₂CH₂OCH₂CH₂O-3,3′-Co(1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)] were determined by the single crystal X-ray diffraction method. Perspectives of application of functionalized cobalt bis(1,2-dicarbolide) derivatives in nuclear medicine are discussed.     

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.     

Formation of “three-bridge” cobalt-copper commo-cluster with the (B-H)3...Cu bond in the reaction of [Cs][commo-3,3′-Co(1,2-C2B9H11)2] with copper(i) and copper(ii) compounds

Zwitterionic 4,8,8′-exo-{Ph₃PCu}-4,8,8′-(μ-H)₃-commo-3,3′-Co(1,2-C₂B₉H₉)-(1′,2′-C₂B₉H₁₀) and ionic [(PPh₃)₃Cu][commo-3,3′-Co(1,2-C₂B₉H₁₁)₂ complexes were synthesized in moderate yields by the reaction of anionic commo-complex [Cs][commo-3,3′-Co-(1,2-C₂B₉H₁₁)₂]) in a CH₂Cl₂ solution with anhydrous CuCl₂ or CuCl in the presence of PPh₃. The complexes were also synthesized by alternative methods and characterized by NMR and X-ray diffraction methods.     

Studies on Am(III) separation from simulated high-level waste using cobalt bis(dicarbollide) (1? ) ion derivative covalently bound to N,N′-di-n-octyl diglycol diamide as extractant and DTPA as stripping agent

The separation of minor actinides from high level liquid waste (HLLW) belongs to the principal challenges in current nuclear treatment. A derivative based on two cobalt bis(dicarbollide) (1^?) ions covalently bound to the N,N??-di-n-octyl diglycolyl amide platform via diethyleneglycol chain with the formula {[(N,N??-(8-(OCH₂ CH₂)₂-1,2-C₂B₉H₁₀)(1??,2??-C₂B₉H₁₁)-3,3??-Co)(N,N??-n-C₈H₁₇)NCOCH₂]₂O}Na₂ (TODGA-COSAN), dissolved in low polar mixture of hexyl methyl ketone and n-dodecane, was used as an extractant for efficient Am(III)/Eu(III) separation from PUREX HLLW. Am(III) could be selectively stripped from loaded organic phase by using a stripping agent composed from 0.05?M DTPA and 1?M citric acid as a buffer and 1?M NaNO₃ at pH?3.0. Separation factor between europium and americium of 13 was achieved. The europium remaining in the organic phase could be consecutively effectively stripped by using solution of ammonium citrate or ammonium citrate with ammonium DTPA at pH~7.     

Electrochemical synthesis of halogen derivatives of bis(1,2-dicarbollyl)cobalt(III)

A convenient electrochemical method for the synthesis of 8,8-dihalogen derivatives of bis(1,2-dicarbollyl)cobalt(III) anion [8,8X₂-3,3-Co(1,2-C₂B₉H₁₀)]^– (X = Cl, Br, I) was developed. The method includes the electrolysis of a solution of alkaline metal halide and tetramethylammonium salt of bis(1,2-dicarbollyl)cobalt(III) in methanol at 50 °C in a one-compartment electrochemical cell with a nickel cathode and platinum anode.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2448–2451, November, 2004.     

New boron-containing bacteriochlorin <Emphasis Type="Italic">p</Emphasis> cycloimide conjugate

A conjugate of the bacteriochlorophyll a derivative with the cobalt bis(dicarbollide) anion [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ was synthesized.     

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.     

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.     

Synthesis, structures, and conductivities of salts (BEDT-TTF)[9,9′(12′)-I2-3,3′-Co(1,2-C2B9H10)2] and (TTF)[9,9′,12,12′-I4-3,3′-Co(1,2-C2B9H9)2]

The radical cation salts of tetrathiafulvalene (TTF) and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with iodo derivatives of cobalt bis(dicarbollide), (TTF)[9,9′,12,12′-I₄-3,3′-Co(1,2-C₂B₉H₉)₂] and (BEDT-TTF)[9,9′(12′)-I₂-3,3′-Co(1,2-C₂B₉H₁₀)₂], respectively, were synthesized and their crystal structures were determined. The introduction of iodine atoms into the lower rim of the dicarbollide ligands, unlike the substitution at the upper rim, leads to insignificant changes in the crystal structure and the conductivity of the radical cation salts compared to the analogous salts based on unsubstituted cobalt bis(dicarbollide).     

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.     

Large magnetic anisotropy of chromium(III) ions in a bis(ethylenedithio)tetrathiafulvalenium salt of chromium bis(dicarbollide), (ET)<Subscript>2</Subscript>[3,3′-Cr(1,2-C<Subscript>2</Subscript>B<Subscript>9</Subscript>H<Subscript>11</Subscript>)<Subscript>2</Subscript>]

The synthesis of a radical-cation salt based on a derivative of tetrathiafulvalene, (ET)₂[3,3′-Cr(1,2-C₂B₉H₁₁)₂] (ET?=?bis(ethylenedithio)tetrathiafulvalenium), was accomplished by electrochemical anodic oxidation of ET in the presence of (Me₄N)[3,3´-Cr(1,2-C₂B₉H₁₁)₂] in the galvanostatic regime. An electric conductivity σ (293 K)?=?7 × 10^?3 Ohm^?1 cm^?1 with semiconductor activation energy E_a???0.1 eV in the range of 127–300 K was observed. The crystal structure of (ET)₂[3,3′-Cr(1,2-C₂B₉H₁₁)₂] was determined by X-ray diffraction at 173 K, revealing the presence of structural tetramers in radical-cation stacks. The magnetic properties of the complex were investigated in the temperature range 1.8–300 K using magnetometry and EPR, showing that the magnetic structure of (ET)₂[3,3′-Cr(1,2-C₂B₉H₁₁)₂] consists of two independent magnetic subsystems. Cation radicals form a rectangular magnetic lattice in the ab-plane with significant antiferromagnetic exchange interactions. The chromium bis(dicarbollide) anions are characterized by unusually strong positive zero-field splitting of the Cr(III) ions, which was confirmed by ab initio calculations.     

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 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.     

Halogenation and thiocyanation of the univalent anion of dodecahydro-7,8-dicarba-nido-undecaborate in a diaphragm electrochemical cell

Iodination, bromination, and thiocyanation reactions of the potassium salt K⁺[7,8-C₂B₉H₁₂]^? are investigated during diaphragm electrolysis. The B(9)-monosubstituted derivatives [9-X-7,8-C₂B₉H₁₁]^? (X = I, SCN) and disubstituted derivatives [9,11-X₂-7,8-C₂B₉H₁₀]^? (X = Br, I) are obtained as alkylammonium salts. The composition and structure of these substances are confirmed by data from elemental analysis and IR and NMR (¹H and ¹¹B) spectroscopy.     

8-Dioxane ferra(III) bis(dicarbollide): A paramagnetic functional molecule as versatile building block for introduction of a Fe(III) centre into organic molecules

The synthesis of a new, paramagnetic closo-[(8-(-CH₂CH₂O)₂-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)-3,3′-Fe]⁰ (3) is reported. This compound can serve as a versatile building block for construction of both anionic and zwitterionic derivatives, as exemplified by the synthesis of a series of compounds of general formula closo-[(8-X-(CH₂CH₂O)₂-1,2-C₂B₉H₁₀)(1′,2′-C₂B₉H₁₁)-3,3′-Fe], bearing organic end groups (X = NC₅H₅ (4), (C₆H₅)₃P (5), OH (6), and 2-O(1-CH₃O-C₆H₄) (7)) attached to the cluster by a diethyleneglycol spacer. Molecular structures of 3, 4, 5 and 7 were determined by single-crystal X-ray diffraction analysis and by the long-time neglected method of paramagnetic, high field NMR (¹H, ¹³C and ¹¹B) spectroscopy.     

Synthesis and structure of 9-hydroxy-1,2-dicarba-closo-dodecaborane(11)

The oxidation of 1,2-C₂B₁₀H₁₂ (1) with 100% nitric acid was studied in two solvents (CH₂C1₂ and CCl₄). Under the action of superacid (CF3SO3H), the compound 9-HO-1,2-C₂B₁₀H₁₁ (2) gives the onium cation 9-H₂O⁺-1,2-C₂B₁₀H₁₁ involved in the salt [9-H₂O⁺-1,2-C₂B₁₀H_n]-CF₃SO₃^?, as demonstrated by ^uB NMR spectroscopy. The experimental and simulated ^uB NMR spectra of the cation 9-H₂O⁺-1,2-C₂B₁₀H₁₁ are in satisfactory agreement with each other. In the presence of a base, compound 2 is transferred from an ethereal solution to an aqueous alkaline solution giving the anion 9-O^?- 1,2-C₂B₁₀H₁₁. The structure of compound 2 was confirmed by ¹H, ¹¹B, ¹¹B¹H, ¹¹B-¹¹B COSY NMR spectroscopy, IR spectroscopy, and gas chromatography mass spectrometry and was additionally established by X-ray diffraction.