Electron interactions in the closo-carboranes 1,2- and 1,7-C2B10H12

Ultra-soft X-ray fluorescence spectra of ortho- and meta-carborane C₂B₁₀H₁₂ were obtained. Ab initio self-consistent field (SCF) quantum-chemical calculations of these molecules were performed to interpret BK and CK spectra. Distinctions between electronic structure of closo-carboranes 1,2- and 1,7-C₂B₁₀H₁₂ are caused by different efficiency in the interaction of carbon and boron atoms. Location of boron atom between carbon atoms leads to stronger delocalization of electron density in meta-carborane molecule. The correlation between molecular orbitals (MOs) of the anion B₁₂H₁₂²⁻ and the closo-carboranes was carried out.     

Electrochemical reduction of the dithiophosphate complexes CpFe(CO)2[η-SP(S)(OR)2], (Cp = η-C5H5 or η-C5Me5)

The reductive electrochemistry of compounds of the type CpFe(CO)₂L (Cp = η-C₅H₅, η-C₅Me₅; L = SP(S)(OEt)₂, SP(S)(OⁱPr)₂) has been examined by polarography, cylic voltammetry and coulometry. The first one-electron reduction step leads to a bond rupture process with formation of a mercury compound, [CpFe(CO)₂]₂Hg, at a mercury electrode and the corresponding dimer species at a platinum electrode. The second reduction step corresponds to the reduction of the dimer [CpFe(CO)₂]₂, except in the polarographic reduction of pentamethylcyclopentadienyl compounds.     

Synthesis and Anti-inflammatory Action of （η-C5H5 ）2Ti（ Sal）2 and （η-C5H5 ）2Ti（Clo）2

IntroductionSince K pf[1]discovered that dicyclopenta die-nyltitanium dichloride possesses antitumour action in1979,a large number of cyclopentadienyltitanium com-plexes with different substituents have been synthe-sized[2,3].The experimental data reveal …     

Synthesis and structure of ansa-cyclopentadienyl pyrrolyl titanium complexes: [(η-C5H4)CH2(2-C4H3N)]Ti(NMe2)2 and [1,3-{CH2(2-C4H3N)}2(η-C5H3)]Ti(NMe2)

Reaction of ansa-cyclopentadienyl pyrrolyl ligand (C₅H₅)CH₂(2-C₄H₃NH) (2) with Ti(NMe₂)₄ affords bis(dimethylamido)titanium complex [(η⁵-C₅H₄)CH₂(2-C₄H₃N)]Ti(NMe₂)₂ (3) via amine elimination. A cyclopentadiene ligand with two pendant pyrrolyl arms, a mixture of 1,3- and 1,4-{CH₂(2-C₄H₃NH)}₂C₅H₄ (4), undergoes an analogous reaction with Ti(NMe₂)₄ to give [1,3-{CH₂(2-C₄H₃N)}₂(η⁵-C₅H₃)]Ti(NMe₂) (5). Molecular structures of 3 and 5 have been determined by single crystal X-ray diffraction studies.     

Indenyl complexes of ruthenium(II) containing optically active diphosphines. X-ray structures of (S,S)-(η-C9H7)-Ru{Ph2PCH(CH3)CH(CH3)PPh2}Cl and of its η-C5H5 analogue

The optically active indenyl complexes ((η⁵-C₉H₇)Ru(L---L)Cl (where L---L is either (S,S)-1,2-dimethyl-1,2-ethanediylbis(diphenylphosphine) (chiraphos) or (R,R)-1,2-cyclopentanediylbis(diphenylphosphine) (cypenphos)) have been synthesized and spectroscopically characterized and compared with the corresponding cyclopentadienyl complexes. Reaction of the new complexes with 2-e-donors give cationic adducts in which the pentahaptocoordination of the indenyl ligand is maintained. The crystal structures of (S,S)-(η⁵-C₉H₇)Ru{Ph₂PCH(CH₃)CH(CH₃)PPh₂}Cl (1) and (S,S)-η⁵-C₅H₅Ru{Ph₂PCH(CH₃)CH(CH₃)PPh₂}Cl (3) have been determined.     

Mechanism of formation of (η-C5H5)2NbH3 from the reaction of (η-C5H5)2NbCl2 with hydridoaluminate reducing agents

The mechanism of the transformation of (η⁵-C₅H₅)₂NbCl₂ to (η⁵-C₅H₅)₂NbH₃ by hydridoaluminate reducing agents has been investigated. Results suggest disproportionation of a niobium(IV) hydrite, leading to the trihydride product and a niobium(III) hydridoaluminate, (η⁵-C₅H₅)₂NbH₂AlR₂, which in turn is converted to the trihydride on hydrolysis. (η⁵-C₅H₅)₂NbH₂AlH₂ has been isolated; deuterium labelling shows that hydrogens exchange between ring and metal-bridging positions in this molecule.     

Platination of [3-X-7,8-Ph2-7,8-nido-C2B9H8] (X=Et, F): Synthesis and characterisation of slipped and 1,2→1,7 isomerised products

The reaction of the labelled carborane ligand [3-Et-7,8-Ph₂-7,8-nido-C₂B₉H₈]²⁻ with a source of {Pt(PMe₂Ph)₂}²⁺ affords non-isomerised 1,2-Ph₂-3,3-(PMe₂Ph)₂-6-Et-3,1,2-closo-PtC₂B₉H₈ (1). The analogous reaction between [3-F-7,8-Ph₂-7,8-nido-C₂B₉H₈]²⁻ and {Pt(PMe₂Ph)₂}²⁺ yields 1,8-Ph₂-2,2-(PMe₂Ph)₂-4-F-2,1,8-closo-PtC₂B₉H₈ (3). Compound 1 has a heavily slipped structure (Δ 0.72 Å), which to some degree obviates the need for C atom isomerisation. However, that it is a kinetic product of the reaction is evident from the fact that it reverts to isomerised 1,8-Ph₂-2,2-(PMe₂Ph)₂-4-Et-2,1,8-closo-PtC₂B₉H₈ (2) slowly at room temperature but more rapidly with gentle warming. The heteroatom and labelled-B atom positions in the isomerised compounds 2 and 3 may be explained most simply by the rotation of a CB₂ face of an intermediate based on the structure of 1. Compounds 1–3 were characterised by a combination of spectroscopic and crystallographic techniques.     

Homogeneous hydrogenation of alk-1-enes and alkynes catalyzed by the 1-[Ir(CO)(PhCN)(PPh3)]-7-C6H5-1,7-(σ-C2B10H10) complex

The complex [Ir(σ-carb)(CO)(PhCN)(PPh₃)], where carb = -7-C₆H₅-1,2C₂B₁₀H₁₀, was found to be an effective catalyst for homogeneous hydrogenation of terminal olefins and acetylenes at room temperature and atmospheric or subatmospheric hydrogen pressure. Internal olefins are not hydrogenated, but simple alk-1-enes are readily converted into the corresponding alkanes. Isomerization of the double bond catalyzed by the metal complex occurs at very small extent. Catalytic hydrogenation of olefins having carboxylate substituents on the unsaturated carbon atoms is prevented by the formation of thermally stable chelate hydridoalkyl complexes of the type I$\text{(H)}$(σ-CHRCHR′C(O)OR″) (σ-carb)(CO)(PPh₃)]. Acetylenes are hydrogenated to alkenes. The alk-1-enes formed in the hydrogenation of the alkynes HCCR in turn undergo the more slow reactions either of hydrogenation to alkanes or isomerization to internal olefins which cannot be further hydrogenated. Hydrogenation of alkynes of the type RCCR′ is stereospecifically cis, yielding cis- olefins. Catalyzed cis → trans isomerization reaction of these internal olefins occurs only to a negligeable extent.     

Benzene complex [(η-9-SMe2-7,8-C2B9H10)Fe(η-C6H6)]+ as a synthon for the cationic ferracarborane moiety

The photochemical reaction of [(η⁵-C₆H₇)Fe(η-C₆H₆)]⁺ (1) with the [(η-9-SMe₂-7,8-C₂B₉H₁₀)]⁻ anion followed by the treatment of the resulting ferracarborane (η-9-SMe₂-7,8-C₂B₉H₁₀)Fe(η⁵-C₆H₇) (2) with hydrochloric acid afforded the benzene complex [(η-9-SMe₂-7,8-C₂B₉H₁₀)Fe(η-C₆H₆)]⁺ (3). The reaction of cation 3 with Bu^tNC produced the isonitrile complex [(η-9-SMe₂-7,8-C₂B₉H₁₀)Fe(^tBuNC)₃]⁺ (4). The structure of the complex [4]PF₆ was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2046–2048, October, 2007.     

Synthesis and reactivity of new heterodinuclear iron/rhenium Cx complexes of the formula (η-C5Me5)Re(NO)(PPh3)(CC)n(η-dppe)Fe(η-C5Me5) (n = 3, 4): Redox properties and a dicobalt hexacarbonyl adduct

We report in this communication the synthesis and characterization of two Fe/Re heterodinuclear complexes 3_n of formula (η⁵-C₅Me₅)Re(NO)(PPh₃)(CC)_n(η²-dppe)Fe(η⁵-C₅Me₅) (n = 3, 4) as well as the hexacarbonyl dicobalt adduct (4) of the hexatriynediyl complex 3₃. We show by cyclic voltammetry that the “electronic communication” between the organometallic endgroups and thereby the thermodynamic stability of the corresponding mixed-valent (MV) parent 3_n⁺ is strongly influenced by bridge extension or by complexation of the [Co₂(CO)₆] fragment. In the case of the hexatriynediyl complex, the MV complex 3₃⁺ or 4 can be isolated by performing the chemical oxidation of 3₃ at low temperature. Spectroscopic studies of this compound and of other stable oxidized redox congeners should now help us to unravel how bridge extension modifies the electronic communication between the different redox-active endgroups in this family of unsymmetrically-substituted polyynediyl compounds.     

Reactions of closo-1,5-C2B3H5 with Cl2 and with BMe3

Reaction of closo-1,5-C₂B₃H₅ with Cl₂ under reduced temperatures in an inert solvent gives 2-Cl-1,5-C₂B₃H₄. Using a hot/cold reactor a mixture of BMe₃ and 1,5-C₂B₃H₅ is converted to a combination of B-mono-, di-, and tri-methyl derivatives of this smallest closo carborane. In addition, B-mono-, di-, tri-, and tetramethyl derivatives of 2,2$\text{-}\text{?}$C₂B₃H₄C₂B₃H₄, as well as the parent dimer, are produced.     

On the reactivity of V(η-C6H3Me3-1,3,5)2I

V(η-C₆H₃Me₃-1,3,5)₂I reacts with reducing agents such as MeLi, Na[AlH₂(OCH₂CH₂OCH₃)₂] or Na to yield the neutral complex V(η-C₆H₃Me₃-1,3,5)₂ in 70–75% yield. Reaction of V(η-C₆H₃Me₃-1,3,5)₂I with compounds containing suitable donor atoms such as THF, P(OMe)₃, CH₃CN or Py yields V(η-C₆H₃Me₃-1,3,5)₂ in 40–45% yield via disproportionation. The complex V(η-C₅H₅)₂I was isolated in low yield, together with V(η-C₆H₃Me₃-1,3,5)₂ from the reaction of V(η-C₆H₃Me₃-1,3,5)₂I with Cp₂Mg in toluene. Reaction of V(η-C₆H₃Me₃1,3,5)₂I or V(η-C₆H₃Me₃-1,3,5)₂ with allyl chloride leads to oxidation of the metal and loss of both mesitylene ligands.     

First examples of η- and η --- η-coordination in triphosphorus analogues of ferrocene. Crystal structure of the iron sandwich complex [Fe(η-C5H5) (η-C2R2P3)W (CO)5] (R = Bu)

Syntheses of the novel sandwich compounds [Fe(η⁵-C₅H₅)(η⁵-C₂R₂P₃)] and [Fe(η⁵-C₅H₅)(η⁵-C₂R₂P₃)W(CO)₅], (R = Bu^t), are described. The mode of attachment of the [W(CO)₅] fragment in the latter compound has been determined by NMR and single crystal X-ray diffraction studies.     

Preparative use of electrode catalyzed substitution reactions; synthesis of Fe(CO)(PPh3)(η-C5H5)COCH3

It is shown that electrode catalysis of substitution reactions can operate even for systems with rather slow chemical steps and, furthermore, for those which are electrochemically irreversible. A procedure is described for synthesis of Fe(CO)(PPh₃)(η⁵-C₅H₅)COCH₃ from Fe(CO)₂(η⁵-C₅H₅)CH₃ and triphenylphosphine. A simplified mechanism for the catalytic chain, is given and discussed in terms of the structure of the reacting species.     

Improved syntheses of bis(ethynyl)-para-carboranes, 1,12-(RCC)2-1,12-C2B10H10 and 1,10-(RCC)2-1,10-C2B8H8 (R = H or Me3Si)

Copper-mediated cross-coupling reactions of the 12-vertex and 10-vertex para carboranes, 1,12-C₂B₁₀H₁₂ and 1,10-C₂B₈H₁₀, with trans-1-iodo-2-chloroethene gave the bis(trans-2-chloroethenyl) carboranes, 1,12-(ClCHCH)₂-1,12-C₂B₁₀H₁₀ and 1,10-(ClCHCH)₂-1,10-C₂B₈H₈, respectively, in good yield. The molecular structures of both compounds were determined by X-ray crystallography, verifying the trans disposition of the chloride and carboranyl substituents across the double bonds. These vinyl carboranes can be converted to bis(ethynyl) carboranes, 1,12-(RCC)₂-1,12-C₂B₁₀H₁₀ and 1,10-(RCC)₂-1,10-C₂B₈H₈ (R = H or Me₃Si), easily, and in high yields. These findings provide the most convenient routes to bis(ethynyl) carboranes from the commercially available carboranes, 1,12-C₂B₁₀H₁₂ and 1,10-C₂B₈H₁₀ reported to date.     

Crystal structure of Fe(η-C5H5BCMe3)2 a “problem structure”

The complex Fe(η⁶-C₅H₅CMe₃)₂ crystallizes in the centrosymmetric triclinic space group P (C_i¹; No. 2) with unit cell dimensions of a 8.770(1) Å, b 8.878(1) Å, c 11.991(1) Å, 107.56(1)°, β 90.85(1)°, γ 90.13(1)°, V 890.0(2) ų and Z = 2. A full sphere of data was collected on a four-circle diffractometer. The structure was solved and refined to R 7.93% for all 3155 independent reflections and R 4.98% for those 2002 data with | F₀ | > 6σ. | F₀ |. The molecules lie on crystallographic inversion centers at 0, 0, 0 and 1/2, 0, 1/2; the crystallographic asymmetric unit therefore consists of two independent half molecules. The molecule centered at 0, 0, 0 (molecule “A”) is ordered and well-defined; that centered on 1/2, 0, 1/2 (molecule “B”)is probably disordered, as indicated by larger “thermal parameters” and a greater range of apparent interatomic distances. Discussion em phasizes the geometry of molecule A, which has precise C_i symmetry with Fe(1A)-B(1A) 2.297(4) Å and Fe(1A)-C(ring) distances ranging from 2.057(6) Å to 2.138(4) Å.     

Complexes of titanium and zirconium based on [C5Me4CH2-(2-C5H4N)] ligand

Half-sandwich [η⁵:η¹-κN-C₅Me₄CH₂-(2-C₅H₄N)]MCl₃ (M = Ti (4), Zr (5)) and sandwich [η⁵-C₅Me₄CH₂-(2-C₅H₄N)][η⁵-C₅Me₅]ZrCl₂ (6) ring-peralkylated complexes have been prepared and characterized. Evidence of the intramolecular coordination of the side-chain pyridyl group both in 4 and 5 in solutions is provided by NMR spectroscopy data. Crystal structure of an adduct 5-py with one molecule of pyridine has been established by X-ray diffraction analysis.     

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.     

Cyclopentadienyl-ruthenium and -osmium chemistry : XXXIX. Syntheses of novel alkynyl-ruthenium complexes. X-Ray structures of two forms of {Ru(PPh3)2(η-C5H5)}2(μ-C4) and of Ru{CCC(O)Me}(PPh3)2(η-C5H5)

Reactions between [Ru(thf)(PPh₃)₂(η-C₅H₅)]⁺ and lithium acetylides have given further examples of substituted ethynylruthenium complexes that are useful precursors of allenylidene and cumulenylidene derivatives. From Li₂C₄, mono- and bi-nuclear ruthenium complexes were obtained: single-crystal X-ray studies have characterised two rotamers of {Ru(PPh₃)₂(η-C₅H₅)}₂(μ-C₄), which differ in the relative cis and trans orientations of the RuL_n groups. Protonation of Ru(CCCCH)(PPh₃)₂(η-C₅H₅) afforded the butatrienylidene cation [Ru(C=C=C=CH₂)(PPh₃)₂(η-C₅H₅)]⁺, which reacted readily with atmospheric moisture to give the acetylethynyl complex Ru{CCC(O)Me}(PPh₃)₂(η-C₅H₅), also fully characterised by an X-ray structural study.     

Synthesis and structure of the iron-substituted silylacetylene [(η-C5H5)Fe(CO)2SiMe2C]2 and its cobalt hexacarbonyl derivative [(η-C5H5)Fe(CO)2SiMe2C]2 · Co2(CO)6

A transition metal-substituted silylacetylene [(η⁵-C₅H₅)Fe(CO)₂SiMe₂C]₂, [FpMe₂SiC]₂ (I) was synthesized and characterized spectroscopically and structurally. I crystallized in the monoclinic space group P2₁/n, A = 13.011(3) Å B = 12.912(3) Å, C = 13.175(5) Å, β = 94.95(2). The acetylene linkage is reactive toward Co₂(CO)₈ to form I. Co₂(CO)₆ (II) which was also characterized spectroscopically and by single crystal X-ray diffraction. II crystallized in the orthorhombic space group Pbca, A = 17.64(2) Å, B = 14.225(10) Å, C = 24.49(2) Å.