Polyhedral metallathiaborane chemistry: Synthesis and characterisation of metallathiaboranes based on the twelve-vertex icosahedral closo-{MSB10H10} unit, where M is Rh or Ir

The reaction of [nido-7-SB₁₀H₁₂] with [RhCl(PPh₃)₃] in the presence of N,N,N′N′-tetramethylnaphthalene-1,8-diamine (tmnd) in CH₂Cl₂ gives twelve-vertex [2,2-(PPh₃)₂-2-H-closo-2,1-RhSB₁₀H₁₀] (1) and eleven-vertex [8,8-(PPh₃)₂-nido-8,7-RhSB₉H₁₀] (2), as major products, plus the dimeric species [{(PPh₃)-closo-RhSB₁₀H₁₀}₂] (3) as a minor product. Reaction of 1 with PMe₂Ph in CH₂Cl₂ results in phosphine exchange and hydride substitution, affording the chloro analogue of 1, [2,2-(PMe₂Ph)₂-2-Cl-closo-2,1-RhSB₁₀H₁₀] (4). By contrast, reaction between [IrCl(PPh₃)₃] and [nido-7-SB₁₀H₁₂] in CH₂Cl₂ with tmnd affords only one product, twelve-vertex [2,2-(PPh₃)₂-2-H-closo-2,1-IrSB₁₀H₁₀] (5). [RhCl₂(η⁵-C₅Me₅)]₂ with [nido-7-SB₁₀H₁₂] under the same conditions gives twelve-vertex [2-(η⁵-C₅Me₅)-closo-2,1-RhSB₁₀H₁₀] (6). All the compounds are characterised by NMR spectroscopy, and by mass spectrometry, and the molecular structure of [2,2-(PMe₂Ph)₂-2-Cl-closo-2,1-RhSB₁₀H₁₀] (4) was established by single-crystal X-ray diffraction analysis. This last rhodathiaborane 4 is fluxional in solution through a process that involves a reversible partial rotation of the {RhCl(PMe₂Ph)₂} unit above the {SB₄} pentagonal face of the {SB₁₀H₁₀} fragment.     

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.     

Synthesis and structure of halogen derivatives of 9-dimethylsulfonium-7,8-dicarba-nido-undecaborane [9-Me2S-7,8-C2B9H11]

Halogenation of 9-dimethylsulfonium-7,8-dicarba-nido-undecaborane [9-SMe₂-7,8-C₂B₉H₁₁] with N-chlorosuccinimide, bromine and iodine gave the expected corresponding halogen derivatives [9-SMe₂-11-X-7,8-C₂B₉H₁₀], where X = Cl (1), Br (2), I (3). In the bromination reaction, [9-SMe₂-6-Br-7,8-C₂B₉H₁₀] (4) was isolated as a minor product being the first example of substitution at a “lower” belt of the 7,8-dicarba-nido-undecaborate cage. The use of excess of bromine resulted in dibromo derivative [9-SMe₂-6,11-Br₂-7,8-C₂B₉H₉] (5). Structures of the compounds prepared were determined using ¹¹B-¹¹B COSY NMR spectroscopy (for all halogen derivatives) and single crystal X-ray diffraction (for compounds 2, 3, and 5).     

Metallacarborane chemistry of the hypho-[6,7-C2B6H13] anion: Reaction with nickelocene and the formation of three multimetallic nickel-boron clusters

The reaction of the hypho-[6,7-C₂B₆H₁₃]⁻ anion (1) with nickelocene and an excess of ‘proton sponge’ (1,8-bis-(dimethylamino-naphthalene)) in boiling acetonitrile leads to the formation of a pair of isomeric trimetallic nickel-boron clusters, [6,7,8-(CpNi)₃-1-CB₅H₆] (2) and [6,7,8-(CpNi)₃-2-CB₅H₆] (3), in a combined yield of 55%. Isomer (2) had been previously prepared from nido-2-CB₅H₉ but in much lower yield. Isomer (3) is without precedent and has been characterized using multi-nuclear NMR spectroscopy and mass spectrometry. Isomer (3) undergoes conversion to (2) via heating in boiling toluene. In addition to this isomeric pair, an interesting nido dimetallacarborane of constitution [6,6′-(CpNi)₂-7,7′-C₂B₆H₈] (4) has been isolated from the same reaction in 5% yield and characterized by single-crystal X-ray diffraction analysis.     

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.     

A new look at the nido-undecaborate system

The structure of the nido-undecaborate anion, [B₁₁H₁₄]⁻, has been re-examined because of what appear to be discrepancies that were observed between our determination of the structure of the anion in [(Cp₂Zr)₂B₅H₈][B₁₁H₁₄] (1) and previously published structures. The structure of 1 indicated the presence of two bridging H atoms and another pseudo-bridging one whereas those of a series of published structures indicate the presence of a plane of symmetry with two bridging H atoms and one endo-H atom. Thus, we undertook a series of structural determinations and also a computational study at the B3LYP/6-31++G(d,p) level. In addition to 1, the species studied included [NBnEt₃][B₁₁H₁₄] (2), [NBnEt₃][7-Br-nido-B₁₁H₁₃] (3) and [NBnEt₃][7-(η¹-dppm)-nido-B₁₁H₁₂] (4). Our structure of 2 indicated the presence of two bridging H atoms and an endo-hydrogen atom with some bridging character but that of 3 contained three bridging atoms. As expected the structure of 4 contains two bridging H atoms. Calculations of bond parameters fit well with the experimental data as do the ¹¹B NMR chemical shifts. The latter were calculated for the average of the two open face configurations, one with two bridging and one endo-hydrogen and the other with three bridging hydrogen atoms. The difference in energies for these two open face configurations is calculated to be 0.36 kJ/mol, which effectively suggests that the two structures are equally favored.     

The preparation of [closo-1-CB9H8-1-COOH-10-(4-C3H7C5H9S)] as intermediate to polar liquid crystals

The preparation of iodo acid [closo-1-CB₉H₈-1-COOH-10-I]⁻ (1) is optimized and scaled from 1 to 40 g of B₁₀H₁₄. The improved preparation of the [arachno-6-CB₉H₁₃-6-COOH]⁻ (5) uses four times smaller volume and can be run conveniently in up to 40 g scale in a 3-L vessel. The optimized oxidation of 5 to [closo-2-CB₉H₉-2-COOH]⁻ (4) requires less oxidant, 12 times smaller volume, and significantly shorter reaction time. The overall yields of the iodo acid 1 as the [NMe₄]⁺ salt are typically 8-10% (10-12 g) for 40 g of B₁₀H₁₄. The iodo acid 1 was transformed to amino acid 8, then to dinitrogen acid 10, and finally to sulfonium acid 2[3] in overall yield of about 13%. The search for a more efficient phosphine ligand for the Pd-catalyzed amination process was not fruitful. Three routes to the sulfonium acid 2[n] were investigated, and the best yield of about 47% was obtained for Cs₂CO₃-assisted cycloalkylation. Liquid crystalline ester of acid 2[3] and 4-butoxyphenol was prepared and investigated.     

Formation of ferraboranes from pentaborane(9) or BH3 · thf and an electron-rich cyclopentadienyl iron phosphine hydride

[(η⁵-C₅R₅)Fe(PMe₃)₂H] (R = H, Me) can be made in good yields in a simple one-pot reaction between FeCl₂, PMe₃, C₅R₅H (R = H, Me) and Na/Hg in thf. Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with pentaborane(9) gives the known metallaborane [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (1) in improved yield as well as the new metallaboranes [(η-C₅H₅)-nido-2-FeB₅H₈{μ-5,6-Fe(η⁵-C₅H₅)(PMe₃)(μ-6,7-H)}] (2), [(η-C₅H₅)(PMe₃)-arachno-2-FeB₃H₈] (3), [(η⁵-C₅H₅)₂-capped-nido-2,3-Fe₂B₄H₈] (4), [(η⁵-C₅H₅)-nido-2-FeB₄H₇(PMe₃)] (5) and [(η⁵-C₅H₅)-nido-2-FeB₅H₈(PMe₃)] (6). Reaction of [(η⁵-C₅Me₅)Fe(PMe₃)₂H] with pentaborane(9) gives predominantly [(η⁵-C₅Me₅)-nido-2-FeB₅H₁₀] (7) and [(η⁵-C₅Me₅)(PMe₃)-arachno-2-FeB₃H₈] (8). Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with 2 equiv. of BH₃ · thf gives low yields of ferrocene and compound 3. Compound 7 thermally isomerises to the apical isomer [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (9) in low yield. Compounds 1 and 7 deprotonate cleanly in the presence of KH at the unique B-H-B bridge to give [(η⁵-C₅H₅)-nido-2-FeB₅H₉⁻][K⁺] (10) and [(η⁵-C₅Me₅)-nido-2-FeB₅H₉⁻][K⁺] (11) respectively, whilst 6 deprotonates more slowly at one of two equivalent B-H-B bridges to give the fluxional anion [(η⁵-C₅H₅)-nido-2-FeB₅H₇(PMe₃)⁻] (12).     

Branched and dendritic metallo-carbosiloxanes with OCH2PPh2MLn end-grafted units

A straightforward method for the preparation of metallo carbosiloxanes of type Si(OCH₂CH₂CH₂SiMe₂[OCH₂PPh₂M(CO)_n])₄ (n = 3, M = Ni, 7a; n = 4, M = Fe, 7b; n = 5: M = Mo, 7c; M = W, 7d), Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₄ (8) and Me₂Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₂ (11) is described. The reaction of Si(OCH₂CH₂CH₂SiMeXCl)₄ (1: X = Me, 2: X = Cl) or Me₂Si(OCH₂CH₂CH₂SiMeCl₂)₂ (9) with HOCH₂PPh₂ (3) produces Si(OCH₂CH₂CH₂SiMe₂(OCH₂PPh₂))₄ (4), Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₄ (5) or Me₂Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₂ (10) in presence of DABCO. Treatment of the latter molecules with Ni(CO)₄ (6a), Fe₂(CO)₉ (6b), M(CO)₅(Thf) (6c: M = Mo; 6d: M = W), respectively, gives the title compounds 7a-7d, 8 and 11 in which the PPh₂ groups are datively bound to a 16-valence-electron metal carbonyl fragment.The formation of analytical pure and uniform branched and dendritic metallo carbosiloxanes is based on elemental analysis, and IR, ¹H, ¹³C{¹H}, ²⁹Si{¹H} and ³¹P{¹H} NMR spectroscopic studies. In addition, ESI-TOF mass spectrometric studies were carried out.     

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.     

Simple protocol for the synthesis of the asymmetric PCP pincer ligand [C6H4-1-(CH2PPh2)-3-(CH(CH3)PPh2)] and its Pd(II) derivative [PdCl{C6H3-2-(CH2PPh2)-6-(CH(CH3)PPh2)}]

The asymmetric PCP pincer ligand [C₆H₄-1-(CH₂PPh₂)-3-(CH(CH₃)PPh₂)] (4) has been synthesized in a facile manner in three simple steps in high yield. Metallation of PCP pincer ligand (4) with [Pd(COD)Cl₂] affords complex [PdCl{C₆H₃-2-(CH₂PPh₂)-6-(CH(CH₃)PPh₂)}] (7) in good yield.     

Synthesis and characterization of hetero-binuclear Co-Rh complexes [CpCoS2C2(B9H10)][Rh(COD)] and [CpCoSe2C2(B10H10)][Rh(COD)]

Two hetero-binuclear complexes [Cp^∗CoS₂C₂(B₉H₁₀)][Rh(COD)] (2a) and [Cp^∗CoSe₂C₂(B₁₀H₁₀)][Rh(COD)] (2b) [Cp^∗ = η⁵-pentamethylcyclopentadienyl, COD = cyclo-octa-1,5-diene (C₈H₁₂)] were synthesized by the reactions of half-sandwich complexes [Cp^∗CoE₂C₂(B₁₀H₁₀)] [E = S (1a), Se (1b)] with low valent transition metal complexes [Rh(COD)(OEt)]₂ and [Rh(COD)(OMe)]₂. Although the reaction conditions are the same, the structures of two products for dithiolato carborane and diselenolato carborane are different. The cage of the carborane in 2a was opened; However, the carborane cage in 2b was intact. Complexes 2a and 2b have been fully characterized by ¹H, ¹¹B NMR and IR spectroscopy, as well as by elemental analyses. The molecular structures of 2a and 2b have been determined by single-crystal X-ray diffraction analyses and strong metal-metal interactions between cobalt and rhodium atoms (2.6260 Å (2a) and 2.7057 Å (2b)) are existent.     

Synthesis of [Ru(CO)2(PPh3)(SP)] and [Ru(CO)(PPh3)2(SP)] and their catalytic activities for the hydroamination of phenylacetylene

The reaction of [Ru(CO)₂(PPh₃)₃] (1) with o-styryldiphenylphophine (SP) (2) gave [Ru(CO)₂(PPh₃)(SP)] (3) in 83% yield. This styrylphosphine ruthenium complex 3 can also be synthesized by the reaction of [Ru(p-MeOC₆H₄NN)(CO)₂(PPh₃)₂]BF₄ (4) with NaBH₄ and 2 in 50% yield. When “Ru(CO)(PPh₃)₃” generated by the reaction of [RuH₂(CO)(PPh₃)₃] (8) with trimethylvinylsilane reacted with 2, [Ru(CO)(PPh₃)₂(SP)] (10) was produced in moderate yield as an air sensitive solid. The spectral and X-ray data of these complexes revealed that the coordination geometries around the ruthenium center of both complexes corresponded to a distorted trigonal bipyramid with the olefin occupying the equatorial position and the C-C bonding in the olefin moiety in 3 and 10 contained a significant contribution from a ruthenacyclopropane limiting structure. Complexes 3 and 10 showed catalytic activity for the hydroamination of phenylacetylene 11 with aniline 12. Ruthenium complex 3 in the co-presence of NH₄PF₆ or H₃PW₁₂O₄₀ proves to be a superior catalyst system for this hydroamination reaction. In the case of the reaction using H₃PW₁₂O₄₀ as an additive, ketimines (13) was obtained in 99% yield at a ruthenium-catalyst loading of 0.1 mol%. Some aniline derivatives such as 4-methoxy, 4-trifluoromethyl-, and 4-bromoanilines can also be used in this hydroamination reaction.     

Synthesis and X-ray structural characterization of the triphenylphosphine derivative of the closo-dodecaborate anion, closo-[B12H11P(C6H5)3][N(n-C4H9)4]

The reaction of a molar excess of closo-[B₁₂H₁₁I][N(n-C₄H₉)₄]₂ (1) with tetrakis(triphenylphosphine)palladium (0), Pd(0)L₄, yields to the formation of the title monoanionic compound, closo-[1-B₁₂H₁₁P(C₆H₅)₃][N(n-C₄H₉)₄] (2). The structure of 2 was determined by X-ray diffraction analysis performed on a single crystal. The mechanism of formation of 2 is also discussed. We suggested a two-step mechanism for the formation of 2 consisting in a oxidative addition of the palladium complex followed by a reductive elimination involving P(C₆H₅)₃ and assisted by Na₂CO₃. To our knowledge, this is the first example of monosubstitution of B₁₂ with formation of boron-phosphorus bond.     

Reactions of small boranes with ruthenium phosphine hydrides: Oligomerisation of monoborane-tetrahydrofuran to a nido-hexaruthenaborane

Reaction of [Ru(PPh₃)₄H₂] with BH₃ · thf at room temperature gives borane oligomerisation with the formation of the 6-vertex metallaborane nido-2-[Ru(PPh₃)₂(H)B₅H₁₀] (1). This cluster is also formed by reaction of [Ru(PPh₃)₄H₂] with nido-B₅H₉. Compound (1) is readily deprotonated by KH in thf at the unique basal B-H-B bridge to give (2). In contrast to [Ru(PPh₃)₄H₂] reaction of [cis-Ru(PMe₃)₄H₂] with BH₃ · thf gives initially the known borohydride [Ru(PMe₃)₃(H)(η²-BH₄)] which reacts with excess BH₃ · thf to give the 5-vertex metallaborane nido-2-[Ru(PMe₃)₃B₄H₈] (3). Reaction of [cis-Ru(PMe₃)₄H₂] with nido-B₅H₉ also gives (3) and nido-2-[Ru(PMe₃)₃B₉H₁₃] (4). [cis-Ru(PMe₃)₄H₂] is conveniently prepared in high yield in a one-pot synthesis by the sodium amalgam reduction of RuCl₃ · 3H₂O in thf with excess PMe₃ under dinitrogen.     

New organomercury(II) compounds containing intramolecular N → Hg interactions: crystal and molecular structure of [2-(Me2NCH2)C6H4]HgCl and [2-(Me2NCH2)C6H4]Hg[S(S)PPh2]

[2-(Me₂NCH₂)C₆H₄]HgCl (1) was prepared by reacting HgCl₂ with [2-(Me₂NCH₂)C₆H₄]Li in diethyl ether. The reactions of 1 with the sodium or ammonium salt of the appropriate thiophosphinato ligand, in 1:1 molar ratio, afford the isolation of [2-(Me₂NCH₂)C₆H₄]Hg[S(S)PR₂] [R=Me (2), Et (3), Ph (4)], [2-(Me₂NCH₂)C₆H₄]Hg[S(O)PPh₂] (5) and [2-(Me₂NCH₂)C₆H₄]Hg[S(S)P(OⁱPr)₂] (6). The compounds were investigated by IR and multinuclear NMR (¹H, ¹³C and ³¹P) spectroscopy. The molecular structures of 1 and 4 were determined by single-crystal X-ray diffraction. Due to the strong intramolecular coordination of the N atom of the pendant CH₂NMe₂ arm [Hg(1)-N(1) 2.764(6) and 2.725(4) Å in 1 and 4, respectively] both compounds exhibit a T-shaped (C,N)HgX core in the molecular unit, with almost linear arrangement of the covalent bonds [C(1)-Hg(1)-Cl(1) 176.93(18)° in 1, and C(1)-Hg(1)-S(1) 169.54(16)° in 4]. The crystals of 1 contain discrete monomeric molecules, while the crystals of 4 contain dimer associations built through asymmetric bridging dithiophosphinato ligands [Hg(1)-S(1) 2.3911(16) Å, Hg(1)?S(2a) 3.102(2) Å], thus resulting in an overall pseudo-trigonal bipyramidal (or seesaw) (C,N)HgS₂ core, with the nitrogen atom and the weekly bonded sulfur atom in equatorial positions [N(1)-Hg(1)?S(2a) 82.01(10)°].     

Reactivity of 2,3-bis(2-pyridyl)pyrazine with [Re2(CO)8(CH3CN)2]: Molecular structures of [Re2(CO)8(C14H10N4)] and [Re2(CO)8(C14H10N4)Re2(CO)8]

The reaction of the labile compound [Re₂(CO)₈(CH₃CN)₂] with 2,3-bis(2-pyridyl)pyrazine in dichloromethane solution at reflux temperature afforded the structural dirhenium isomers [Re₂(CO)₈(C₁₄H₁₀N₄)] (1 and 2), and the complex [Re₂(CO)₈(C₁₄H₁₀N₄)Re₂(CO)₈] (3). In 1, the ligand is σ,σ′-N,N′-coordinated to a Re(CO)₃ fragment through pyridine and pyrazine to form a five-membered chelate ring. A seven-membered ring is obtained for isomer 2 by N-coordination of the 2-pyridyl groups while the pyrazine ring remains uncoordinated. For 2, isomers 2a and 2b are found in a dynamic equilibrium ratio [2a]/[2b]  =  7 in solution, detected by ¹H NMR (−50 °C, CD₃COCD₃), coalescence being observed above room temperature. The ligand in 3 behaves as an 8e-donor bridge bonding two Re(CO)₃ fragments through two (σ,σ′-N,N′) interactions. When the reaction was carried out in refluxing tetrahydrofuran, complex [Re₂(CO)₆(C₁₄H₁₀N₄)₂] (4) was obtained in addition to compounds 1-3. The dinuclear rhenium derivative 4 contains two units of the organic ligand σ,σ′-N,N′-coordinated in a chelate form to each rhenium core. The X-ray crystal structures for 1 and 3 are reported.     

Reactivity differences between nickel and palladium complexes bearing 1,2-diphosphino-1,2-dicarba-dodecaborane ligand

AgOTf (OTf = trifluoromethanesulfonate) shows the reactivity differences when it reacts with carborane complexes [MCl₂{(PPh₂)₂(C₂B₁₀H₁₀)}] (M = Ni (2), Pd (3)). The reaction of AgOTf with the palladium complex 3 affords [Pd₂(μ-OTf)₂{(PPh₂)₂(C₂B₉H₁₀)}₂] (4) in high yields, while corresponding reaction between the nickel complex 2 and AgOTf leads to the formation of binuclear complexes [Ni{(PPh₂)₂(C₂B₉H₁₀)}](μ-Cl)₂[Ag{(PPh₂)₂(C₂B₁₀H₁₀)}] (5) and [Ag₂(μ-Cl)₂ {(PPh₂)₂ (C₂B₁₀H₁₀)}₂] (6). The carborane cage of complexes 4 and 5 were broken to form nido-carboranes. It is believed the group 10 metals themselves play an important role in opening the closo-carborane skeleton. Directly stirring [(PPh₂)₂(C₂B₁₀H₁₀)] with AgOTf afforded [Ag₂(μ-OTf)₂{(PPh₂)₂(C₂B₁₀H₁₀)}₂] (7), which is also used to react with 2 and 3. The reaction between 2 and 7 gives only 4 in high yields, however, stirring the mixture of 3 and 7 affords [Pd₂(μ-Cl)₂{(PPh₂)₂(C₂B₉H₁₀)}₂] (8), [Pd{(PPh₂)₂(C₂B₉H₁₀)}₂] (9) and 6. All these complexes have been characterized by IR, ¹H NMR, ¹¹B NMR and elemental analyses. Complexes 2, 4-9 have also been determined by single-crystal X-ray diffraction analyses.     

Trifluoroacetylacetonate rhodium(III) methyl complexes, cis-[Rh(TFA)(PPh3)2(CH3)(L)][BPh4] and cis-[Rh(TFA)(PPh3)2(CH3)(I)] (L = CH3CN, NH3, pyridine), in comparison with their acetylacetonate analogs

The oxidative addition of CH₃I to planar rhodium(I) complex [Rh(TFA)(PPh₃)₂] in acetonitrile (TFA is trifluoroacetylacetonate) leads to the formation of cationic, cis-[Rh(TFA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (1), or neutral, cis-[Rh(TFA)(PPh₃)₂(CH₃)(I)] (4), rhodium(III) methyl complexes depending on the reaction conditions. 1 reacts readily with NH₃ and pyridine to form cationic complexes, cis-[Rh(TFA)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (2) and cis-[Rh(TFA)(PPh₃)₂(CH₃)(Py)][BPh₄] (3), respectively. Acetylacetonate methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(I)] (5), was obtained by the action of NaI on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] in acetone at −15 °C. Complexes 1-5 were characterized by elemental analysis, ³¹P{¹H}, ¹H and ¹⁹F NMR. For complexes 2, 3, 4 conductivity data in acetone solutions are reported. The crystal structures of 2 and 3 were determined. NMR parameters of 1-5 and related complexes are discussed from the viewpoint of their isomerism.     

Reaction of CpCo(PPh3)2 with diphenylphosphinoalkynes: Syntheses and X-ray structures of 1,3-cyclobutadiene-substituted CpCoCb diphosphine and 2,5-cobaltacyclopentadiene diphosphine dioxide

A potentially bidentate cobalt-containing phosphine ligand, [(η⁵-C₅H₅)Co(η⁴-1,3-(PPh₂)₂C₄Ph₂)] (trans-1), was prepared from the reaction between PhCCPPh₂ and CpCo(PPh₃)₂ obtained in situ from CoCl(PPh₃)₃ and NaCp. The cobaltacycle [(η⁵-C₅H₅)(PPh₃)Co(2,5-(PPh₂)₂C₄H₂)] (2) was prepared from the reaction of CpCo(PPh₃)₂ with HCCPPh₂. An oxidized product [(η⁵-C₅H₅)(PPh₃)Co(2,5-(P(O)Ph₂)₂C₄H₂)] (4), was obtained upon the attempted isolation of 2 using CTLC. Both 2 and 4 failed to produce [(η⁵-C₅H₅)Co(η⁴-1,2-(PPh₂)₂C₄H₂)] or its oxidized analog, respectively, upon thermal activation. The performance of phosphine 1 in the Suzuki coupling of several aryl chlorides with phenylboronic acid in the presence of Pd(OAc)₂ was evaluated.