- Sublimation study of triphenyl boron and the bond-dissociation enthalpy of B-C6H5
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The sublimation pressures of triphenyl boron, B(C6H5)3, in the temperature range 340 to 380 K have been determined from simultaneous measurements of the rate of mass effusion and torsional recoil.The measured vapor pressures expressed by the equations: log10(pK/p0) = (9.52 +/- 0.07) - (5.326 +/- 0.026)*103(K/T), log10(pτ/p0) = (10.08 +/- 0.06) - (5.518 +/- 0.022)*103(K/T) where pK and pτ are the pressures measured by the Knudsen effusion and torsional recoil techniques, respectively, and p0 = 101.325 kPa, confirm that triphenyl boron is a monomer in the vapor phase in the temperature range of the measurements.The mean standard molar enthalpy and entropy of sublimation (p0 = 101.325 kPa) derived from these equations are: ΔsubH0m = (103.8 +/- 2.5) kJ*mol-1 and ΔsubS0m = (187.6 +/- 7.6) J*K-1*mol-1.The mean molar bond-dissociation enthalpy (B-C6H5) is calculated to be (459 +/- 11.6) kJ*mol-1.
- Govorchin, Steven W.,Kana'an, Adli S.,Kanamueller, Joseph M.
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- [4-tBu-2,6-{P(O)(OiPr)2}2C6H 2SnL]+: An NHC-stabilized organotin(II) cation and related derivatives
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The organotin(II) salts [4-tBu-2,6-{P(O)(OiPr)2} 2C6H2SnL]X (1: X=B[3,5-(CF3) 2C6H3)]4; 2: X=BPh4) and [4-tBu-2,6-{P(O)(OiPr)2}2
- Wagner, Michael,Zoeller, Thomas,Hiller, Wolf,Prosenc, Marc H.,Jurkschat, Klaus
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- Stabilization and Transfer of the Transient [MesP4]- Butterfly Anion Using BPh3
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The transient bicyclo[1.1.0]tetraphosphabutane anion, generated from white phosphorus (P4) and MesLi (Mes=2,4,6-tBu3C6H2), can be trapped by BPh3 in THF. This Lewis acid stabilized anion can be used as an [RP4]- transfer agent, reacting cleanly with neutral Lewis acids (B(C6F5)3, BH3, and W(CO)5) to afford unique singly and doubly coordinated butterfly anions, and with the trityl cation to form a neutral, nonsymmetrical, all-carbon-substituted P4derivative. This reaction path enables a simple, stepwise functionalization of white phosphorus. Trap and transfer: The bicyclo[1.1.0]tetraphosphabutane anion (see scheme, center), generated from P4 and MesLi (Mes=2,4,6-tBu3C6H2), can be trapped by BPh3 in THF. The anion can be used as an [RP4]- transfer agent, reacting with neutral Lewis acids (B(C6F5)3, BH3, and W(CO)5) to afford unique singly and doubly coordinated butterfly anions and with the trityl cation to form a neutral, nonsymmetrical P4 derivative.
- Borger, Jaap E.,Ehlers, Andreas W.,Lutz, Martin,Slootweg, J. Chris,Lammertsma, Koop
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- Borane-protected cyanides as surrogates of h-bonded cyanides in [FeFe]-hydrogenase active site models
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Triarylborane Lewis acids bind [Fe2(pdt)(CO)4(CN) 2]2- [1]2- (pdt2- = 1,3-propanedithiolate) and [Fe2(adt)(CO)4(CN) 2]2- [3]2- (adt2- = 1,3-azadithiolate, HN(CH2S-)2) to give the 2:1 adducts [Fe2(xdt)(CO)4(CNBAr3) 2]2-. Attempts to prepare the 1:1 adducts [1(BAr 3)]2- (Ar = Ph, C6F5) were unsuccessful, but related 1:1 adducts were obtained using the bulky borane B(C6F4-o-C6F5)3 (BAr F3). By virtue of the N-protection by the borane, salts of [Fe2(pdt)(CO)4(CNBAr3)2] 2- sustain protonation to give hydrides that are stable (in contrast to [H1]-). The hydrides [H1(BAr3)2]- are 2.5-5 pKa units more acidic than the parent [H1]-. The adducts [1(BAr3)2]2- oxidize quasi-reversibly around -0.3 V versus Fc0/+ in contrast to ca. -0.8 V observed for the [1]2-/- couple. A simplified synthesis of [1] 2-, [3]2-, and [Fe2(pdt)(CO) 5(CN)]- ([2]-) was developed, entailing reaction of the diiron hexacarbonyl complexes with KCN in MeCN.
- Manor, Brian C.,Ringenberg, Mark R.,Rauchfuss, Thomas B.
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- METHOD FOR SYNTHESIZING ORGANIC MAGNESIUM COMPOUND, METHOD FOR SYNTHESIZING ORGANIC BORONIC ACID COMPOUND, AND COUPLING METHOD
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An object is to establish a technology with which an organic magnesium compound can be easily and efficiently synthesized at a low cost with few steps that do not involve a complex chemical method. A method for synthesizing an organic magnesium compound includes, in a reaction solvent, reacting an organic halide represented by General Formula I (Ra—Xa) with a dispersion product obtained by dispersing sodium in a dispersion solvent to obtain an organic sodium compound represented by General Formula II (Ra—Na), and reacting the obtained organic sodium compound with a magnesium halide represented by General Formula III (Mg—(Xb)2) to obtain an organic magnesium compound represented by General Formula IV (Ra—Mg—Xb).
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Paragraph 0016; 0082-00841
(2021/03/13)
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- Lewis Acidic Boranes, Lewis Bases, and Equilibrium Constants: A Reliable Scaffold for a Quantitative Lewis Acidity/Basicity Scale
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A quantitative Lewis acidity/basicity scale toward boron-centered Lewis acids has been developed based on a set of 90 experimental equilibrium constants for the reactions of triarylboranes with various O-, N-, S-, and P-centered Lewis bases in dichloromethane at 20 °C. Analysis with the linear free energy relationship log KB=LAB+LBB allows equilibrium constants, KB, to be calculated for any type of borane/Lewis base combination through the sum of two descriptors, one for Lewis acidity (LAB) and one for Lewis basicity (LBB). The resulting Lewis acidity/basicity scale is independent of fixed reference acids/bases and valid for various types of trivalent boron-centered Lewis acids. It is demonstrated that the newly developed Lewis acidity/basicity scale is easily extendable through linear relationships with quantum-chemically calculated or common physical–organic descriptors and known thermodynamic data (ΔH (Formula presented.)). Furthermore, this experimental platform can be utilized for the rational development of borane-catalyzed reactions.
- Mayer, Robert J.,Hampel, Nathalie,Ofial, Armin R.
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supporting information
p. 4070 - 4080
(2021/01/29)
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- Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes
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Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.
- Geng, Jiao,Hu, Xingbang,Liu, Qiang,Wu, Youting,Yang, Liu,Yao, Chenfei
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supporting information
p. 3685 - 3690
(2021/05/31)
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- Iodine-catalyzed synthesis of N,N'-chelate organoboron aminoquinolate
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We disclose a novel method for the synthesis of fluorescent N,N'-chelate organoboron compounds in high efficiency by treatment of aminoquinolates with NaBAr4/ R'COOH in the presence of an iodine catalyst. These compounds display high air and thermal stability. A possible catalytic mechanism based on the results of control experiments has been proposed. Fluorescence quantum yield of 3b is up to 0.79 in dichloromethane.
- Qiu, Renhua,Yang, Tianbao,Cao, Xin,Zhang, Xing-Xing,Ou, Yifeng,Au, Chak-Tong,Yin, Shuang-Feng
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supporting information
p. 12430 - 12443
(2020/11/10)
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- Examining the Effects of Monomer and Catalyst Structure on the Mechanism of Ruthenium-Catalyzed Ring-Opening Metathesis Polymerization
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The mechanism of Ru-catalyzed ring-opening metathesis polymerization (ROMP) is studied in detail using a pair of third generation ruthenium catalysts with varying sterics of the N-heterocyclic carbene (NHC) ligand. Experimental evidence for polymer chelation to the Ru center is presented in support of a monomer-dependent mechanism for polymerization of norbornene monomers using these fast-initiating catalysts. A series of kinetic experiments, including rate measurements for ROMP, rate measurements for initiation, monomer-dependent kinetic isotope effects, and activation parameters were useful for distinguishing chelating and nonchelating monomers and determining the effect of chelation on the polymerization mechanism. The formation of a chelated metallacycle is enforced by both the steric bulk of the NHC and by the geometry of the monomer, leading to a ground-state stabilization that slows the rate of polymerization and also alters the reactivity of the propagating Ru center toward different monomers in copolymerizations. The results presented here add to the body of mechanistic work for olefin metathesis and may inform the continued design of catalysts for ROMP to access new polymer architectures and materials.
- Wolf, William J.,Lin, Tzu-Pin,Grubbs, Robert H.
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supporting information
p. 17796 - 17808
(2019/11/11)
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- PHOTOBASE GENERATOR
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There is provided a photobase generator and a photosensitive resin composition containing the photobase generator. The photobase generator includes an ammonium salt represented by general formula (1). In formula (1), R1 to R4 independently represent an alkyl group having 1 to 18 carbon atoms or Ar, wherein at least one of R1 to R4 represents Ar; Ar represents an aryl group having 6 to 14 carbon atoms (excluding carbon atoms contained in a substituent as mentioned below), wherein some of hydrogen atoms in the aryl group may be independently substituted by an alkyl group having 1 to 18 carbon atoms or the like; Y+ represents an ammonio group represented by general formula (2) or (3); and E represents a hydrogen atom or a group represented by general formula (5).
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Paragraph 0090
(2016/02/03)
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- Coordination complexes of Ph3Sb2+ and Ph 3Bi2+: Beyond pnictonium cations
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The syntheses of salts containing ligand-stabilized Ph3Sb 2+ and Ph3Bi2+ dications have been realized by in situ formation of Ph3Pn(OTf)2 (Pn=Sb or Bi) and subsequent reaction with OPPh3, dmap and bipy. The solid-state structures demonstrate diversity imposed by the steric demands and nature of the ligands. The synthetic method has the potential for broad application enabling widespread development of the coordination chemistry for PnV acceptors. A coordinated effort: The synthesis and characterization of OPPh 3, dmap (4-(dimethylamino)pyridine), and bipy (2,2′-bipyridine) complexes of SbV and BiV are reported. The solid-state structures demonstrate structural diversity driven by the steric demands and the nature of the ligands.
- Robertson, Alasdair P. M.,Burford, Neil,McDonald, Robert,Ferguson, Michael J.
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supporting information
p. 3480 - 3483
(2014/04/03)
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- N-Triphenylboryl- and N,N′-bis(triphenylboryl)benzo-2,1,3- telluradiazole
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Being isoelectronic and isostructural analogues of N-alkyl-substituted telluradiazolyl cations, the adducts of triphenylborane with benzo-2,1,3-telluradiazole provide an electrically neutral point of reference with which the properties of the heterocyclic
- Cozzolino, Anthony F.,Bain, Alex D.,Hanhan, Stephanie,Vargas-Baca, Ignacio
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supporting information; experimental part
p. 4043 - 4045
(2009/12/25)
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- Sodium tetraarylborates as effective nucleophiles in rhodium/diene- catalyzed 1,4-addition to β,β-disubstituted α,β-unsaturated ketones: Catalytic asymmetric construction of quaternary carbon stereocenters
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(Chemical Equation Presented) A rhodium-catalyzed 1,4-addition of sodium tetraarylborates to β,β-disubstituted α,β-unsaturated ketones is described. Highly efficient asymmetric catalysis has also been achieved by employing a readily available chiral diene
- Shintani, Ryo,Tsutsumi, Yosuke,Nagaosa, Makoto,Nishimura, Takahiro,Hayashi, Tamio
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p. 13588 - 13589
(2009/12/31)
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- Halide abstraction as a route to cationic transition-metal complexes containing two-coordinate gallium and indium ligand systems
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Halide abstraction chemistry offers a viable synthetic route to the cationic two-coordinate complexes [{Cp*Fe(CO)2} 2(μ-E)]+ (7, E = Ga; 8, E = In) featuring linear bridging gallium or indium atoms. Structural, spectroscopic, and computational studies undertaken on 7 are consistent with appreciable Fe-Ga π-bonding character; in contrast, the indium-bridged complex 8 is shown to feature a much smaller π component to the metal-ligand interaction. Analogous reactions utilizing the supermesityl-substituted gallyl or indyl precursors of the type (η5-C5R5)Fe(CO)2E(Mes*)X, on the other hand, lead to the synthesis of halide-bridged species of the type [{(η5-C5R5)Fe(CO)2E(Mes*)} 2(μ-X)]+, presumably by trapping of the highly electrophilic putative cationic diyl complex [(η5-C 5R5)Fe(CO)2E(Mes*)]+.
- Bunn, Natalie R.,Aldridge, Simon,Kays, Deborah L.,Coombs, Natalie D.,Rossin, Andrea,Willock, David J.,Day, Joanna K.,Jones, Cameron,Ooi, Li-Ling
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p. 5891 - 5900
(2008/10/09)
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- Fe=B double bonds: Synthetic, structural, and reaction chemistry of cationic terminal borylene complexes
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Application of halide abstraction chemistry to asymmetric haloboryl complexes (η5-C5-Me5)Fe(CO) 2B(ERn)X leads to the first synthetic route to cationic multiply bonded group 13 diyl species, [(η5-C5Me 5)Fe(CO)2B(ERn]+. The roles of steric bulk and π electron release within the ERn substituent in generating tractable borylene complexes have been probed, as has the nature of the counterion. A combination of spectroscopic, structural, and computational techniques leads to the conclusion that the bonding in complexes such as [η5-C5Me5)Fe-(CO)2B(Mes)] + is best described as an Fe=B double bond composed of B→Fe σ donor and Fe→B π back-bonding components. An extended study of the fundamental reactivity of cationic borylene systems reveals that this is dominated not only by nucleophilic addition at boron but also by iron-centered substitution chemistry leading to overall displacement of the borylene ligand.
- Coombs, Deborah L.,Aldridge, Simon,Rossin, Andrea,Jones, Cameron,Willock, David J.
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p. 2911 - 2926
(2008/10/09)
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- Synthesis, characterization and reactivity of heterobimetallic complexes (η5-C5R5)Ru(CO)(μ-dppm)M(CO)2 (η5-C5H5) (R = H, CH3; M = Mo, W). Interconversion of hydrogen/carbon dioxide and formic acid by these complexes
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The heterobimetallic complexes [(η5-C5R5)Ru(CO)(μ-dppm) M(CO)2(η5-C5H5)] (M = Mo, W; R = H, CH3) (1-4) are prepared by metathetical reactions between (η5-C5R5)Ru(dppm)Cl and Na+[(η5-C5H5) M(CO)3]-. IR spectroscopic and X-ray structural studies show that each of these complexes contains a semi-bridging carbonyl ligand. The low activity of these complexes in catalytic CO2 hydrogenation to formic acid might be attributed to their non-facile reactions with H2 to yield the active dihydride species. The metal-metal bonds can be protonated to form the cationic complexes, which contain strong Ru-H-M bridges. The bridging hydrogen atom is weakly acidic since it can be removed by a strong base, and it protonates BPh4- to give BPh3 and benzene. It also reacts with the hydridic hydrogen of Et3SiH to yield H2. The bridging hydrogen, however, cannot be removed by hydride scavengers such as Ph3C+OTf- and Me3Si+OTf-. The sluggishness of the catalytic formic acid decomposition by 1-4 is attributable to the stability of the protonated bimetallic intermediate [(η5-C5R5)Ru(CO)(μ-dppm)(μ-H) M(CO)2(η5-C5H5)]+ HCOO- formed during the catalysis.
- Man, Man Lok,Zhou, Zhongyuan,Ng, Siu Man,Lau, Chak Po
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p. 3727 - 3735
(2007/10/03)
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- Synthesis and study of ruthenium silylene complexes of the type [(η5-C5Me5)(Me3P) 2Ru=SiX2]+ (X = thiolate, Me, and Ph)
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Various ruthenium silyl complexes of the type Cp*(Me3P)2RuSiR3 (Cp* = η5-C5Me5; SiR3 = SiCl3 (1), Si(NMe2)3 (2), Si(SEt)3 (3), Si(S-2-Naph)3 (4), Si[S(CH2)3S]Ph (5), Si(SCy)2Cl (6), and Si(SMes)2Cl (7, Mes = 2,4,6-trimethylphenyl)) were prepared by the reaction of Cp*(Me3P)2RuCH2SiMe3 with the appropriate silane HSiR3. Compound 3 was converted to the trifiate Cp*(Me3P)2RuSi(SEt)2OTf (8) by the reaction of 3 with Me3SiOTf. Similar reactions produced Cp*(Me3P)2RuSi(NMe2)2OTf (13), Cp*(Me3P)2RuSi(NMe2)(OTf)2 (14), Cp*(Me3P)2RuSi(SMes)2OTf (18), and Cp*(Me3P)2RuSi(SMes)(Cl)OTf (19). By NMR spectroscopy, compound 8 in dichloromethane solution appears to possess a labile trifiate group. Reactions of the triflates 8 and Cp*(Me3P)2RuSi(S-p-Tol)2OTf (10) with NaBPh4 provided the silylene complexes [Cp*(Me3P)2RuSi(SR)2][BPh4] (20, R = Et; 21, R = p-Tol). Similarly, the reaction of 6 with NaBPh4 gave [Cp*(Me3P)2RuSi(SCy)2][BPh4] (22), and the reaction of 4 with B(C6F5)3 produced [Cp*(Me3P)2RuSi(S-2-Naph)2][MeB(C 6F5)3] (23). Silylene complexes 20-23 display characteristic 29Si NMR shifts in the region of δ 250-270. The non-heteroatom-stabilized silylene complexes [Cp*(Me3P)2RuSiR2][B(C6F 5)4] (24, R = Me; 25, R = Ph), obtained via reactions of (Et2O)LiB(C6F5)4 with Cp*(Me3P)2RuSiR2OTf (11, R = Me; 12, R = Ph) exhibit 29Si NMR shifts around δ 300. The crystal structure of 24 revealed a Ru-Si distance of 2.238(2) A, and the Cp*(centroid)-Ru-Si-Me dihedral angle is 34°. Compound 24 reacts quantitatively with 1 equiv of PMe3 or PPh3 in dichloromethane-d2 to form the base-stabilized silylene complexes [Cp*(Me3P)2RuSiMe2(PR 3)][B(C6F5)4] (28, R = Me; 29, R = Ph), identified by 1H and 31P NMR spectroscopy. These complexes are thermally labile and decompose with elimination of the dimethylsilylene fragment to give [Cp*(Me3P)2RuPR3][B(C6F 5)4] (R = Me, Ph). The ylide CH2PPh3 reacts with 24 to form [Cp*(Me3P)2RuSiMe2CH2PPh 3][B(C6F5)4] (32a), and the characterization of [Cp*(Me3P)2RuSiMe2CH2PPh 3][OTf] (32b) by X-ray crystallography suggests that the complex is best viewed as a ruthenium silyl derivative with the positive charge localized on the ylide phosphorus atom. Reactions of 20 and 24 with hydrogen proceed slowly and result in relatively complex product mixtures that contain various ruthenium hydride species. The reaction involving 20 also produced HSi(SEt)3, perhaps via redistribution of initially formed H2Si(SEt)2. For the reaction of 24 with hydrogen, no H2SiMe2 was detected in the product mixture. The reaction of 20 with H3SiSiPh3 gave [Cp*(Me3P)2Ru(H)(SiH2SiPh 3)][BPh4] (35) and HSi(SEt)3, and the corresponding reaction of H3SiMes in dichloromethane gave [Cp*(Me3P)2RuHCl][BPh4] (34), BPh3, and H2SiMes(SEt), among other products. By NMR spectroscopy, the intermediate [Cp*(Me3P)2Ru(H)(SiH2Mes)][BPh 4] (36) was observed for the latter process. Compound 36, generated independently by reaction of [Cp*(Me3P)2Ru(NCMe)][BPh4] with H3SiMes, was shown to react with HSi(SEt)3 to give H2SiMes(SEt).
- Grumbine, Steven K.,Mitchell, Gregory P.,Straus, Daniel A.,Don Tilley,Rheingold, Arnold L.
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p. 5607 - 5619
(2008/10/08)
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- Disproportionation of cationic zirconium complexes: A possible pathway to the deactivation of catalytic cationic systems
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Protonolysis of the zirconium borohydride [(C5H4R)2Zr(BH4)2] (R = H, Me, SiMe3) with NHMe2PhBPh4 in THF leads to the corresponding cationic zirconium complex [(C5H4R)2Zr-(BH4)(THF)]BPh 4, and the structure of [(C5H4Me)2Zr(BH4)(THF)]BPh 4 was determined. In the presence of phosphine, PMe2Ph, the formation of the cationic hydride [(C5H4R)2ZrH-(PMe2Ph) 2]BPh4 is observed by 1H and 31P NMR followed by a disproportionation and a redox reaction with [BPh4]-, giving the neutral [(C5H4R)2ZrH(μ-H)]2 and the cationic ZrIII species [(C5H4R)2Zr(PMe2Ph) 2]BPh4 characterized by EPR spectroscopy and suggesting a probable pathway in the deactivation of cationic catalyst systems.
- Choukroun, Robert,Douziech, Bénédicte,Donnadieu, Bruno
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p. 5517 - 5521
(2008/10/08)
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- Synthesis and Reactivity of the Labile Dihydrogen Complex [{MeC(CH2PPh2)3}Ir(H2)(H) 2]BPh4
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The novel Ir(III) nonclassical tetrahydrido complex [(triphos)Ir(H2)(H)2]BPh4 (4BPh4) has been prepared by hydrogenation of the ethene dihydride complex [(triphos)Ir(C2H4)(H)2]BPh4 in either the solid state (PH2 ≥ 1 atm) or CH2Cl2 solution (PH2 ≥ 3 atm) [triphos = MeC(CH2PPh2)3]. Complex 4BPh4 is very labile in solution and can be isolated in the solid state exclusively from solid-gas reactions. Characterization of 4BPh4 in solution can be achieved by high-pressure NMR and IR spectroscopies, however. Various deuterated isotopomers of [(triphos)Ir(H2)(H)2]+ have been obtained in CD2Cl2 solution at low temperature by treatment of the trihydride [(triphos)IrH3] with DOSO2CF3. On the basis of a variety of NMR experiments, the complex cation [(triphos)Ir(H2)(H)2]+ is assigned an octahedral structure where two terminal hydride ligands and a dihydrogen molecule are trans to the phosphorus atoms of a facial triphos ligand. Complex 4BPh4 dissolves in THF at room temperature yielding [(triphos)IrH3], BPh3, and benzene; a similar reaction occurs in acetone, whereas in C2HCl2 the complex loses H2 converting to the dimers cis- and trans-[(triphos)IrH(μ-H)2HIr(triphos)](BPh4) 2.
- Bianchini, Claudio,Moneti, Simonetta,Peruzzini, Maurizio,Vizza, Francesco
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p. 5818 - 5825
(2008/10/09)
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- Asymmetric Ethynes. Syntheses of Ethynylferrocene Paradigms
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Synthetic methods to bifunctional ethynes have been examined. Direct ethynylation, the Stephens-Castro reaction, the Pd-catalysed Hagihara coupling, transmetalation reactions and nucleophilic additions have been evaluated in the preparation of substituted
- Polin, Johann,Schottenberger, Herwig,Schwarzhans, Karl Eberhard
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p. 1683 - 1690
(2007/10/03)
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- Skeletal rearrangements of arylborane complexes mediated by redox reactions: thermal and photochemical oxidation by metal ions
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A variety of metal salts have been found to undergo reduction by thermal and photochemical interaction with tetraarylborate salts and with neutral alkyl- and aryl-borane complexes.In the cases of Cu2+, Cu+, Ni2+, Co2+, Pd2+, Pt2+, Ag+, Zn2+, Hg2+, Sn2+, Pb2+ and Rh3+ salts, such photochemical reductions with NaBPh4 led to the deposition of the free metal, while a number of binary mixtures of metal salts led to the codeposition of both metals, sometimes as true alloys, under such photoreduction.In the course of these reductions the arylboratereductants underwent oxidative coupling of the aryl groups to form biaryls in a strictly intra-ionic (for BAr4-) or intramolecular (Ar3B) manner respectively.Individual studies of the photochemistry of the tetraarylborate anion itself, of cuprous tetraphenylborate and of the triphenylborane-pyridine complex have adduced evidence for a gamut of reactive intermediates capable of serving as the photoreductant for metal ions, such as triarylborane radical anions, diarylborate(I) anions or arylborenes, 7-borabicycloheptadiene anions or neutral complexes and finally arylborohydride anions or arylboron hydrides.The role of these intermediates both in the photoinduced skeletal rearrangements of arylboranes and in the concomitant reduction of metal ions is discussed in critical detail.Key words: Boron; Aryl; Oxidation; Copper; Nickel; Zinc
- Eisch, John J.,Shah, Jamshed H.,Boleslawski, Marek P.
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- In situ measurements of tetraphenylboron degradation kinetics on clay mineral surfaces by IR
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An attenuated total reflectance Fourier transform infrared (ATR-IR) spectroscopic method has been developed to quantitatively measure, in situ, the surface-facilitated degradation of tetraphenylboron (TPB) in fully aquated clay pastes. Two pathways for degradation of TPB could be studied both independently and simultaneously. Surface-facilitated oxidation of TPB to diphenylboric acid (DPBA) at Lewis acid sites on clay mineral surfaces was investigated on three members of the smectite family of clays. -from Authors
- Hunter,Bertsch
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p. 686 - 691
(2007/10/03)
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- Molecular solid-state organometallic chemistry of tripodal (polyphosphine)metal complexes. Catalytic hydrogenation of ethylene at iridium
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The solid-gas reactions of [(tripohs)Ir(H)2(C2H4)]BPh4 (1) with CO, C2H4, and H2 are described [triphos = MeC(CH2PPh2)3]. The gaseous reactants promote the elimination of ethane from 1 and the formation of [(triphos)Ir(CO)2]BPh4, [(triphos)Ir(C2H4)2]BPh4, and [(triphos)Ir(H)2]BPh4, respectively. The latter 16-electron species is isolable in the solid state at temperatures 2]+ dimerizes in the solid state to give the tetrahydride [(triphos)HIr(μ-H)2HIr(triphos)]2+. Dimerization is avoided when the unsaturated fragment is incorporated into the lattice of a polyoxometalate cluster such as PW12O403-. The complex [(triphos)Ir(H)2(C2H4)]BPh4 is an effective catalyst for the hydrogenation of ethylene in the solid state at 60 °C. Comparisons are made with analogous fluid solution-phase systems.
- Bianchini, Claudio,Farnetti, Erica,Graziani, Mauro,Kaspar, Jan,Vizza, Francesco
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p. 1753 - 1759
(2007/10/02)
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- PHENYLATION OF PLATINUM(II) THIOETHER COMPLEXES BY TETRAPHENYLBORATE(III) IN SOLID STATE AND NITROMETHANE SOLUTION
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Platinum(II) complexes of the type (1+) (thioether = dimethyl sulfide, thioxane) are capable of abstracting a phenyl group from the BPh4(1-) counterion with formation of trans- compounds.Thermal reactions proceed both in the solid phase and in nitromethane solution at elevated temperature and have preparative importance.Phenylation of the Pt(II) centre also occurs in reaction between and AgBPh4 in CH2Cl2 suspension.Brief X-ray crystallographic structural data for trans- and X (thioether = Me2S, tx, X=SO3CF3; thioether = Me2S, X=PF6) are reported. Key words: Platinum(II) thioether complexes; phenyl abstraction; tetraphenylborate ion; synthesis of thioether complexes; silver tetraphenylborate; X-ray structures.
- Kukushkin, Vadim Yu.,Loevqvist, Karin,Noren, Bertil,Oskarsson, Ake,Elding, Lars Ivar
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p. 253 - 256
(2007/10/02)
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- Synthesis and reactivity of the metal-substituted borane (CO)4CoBH2·THF. Preparation of the ambiphilic clusters (CO)9Co3C(CH2)nOH (n = 4, 5)
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The reaction Co2(CO)8 + 2BH3·THF → 2(CO)4CoBH2·THF (I) + H2 has been demonstrated to occur cleanly at -15°C in THF. I has been characterized by low-temperature 11B NMR and infrared spectroscopies as well as classical chemical analysis. The formation of I bears a remarkable similarity to that of (CO)4CoSiR3. Displacement of the bound THF of I occurs with Lewis bases, and the Lewis acidity of I relative to that of BH3·THF for SMe2 has been estimated. Displacement of [Co(CO)4]- from I occurs easily; e.g., reaction with PhMgBr yields PhBH2. I readily accepts hydride from [HFe2(CO)8]-, losing [Co(CO)4]- but reduces the CO ligands of hydride-free metal carbonylate anions. I is a very active reducing agent and above 10°C cleaves THF and condenses with hydrocarbyl and metal fragments to yield a mixture of clusters including an unusual tailed cluster (CO)9Co3C(CH2)nOH (n = 4,5) (II). A deuterium labeling experiment showed that four of the n carbons in the hydrocarbyl chain of II arise from THF. The results of an X-ray diffraction study suggest association of II in the solid state. [Crystals of II (the ratio of II with n = 5/n = 4 is 4) form in the space group R3 with unit cell parameters a = 34.409 (15) A?, b = 34.398 (21) A?, c = 8.575 (5) A?; β = γ = 90°, γ = 120°, V = 8789.8 A?3, and Z = 18. Solution was by direct methods, and all atoms were refined to R1 = 0.077 and R2 = 0.096 for 1443 independent reflections (Fo > 3σ(Fo)). Because of the disorder caused by the cocrystallization of species with different chain lengths, the last two atoms at the OH end of the chain could not be fully defined.] Association of II in solution is shown by a 1H NMR study, thereby demonstrating that II behaves as an ambiphilic cluster.
- Basil, John D.,Aradi, Allen A.,Bhattacharyya, Nripendra K.,Rath, Nigam P.,Eigenbrot, Charles,Fehlner, Thomas P.
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p. 1260 - 1270
(2008/10/08)
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- Regiospecific condensation of methyl propiolate with 2,3-dimethyl-2-butene mediated by the electrophilic η5-cyclopentadienyl dinitrosyl tetrafluoroborate salts of the group 6 metals
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This paper first describes some reaction of the Cp′M(NO)2+ cations as their BF4- salts that further delineate their electrophilic character. It then describes in detail the utilization of these cations for the synthesis of the complete series of six cationic lactone complexes. By their regiospecific mediation of the reaction between methyl propiolate and 2,3-dimethyl-2-butene, which involves concomitant metal-carbon, carbon-oxygen, and carbon-carbon bond formation. Furthermore, the paper presents details of the O-demethylation of these six cationic species to their neutral Cp′M(NO)2(η1-lactone) derivatives, from which the lactone ligands may be liberated by treatment with iodine. It also describes how exposure of both neutral lactone complexes of tungsten to air leads to their being cleanly converted to the corresponding dioxo derivatives. Finally, it presents complete characterization data for all the new organometallic complexes isolated during this work.
- Legzdins,Richter-Addo,Einstein,Jones
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p. 431 - 439
(2008/10/08)
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- Uebergangsmetall-Carben-Komplexe CXXXXI. Untersuchungen zum Reaktionsverhalten der Carben-Komplexe cis-(CO)4(SnPh3)Re (R = iPr, chex) gegenueber Lewis-Saeuren
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In the reaction of cis-(CO)4(SnPh3)Re (R = iPr (isopropyl), chex (cyclohexyl)) with BI3 the Lewis acid attacks the triphenylstannyl ligand.Substitution of a phenyl for a iodine group leads to equilibrium mixtures of rhenium carbene complexes of general formulacis-(CO)4(SnPh3-xIx)Re (x = 1-3; R = iPr, chex).By changing the solvent and ratio of reactants, the equilibria can be shifted such that only one major product is formed.Thus this reaction pathway can be used for the preparation of cis-(CO)4(SnPhI2)Re (R = iPr, chex).Even when a large excess of BI3 is present electrophilic attack by the Lewis acid on the carbene ligand is not observed.Synthesis of cis(CO)4(SnPh3-xIx)Re (x = 1-3; R = iPr, chex) can be achieved in high yield by reaction of cis-(CO)4(SnPh3)Re (R = iPr, chex) with one, two or three equivalents of HI.This reaction, with successive rupture of the tin-carbon bonds in the triphenyl stannyl ligand and the simultaneous formation of benzene, affords the desired substitution product irreversibily.Reaction of cis(CO)4(SnPh3)Re (R = iPr, chex) with I2 gives the compounds cis-(CO)4(SnI3)Re (R = iPr, chex), in relatively low yields.
- Filippou, Alexander Constantin,Fischer, Ernst Otto,Alt, Helmut Guido
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p. 325 - 336
(2007/10/02)
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- FREE RADICAL FORMATION IN THE PHOTOOXIDATIVE ALKYLATIONS OF DICYANONAPHTHALENE WITH ALKYLTRIPHENYLBORATE SALTS.
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One electron oxidation of alkyltriphenylborate salts leads to carbon-boron bond cleavage and the formation of free alkyl radicals.
- Lan, J. Y.,Schuster, Gary B.
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p. 4261 - 4264
(2007/10/02)
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- Oxidation Intermediates of Borohydride and Tetraphenylborate Ions in Aqueous Solutions obtained by Pulse Radiolysis
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Absorption spectra of one-electron oxidized intermediates (the H4B and the Ph4B radicals) were observed upon the oxidation of H4B(1-) and Ph4B(1-) by the azide radical (N3), Br2(1-), or (SCN)2(1-) in pulse-irradiated solutions; the spectra
- Horii, Hideo,Taniguchi, Setsuo
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p. 915 - 916
(2007/10/02)
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- Reactivity of CS2 and Et3P·CS2 toward copper(I)-phosphine complexes. X-ray crystal structure of the complex [(PPh3)2Cu(S2CPEt3)]BPh4
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Carbon disulfide reacts with the complexes (PEt3)3CuBPh4 (1) and (PPh3)3CuBPh4 (2), affording [(PEt3)2Cu(S2CPEt3)]BPh4 (3) and (PPh3)2Cu(S2CPh) (4), respectively. Compound 3 is formed by CS2 insertion into a copper-phosphorus bond; 4 is formed by copper-assisted phenylation of CS2 by BPh4-. The phosphoniodithiocarboxylate complexes 3 and [(PPh3)2Cu(S2CPEt3)]BPh4 (5) are obtained by addition of the zwitterion Et3P·CS2 to 1 and 2, respectively. The X-ray structure of 5 is reported. Pathways to the formation of 3 and 4 are proposed.
- Bianchini, Claudio,Ghilardi, Carlo A.,Meli, Andrea,Orlandini, Annabella
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p. 2188 - 2191
(2008/10/08)
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- Process for the preparation of triarylborane
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Preparation of triarylboranes, e.g. triphenylborane by reacting an alkali metal, e.g. sodium; an organohalide, e.g. chlorobenzene and an orthoborate ester, e.g. triisopropylorthoborate in an inert organic solvent, recovering the borane by contacting the reaction product with water, removing alcohol from the aqueous mixture and contacting the resultant material with acid to a pH not less than about 6 to form the borane.
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- Process for the preparation of triarylboranes
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Preparation of triarylboranes, e.g. triphenylborane by reacting an alkali metal, e.g. sodium; an organohalide, e.g. chlorobenzene and an orthoborate ester, e.g. triisopropylorthoborate in an inert organic solvent, recovering the borane by contacting the reaction product with water while maintaining the ratio of borane to hydrolysis products (e.g. borinic acid) at at least 13/1, distilling volatiles from the aqueous mixture and contacting the resultant material with acid to a pH not less than about 6 to form the borane.
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- Process for the preparation of triarylborane
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Preparation of triarylboranes, e.g. triphenylborane by reacting an alkali metal, e.g. sodium; an organohalide, e.g. chlorobenzene and an orthoborate ester, e.g. triisopropylorthoborate in an inert organic solvent, recovering the borane by contacting the reaction product with water, distilling volatiles from the aqueous mixture and contacting the resultant material with acid to a pH not less than about 6 to form the borane.
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