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Reaction of the trityl cation in [Ph3C+][B(C6F5)4–] with the n-butyl anion in (BDI)MgnBu led to s-hydride abstraction and formation of Ph3CH, 1-butene, and [(BDI)Mg+][B(C6F5)4–] (1) (BDI = CH[C(CH3)N-Dipp]2; Dipp = 2,6-diisopropylphenyl). The “naked” Mg center in 1 is weakly bound to B(C6F5)4– through two Mg···F interactions. Addition of arenes to 1 gave strongly bound cationic magnesium π–arene complexes (BDI)Mg+·arene in good yields arene = benzene (94%), toluene (74%), m-xylene (82%), and mesitylene (63%). 1,2,4,5-Tetramethylbenzene is too bulky to give a coordination complex. Crystal structures of these π-arene complexes show η3–arene–Mg interactions for the smaller arenes (benzene, toluene and m-xylene). In each case, the coordination sphere was filled by an additional Mg···F interaction. For mesitylene, η6-coordination was found, leaving no space at the metal for supplementary Mg···F interaction. Dissolved in C6D5Br, all arene complexes are in association–dissociation equilibrium: (BDI)Mg+ + arene ⇄...

An efficient protocol for synthesis of indenyl rhodium complexes with arene ligands has been developed. The hexafluoroantimonate salts [(η5-indenyl)Rh(arene)](SbF6)2 (arene = benzene (2a), o-xylene (2b), mesitylene (2c), durene (2d), hexamethylbenzene (2e), and [2.2]paracyclophane (2g)) were obtained by iodide abstraction from [(η5-indenyl)RhI2]n (1) with AgSbF6 in the presence of benzene and its derivatives. The procedure is also suitable for the synthesis of the dirhodium arene complex [(μ-η:η′-1,3-dimesitylpropane){Rh(η5-indenyl)}2](SbF6)4 (3) starting from 1,3-dimesitylpropane. The structures of [2e](SbF6)2, [2g](SbF6)2, and [3](SbF6)4 were determined by X-ray diffraction. The last species has a sterically unfavorable conformation, in which the bridgehead carbon atoms of the indenyl ligand are arranged close to the propane linker between two mesitylene moieties. Experimental and DFT calculation data revealed that the benzene ligand in 2a is more labile than that in the related cyclopentadienyl complex...

Our interest in the chemistry of antimony derivatives has led us to investigate the synthesis and properties of 4-(diphenylstibino)-2,2′-bipyridine (LSbPh2). This new ligand, which could be obtained by reaction of 4-lithio-2,2′-bipyridine with Ph2SbCl, was treated with Pt(CH3CN)2Cl2 to afford the platinum complex LSbPh2PtCl2 (1). Interestingly, the latter reacts with PhICl2 to afford LSbCl2Ph2PtCl2 (2), a complex in which the peripheral stibine moiety has been converted into a dichlorostiborane. Complexes 1 and 2 have both been fully characterized. Computational, UV–vis, and cyclic voltammetry studies show that oxidation of the antimony atom leads to a lowering of the bipy-centered LUMO, indicating that 2 is more electron deficient than 1. A congruent picture emerges from reactivity studies, which show that 2 is a more active catalyst for the hydroarylation of ethyl propiolate by mesitylene.

The factors responsible for the experimentally observed acceleration of π-acid-catalyzed reactions induced by α-cationic phosphines and group 15 analogues have been computationally explored within the density functional theory framework. To this end, the gold(I)-catalyzed hydroarylation reactions of phenylacetylene and mesitylene involving both neutral and cationic ligands (L) have been quantitatively analyzed in detail using the combination of the activation strain model of reactivity and the energy decomposition analysis methods. It is found that the activating effect of the cationic ligand finds its origin in the much stronger interaction between the deformed reactants along the entire reaction coordinate, which in turn derives from the much higher π(acetylene) → σ*(Au–L) interaction in the initially formed acetylene-gold(I) π-complex.

Electrophilic terminal phosphinidene complexes [R1P-W(CO)5] bearing 2-alkynylphenyl R1 substituents undergo a spontaneous cyclization to give intermediate five-membered species which are able to perform an electrophilic substitution reaction with toluene and mesitylene. An intramolecular version of this reaction is possible with appropriate R substituents on the C≡C triple bond.

Reactions of [(C2H4)2RhCl]2 or [(coe)2RhCl]2 (coe = cyclooctene) with AgPF6 and arenes, followed by addition of 3-hexyne, give the cyclobutadiene complexes [(C4Et4)Rh(arene)]+ in 40–65% yield (arene = tert-butylbenzene, p-xylene, mesitylene, 4-mesitylbutanoic acid). In the absence of arenes, the hexaethylbenzene complex [(C4Et4)Rh(C6Et6)]+ is formed in 70% yield as a result of cyclotrimerization of 3-hexyne in the coordination sphere of rhodium. Similar reaction of [(coe)2IrCl]2 with AgPF6 and 3-hexyne leads to [(C4Et4)Ir(C6Et6)]+, which is apparently the first reported cyclobutadiene iridium complex. DFT calculations suggest that formation of the model cyclobutadiene complex [(C4Me4)Rh(C6H6)]+ from bis(alkyne) intermediate [(C2Me2)2Rh(C6H6)]+ can proceed via a metallacycle transition state with a low energy barrier of 14.5 kcal mol–1.

The complex [Pd{C6H4NHCHO-2}I(tBubpy)] (A, tBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine) reacts with CO or XyNC, affording the benzoyl or iminobenzoyl complexes [Pd{C(O)C6H4NHCHO-2}I(tBubpy)] (1) or [Pd{C(═NXy)C6H4NHCHO-2}I(tBubpy)] (2), respectively. Dehydroiodination of 2 with Tl(acac) (acacH = acetylacetone) produced the iminobenzoyl(amide) complex [Pd{C,N-C(═NXy)C6H4NCHO-2}(tBubpy)] (3) from which complex [Pd{C,N-C(═NXy)C6H4NCHO-2}(CNXy)2] (4) was obtained upon substitution of the tBubpy ligand with 2 equiv of XyNC. Heating complex 3 in mesitylene at 160 °C for 3 h caused tBubpy loss, and the generated coordination vacancies were occupied by the amido oxygen and the iminobenzoyl nitrogen atoms, both acting as bridging ligands to give the tetranuclear species [Pd4{N,O-{C,N-C(═NXy)C6H4NCHO-2}4] (5). Removal of the iodo ligand in A by reacting it with TlOTf (OTf = trifluoromethanesulfonate, triflate) caused coordination of the amido oxygen atom to give the cationic complex [Pd{C,O-C6H4NHCHO-2}(tBubpy)]OTf...

C–H activations of a C(sp2)–H bond in benzene or a C(sp3)–H bond in mesitylene at 80 °C under CO pressure in undried solvents without rigorous exclusion of air and moisture can be effected with the 18e complexes Cp*W(NO)(H)(η3-CH2CHCMe2) (1), Cp*W(NO)(H)(η3-CH2CHCHMe) (2), and Cp*W(NO)(H)(η3-CH2CHCHPh) (3) (Cp* = η5-C5Me5). These activations are regiospecific and afford in the case of complex 1 good yields of the unsymmetrical saturated ketones 4-methyl-1-phenylpentan-1-one (5) and 1-(3,5-dimethylphenyl)-5-methylhexan-2-one (8), respectively, in which the alkyl groups result from hydrogenation of the allyl ligand in the organometallic reactant. Complex 2 reacts similarly, but complex 3 only produces the ketone from its reaction with CO in benzene. Theoretical calculations indicate that the key mechanistic feature of these conversions is the formation of a 16e η2-alkene complex which is generated by the regiospecific migration of the hydride ligand onto the tertiary carbon of the allyl ligand. The 16e Cp*W...

The functionalization of dendrimers and other macromolecules with cationic redox-active organometallics remains a target toward metal-containing dendrimers and polymers that can serve in particular as polyelectrolytes and multielectron redox reagents. Along this line, we report the click functionalization of organometallics and dendrimers with a redox-active ethynylarene iron complex, [FeCp(η6-ethynylmesitylene)][PF6], 3, easily available from [FeCp(η6-mesitylene)][PF6], 1. Complex 3 reacts with azidomethylferrocene upon catalysis by copper sulfate and sodium ascorbate (CuAAC reaction) to give a bimetallic complex that is reduced on the mesitylene ligand to a mixture of isomeric cyclohexadienyl complexes. Complex 3 also reacts according to the same click reaction with zeroth- and first-generation metallodendrimers containing, respectively, 9 and 27 azido termini to provide new polar polycationic metallodendrimers that are reversibly reduced, on the electrochemical time scale, to 19-electron FeI species.

The strong neutral Bronsted acids [(R)OH→Al(OC(CF3)3)3] (R = −C(CF3)3 (1), −C6F5 (2), (−)-menthyl (3)) were synthesized by complexation of perfluoro tert-butyl alcohol, pentafluorophenol, and (−)-menthol with the Lewis superacid Al(OC(CF3)3)3. The 1:1 composition of the compounds was proven by NMR (except for compound 2), IR, and partially Raman spectroscopy and X-ray crystallography. Of the structures, 2 crystallized with a coordinated toluene molecule, which might be seen as a frozen intermediate or prestep to form the classical Wheland complex of protonated toluene. This interaction was calculated to be exothermic by 32 (no dispersion) or 88 kJ mol–1 (Grimmes D3 dispersion correction included @ RI-BP86/SV(P)). 1 proved suitable to protonate mesitylene and Et2O, giving the acidic cationic Bronsted acids [H(C6H3(CH3)3)]+ (4b) and [H(OEt2)2]+ (5) with the respective weakly coordinating anion [Al(OC(CF3)3)4]−. In dichloromethane solution 4b decomposes at room temperature, leaving the room-temperature-stabl...

The methyl cyclopropyl hydrotris(3,5-dimethylpyrazolyl)borate complex TpMe2NbMe(c-C3H5)(MeCCMe) reacts smoothly with different alkylaromatics XH at 308 K to yield methane and TpMe2NbX(c- C3H5)(MeCCMe). NMR data show that for mesitylene and 1,4-dimethylbenzene, selective benzylic CH bond activation is observed, giving the benzyl cyclopropyl complexes TpMe2Nb(CH2Ar′)(c- C3H5)(MeCCMe) (Ar′ = 3,5-Me2C 6H3, 4-MeC6H4, respectively). Selective arene CH bond activation is observed with 1,2-dimethylbenzene, yielding TpMe2Nb(3,4-Me2C6H3)(c- C3H5)(MeCCMe). With 1,3-dimethylbenzene, a 3:1 mixture of arene and benzylic CH activated products, TpMe2Nb(3,5-Me 2C6H3)(c-C3H5)(MeCCMe) and TpMe2Nb(CH2-3-MeC6H4)(c-C 3H5)(MeCCMe), is observed, translating to a 18:1 preference for aromatic versus benzylic CH bond activation on a per CH bond basis. Kinetic studies are consistent with rate-limiting intramolecular β-H abstraction of methane to yield a transient unsaturated η2- cyclopropene intermediate. This intermediate reacts rapidly with the aromatic or benzylic CH bond of the arene via 1,3-addition across a Nb(η2- cyclopropene) bond. DFT calculations suggest that the observed selectivities are a result of the steric influence of the methyl groups on the arene ring, which blocks activation of an ortho C-H bond. © 2011 American Chemical Society.

The reaction of (PiPr3)2NiCl2 with the anthracene adduct (THF)3Mg(η2-C14H10) in THF provides the anthracene adduct (PiPr3)2Ni(η2-C14H10). In aromatic solvents (benzene, toluene, mesitylene) a therm...

The reaction of SnC(SiMe3)2CH2CH2C(SiMe3)2/ArI (Ar = Ph, 2,4,6-triisopropylphenyl) with cyclohexane, diethyl ether, tetrahydrofuran (THF), toluene, and mesitylene yields C−H activation products in which a new Sn−C bond is formed at the location of the weakest C−H bond. The regioselectivity of this reaction with trans-4-methyl-2-pentene and 4-methyl-2-pentyne was explored as a function of aryl halide for PhI, 2,4,6-trimethyliodobenzene, 2,4,6-triisopropyliodobenzene, 4-iodoanisole, 4-iodobenzonitrile, and 2,6-mesityliodobenzene. A degree of regiochemical control could be obtained as highlighted by increased amounts of primary activation. The use of 2,4,6-tert-butyliodobenzene resulted in C−H activation of the ortho tert-butyl groups in all solvents tried. The primary kinetic isotope effect for the reaction of SnC(SiMe3)2CH2CH2C(SiMe3)2/2,4,6-triisopropyliodobenzene with toluene/toluene-d7 was found to be 4.9 ± 0.5.

The synthesis and characterization of the complexes [(cyclohexenyl)Ni(NCMe)2][B(ArF)4] (1) and [(cyclohexenyl)Ni(mesitylene)][B(ArF)4] (2) are reported. Abstraction of the nitrile ligands in 1 with B(C6F5)3 yields a “ligand-free” [(cyclohexenyl)NiII]+ species which coordinates 1,3-dienes, including butadiene (BD), isoprene (IP), 1,3-cyclohexadiene (1,3-CHD), 1,4-cyclohexadiene (1,4-CHD), and 2,3-dimethyl-1,3-butadiene (DMBD) at low temperatures. Diene insertion is observed at temperatures above ca. −20 °C. An s-trans diene complex is formed upon coordination of DMBD. Hydrogen transfer is observed when complex 2 is exposed to 1-hexene or cyclopentadiene to generate new allyl nickel complexes and 1 equiv of cyclohexene. Polymerization of 1,3-CHD and DMBD with 2 is described, and a coupling product formed between DMBD and 2 is observed and characterized.

The displacement of η2-coordinated arenes [arenes = benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene] from the photolytically generated CpMn(CO)2(η2-arene) complex by pyridine was stu...

[(2-R-allyl)M(arene)]+ complexes (M = Pd, Ni; R = H, CH3, Cl; arene = mesitylene, hexamethylbenzene) have been synthesized via halide abstraction from the corresponding allyl halide dimers, [(allyl...

o-(Hydroxydimethylsilyl)(dimesitylboryl)benzene (1) underwent intramolecular cyclization to give 5,5-dimesityl-2,2-dimethyl-3,4-benzo-1,2,5-oxasilaboracyclopentene (4) and mesitylene by boron−aryl bond cleavage. Whereas triethylamine as an additive accelerated the cyclization, DBU stabilized a silyloxyborate complex, 1,8-diazabicyclo[5.4.0]-7-undecenium 5,5-dimesityl-2,2-dimethyl-3,4-benzo-1,2,5-oxasilaboratacyclopentene, which was characterized by X-ray crystallographic analysis and HF calculations. The deuterium-labeling experiments revealed that the hydrogen migrated from the hydroxyl group in 1 to the leaving mesitylene.

Product/reactant ratios (Y) were determined for the reactions CpRu(η6-DBT)+ + L ⇌ CpRu(η6-L)+ + DBT (where DBT is dibenzothiophene and L is a homo- or heterocyclic arene), which were conducted under UV photolysis conditions. In the photostationary state, the Y values for the different arenes decrease in the following order: mesitylene (17) > toluene (13) > indole (9.1) > carbazole (6.7) > benzene (5.9) > fluorene (5.1) > biphenyl (3.9) > DBT (1.0) > phenanthrene (0.65) > naphthalene (0.35). In general, alkyl-substituted arenes have a higher binding affinity than the parent arene, except for tert-butyl groups, which decrease the Y values. These trends in η6-arene binding to CpRu+ provide a basis for understanding competitive adsorption of arenes on metal sites of hydrotreating catalysts. Such arene components in petroleum feedstocks reduce the rates of hydrodesulfurization of dibenzothiophenes.

A comparison between the mononuclear platinum complexes of three structurally different monoanionic borato ligands is presented: [Ph_2B(pyrazolyl)_2]- ([Ph_2B(pz)_2], 1), [4-Ph_3B(2,2‘-bipyridine)]- ([(4-BPh_3)bpy], 2), and [Ph_2B(CH_2PPh_2)_2]- ([Ph_2BP_2], 3). The new bipyridylborate ligand 2 is introduced in this study. The relative trans influence of these ligands has been assessed by comparison of the structural and spectroscopic (NMR) data of the platinum dimethyl complexes [[Ph_2B(pz)_2]Pt(Me)_2][NBu_4] (4), [[(4-BPh_3)bpy]Pt(Me)_2][NBu_4] (5), and [[Ph_2BP_2]Pt(Me)_2][ASN] (6). The neutral complexes [Ph_2B(pz)_2]Pt(Me)(NCCH_3) (7), [Ph_2B(pz)_2]Pt(Me)(CO) (8), [Ph_2B(pz)_2]Pt(Me)(P(C_6F_5)_3) (9), [(4-BPh_3)bpy]Pt(Me)(NCCH_3) (10), [(4-BPh_3)bpy]Pt(Me)(CO) (11), and [(bpy)Pt(Me)(CO)][BPh_4] (12) were prepared, and the carbonyl complexes 8, 11, and 12 provide information pertaining to the relative electron-releasing character of each ligand type. The CO stretching frequencies suggest that the charged borate moiety renders the borato ligands more electron-donating than their neutral analogues. Of the neutral platinum methyl solvento complexes supported by ligands 1, 2, and 3, only those of 1 display very different C−H activation propensities. Upon protonation or methide abstraction in benzene at room temperature, complex 4 rapidly activates two molecules of benzene to generate [[Ph_2B(pz)_2]Pt(Ph)_2][NBu_4] (13). Isotopic scrambling of deuterium into methane in C_6D_6 solvent suggests the intermediacy of a methane σ-adduct in this reaction. The double C−H activation reaction can be halted by addition of acetonitrile to trap the intermediate [Ph_2B(pz)_2]Pt(Ph)(NCCH_3) (14). Complex 3 also displays reactivity toward the benzylic C−H bonds of mesitylene at room temperature to form [Ph_2B(pz)_2]Pt(pzH)(CH_2C_6H_3(CH_3)_2) (15) in modest yield.

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The bis((dimethylphosphino)methyl)-substituted alcohol (Me2PCH2)2CHOH (1) was prepared from the respective bis(3,5-dimethylbenzyl)phosphonium dichloride by reductive elimination of mesitylene with lithium alanate in 56% yield. Deprotonation with n-butyllithium or elemental sodium gave the respective alkali metal alcoholates [(Me2PCH2)2CHOM]6 (M = Li (2), Na (3)). Both compounds have a core consisting of two stacked M3O3 hexagons held together by short M−O bonds. In 2, in addition to three oxygen atoms, each lithium atom is coordinated by one phosphino group of an adjacent ligand in a distorted tetrahedral geometry (Li−P = 2.60(1) A). In 3 each sodium atom is coordinated by two phosphino groups from different ligands in addition to the oxygen atoms. The coordination geometry at the sodium atom is a distorted trigonal bipyramid (O3P2), the two phosphine donors being in axial and equatorial positions, respectively (Na−P = 3.083(2), 3.151(2) A). The tris((dimethylphosphino)methyl)-substituted alcohol (Me2PCH2...

Novel zerovalent arene complexes bearing two dimethyl fumarate ligands, Ru(η6-arene)(dimethyl fumarate)2 (arene = benzene (2a), toluene (2b), p-xylene (2c), mesitylene (2d), hexamethylbenzene (2e), tert-butylbenzene (2f), anisole (2g), N,N-dimethylaniline (2h), biphenyl (2i), methyl benzoate (2j), naphthalene (2k)), were synthesized via the direct ligand exchange reaction of Ru(η6-cot)(dimethyl fumarate)2 (1; cot = 1,3,5-cyclooctatriene) with arenes. The detailed structures of 2g,h were determined by X-ray crystallography, which revealed that the coordination geometry can be represented by a highly distorted trigonal bipyramid.

We report one-pot syntheses for a series of complexes of the type [(η6-arene)RuIIMe(PPh3)2][AlCl2Me2] in high yields and X-ray structures of the η6-C6H6 and η5-thiophene derivatives. Other derivatives include fluorobenzene and mesitylene complexes, and all of the complexes are synthesized by addition of AlMe3 to RuCl2(PPh3)3 in the neat arene solvent or in an admixture with hexane for thiophene and fluorobenzene.

Thermolyses (70 °C, 40 h) of Cp*W(NO)(CH2CMe3)2 (1) and Cp*W(NO)(CH2CMe3)(CH2C6H5) (2) in xylenes, mesitylene, and α,α,α-trifluorotoluene generate mixtures of the corresponding aryl and/or benzyl p...

The reaction of 1,3,5-triiodomesitylene (C6Me3I3) with a mixture of [Pd(dba)2] and PR3 leads to the mononuclear complexes trans-[Pd(C6Me3I2)I(PR3)2] (R = Ph (1), R3 = Me2Ph (2)) or the dinuclear co...

Treatment of (TMEDA)Pt(C3F7)Me (TMEDA = tetramethylethylenediamine) with 1,3-bis[(diphenylphosphino)methyl]benzene (PCPH) in mesitylene under reflux affords the first known pincer complex of a grou...

Reaction of the dimers [RuCl2(arene)]2 (arene = benzene, p-cymene, mesitylene) with bis(oxazolines) (N-N = bis(2-oxazoline) (box), 2,2-bis(2-oxazolinyl)propane (bop), 1,2-bis(2-oxazolinyl)benzene (benbox)) in the presence of NaSbF6 gives the complexes [RuCl(N-N)(arene)][SbF6] (1−8), which have been fully characterized. Treatment of these cations with AgSbF6 generates dications which in some cases are enantioselective catalysts for Diels−Alder reaction of methacrolein and cyclopentadiene. Two complexes, [RuCl(iPr-benbox)(p-cymene)][SbF6] (5) and [Ru(OH2)(iPr-bop)(mes)][SbF6]2 (10; mes = mesitylene), have been characterized by X-ray crystallography.

The CpFe+-induced nona-allylation of mesitylene was largely improved by scaling up and carrying out the reaction of [FeCp(η6-1,3,5-C6H3Me3][PF6] with KOH/DME under ambient conditions (95% yield), followed by recycling this organoiron precursor by visible-light photolysis in CH2Cl2 using a 100 W desk lamp in the presence of mesitylene (95% recovery yield).

Mono- and dihydridoosmium(II) compounds with [(mes)Os{iPr2P(CH2)nY}] (mes = mesitylene, 1,3,5-trimethylbenzene; n = 2, Y = NMe2, OMe; n = 3, Y = NMe2) as a molecular unit are prepared from the dichloro derivatives [(mes)OsCl2{iPr2P(CH2)nY}] and magnesium amalgam in THF in the presence of ethanol. Upon treatment of [(mes)Os(X)Cl{κ1(P)-iPr2P(CH2)2Y}] (X = H, Cl) with AgPF6 in CH2Cl2 cationic complexes with iPr2P(CH2)2Y as a chelating ligand are obtained. The compounds with Y = OMe react (for X = Cl) with L = CO and CNMe by opening of the chelate bond to give the PF6 salts [(mes)Os(L)Cl{κ1(P)-iPr2P(CH2)2Y}]PF6 and (for X = H) with KOtBu by fragmentation of the functionalized phosphine to afford the neutral complex [(mes)OsH(OMe)(iPr2PCHCH2)]. The reaction of the chelate compound [(mes)OsCl{κ2(P,O)-iPr2PCH2C(OMe)O}]PF6 with KOtBu leads to the formation of the corresponding uncharged phosphanyl ester enolate−osmium(II) complex by proton abstraction from the PCH2 unit. The ester enolate complex reacts with phen...

The (PNP)Ir fragment displays a thermodynamic preference for the oxidative addition of aromatic vs benzylic C−H bonds. However, in the case of the mesitylene activation products, the benzylic isome...

The reactions of (η6-arene)Mo(CO)2(Sol) and M(CO)5(Sol) with CO have been studied in a range of alkane solvents (Sol), and the kinetic and activation parameters have been determined (M = Cr, Mo, or W). For M = Cr the ΔH⧧ is constant (22 ± 2 kJ mol-1), while the ΔS⧧ term becomes less negative as the alkane chain length increases. For the larger metals the variation in kinetic and activation parameters is less significant. Solvent displacement by CO involves an interchange mechanism for the Cr system, while for Mo or W complexes the mechanism is more associative in character. The photochemistry of (η6-arene)Mo(CO)3 (arene = benzene, mesitylene, p-xylene, or hexamethylbenzene) compounds was investigated by laser flash photolysis, supported by matrix isolation and time-resolved infrared spectroscopy (TRIR). In contrast to the behavior to the analogous (η6-arene)Cr(CO)3, it is found that the efficiency for photochemical expulsion of CO from (η6-mesitylene)Mo(CO)3 is markedly wavelength dependent (ΦCO = 0.587, ...

The heterocubane [Rh(μ3-I)(C4H4BPh)]4 (1) reacts with Ag+ salts in acetonitrile to give the labile salt [Rh(NCMe)3(C4H4BPh)]BF4 (2). This salt 2 reacts with hexamethylbenzene (hmb) to give the arene complex [Rh(C4H4BPh)(hmb)]BF4 (3), and with mesitylene [Rh(1,3,5-C6H3Me3)(C4H4BPh)]BF4 (4) is obtained. Complex 2 loses acetonitrile under vacuum to produce the polymeric salt catena-[{Rh(μ,η5:η6-C4H4BPh)}BF4]x (5). Insight into the essential structural features of this polymer provided its radial distribution function obtained from a wide-angle X-ray scattering experiment. When treated with acetonitrile, complex 5 regenerates 2 and with pyridine affords [Rh(py)3((C4H4BPh)]BF4 (6). Crystallization from a solution of [Rh(μ3-I)(C4H4BPh)]4 (1) and the corresponding methylborole complex [Rh(μ3-I)(C4H4BMe)]4 (1/1) in CH2Cl2 produces the trinuclear complex (η5-C4H4BPh)Rh(μ3-I)3Rh(μ,η5:η6-C4H4BPh)Rh(η5-C4H4BMe)·CH2Cl2 (7) with a bridging μ,η5:η6-C4H4BPh ligand; complex 7 was characterized by an X-ray structure determ...

Gas-phase reactions of M+, M2+, MO+ (M = Th and U), and UO2+ with several arenes (benzene, naphthalene, toluene, mesitylene, hexamethylbenzene, and 1,3,5-tri-tert-butylbenzene) have been studied by...

The radiative association reactions of gas-phase Cr+ with benzene and three of its methyl derivatives (toluene, p-xylene, and mesitylene) were studied in the Fourier-transform ion cyclotron resonance ion trap. Sequential formation of the monomer complexes and the sandwich dimer complexes was observed, and the kinetics were analyzed by a recently developed canonical transition-state theory approach to give estimates of the binding energies. The bond strength of Cr+−(C6H6) was assigned as 1.70 ± 0.15 eV, and the bond strengths increased slightly with increasing methyl substitution, reaching 2.0 eV for mesitylene. The bond strength for Cr+(C6H6)−(C6H6) was assigned as 2.2 ± 0.4 eV, with similar values (within large uncertainties) for the other sandwich complexes. The Cr+−(C6H6) value was in good agreement with the value from collision-induced dissociation, and a best value of 1.73 ± 0.10 eV for this bond strength is recommended.

The gas-phase reaction of XCr+ (X = C6H6, NH3) and (NH3)2Cr+ with arenes (L) leads to XCrL+, LCr+, and L2Cr+ complexes. The pattern and the efficiency of the two classes of complex formation processes allow a clear distinction between simple arenes, such as toluene and mesitylene, yielding ultimately sandwich-type L2Cr+ complexes, and α,ω-diphenylalkanes, yielding only LCr+ complexes, where a common sandwich-type structure is achieved by simultaneous coordination of the metal cation with the two aryl rings. The critical parameter controlling the extent of chelate coordination is the length of the methylene chain joining the two rings. A different behavior is displayed by ligands such as trans-stilbene and [2.2]paracyclophane, where only one aryl ring is involved in the stepwise NH3 substitution from (NH3)2Cr+. Under low pressure, and hence inefficient collisional deactivation, the Cr+ reaction with the selected arenes is governed by relative binding energies and radiative cooling efficiencies of the ensui...

The rhodium sandwich complexes [Rh(η6-arene)(η5-7-NHBut-7-CB10H10)] (arene = C6H5Me (2b), C6H3Me3-1,3,5 (3), MeC6H4C6H4Me-4,4‘ (4), [22](1,4)-C16H16 (5)) have been prepared from reactions between 1:1 mol mixtures of the arenes and [RhCl(PPh3)(η5-7-NH2But-7-CB10H10)] (1a) in CH2Cl2 in the presence of AgBF4. The crystal structures of 3 and 5 have been determined by X-ray diffraction confirming that in these species the rhodium is pentahapto coordinated on one side by the formally three-electron-donor 7-NHBut-7-CB10H10 and on the other in the hexahapto manner by a mesitylene molecule and one C6H4 ring of the cyclophane, respectively. The reaction between 4 and [Mo(CO)3(NCMe)3] in THF gave the dirhodium complex [Rh2(CO)2(η5-7-NH2But-7-CB10H10)2] (6), the structure of which has been established by X-ray diffraction. In the molecule two Rh(CO)(η5-7-NH2But-7-CB10H10) fragments are held together by a Rh−Rh bond which is spanned by two B−H⇀Rh two-electron three-center bonds employing in each CBBBB ring ligating a ...

Treatment of the neutral trimethyl compounds Cp*MMe3 (M = Ti, Zr, Hf) with the highly electrophilic borane B(C6F5)3 in methylene chloride in the presence of various arenes results in methyl carbanion abstraction and coordination of the arene to form complexes of the type [Cp*MMe2(η6-arene)][MeB(C6F5)3] (M = Ti, Zr, Hf; arene = benzene, toluene, m- and p-xylene, anisole, styrene, mesitylene). Indications of relative metal−arene affinities have been gleaned from a variety of low-temperature 1H NMR experiments, and it seems that both steric and electronic factors play significant roles in determining stabilities. The crystal and molecular structures of [Cp*HfMe2(η6-toluene)][MeB(C6F5)3] have been determined; as anticipated, there are no significant contacts between anion and cation, and the latter assumes a bent-metallocene type of structure.

Mesitylene may be lithiated almost quantitatively by Lin-Bu in a large excess of tmeda, resulting in the formation of the solvent-separated ion pairs [Li(tmeda)2]+[(tmeda)Li(CH2C6H3-3,5-Me2)2]- (1)...

The enthalpies of reaction of Cp*Ru(CH3CN)3OTf (Cp* = eta5-C5(CH3)5, OTf = O3SCF3) with a series of arenes have been measured by solution calorimetry. The results of this study are used to establish the following relative stability scale leading to the formation of Cp*Ru(arene)OTf complexes in THF (in kcal/mol): naphthalene, -1.7 +/- 0.1; benzene, -3.4 +/- 0.1; biphenyl, -3.6 +/- 0.1; toluene, -4.3 +/- 0.2; p-xylene, -4.6 +/- 0.2; (trimethylsilyl)benzene, -5.0 +/- 0.2; anisole, -5.4 +/- 0.2; mesitylene, -5.5 +/- 0.1; indole, -7.3 +/-0.2; NN-dimethylaniline, -7.5 +/- 0.1; p-bis(dimethylamino)benzene, -8.3 +/- 0.2. The solid-state structure of one of these arene complexes, Cp*Ru[C6H5(Si(CH3)3)]OTf, was determined by a low-temperature data collection X-ray crystallographic study. This investigation illustrates the presence of steric interactions between the phenyl TMS methyl groups and the Cp* methyl group and explains the small measured enthalpy of reaction. The enthalpies of arene substitution from Cp*Ru(CH3CN)3OTf span some 6.6 kcal/mol and vary as a function of the electron-donating ability of the arene. Factors affecting the Ru-arene bond energy are discussed, and thermodynamic comparisons with other organometallic systems are presented.

The problem of ligand exchange or loss in the formation of organometallic alkaline-earth-transition-metal complexes can be minimized by ensuring that any exchange would be degenerate or would require an unfavorable transfer of ligands. This approach is illustrated in the formation of chloride-bridged calcium-group 4 dimers and in an isocarbonyl-linked calcium-chromium dimer. Bis(pentamethylcyclopentadienyl)calcium Cp*{sub 2}Ca, reacts with Cp*{sub 2}ZrCl{sub 2}, Cp*{sub 2}HfCl{sub 2}, and Cp*{sub 2}ThCl{sub 2} in toluene to yield 1:1 adducts. Orange-yellow crystals of Cp*{sub 2}HfCl({mu}-Cl)CaCp* grown from toluene are triclinic, space group P{bar 1}, with a = 11.146 (4) {angstrom}, b = 16.942 (6) {angstrom}, c = 11.109 (3) {angstrom}, {alpha} = 103.34 (3){degrees}, {beta} = 94.89 (3){degrees}, {gamma} = 102.50 (3){degrees}, and D(calcd) = 1.398 g cm{sup -3} for Z = 2. The structure consists of two bent metallocene units with a single {mu}-Cl and a terminal Cl on hafnium: Ca-{mu}-Cl = 2.864 (3) {angstrom}, Hf-{mu}-Cl = 2.463 (3) {angstrom}, Hf-Cl(t) = 2.383 (3) {angstrom}, and Ca-Cl-Hf = 161.3 (1){degrees}. Cp*{sub 2}Ca reacts with Cp*{sub 2}Zr(CO){sub 2} and mesitylene chromium tricarbonyl in toluene in yield 1:1 adducts. In the solid state, the calcium-chromium adduct exists as a tetranuclear species, constructed around a 12-membered ring consisting of twomore » Ca and Cr atoms and four carbonyl groups. 39 refs., 2 figs., 4 figs.« less