104453-08-9Relevant academic research and scientific papers
1H- and 2H-T1 relaxation behavior of the rhodium dihydrogen complex [(triphos)Rh(η2-H2)H2]+
Bakhmutov, Vladimir I.,Bianchini, Claudio,Peruzzini, Maurizio,Vizza, Francesco,Vorontsov, Evgeny V.
, p. 1655 - 1660 (2008/10/08)
Protonation of the classical trihydride [(triphos)RhH3] (2) at 210 K in either THF or CH2Cl2 by either HBF4·OMe2 or CF3SO2OH gives the nonclassical η2-H2 complex [(triphos)Rh(η2-H2)H2]+ (1) [triphos = MeC(CH2PPh2)3]. Complex 1 is thermally unstable and highly fluxional in solution. In THF above 230 K, 1 transforms into the solvento dihydride complex [(triphos)Rh(η1-THF-d8)H2]+ (5) that, at room temperature, quickly converts to the stable dimer trans-[{(triphos)RhH}2(μ-H)2]2+ (trans-6). In CH2Cl2, 1 is stable up to 240 K. Above this temperature, the η2-H2 complex begins to convert into a mixture of trans- and cis-6, which, in turn, transform into the bridging-chloride dimers trans- and cis-[{(triphos)RhH}2(μ-Cl)2]2+ at room temperature. Complex 1 contains a fast-spinning H2 ligand with a T1(min) of 38.9 ms in CD2Cl2 (220 K, 400 MHz). An NMR analysis of the bis-deuterated isotopomer [(triphos)RhH2D2]+ (1-d2) did not provide a J(HD) value. At 190 K, the perdeuterated isotopomers [(triphos)RhD3] (2-d3) and 1-d4 show T1(min) values of 16.5 and 32.6 ms (76.753 MHz), respectively, for the rapidly exchanging deuterides. An analogous 2-fold elongation of T1(min) is also observed on going from [(triphos)IrD3] to [(triphos)Ir(η2-D2)D2]+. A rationale for the elongation of T1(min) in nonclassical polyhydrides is proposed on the basis of both the results obtained and recent literature reports.
Insertion of iridium into C-H and C-S bonds of 2,5-dimethylthiophene, 2-methylbenzothiophene and 4,6-dimethyldibenzothiophene
Bianchini, Claudio,Casares, Juan A.,Masi, Dante,Meli, Andrea,Pohl, Wolfgang,Vizza, Francesco
, p. 143 - 155 (2007/10/03)
C-H insertion thienyl products are selectively formed at early times of the interaction of the unsaturated 16e- fragment [(triphos)IrH] with 2,5-dimethylthiophene (Me2T), 2-methylbenzothiophene (MeBT) and 4,6-dimethyldibenzothiophene (Me2DBT) [triphos = MeC(CH2PPh2)3]. C-S insertion to give six-membered metallathiacycle products occurs as a thermal step only for Me2T and MeBT. The C-S insertion products are isolated as both kinetic and thermodynamic stereoisomers. The thermodynamic C-S insertion product of MeBT, endo-[(triphos)Ir(η3-S,C,C-S(C6H4)CH=C(Me)H)], has been characterized by X-ray diffraction studies.
Synthesis and Reactivity of the Labile Dihydrogen Complex [{MeC(CH2PPh2)3}Ir(H2)(H) 2]BPh4
Bianchini, Claudio,Moneti, Simonetta,Peruzzini, Maurizio,Vizza, Francesco
, p. 5818 - 5825 (2008/10/09)
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.
HDS model systems. Coordination, opening, and hydrogenation of benzo[b]thiophene at iridium
Bianchini, Claudio,Meli, Andrea,Peruzzini, Maurizio,Vizza, Francesco,Moneti, Simonetta,Herrera, Verónica,Sánchez-Delgado, Roberto A.
, p. 4370 - 4381 (2007/10/02)
The η4-benzene complexes [(triphos)Ir(C6H6)]Y (Y = BPh4, 1a; PF6, 1b) react with benzo[b]thiophene (BT) at room temperature to give the unprecedented [(triphos)Ir(η3-C,C,S-C8H6S)]Y (Y = BPh4, 2a; PF6, 2b) in which intact BT is coordinated to the metal center through the S atom and the C2=C3 bond. 2a and 2b are transformed upon mild thermolysis into the iridabenzothiabenzene complexes [(triphos)Ir(η2-C,S-C8H6S)]Y (Y = BPh4, 3a; PF6, 3b). An X-ray analysis has been carried out on 3a·1.5THF·0.5EtOH. The coordination geometry around iridium may be described as a distorted trigonal-bipyramid, the metal center being surrounded by the three phosphorus atoms of triphos and by a carbon and a sulfur atom from a C-S-cleaved BT molecule. Crystal data: triclinic, space group P1, a = 17.391(3) A?, b = 16.957(4) A?, c = 12.795(3) A?, α = 77.51(2)°, β= 80.98(2)°, γ = 75.50(2)°, Z = 2, dcalcd = 1.31 g cm-3, nobsd = 7636, R = 0.072. Interaction of 2a with CO (1 atm, 20°C) yields [(triphos)Ir(CO)2]BPh4 (4) plus free BT, whereas 3a requires more drastic conditions (5 atm, 70°C) to eliminate BT and produce 4. 2a also reacts with H2 (1 atm, 20°C) to produce [(triphos)Ir(H)2(η1-S-BT)]BPh4 (5), which can be independently prepared by treatment of [(triphos)Ir(H)2(THF)]BPh4 with BT; at 5 atm H2, free BT is obtained together with [(triphos)Ir(H)3], BPh3, and benzene, as a result of a heterolytic splitting of H2 at the [(triphos)Ir(H)2]+ fragment assisted by the BPh4- counteranion. The C-S-cleaved BT in 3a is readily hydrogenated (5 atm, 20°C) to 2-ethylbenzenethiolate, producing [(triphos)Ir(H)2{o-S-(C6H4)C2H 5}] (8) plus BPh3 and benzene also via heterolytic splitting of H2 assisted by BPh4-; protonolysis of 8 with 2 equiv HCl produces (triphos)IrCl3 with concomitant liberation of 2-ethylbenzenethiol, a primary product of BT HDS. If the PF6- analogue 3b is used instead, the reaction with H2 under identical conditions yields the thiolate-bridged dimer [(triphos)IrH{μ-o-S(C6H4)C2H 5}2HIr(triphos)] (PF6)2 (9b). 3a also reacts with LiHBEt3 to give [(triphos)Ir(H)(η2-C,S-C8H6S)] (11), which converts in THF solution at 66°C into [(triphos)Ir(η3-S(C6H4)-CH=CH2)] (12) by hydride migration to C2; neither 11 nor 12 react with H2 under mild conditions. Addition of HBF4·OEt2 to 12 yields [(triphos)Ir(η4-S(C6H4)C(H)Me)]BF 4 (13c), which does react with H2 even at 1 atm to give the thiolate-bridged dimer [(triphos)IrH{μ-o-S(C6H4)C2H 5}2HIr(triphos)](BF4)2 (9c). 13c also reacts with H- to give [(triphos)IrH(η2-S(C6H4)C(H)Me)] (14), which in turn reacts with H2 and HBF4·OEt2 to yield 8 and 9c, respectively.
Thermal and photochemical C-H bond activation reactions at iridium. π-Coordination vs C-H cleavage of ethene, styrene, and phenylacetylene
Bianchini, Claudio,Barbaro, Pierluigi,Meli, Andrea,Peruzzini, Maurizio,Vacca, Alberto,Vizza, Francesco
, p. 2505 - 2514 (2008/10/08)
Thermolysis of [(triphos)Ir(H)2(C2H5)] (1) in various solvents (benzene, THF, MeCN, DMF) results in formation of the 16-electron fragment [(triphos)IrH] and ethane. The reactive intermediate is capable of insertion into the C-H bonds of either solvents or appropriate substrates (1-alkynes, ethene), generally affording σ-organyl dihydrides of the formula [(triphos)Ir(H)2(σ-organyl)] (organyl = C6H5, CH2CN, C≡CPh, C≡CCO2Et, CH=CH2). The hydride carbonyl [(triphos)IrH(CO)] and dimethylamine are produced by reaction with N,N-dimethylformamide. Thermolysis of 1 in THF at 66°C in the presence of ethene (1-4 atm) gives the vinyl hydride [(triphos)Ir(H)2(CH=CH2)] (8) and the π-complex [(triphos)IrH(C2H4)] (7) in a kinetic product ratio showing that π-complexation is not a precursor for C-H insertion. Under the same reaction conditions, styrene gives selectively the π-complex [(triphos)IrH(CH2=CHPh)] (9). UV irradiation of 7 and 9 in either benzene or THF at 20°C promotes insertion of iridium into the C-H bonds to give 8 and a 1:1 mixture of the E and Z styryl complexes [(triphos)Ir(H)2(CH=CHPh)] (11, 12), respectively. Secondary photolysis on either 8 or 11 and 12 results in photoejection of ethene and dihydrogen, respectively. In the case of the vinyl complex, the reactive intermediate is trapped by the solvent, whereas the styryl dihydrides are converted to the stable π-alkyne hydride [(triphos)IrH(HC≡CPh)]. The latter complex is also obtained by photolysis of [(triphos)Ir(H)2(C≡CPh)] in THF at 20°C. Both the vinyl dihydride and the styryl dihydrides are thermodynamically unstable and convert to the corresponding π-olefin complex in refluxing THF. Irradiation of 1 in either THF or benzene at 20°C produces several metal products and gases (C2H6, C2H4, and H2) due to the occurrence of both primary and secondary photolysis reactions. Irradiation of the trihydride [(triphos)Ir(H)3] in benzene results in formation of the phenyl dihydride [(triphos)Ir(H)2(Ph)] and evolution of H2. Possible mechanisms for the thermal and photochemical reactions are discussed.
Molecular solid-state organometallic chemistry of tripodal (polyphosphine)metal complexes. Catalytic hydrogenation of ethylene at iridium
Bianchini, Claudio,Farnetti, Erica,Graziani, Mauro,Kaspar, Jan,Vizza, Francesco
, p. 1753 - 1759 (2007/10/02)
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.
Assembling ethylene, alkyl, hydride, and CO ligands at iridium
Barbara, Pierluigi,Bianchini, Claudio,Meli, Andrea,Peruzzini, Maurizio,Vacca, Alberto,Vizza, Francesco
, p. 2227 - 2238 (2008/10/08)
The iridacyclopropane complex [(tripos)Ir(Cl)(C2H4)] is the starting point to synthesize a number of stable iridium complexes containing various combinations of participative ligands such as hydride, ethylene, alkyls and heteroalkyls, alkynes, and carbon monoxide: Ir(H)(C2H4), Ir(H)2(C2H4), Ir(C2H5)(C2H4), Ir(CO)2, Ir(H)(C2H5)(CO), Ir(H)2(CO), Ir(H)2(CH2CH2PEt3), Ir(H)3, Ir(H)2(C2H5), Ir(H)2(C3H7), Ir(C2H4)2, Ir(RC≡CR), IrH(μ-H)2HIr, and IrH(μ-Cl)2HIr. Due to the tripodlike structure of the ligand MeC(CH2PPh2)3 (triphos), all the complexes invariably exhibit a facial arrangement of the phosphorus and non-phosphorus ligands. The contemporaneous availability of so many related species has allowed a comparative experimental study on several important reactions. These include (i) reductive elimination of C-H and H-H bonds from dihydride alkyl complexes, (ii) reductive elimination of H-H bonds vs hydride migration in dihydride ethylene species, (iii) nucleophilic additions to coordinated double bonds, (iv) phosphine arm dissociation in triphos complexes, and β-H elimination vs C-H bond reductive elimination in hydride alkyl complexes. In most instances, such reactions are characterized by stereo- and chemoselectivity. Valuable information on the role played by the nature of the metal and of the phosphine ligands in determining the reactivity has been provided by a comparison among strictly related Rh and Ir complexes containing either triphos or three comparable monophosphines.
Gold-Rhodium and Gold-Iridium Hydride Clusters
Albinati, Alberto,Demartin, Francesco,Janser, Philipp,Rhodes, Larry F.,Venanzi, Luigi M.
, p. 2115 - 2125 (2007/10/02)
The hydrides MH3(tripod) (M=Rh and Ir; tripod=triphos and triars) react with + cations to give heterometallic species of the types +, type A, 2+>, type B, and (tripod)MH2(Au(L
SOME IRIDIUM(I) AND IRIDIUM(III) COMPLEXES WITH THE TRIPOD-LIKE LIGAND CH3C(CH2PPh2)3 (triphos) AND THE X-RAY CRYSTAL STRUCTURE OF
Janser, P.,Venanzi, L. M.,Bachechi, F.
, p. 229 - 242 (2007/10/02)
The compound (1), has been reinvestigated and its X-ray crystal structure is reported.The crystals are orthorhombic, space group Pbca, with a 18.941(6), b 22.193(8), c 17.501(7) Angstroem, Z = 8.The structure was solved by the heavy atom method and refined by full-matrix least-squares to the conventional R factor value of 0.074 for 6462 reflections.The metal atom coordination is trigonal bipyramidal, with the three phosphorus atoms occupying one axial and two equatorial positions.The other equatorial position is occupied by CO while Cl is coordinated axially.Compound 1 readily undergoes a series of oxidative-addition reactions with H2, HCl and Cl2, giving + (4) + (3), and (IrCl3(triphos)> (5), respectively.Compounds (IrH(CO)(triphos)> (2) and nCl3-n(triphos)> (n = 1,2,3) have also been obtained from 1 and 5, respectively, by treating them with a variety of hydride sources.
