25734-54-7Relevant academic research and scientific papers
Synthesis, characterization, and reactivity of a rhenium complex with a corannulene-based ligand
Chin, Robert M.,Baird, Benjamin,Jarosh, Michael,Rassman, Shane,Barry, Brian,Jones, William D.
, p. 4829 - 4832 (2003)
A new rhenium carbonyl complex, exo-(η5-C20H17)Re(CO)3 (3), containing a corannulene-derived ligand has been synthesized in 12% yield. The X-ray structure determination of 3 shows that the rhenium center is bound to the exo face of the bowl-shaped ligand. The reaction of 3 with PPh3 in benzene at 70°C produces trans,mer-Re(H)(PPh3)2(CO)3 and C20H16 (4), a bowl-shaped dibenzofulvene type molecule. The reaction of 3 with PPh3 proceeds via an η5-η3-η1 ring slip followed by a β-hydride elimination.
Homogeneous CO hydrogenation: Ligand effects on the lewis acid-assisted reductive coupling of carbon monoxide
Miller, Alexander J. M.,Labinger, Jay A.,Bercaw, John E.
, p. 4499 - 4516 (2011/01/09)
Structure-function studies on the role of pendent Lewis acids in the reductive coupling of CO are reported. Cationic rhenium carbonyl complexes containing zero, one, or two phosphinoborane ligands (Ph2P(CH 2)nB(C8H14), n = 1-3) react with the nucleophilic hydride [HPt(dmpe)2]+ to reduce [M-CO] + to M-CHO; this step is relatively insensitive to the Lewis acid, as both pendent (internal) and external boranes of appropriate acid strength can be used. In contrast, whether a second hydride transfer and C-C bond forming steps occur depends strongly on the number of carbon atoms between P and B in the phosphinoborane ligands, as well as the number of pendent acids in the complex: shorter linker chain lengths favor such reductive coupling, whereas longer chains and external boranes are ineffective. A number of different species containing partially reduced CO groups, whose exact structures vary considerably with the nature and number of phosphinoborane ligands, have been crystallographically characterized. The reaction of [(Ph2P(CH 2)2B(C8H14))2Re(CO) 4]+ with [HPt(dmpe)2]+ takes place via a hydride shuttle mechanism, in which hydride is transferred from Pt to a pendent borane and thence to CO, rather than by direct hydride attack at CO. Addition of a second hydride in C6D5Cl at -40 °C affords an unusual anionic bis(carbene) complex, which converts to a C-C bonded product on warming. These results support a working model for Lewis acid-assisted reductive coupling of CO, in which B (pendent or external) shuttles hydride from Pt to coordinated CO, followed by formation of an intramolecular B-O bond, which facilitates reductive coupling.
Preparations, structures, and electrochemical studies of aryldiazene complexes of rhenium: Syntheses of the first heterobinuclear and heterotrinuclear derivatives with bis(diazene) or bis(diazenido) bridging ligands
Albertin, Gabriele,Antoniutti, Stefano,Bacchi, Alessia,Ballico, Giovanni B.,Bordignon, Emilio,Pelizzi, Giancarlo,Ranieri, Maria,Ugo, Paolo
, p. 3265 - 3279 (2008/10/08)
The mono- and binuclear aryldiazene complexes [Re(C6H5N=NH)(CO)(5-n)P(n)]BY4 (1-5) and [{Re(CO)(5-n)P(n)}2-(μ-HN=NAr-ArN=NH)](BY4)2 (6-12) [P = P(OEt)3, PPh(OEt)2, PPh2OEt; n = 1-4; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-(2-CH3)C6H3-C6H3(2-CH3), 4,4'-C6H4-CH2-C6H4; Y = F, Ph) were prepared by reacting the hydride species ReH(CO)(5-n)P(n) with the appropriate mono- and bis(aryldiazonium) cations. These compounds, as well as other prepared compounds, were characterized spectroscopically (IR; 1H, 31P, 13C, and 15N NMR data), and 1a was also characterized by an X-ray crystal structure determination. [Re(C6H5N=NH)(CO){P(OEt)3}4]BPh4 (1a) crystallizes in space group P1 with a = 15.380(5) A, b = 13.037(5) A, c = 16.649(5) A, α = 90.33(5)°, β = 91.2(1)°, γ = 89.71(9)°, and Z = 2. The 'diazene-diazonium' complexes [M(CO)3P2(HN=NAr-ArN≡N)]-(BF4)2 (13-15, 17) [M = Re, Mn; P = PPh2OEt, PPh2OMe, PPh3; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4] and [Re(CO)4(PPh2OEt)(4,4'-HN=NC6H4-C6H4N≡N)](BF4)2 (16b) were synthesized by allowing the hydrides MH(CO)3P2 or ReH(CO)4P to react with equimolar amounts of bis(aryldiazonium) cations under appropriate conditions. Reactions of diazene-diazonium complexes 13-17 with the metal hydrides M2H2P'4 and M2'H(CO)(5-n)P''(n) afforded the heterobinuclear bis(aryldiazene) derivatives [M1(CO)3P2(μ-HN=NAr-ArN=NH)M2HP'4](BPh4)2 (ReFe, ReRu, ReOs, MnRu, MnOs) and [M1(CO)3P2(μ-HN=NAr-ArN=NH)M2'-(CO)(5-n)P''(n)](BPh4)2 (ReMn, MnRe) [M1 = Re, Mn; M2 = Fe, Ru, Os; M2' = Mn, Re; P = PPh2OEt, PPh2OMe; P', P'' = P(OEt)3, PPh(OEt)2; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4; n = 1, 2]. The heterotrinuclear complexes [Re(CO)3(PPh2OEt)2(μ-4,4'-HN=NC6H4-C6H4N=NH)M{P(OEt)3}4(μ-4,4'-H N=NC6H4-C6H4N=NH)Mn(CO)3(PPh2OEt)2](BPh4)4 (M = Ru, Os) (ReRuMn, ReOsMn) were obtained by reacting the heterobinuclear complexes ReRu and ReOs with the appropriate diazene-diazonium cations. The heterobinuclear complex with a bis(aryldiazenido) bridging ligand [Mn(CO)2(PPh2OEt)2(μ-4,4'-N2C6H4-C6H4N2)Fe{P(OEt)3}4]BPh4 (MnFe) was prepared by deprotonating the bis(aryldiazene) compound [Mn(CO)3(PPh2OEt)2(μ-4,4'-HN=NC6H4-C6H4N=NH)Fe(4-CH3C6H4CN){P(OEt )3}4](BPh4)3. Finally, the binuclear compound [Re(CO)3(PPh2OEt)2(μ-4,4'-HN=NC6H4-C6H4N2)Fe(CO)2{P(OPh)3}2](BP h4)2 (ReFe) containing a diazene-diazenido bridging ligand was prepared by reacting [Re(CO)3(PPh2OEt)2(4,4'-HN=NC6H4-C6H4N≡N)]+ with the FeH2(CO)2{P(OPh)3}2 hydride derivative. The electrochemical reduction of mono- and binuclear aryldiazene complexes of both rhenium (1-12) and the manganese, as well as heterobinuclear ReRu and MnRu complexes, was studied by means of cyclic voltammetry and digital simulation techniques. The electrochemical oxidation of the mono- and binuclear aryldiazenido compounds Mn(C6H5N2)(CO)2P2 and {Mn(CO)2P2}2(μ-4,4'-N2C6H4-C6H4N2) (P = PPh2OEt) was also examined. Electrochemical data show that, for binuclear compounds, the diazene bridging unit allows delocalization of electrons between the two different redox centers of the same molecule, whereas the two metal centers behave independently in the presence of the diazenido bridging unit.
Cationic hydrogen complexes of rhenium. 2. Synthesis, reactivity, and competition studies
Heinekey,Radzewich, Catherine E.,Voges, Mark H.,Schomber, Beth M.
, p. 4172 - 4181 (2007/10/03)
Cationic rhenium dihydrogen complexes, [Re(H2)(PR3)2(CO)3]B(Ar')4 (PR3 = PCy3, PiPr3, PiPrPh2, PPh3; Ar' = 3,5-(CF3)2C6H3), have been prepared by the protonation of ReX(PR3)2(CO)3 (X = H, CH3) with [H(Et2O)2]B(Ar')4 under a hydrogen atmosphere. Deuterium is incorporated into the H2 ligand when placed under a D2 atmosphere and large JHD values (30-33 Hz) are consistent with a dihydrogen formulation. Relaxation data indicate very short T(1 min) for these complexes. These complexes are susceptible to heterolytic cleavage of dihydrogen, and the reactivity with several bases has been investigated. Under vacuum or argon atmosphere the complexes readily lose hydrogen to form 16-electron complexes. In the solid state, [Re(PCy3)2(CO)3]B(Ar')4 exhibits an agostic interaction to a β C- H bond of the phosphine ligand. Variable-temperature 31P{1H} NMR spectra of [Re(PCy3)2(CO)3]B(Ar')4 indicate a dynamic process involving hindered rotation about the Re-P bond. Competition studies have been conducted, and the hydrogen binding affinity is higher for [Re(H2)(PCy3)2(CNtBu)3]B(Ar')4 (5) than for [Re(H2)(PCy3)2(CO)3]B(At')4 (2a). Similar experiments also find that 5 also binds hydrogen preferentially over W(H2)(PCy3)2(CO)3.
Reactions of coordinated diazene in rhenium and tungsten complexes. Deprotonation of ligated NH=NH and subsequent H-migration to carbonyl ligands to give metal formyls
Cheng, Tan-Yun,Peters, Jonas C.,Hillhouse, Gregory L.
, p. 204 - 207 (2007/10/02)
The tungsten diazene complex [trans,trans- W(NH=NH)(CO)2(NO)(PPh3)2+][SO3CF3-] (1) reacts with NH2R (R = H, CH3, NH2) to give trans,trans-W(η1-OSO2CF3)(CO)2(NO)(PPh3)2 (2), trans,trans-W(H)(CO)2(NO)(PPh3)2 (3), and [trans,trans- W(NH2NH2)(CO)2(NO)(PPh3)2+][SO3CF3-] (4). If the reaction of NH2R with 1 is monitored at -78 °C, intermediates in the formation of 3 can be observed, which have been characterized as the neutral 6-coordinate formyl complexes trans-W(CH=O)(CO)(NO)(NH2R)(PPh3)2 (5a, R = H; 5b, R = CH3; 5c, R = NH2) on the basis of multinuclear (1H, 13C, 31P) NMR spectroscopy and 2H and 13C labeling experiments. The noncoordinating Bronsted base NaN(SiMe3)2 reacts with 1 to give 3 in 47% isolated yield, but because of the absence of a coordinating Lewis base, no formyl intermediate was observed. A reaction mechanism for the formation of hydride 3 is proposed involving (i) deprotonation of the diazene ligand in 1 by NH2R, (ii) H- migration from nitrogen to a carbonyl ligand to give the formyl complexes 5, and (iii) H-migration from the formyl ligand to the metal to give the neutral hydride product 3. The isoelectronic rhenium diazene complex [trans,mer- Re(NH=NH)(CO)3(PPh3)2+][SO3-CF3-] (9) has been prepared and shown to undergo a similar reaction with NH2CH3 to give trans,mer- Re(H)(CO)3(PPh3)2 (6) in 80% yield.
Synthesis and characterization of aminomethyl complexes of rhenium
Gibson, Dorothy H.,Owens, Kathryn
, p. 1216 - 1218 (2008/10/08)
Reductions of rhenium aminocarbene complexes mer,trans-M(CO)3(PPh3)2CHNHR+CF 3SO3- (M = Re; R = CH2Ph, CH(CH3)2; 1a,b, respectively) by Et4
Separating the Re-H and H-H dipole-dipole contributions to the 1H NMR spin-lattice relaxation rate of the hydride ligand in mer,trans-ReH(CO)3(PPh3)2 by deuteration
Luo, Xiao-Liang,Liu, Hong,Crabtree, Robert H.
, p. 4740 - 4742 (2008/10/08)
The reaction of mer,trans-ReCl(CO)3(PPh3)2 with LiAlH4 in THF at room temperature gives mer,trans-ReH(CO)3(PPh3)2 (1). The temperature dependence of the 1H NMR spin-lattice (T1) relaxation rate of the hydride resonance of 1 is studied to try to understand the excess T1 relaxation often found for rhenium hydride complexes. Our previous assumption that the dipole-dipole relaxation mechanism is dominant is confirmed. Two main dipole-dipole contributions are identified. One is from the usual proton-proton dipole-dipole (HHDD) relaxation between the hydride ligand and the protons of the phosphine ligands, and the other from the rhenium-hydride dipole-dipole (ReHDD) relaxation. The two contributions can be separated by studying mer,trans-ReH(CO)3(PPh3-d15)2 (1-d30). The two components come to a minimum T1 value at different temperatures. The T1(min) value observed for the ReHDD relaxation in 1-d30 is consistent with an Re-H bond distance of 1.75 ?, which is in satisfactory agreement with those determined by neutron diffraction studies on other rhenium hydride complexes.
Synthesis and thermolysis of neutral metal formyl complexes of molybdenum, tungsten, manganese, and rhenium
Gibson,Owens,Mandal,Sattich,Franco
, p. 498 - 505 (2008/10/08)
The possible intermediacy of catalyst-bound formyls in syngas transformations has prompted efforts to prepare and study the chemistry of transition-metal formyl complexes over more than a decade. We have used a mild borohydride in our reactions with metal carbonyl cations and have introduced some variations into the syntheses which allow, in almost all cases, for the pure formyl complex to be precipitated from solution as it is formed. The formyl complexes and their cationic precursors are shown. Seven of the formyls are new; improved procedures have been established for the other four. All but one of the compounds have been isolated.
Synthesis, structures, and C-H bond activation reactions of HRe(PR3)2(L)3 complexes
Jones, William D.,Maguire, John A.
, p. 1728 - 1737 (2008/10/08)
The reactions of (η4-C5H6)Re(PPh3) 2H3 with a variety of ligands L are found to give substitution products in which cyclopentene is displaced from the metal. For the cases in whieh L = CO or CNR (R = Me, Et, i-Pr, t-Bu, CH2CMe3, c-C6H11, and 2,6-xylyl), products of the formulation HRe(PPh3)2L3 are obtained. The complex HRe(PPh3)2(CNMe)3 was found to be of the mer configuration, crystallizing in the triclinic space group P1 with a = 11.201 (5) A?, b = 18.630 (6) A?, c = 9.433 (4) A?, α = 98.74 (4)°, β = 105.00 (4)°, γ = 103.05 (4)°, V = 1805.4 (3.3) A?3, dcalcd = 1.536 g/cm3, and Z = 2. Reaction with L = PMe3 is found to give only HRe(PMe3)5, which crystallizes in the monoclinic space group C2/m with a = 15.698 (6) A?, b = 10.869 (5) A?, c = 15.092 (4) A?, β = 107.88 (3)°, V = 2450.5 (3.1) A?3, dcalcd = 1.538 g/cm3, and Z = 4. This complex undergoes H/D exchange of all hydrogen atoms with C6D6 solvent upon irradiation or heating to 105°C and catalytically exchanges deuterium from the solvent into added free PMe3. With L = PEt3, an intermediate in which one of the PPh3 ligands has undergone ortho metalation is isolated. H2Re(PEt3)3-(PPh2C6H 4) was found to crystallize in the orthorhombic space group Pcab with a = 19.285 (5) A?, b = 32.437 (7) A?, c = 12.150 (4) A?, V = 7600.7 (5.7) A?3, dcalcd = 1.405 g/cm3, and Z = 8. The complex shows a pentagonal-bipyramid geometry with axial PEt3 groups. Fluxional interchange of the two distinct hydride ligands and the axial and equatorial PEt3 ligands is observed. Reaction with L = DMPE gives ReH-(DMPE)2(PPh3), which was found to crystallize in the triclinic space group P1 with a = 10.523 (6) A?, b = 18.599 (8) A?, c = 10.511 (5) A?, α = 90.94 (4)°, β = 117.37 (4)°, γ = 105.85 (5)°, V = 1732.9 (8.5) A?3, dcalcd = 1.512 g/cm3, and Z = 2. The complex displays a cis-octahedral structure.
HYDROGEN ABSTRACTION AND DIMERISATION REACTIONS OF SOME ORGANO-TRANSITION METAL FREE RADICALS
Armstead, Judith A.,Cox, David J.,Davis, Reg
, p. 213 - 220 (2007/10/02)
The 17-electron species (M=Mn, Re, x=0; M=Mn, Re; L=Ph3P, x=1, 2; M=Mn, Re; L=(o-MeC6H4O)3P, x=2; M=Mn; L=(p-ClC6H4O)3P, (PhO)3P, x=2; M=Mn; L=P(OMe)3, x=3) have been generated by one electron oxidation of the corresponding anions and show ty
