12146-37-1Relevant articles and documents
Chromium(0) and Molydenum(0) Complexes with a Pyridyl-Mesoionic Carbene Ligand: Structural, (Spectro)electrochemical, Photochemical, and Theoretical Investigations
Albold, Uta,Beerhues, Julia,Bens, Tobias,Boden, Pit,Di Martino-Fumo, Patrick,Gerhards, Markus,Neuman, Nicolás I.,Sarkar, Biprajit,Sobottka, Sebastian
supporting information, p. 15504 - 15513 (2020/11/02)
This work reports on the synthesis and in-depth electrochemical and photochemical characterization of two chromium(0) and molydenum(0) metal complexes with bidentate pyridyl-mesoionic carbene (MIC) ligands of the 1,2,3-triazol-5-ylidene type and carbonyl coligands. Metal complexes with MIC ligands have turned out to have very promising electrocatalytic and photochemical properties, but examples of MIC-containing complexes with early-transition-metal centers remain extremely rare. The electrochemistry of these new MIC complexes was studied by cyclic voltammetry and especially spectroelectrochemistry in the IR region consistent with a mainly metal-centered oxidation, which is fully reversible in the case of the chromium(0) complex. At the same time, the two reduction steps are predominantly ligand-centered according to the observed near-IR absorbance, with the first reduction step being reversible for both systems. The results of the electron paramagnetic resonance studies on the oxidized and reduced species confirm the IR spectroelectrochemistry experiments. The photochemical reactivity of the complexes with a series of organic ligands was investigated by time-resolved (step-scan) Fourier transform infrared (FTIR) spectroscopy. Interestingly, the photoreactions in pyridine and acetonitrile are fully reversible with a slow dark reverse reaction back to the educt species over minutes and even hours, depending on the metal center and reagent. This reversible behavior is in contrast to the expected loss of one or several CO ligands known from related homoleptic as well as heteroleptic M(CO)4L2 α-diimine transition-metal complexes.
Palladium-free aminocarbonylation of aryl, benzyl, and styryl iodides and bromides by amines using Mo(CO)6 and norbornadiene
Iranpoor, Nasser,Firouzabadi, Habib,Motevalli, Somayeh,Talebi, Mohsen
, p. 418 - 426 (2013/01/15)
A simple and efficient method is described for aminocarbonylation of aryl, benzyl, and styryl iodides and bromides using the in situ generated molybdenum tetracarbonyl norbornadiene [Mo(CO)4(nbd)] complex as a suitable source of carbon monoxide.
CO release from norbornadiene iron(0) tricarbonyl complexes: Importance of ligand dissociation
Atkin, Anthony J.,Fairlamb, Ian J. S.,Ward, Jonathan S.,Lynam, Jason M.
, p. 5894 - 5902,9 (2020/08/31)
An investigation into the CO-releasing properties of a range of iron tricarbonyl and chromium and molybdenum tetracarbonyl complexes is presented. Iron tricarbonyl complexes containing the 2,5-bicyclo[2.2.1]heptene (norbornadiene) ligand are shown to be effective CO-releasing molecules, in which the rate and extent of CO release may be modulated by modification of the norbornadiene framework. Species containing the parent norbornadiene and those with a substituent at the 7-position of the organic ligand exhibit CO release; those containing ester substituents at the 2- and/or 3-positions do not. A mechanism for CO release in this species is proposed which involves initial norbornadiene dissociation, a suggestion which is supported by the spectroscopic data and the observation that the addition of excess substituted norbornadiene retards the rate of CO release. CO release from the diester-containing norbornadiene complex may be promoted photochemically, and cell viability studies indicate that in the absence of light this complex is nontoxic, making it an excellent candidate for further study as a photo-CO-RM. Both the chromium and molybdenum tetracarbonyl complexes release CO, which in the case of the molybdenum analogue is rapid.
Facile hydrosilylation of norbornadiene by silanes R3SiH and R2SiH2 with molybdenum catalysts
Stosur, Magdalena,Szymańska-Buzar, Teresa
, p. 98 - 105 (2009/01/23)
Photochemically activated [Mo(CO)6] and [Mo(CO)4(η4-nbd)] have been demonstrated to be very effective catalysts for hydrosilylation of norbornadiene (nbd) by tertiary (Et3SiH, Cl3SiH) and secondary (Et2SiH2 and Ph2SiH2) silanes to give 5-silyl-2-norbornene, which under the same reaction conditions transform in ring-opening metathesis polymerization (ROMP) to unsaturated polymers and to a double hydrosilylation product, 2,6-bis(silyl)norbornane. The yield of a particular reaction depends very strongly on the kind of silane involved. The reaction products were identified by means of chromatography (GC-MS) and 1H and 13C NMR spectroscopy. In photochemical reaction of [Mo(CO)4(η4-nbd)] and Ph2SiH2 in cyclohexane-d12, η2-coordination of the Si{single bond}H bond to the molybdenum atom is supported by 1H NMR spectroscopy due to the detection of two equal-intensity doublets with 2JH{single bond}H = 5.4 Hz at δ 6.12 and -5.86 ppm.
Photochemical reactions of cis-[(η4-NBD)M(CO)4] (NBD = norbornadiene; M = Cr, Mo) olefin complex with ligand, containing S and N donor atoms
Subasi,Karahan,Ercag
, p. 886 - 890 (2009/01/23)
New complexes cis-[M(CO)4-DABRd] (M = Cr(I), Mo(II) and fac-[M(CO)3-SAT] (M = Cr(III), Mo(IV)) have been synthesized by the photochemical reactions of cis-[(η4-NBD)M(CO)4] (NBD is norbornadiene; M=Cr, Mo) with 5-(4-dimethylaminobenzylidene) rhodanine (DABRd) and salicylidene-3-amino-1,2,4-triazole (SAT) ligands and characterized by elemental analysis, FT-IR and 1H NMR spectroscopy, and mass spectrometry. The spectroscopic studies show that the DABRd ligand acts as a bidentate ligand coordinating via both NH-(S)C=S sulfur donor atoms in I and II and SAT ligand behaves as a tridentate ligand coordinating via its all imine nitrogen-C=N-donor atoms in III and IV to the metal center.
Reactions of Di(1-cyclohepta-2,4,6-trienyl)sulfane, S(C7H 7)2, with derivatives of the hexacarbonyls, M(CO) 6 (M = Cr, Mo, W)
Herberhold, Max,Liu, Jinnan,Milius, Wolfgang,Tok, Oleg,Wrackmeyer, Bernd
, p. 2438 - 2449 (2008/10/09)
Mononuclear carbonylmetal complexes of chromium, molybdenum and tungsten containing the sulfane S(C7H7)2 (1) have been obtained starting from precursors such as the THF-stabilized pentacarbonylmetal fragments, [M(CO)5](thf), the acetonitrile intermediates M(CO) 6-x(CH3CN)x (x = 1, 2, 3) (M = Cr, Mo, W) or the η4-norbornadiene complexes M(CO)4(C 7H8) (M = Cr, Mo). In addition to the pentacarbonyls, M(CO)5[S(C7H7)2] (M = Cr (2a), Mo (2b), W (2c)) which contain 1 unchanged as a two-electron sulfane ligand with two pending cyclohepta-2,4,6-trienyl substituents, isomeric complexes M(CO) 5[S(CH2Ph)(C7H7)] (M = Cr (3a), W (3c)) were obtained at higher temperatures (40-50°C) in which one of the two organic groups has been transformed into a benzyl substituent. In the tetracarbonyls, cis-M(CO)4[S(C7H7) (η2-C7H7)] (M = Mo (4b), W (4c)), the ligand 1 serves as an olefinic sulfane four-electron chelate ligand. The reaction of either Mo(CO)6 or (mesitylene)Mo(CO)3 with S(C7H7)2 (1) in boiling THF leads to the sulfur-free ditropyl complex Mo(CO)3[(η6-C 7H7)-C7H7] (5b, two isomers). The 1H and 13C NMR spectra of the new complexes 2-4 reveal various dynamic processes including pyramidal inversion of the sulfur atom and [1,7]-sigmatropic shifts at the C7H7 ring. The molecular structures of 2c, 3a, 4b and 4c have been determined by X-ray crystallography.
Kinetics of the substitution of norbornadiene in tetracarbonyl(norbornadiene)molybdenum(0) by 2,2'-bipyridine
Kayran, Ceyhan,Okan, Eser
, p. 281 - 286 (2007/10/03)
The kinetics of the thermal substitution of norbornadiene (nbd) by 2,2'-bipyridine (2,2'-bipy) in (CO)4Mo(C7H9) was studied by quantitative FT-IR and UV-VIS spectroscopy. The reaction rate exhibits first-order dependence o
Stereochemical nonrigidity in heterobimetallic complexes containing the bent metallocene-thiolate fragment
Darensbourg, Marcetta Y.,Pala, Magdalena,Houliston, Stephen A.,Kidwell, K. Paul,Spencer, David,Chojnacki, Stephen S.,Reibenspies, Joseph H.
, p. 1487 - 1493 (2008/10/08)
The physical properties and reactions of Cp2Ti(S-p-C6H4X)2 (1) and Cp2Ti(μ-S-p-C6H4X)2Mo(CO) 4 (2) (X = Cl, H, CH3, OCH3) complexes as well as the mechanism of the Cp site equilibration process in bimetallic complexes were investigated. Cyclic voltammographs recorded in CH2Cl2 showed two reversible waves for Ti(IV) ? Ti(III) and Mo(0) ? Mo(I) processes in 2 and one reversible wave for Ti(IV) ? Ti(III) in 1. Positions of these waves varied uniformly with the Hammett σ parameter of the X substituent. Variable-temperature 1H NMR studies provided values for ΔG? of the Cp equilibration process which are ca. 30 kJ/mol smaller than ΔG? for Cp2Ti(S-p-C6H4X)2 displacement from 2 by CO. This indicates that the fluxional process in 2 does not occur through a ligand dissociation process and argues for a mechanism of pyramidal inversion on sulfur. The X-ray structure for Cp2Ti(μ-S-p-C6H4Cl)2Mo(CO) 4 (2a) is reported. Complex 2a crystallizes in the monoclinic space group P21/n, with a = 12.396 (7) A?, b = 16.78 (2) A?, c = 12.838 (9) A?, β = 94.29 (5)°, Z = 4, and V = 2662 (3) A?3. The Ti atom is in pseudotetrahedral coordination environment whereas the Mo is octahedrally coordinated. The S1-Ti-S2 and S1-Mo-S2 angles are obtuse (100.8 (1) and 97.6 (1)°, respectively) and Ti-S-Mo angles are acute (80.8 (1)°) in the planar Ti-S2-Mo ring, supportive of metal-metal interactions implied by spectroscopic and electrochemical data. The phenyl groups are in an anti arrangement with respect to the Ti-S2-Mo plane.
Carbon monoxide induced allyl coupling from Mo2(μ2-η3-allyl)2(η 3-allyl)2 yielding the labile complex Mo(CO)4(η4-1,5-hexadiene)
Blau, Reed J.,Siriwardane, Upali
, p. 1627 - 1630 (2008/10/08)
Carbon monoxide induces the reductive elimination of two pairs of allylic ligands from Mo2(μ2-η3-allyl)2(η 3-allyl)2 with the accompanying cleavage of the Mo-Mo quadruple bond. Mo(η4-1,5-hexadiene)(CO)4 is obtained from the reaction of 8 equiv of CO with Mo2(μ2-η3-allyl)2(η 3-allyl)2. Structural data for and the reactivity of Mo(η4-1,5-hexadiene)(CO)4 suggest that 1,5-hexadiene is bound very weakly to molybdenum.
The photochemistry of M(CO)4(η4-norbornadiene) complexes of group 6 transition metals (M= Cr, Mo, W) in low-temperature matrices
Grevels, Friedrich-Wilhelm,Jacke, Juergen,Koltzbuecher, Werner E.,Schaffner, Kurt,Hooker, Richard H.,Rest, Antony J.
, p. 201 - 224 (2007/10/02)
Photolysis of M(CO)4(η4-norbornadiene) group 6 metal complexes (1) in low-temperature matrices involves both loss of CO and cleavage of metal-olefin bonds to an extent depending on the metal and on the excitation wavelength.In inert matrices me
