Tricarbonylchromium Complexes Research Articles

(η6-arene)tricarbonylchromium complexes of 1,3-benzodioxoles

The interaction of triammine(tricarbonyl)chromium with 1,3-benzodioxole or some its derivatives (2,2-dimethyl-1,3-benzodioxole, 2-methyl-1,3-benzodioxole, 2-phenyl-1,3-benzodioxole) led to corresponding (η6–1,3-benzodioxole)tricarbonylchromium complexes. The novel compounds were characterized by NMR spectrometry and mass-spectroscopy. The performed single-crystal X-ray diffraction study confirmed the formation of complexes via η6-coordination of 1,3-benzodioxole ligand by chromium atom. It was shown that in the case of 2-phenyl-1,3-benzodioxole both benzodioxole or phenyl fragments may be coordinated by Cr(CO)3 moiety. The performed calculations have shown the possibility of intramolecular η6- η6-haptotropic rearrangement. The antimicrobial activity of the obtained tricarbonylchromium complexes has been evaluated.

How a Chromium Tricarbonyl Complex Catalyzes the [3 + 2] Cycloaddition Reaction of N-Substituted Phenylnitrones with Styrene: A Molecular Electron Density Theory Analysis

The reaction mechanisms of [3 + 2] cycloaddition (32CA) between two N-substituted phenylnitrones (NPPN and NtBPN) and styrene (STY) in the presence of a chromium tricarbonyl complex (Cr(CO)3) have been studied within the framework of molecular electron density theory at the MPWB1K/6-311G(d,p) level. Activation energy analysis reveals that these 32CA reactions take place with high activation barriers due to their non-polar character and with the exo/ortho approach as a favorable reaction path. The activation energy of TS1 series (NPPN) is about 5–6 kcal/mol lower than that of the TS2 series (NtBPN), due to the steric hindrance of tert-butyl at the TS2 structures. Coordination of chromium tricarbonyl to each reactant to form the corresponding complex slightly increases the nucleophilic and electrophilic character of NPPN:Cr, NtBPN:Cr, and STY:Cr, which can be considered a strong nucleophile and electrophile able to participate in a polar 32CA reaction. This polar character in the presence of the chromium tricarbonyl complex was verified by the higher (up to 0.20e) values of global electron density transfer for Cr(CO)3-coordinated transition states. Electron localization function analysis along the exo/ortho reaction path reveals the non-concerted mechanism in the formation of a new bond with the initial appearance of a C–C single bond followed by the O–C one.

Topological unraveling of the [3+2] cycloaddition (32CA) reaction between N-methylphenylnitrone and styrene catalyzed by the chromium tricarbonyl complex using electron localization function and catastrophe theory

We have investigated the reaction mechanisms of [3+2] cycloaddition (32CA) between N-methylphenylnitrone and styrene catalyzed by the chromium tricarbonyl complex at the MPWB1K/6-311G(d,p) level of approximation.

Synthesis and isomerism of Cr and Mn phosphonioallene complexes

Earlier, we have discovered the UV-promoted four-component reaction between (arene)chromium and cyclopentadienylmanganese tricarbonyl complexes, propargyl alcohol, PPh3, and HBF4 to afford isomeric terminal and internal phosphonioallene complexes. The present study revealed additional details for this reaction and was extended either to similar manganese and chromium complexes, or to propargyl alcohol derivatives (НС≡ССМе2ОН, DC≡CCH2OMe). In particular, the use of d1-propargyl methyl ether allowed us to exclude possible isomerization of propargylphosphonium to allenylphosphonium in the coordination sphere. The photolysis of CpMn(CO)3 and Cp∗Mn(CO)3 in the presence of propargyl alcohols afforded η2-alkyne complexes, which were then reacted in situ with acid and PPh3 under dark conditions. With unsubstituted propargyl alcohols, the terminal anti-isomer was the only product in both cases, while the internal isomer is exclusively produced in the reactions of both Cr and Mn complexes with 2-methylbut-3-yn-2-ol. Issues related to the isomeric ratio are discussed and the data obtained are compared with those for similar known metal complexes. The obtained compounds were characterized by IR, 1H, 31P, and 13C NMR spectroscopy and the structures of complexes IX and XIII were confirmed by X-ray diffraction.

Ag/Pd Cocatalyzed Direct Arylation of Fluoroarene Derivatives with Aryl Bromides.

Diverse C–H functionalizations catalyzed by Pd employ Ag(I) salts added as halide abstractors or oxidants. Recent reports have shown that Ag can also perform the crucial C–H activation step in several of these functionalizations. However, all of these processes are limited by the wasteful requirement for (super)stoichiometric Ag(I) salts. Herein, we report the development of a Ag/Pd cocatalyzed direct arylation of (fluoroarene) chromium tricarbonyl complexes with bromoarenes. The small organic salt, NMe4OC(CF3)3, added as a halide abstractor, enables the use of a catalytic amount of Ag, reversing the rapid precipitation of AgBr. We have shown through H/D scrambling and kinetic studies that a (PR3)Ag-alkoxide is responsible for C–H activation, a departure from previous studies with Ag carboxylates. Furthermore, the construction of biaryls directly from the simple arene is achieved via a one-pot chromium tricarbonyl complexation/C–H arylation/decomplexation sequence using (pyrene)Cr(CO)3 as a Cr(CO)3 donor.

Comparison of Experimental and Experimental–Theoretical Topological Characteristics of the Electron Density in the Crystalline Complex η6-[3-Acetyltetrahydro-6-Phenyl-2Н-1,3-oxazine]tricarbonylchromium(0)

Experimental and experimental–theoretical studies (using the molecular invariom) of the electron density distribution are performed for the η6-[3-acetyltetrahydro-6-phenyl-2Н-1,3-oxazine]tricarbonylchromium(0) complex. The topological characteristics of the electron density (ρ(r), ∇2ρ(r)) at the critical points (3, –1) coincide in the experimental and experimental–theoretical distributions within the “transferability indices.” The experimental–theoretical study more reliably localizes the “expected” critical points (3, –1) between the chromium atom and arene ligand.

Trifluoromethyl-Substituted Benzocyclobutenone and Benzocyclobutenedione: The Structure Anomaly of (Benzocyclobutenedione)tricarbonylchromium Complexes

The syntheses of methoxy- and trifluoromethyl-substituted benzocyclobutenone and benzocyclobutenedione tricarbonylchromium complexes are described. As with the unsubstituted complex, a route via the respective acetals was used. However, attempts to hydrolyze rac-tricarbonyl[1,2-bis(ethylenedioxy)-3-(trifluoromethyl)benzocyclobutene]chromium(0) (rac-12) resulted in only a single hydrolysis and led to rac-tricarbonyl{η6-[2-(ethylendioxy)-3-(trifluoromethyl)benzocyclobutenone]}chromium(0) (rac-14) with different regioselectivity in comparison to the respective reaction of the methoxy-substituted derivative. The synthesis of the desired rac-tricarbonyl[3-(trifluoromethyl)benzocyclobutenedione]chromium(0) (rac-13) was finally achieved by a route via an acyclic diacetal. Compounds were characterized spectroscopically and in a number of cases also by crystal structure analyses. The unusual bending of the annelated cyclobutenedione ring toward the tricarbonylchromium moiety was observed for rac-tricarbonyl-[η6-(m...

Asymmetric synthesis of secondary benzylic alcohols via arene chromium tricarbonyl complexes

(Aryl aldehyde)- and (aryl ketone)-chromium tricarbonyl complexes ortho-substituted with the chiral auxiliary O-methyl-N-(α-methylbenzyl)hydroxylamine undergo diastereoselective addition of Grignard reagents and Super-Hydride®, respectively, to give the corresponding secondary alcohols in high diastereoisomeric purity. These compounds may be easily decomplexed and deprotected to give the corresponding enantiopure amino alcohols.

DFT study of chromium tricarbonyl complexes of coronene and kekulene

A quantum chemical study of the mechanism and determination of the activation barriers of intramolecular η6,η6-inner-ring haptotropic rearrangements (IHR), consisting in moving a chromium tricarbonyl group Cr(CO)3 from one six-membered aromatic ring to another, are carried out using the density functional theory (DFT) for the respective η6-complexes of coronene I and kekulene II. The stationary states on the potential energy surface, determining the mechanism of η6,η6-IHR, have a lower hapticity, which is of interest for catalysis because of the possibility of coordinating an additional substrate and reagent around the transition metal during the rearrangement. The processes of η6,η6-IHR complexes I and II occur with similar energy barriers (ΔG≠ ≈ 20–25 kcal/mol) that are lower than the barriers (ΔG≠ ≈ 30 kcal/mol) of similar transformations previously calculated or measured for naphthalene complexes and a number of small polyaromatic hydrocarbons.

19 π(アレーン)トリカルボニルクロム錯体の位置選択的リチウム化反応及びRabelomycinの合成研究

19 π(アレーン)トリカルボニルクロム錯体の位置選択的リチウム化反応及びRabelomycinの合成研究

Intricacies of ligand coordination in tricarbonylchromium(0) complexes with ortho- and para-fluorobiphenyls.

The steric and electronic factors that influence which of the two rings of a substituted biphenyl ligand coordinates to chromium are of interest and it has been suggested that haptotropic rearrangements within these molecules may be limited if the arene-arene dihedral angle is too large. Two tricarbonylchromium(0) complexes and their respective free ligands have been characterized by single-crystal X-ray diffraction. In the solid state, tricarbonyl[(1',2',3',4',5',6'-η)-2-fluoro-1,1'-biphenyl]chromium(0), [Cr(C12H9F)(CO)3], (I), exists as the more stable isomer with the nonhalogenated arene ring ligated to the metal center. Similarly, tricarbonyl[(1',2',3',4',5',6'-η)-4-fluoro-1,1'-biphenyl]chromium(0) crystallizes as the more stable isomer with the phenyl ring bonded to the Cr0 center. The arene-arene dihedral angles in these complexes are 55.77 (4) and 52.4 (5)°, respectively. Structural features of these complexes are compared to those of the DFT-optimized geometries of ten tricarbonyl[(η6-C6H5)(4-F-C6H4)]chromium model complexes. The solid-state structures of the free ligands 2-fluoro-1,1'-biphenyl and 4-fluoro-1,1'-biphenyl, both C12H9F, exhibit arene-arene dihedral angles of 54.83 (7) and 0.71 (8)°, respectively. The molecules of the free ligands occupy crystallographic twofold axes and exhibit positional disorder. Weak intermolecular C-H...F interactions are observed in all four structures.

Asymmetric ortho-deprotonation of (η6-arene) chromium tricarbonyl complexes substituted with a chiral hydroxylamine

The use of O-methyl-N-(α-methylbenzyl)hydroxylamine as a novel chiral auxiliary in asymmetric ortho-deprotonation of the (η6-arene) chromium tricarbonyl complexes is described. Upon quenching of the resultant ortho-lithiated complex with an electrophile, 1,2-disubstituted (η6-arene) chromium tricarbonyl complexes were obtained in good yield and excellent levels of diastereoselectivity.

Quantum chemical study of the structures and dynamic behavior of tricarbonyl complexes of Group 6 metals (Cr, Mo, W) with polyaromatic hydrocarbons using the density functional theory

The quantum chemical study of the mechanism was performed for tricarbonyl η6-complexes of coronene I-M and kekulene II-M (M = Cr, Mo, W) by the density functional method. The activation barriers of η6,η6-interring haptotropic rearrangements (IHR), being the migration of the metaltricarbonyl group M(CO)3 from one six-membered aromatic ring to another, were determined. The processes of η6,η6-IHR in the metal tricarbonyl complexes with relatively high polycyclic aromatic hydrocarbons (PAH) I and II occur with close energy barriers (ΔG≠ ≈ 20—25 kcal mol–1), which are lower than the barriers (ΔG≠ ~ 30 kcal mol–1) of similar transformations measured or calculated earlier for the chromium tricarbonyl complexes of naphthalene and its derivatives and other PAH. For the molybdenum tricarbonyl complexes the activation barriers of η6,η6-IHR decrease additionally by ~ 5 kcal mol–1 compared to those for the chromium tricarbonyl complexes, whereas for the tungsten tricarbonyl complexes they increase again and become approximately equal to the activation barriers of similar chromium tricarbonyl complexes. All stationary states on the potential energy surface determining the mechanism of η6,η6-IHR are characterized by a decrease in hapticity compared to the initial and final complexes.

The first nucleophilic C-H perfluoroalkylation of aromatic compounds via (arene)tricarbonylchromium complexes.

The first nucleophilic perfluoroalkylation of arenes is based on the arene π-system activation via (η6-arene)tricarbonylchromium complexes. Perfluoroalkyl anions generated from Me3SiRF and a fluoride ion source [Me4N]F exclusively attack the arene ligand under mild conditions. The formed negatively charged analogs of Meisenheimer adducts readily undergo a one-pot oxidation to perfluoroalkyl arenes.

Selective Synthesis of Enantiomeric η6‐Arene Chromium Tricarbonyl Complexes with Epimeric Pyrroloimidazolones

AbstractA pair of epimeric l‐proline derived chiral auxiliaries have been developed for the diastereoselective lithiation–substitution of η6‐arene chromium tricarbonyl complexes. Lithiation of the anti epimer affords planar chiral imidazolones in >95:5 dr upon electrophile quench. Application of the same reaction sequence to the syn epimer provides products with opposite planar chirality in equally high levels of diastereomeric purity. The ortho‐substituted epimeric imidazolones give rise to planar chiral enantiomers upon acid‐induced elimination, thus precluding the need to prepare a d‐proline‐derived starting material.magnified image

Expensive tripodal rotation in η6-chromium tricarbonyl complexes of phosphabenzenes-Insights from DFT study

Tripodal rotation of Cr(CO)3 moiety complexed to mono, di and tri phosphabenzenes have been studied at B3LYP/LANL2DZ level. In most cases, the conformational minima has preferential orientation of Cr(CO)3 moiety in the anti eclipsed position relative to majority of the phosphorus atoms in the ring although instances of staggered minima in 12DPBC, 14DPBC & 124TPBC have also been reported. We observed large torsional barrier of 6.49kcal/mol (36 folds relative to benzene chromiumtricarbonyl complexes) for 1,3,5-triphosphabenzene chromiumtricarbonyl complex. Based on our observations through NBO analysis, we have attempted to provide interesting insights on conformational preferences and the hyperconjugative stabilisations (bonding/backbonding interactions) that decide these conformational preferences and torsional barrier. Furthermore, we also noted correlation between activation hardness and rotational barrier which explains the unique conformation assumed by 1,3,5-triphosphabenzene chromium tricarbonyl complex.

A chromium tricarbonyl complex featuring the 4,6-bis(diphenylphosphinomethyl)dibenzothiophene (PSPPh) ligand.

The new PSP pincer ligand 4,6-bis(diphenylphosphinomethyl)dibenzothiophene (PSPPh) was prepared in 89 % yield. With this ligand, a solvothermal synthesis of a Cr complex of the type [Cr(κ3P,S,P-PSP)(CO)3] is described. The X-ray structure of this compound is presented. We demonstrate that the solvothermal synthesis technique provides a powerful, simple, and practical synthetic method resulting in a high isolated yield in a short reaction time.Graphical abstractElectronic supplementary materialThe online version of this article (doi:10.1007/s00706-016-1707-9) contains supplementary material, which is available to authorized users.

The effect of fluorine substitution on the conformation and aromaticity of η6-fluoro arene chromium tricarbonyl complexes – Density functional insights

Conformational space of tripodal rotation of chromium carbonyl moiety of fluorine substituted η6-benzenetricarbonylchromium (BC) has been studied computationally at B3LYP/LANL2DZ level. The study throws light on delicate preference of the tripodal stool either to remain staggered (or) eclipsed at fluorine atoms. The differential fluorine effect is exuberantly manifested through nearly 29 folds increase in rotational barrier of 1,3,5 fluorine substituted BC relative to BC. Other interesting correlations such as number of fluorines with interaction energies, with aromaticity and other orbital level interactions are also discussed.

DFT study of molecular structures and 13C NMR parameters of two fluorinated biphenyls and their η6-tricarbonylchromium complexes

The molecular structures of 2,2′-difluoro-6,6′-dimethylbiphenyl, 4,5-difluoro-9,10-dihydrophenanthrene and of their η6-tricarbonylchromium complexes have been discussed in the light of the results of molecular energy calculations. Also the isotropic magnetic shielding constants and carbon–fluorine spin–spin coupling constants for these objects have been calculated and compared with the experimental values of 13C NMR chemical shifts and J constants. The calculational methods used were: DFT/BHandH/6-311++G(2d,p) and/or DFT/B3LYP/6-311++G(2d,p). It has been confirmed that experimental 13C NMR chemical shifts for η6-arene tricarbonylchromium complexes can be satisfactorily predicted using both methods, although the method exploiting BHandH functional is not able to reproduce the 13C NMR chemical shifts of Cr(CO)3 carbon atoms. On the other hand, this method provides the J(13C, 19F) values which are close to the experimental ones.

Gold(I)-catalyzed asymmetric desymmetrization of meso-alkynyl diols and kinetic resolution of the corresponding DL-diols: effects of celite filtration and silver salts.

The asymmetric desymmetrization of meso-2-alkynylbenzenediols through the use of a combination of axially chiral diphosphine(AuCl)2 precatalysts and silver salt co-catalysts gave optically active isochromene compounds with high enantioselectivities in good yields. The corresponding DL-diol isomers underwent efficient kinetic resolution to give the cyclized isochromenes and recovered diols with high enantioselectivities under similar conditions. The high reactivity and selectivity in the desymmetrization of the meso-diols is independent of the combination of axially chiral diphosphine(AuCl)2 precatalyst and silver salt co-catalyst, whereas the corresponding tricarbonylchromium complexes of alkynylbenzenediols were affected by the combination of the diphosphine(AuCl)2 and silver salt. The reactivity was largely dependent on the nature of the gold(I) species.