Arene Tricarbonylchromium Complexes Research Articles

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.

Erratum to: Arenetricarbonylchromium Complexes in Polymerization Transformations by Radical Initiation of Vinyl Polymerization

Erratum to: Arenetricarbonylchromium Complexes in Polymerization Transformations by Radical Initiation of Vinyl Polymerization

Arenetricarbonylchromium Complexes in Polymerization Transformations by Radical Initiation of Vinyl Polymerization

The article is devoted to the systematization of investigations of arenetricarbonylchromium complexes in radical polymerization transformation at the initiation of vinyl polymerization. The presented data are shown that these compounds are promising and interesting model systems for the study of the phenomenon of the metal atom action on the reactivity of the monomer π-bond. The correlation between the structure of metal-containing monomers and polymerization parameters, as well as the molecular mass properties of the resulting polymers, are discussed.

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.

Generation of Aryl Grignard Reagents from Arene Chromium Tricarbonyl Complexes by Mg(TMP)2·2LiCl and Their Application to Murahashi Coupling

A mild and straightforward synthesis of biaryls is described that is performed through direct arylation of the C–H bond of (arene)Cr(CO)3 upon deprotonation with Mg(2,2,6,6-tetramethylpiperazide)2·2LiCl and subsequent palladium-catalyzed cross-coupling reaction.

Isolation and structure of the anti,anti isomer and a DFT study of it and the syn,anti isomer of bis(tricarbonylchromium)dibenzo-[a,e]cyclooctatetraene. Evidence for an attractive electrostatic interaction between carbonyl oxygen atoms and Cr(CO)3-coordinated arene carbon atoms

When dibenzo[a,e]cyclooctatetraene and hexacarbonylchromium are refluxed in di-n-butyl ether/THF for an extended period, both the syn,anti and anti,anti isomers of the bis-tricarbonylchromium complex are obtained. After separation by column chromatography, the syn,anti:anti,anti isomer ratio is approximately 12:1. The anti,anti arrangement of the Cr(CO)3 groups was verified by X-ray crystallographic structure determination. The orientations of the two tricarbonylchromium tripods relative to the 1,2-disubstituted arene rings differ. One is exo staggered while the other is eclipsed. Intermolecular C–H⋯O hydrogen bonding is prevalent in the crystal and is reminiscent of the syn,anti isomer. A dimeric motif in the solid resulting from C–H⋯π interactions is observed. DFT calculations on both isomers confirms that the syn,anti isomer is favored. The preferred orientation for the anti Cr(CO)3 groups in both cases is exo staggered. However, the barrier to rotation is low, allowing hydrogen bonding to readily overcome this barrier and control the orientation of the tripod. While thermodynamic consideration support the preference for the syn,anti isomer, kinetic factors may also be important as this isomer would be formed preferentially due to steric inhibition of the diene coordination site by the mononuclear anti isomer. The stabilization of the syn,anti isomer occurs by an electrostatic attraction of the syn carbonyl groups with the anti Cr(CO)3-coordinated arene carbon atoms. A reexamination of the structural parameters verifies nonbonded carbon–oxygen distances less than the sum of the van der Waals radii in the syn,anti isomer. A search of the Cambridge Structural Database results in a significant number of interactions of this nature for arenetricarbonylchromium complexes.

Preparation of Arene Chromium Tricarbonyl Complexes Using Continuous-Flow Processing: (η6-C6H5CH3)Cr(CO)3 as an Example

Abstract A continuous-flow approach to the direct synthesis of arene chromium tricarbonyl complexes is presented. By working in flow mode, it is possible to avoid some of the problems of batch synthesis, especially sublimation of the Cr(CO)6 starting material and the competitive decomposition of the product during the lengthy reaction times. Heating at 220 °C and operating with a residence time of 10 min through the heated zone allows for the synthesis of (η6-C6H5CH3)Cr(CO)3 as an example, along with a selection of other (arene)Cr(CO)3 complexes.

ChemInform Abstract: Planar Chiral (η5‐Cyclohexadienyl)‐ and (η6‐Arene)‐tricarbonylmanganese Complexes: Synthetic Routes and Application.

AbstractReview: ca. 60 refs.

Photolysis of arene chromium tricarbonyl complexes in presence of amine–boranes: Observation of σ-borane complexes in solution

Activation of the B–H σ-bond of amine–boranes on the chromium(0) center of arene chromium tricarbonyl complexes ( η 6-arene)Cr(CO) 3 (arene = fluorobenzene, 1a; benzene, 1b and mesitylene, 1c) has been studied. Photolysis of 1b in presence of ammonia–borane (H 3N·BH 3, AB) and tert-butylamine–borane ( t BuH 2N·BH 3, TBAB) resulted in H 2 evolution and precipitation of a BNH x polymer. On the other hand, photolysis in the presence of trimethylamine–borane (Me 3N·BH 3, TMAB) resulted in the formation of a σ-borane complex ( 2) along with Cr(CO) 5( η 1-HBH 2·NMe 3) ( 3). The σ-borane complexes ( η 6-arene)Cr(CO) 2( η 1-HBH 2·NMe 3) (arene = fluorobenzene, 2a; benzene, 2b and mesitylene, 2c) were characterized in solution by 1H, 11B, and 13C NMR spectroscopy. Electron withdrawing substituents on the arene ring provide the more stable σ-borane moiety in this series of complexes.

Planar chiral (η5-cyclohexadienyl)- and (η6-arene)-tricarbonylmanganese complexes: synthetic routes and application

Planar chiral arenetricarbonylchromium complexes have been intensively investigated and they have been applied as valuable building blocks for asymmetric synthesis and as ligands for asymmetric catalysis. In contrast, in the field of the isoelectronic cationic [(η(6)-arene)Mn(CO)(3)](+) complexes, until these last 10 years, very few studies were published involving nonracemic planar chiral cationic complexes and their potential applications, certainly because of the difficult access to enantiopure starting material. In 2009, however, the discovery of the first resolution of such compounds opened a new area for their application in the field of organic as well as of organometallic enantioselective syntheses. We felt it important to write a review on this subject to give an up-to-date summary of the methodologies used to prepare enantiomerically pure planar chiral neutral [(η(5)-cyclohexadienyl)Mn(CO)(3)] and cationic [(η(6)-arene)Mn(CO)(3)](+) complexes as well as their potential in enantioselective synthesis.

ChemInform Abstract: Arenetricarbonylchromium Complexes as Chiral Auxiliaries: Asymmetric Synthesis of β-Lactams.

ChemInform Abstract: Arenetricarbonylchromium Complexes as Chiral Auxiliaries: Asymmetric Synthesis of β-Lactams.

ChemInform Abstract: Chiral Arene Chromium Tricarbonyl Complexes as Enantioselective Catalysts: Highly Selective 1,2-Alkyl Additions to Aldehydes.

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ChemInform Abstract: Dimethyldioxirane in Organometallic Chemistry: A Convenient Procedure for the Decomplexation of Arene Chromium Tricarbonyl Compounds.

Abstract Arene chromium tricarbonyl complexes 1 react with dimethyldioxirane to give the corresponding arene derivatives 2 in quantitative yields. The reaction is rapid, highly chemoselective and involves an easy manipulation procedure. In addition, the reaction course could be monitored by colour change, thus avoiding the possible further oxidation of substituents linked to the aromatic ring. However, the complex with thioanisole was chemoselectively oxidized with dimethyldioxirane to the corresponding sulfoxide complex.

Origin of the regioselectivity in an intramolecular nucleophilic addition to arene chromium tricarbonyl complexes

The source of the regioselectivity in the intramolecular nucleophilic addition of nitrile-stabilized carbanions to arene chromium tricarbonyl complexes was investigated for seven different substitution patterns on the arenes. All of the arenes are 1,4-dioxygenated and the substitution varies in the oxygen substituent and in the substituents of the arene carbons (hydrogen and alkyl). The regioselectivity is correlated with the preferred conformations of the chromium tricarbonyl group which in turn was determined by solution and solid-state 13C NMR spectroscopy, 1H NMR spectroscopy in solution as well as X-ray diffraction. In the four complexes analyzed by X-ray diffraction and the three complexes analyzed by solid-state 13C NMR spectroscopy, there was only one complex where it was found that the preferred conformation of the –Cr(CO) 3 is different in solution than it is in the solid-state.

SOLVATOCHROMIC AND SUBSTITUENT EFFECT ON ELECTRONIC ABSORPTION OF ARENETRICARBONYLCHROMIUM(0) COMPLEXES

A number of arenetricarbonylchromium(0) complexes, [(η6-arene)Cr(CO)3], in which arene = benzene, chlorobenzene, phenyltrimethylsilane, and acenaphthene were synthesized. Electronic absorptions of these complexes were recorded in various solvents, ranging from polar to non polar ones; i.e. methanol, methylene chloride, chloroform, benzene, and isooctane. These chromium tricarbonyl complexes show lowest electronic absorption in the energy range of 313 - 320 nm, with relatively high intensity (ε = 0,9 - 2,0 x 104 M-1cm-1). Detailed discussion of the solvent and substituent effect on electronic absorption of these complexes are presented in this article. Keywords: solvatochromic and substituent effect, chromium tricarbonyl complexes, electronic absorption

ChemInform Abstract: Stereoselective Route to Mitosanes via Tricarbonyl η6 Arene Chromium Complexes.

Abstract Stereoselective reduction followed by metalation of a η6 arene chromium tricarbonyl complex allows rapid access to substituted mitosanes, whose skeleton mimics the mitomycin family of antitumour agents.

ChemInform Abstract: Stereoselective Bis-functionalizations of Arene Chromium Tricarbonyl Complexes via Brook Rearrangements.

An efficient method has been developed for the stereoselective bis-functionalization of arene chromium tricarbonyl complexes. Initial nucleophilic addition of organolithium reagents to a carbonyl moiety is followed by a 1,4-carbon to oxygen silyl migration (Brook rearrangement) and alkylation of the resultant aryl anion.

ChemInform Abstract: Directed Lithiation in Arenetricarbonylchromium(0) Complexes: Assessment of Some Directing Group Specificities and of Electrophilic Quench Efficacies.

Abstract The synthesis of a series of phenol ethers and 4-triisopropylsilyloxymethylphenol ethers and their η6-tricarbonylchromium(0) complexes are reported. The directed lithiation of these followed by quenching with a series of electrophiles gave access to a wide range of functionalised complexes for use in synthesis.

The Stereospecific Ligand Exchange at a Pseudo‐Benzylic T‐4 Iridium Centre in Planar‐Chiral Cycloiridium (η6‐Arene)tricarbonylchromium Complexes

The stereospecificity of ligand exchange at the Ir(III) centre of a cycloiridium arenetricarbonylchromium complex has been established experimentally by various analytical methods as well as by X-ray diffraction structural analysis and computational investigations. Two new cases of phenyl and methyl iridium(III) complexes have been prepared by reaction of (S(P)*,R(Ir)*-chlorido{2-[(tricarbonyl)(eta(6)-phenylene-kappaC(1'))chromium(0)]pyridine-kappaN}(pentamethylcyclopentadienyl)iridium(III) with PhMgBr and MeMgBr. The determining influence of electrostatic repulsion has been established by means of density functional theory at the Becke-Perdew/TZP(ZORA) level by using, among other means, energy partitioning analysis. It is also shown that the Cr(CO)(3) fragment is likely to ease the ionic cleavage of the Ir-Cl bond in chlorido cycloiridium tricarbonylchromium complexes in a way similar to that already established for the solvolysis of benzyl halide complexes, that is, through a direct interaction of the Cr(0) centre with the cationic Ir(III) centre.

Reactions of Complex Ligands. Part 107 Densely Substituted Hydroquinoid Phenanthrene and Triphenylene Cr(CO)3 Complexes: Chromium‐Templated Synthesis and Molecular Structure

AbstractDensely substituted hydroquinoid phenanthrene (10–18), acephenanthrene (19), and triphenylene chromium tricarbonyl complexes (20–22) have been prepared via benzannulation of naphthalenyl (1–7), acenaphthenyl (8) and phenanthrenyl carbene complexes (9), respectively. The naphthalenyl, acenaphthenyl and phenanthrenyl carbene complexes 1–9 were obtained in 52–88 % yield starting from commercially available bromoarenes by dehalolithiation, addition of hexacarbonyl chromium to the lithioarene and O‐alkylation of the resulting acyl chromates with trimethyloxonium tetrafluoroborate (Fischer route). The benzannulation of the aryl carbene complexes (either with 3‐hexyne / (t‐butyl)dimethylsilyl chloride or with (t‐butyl)dimethylsilylethyne) allowed the regiospecific synthesis of the oligocyclic hydroquinoid arene tricarbonyl chromium complexes 10–22 in 44–94 % yield thus providing a two‐step synthesis with overall yields of 18 ‐ 80 %. Under the kinetic reaction conditions used the metal atom is exclusively coordinated to the persubstituted terminal hydroquinoid ring. The molecular structures of phenanthrene complexes 10, 12–14, and 16, acephenanthrene complex 19, and triphenylene complexes 20 and 21 in the solid state have been determined by X‐ray crystallography. The carbonyl ligands either adopt an eclipsed (10, 12, 14, 16, 19, 20) or staggered (13, 21) exo‐conformation pointing away from the center of the phenanthrene, acephenanthrene and triphenylene ligands, respectively. The coordination of the metal atom to the hydroquinoid ring is unsymmetric with the largest metal‐carbon distances found between the chromium atom and one bridgehead carbon and the ring carbon atom bearing the bulky (t‐butyl)dimethylsilyloxy (TBDMSO) substituent.