Tricarbonylchromium Complexes Research Articles

Chromium Tricarbonyl and Chromium Benzene Complexes of Graphene, Their Properties, Stabilities, and Inter‐Ring Haptotropic Rearrangements – A DFT Investigation

AbstractThe structures, electronic properties, stabilities, mechanisms, and activation barriers of the intramolecular inter‐ring haptotropic rearrangements (η6,η6‐IRHRs) of chromium tricarbonyl and chromium benzene complexes of graphene were modeled by DFT calculations. All of the above calculated characteristics are in good agreement with the experimental data for related complexes with ultralarge, large, and medium‐sized polyaromatic ligands (PALs). Generally η6,η6‐IRHRs between isomer complexes with organometallic groups (OMGs) in different positions in graphene ligand proceeds via η3‐transition states with activation barriers considerably lower (<25 kcal/mol) than those of the corresponding rearrangements in medium‐sized PALs (>30 kcal/mol). This could be explained by the reduction of electron density and the increase of electron mobility inside graphene molecules, which weaken metal–ligand bonds and facilitate rearrangements.

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.

ChemInform Abstract: Asymmetric Transformations by Deprotonation Using Chiral Lithium Amides

AbstractReview: 392 refs.

Chemistry of unsaturated arenetricarbonylchromium compounds 1. Reaction of (η6-arene)tricarbonylchromium complexes of nitrones with methyl phenylpropiolate

The reactions of nitrones of the composition (CO)3CrC6H5CH=N+(O−)R (R = Me, Ph, or But) with substituted acetylene were studied. The reactions proceed with high regioselectivity and give 4-isoxazolines (yields 50–60%). The composition and structures of these products were characterized by physicochemical methods. The reactions also afford (η6-benzaldehyde)tricarbonylchromium, coordinated Schiff bases, and azoxy derivatives as thermal decomposition products of the starting nitrones. The reactions of uncoordinated nitrones with methyl phenylpropiolate were also investigated. These reactions produce 4-isoxazolines along with cyclic substituted isoxazolinones.

ChemInform Abstract: Gold(I)‐Catalyzed Asymmetric Induction of Planar Chirality by Intramolecular Nucleophilic Addition to Chromium‐Complexed Alkynylarenes: Asymmetric Synthesis of Planar Chiral (1H‐Isochromene and 1,2‐Dihydroisoquinoline)chromium Complexes.

Gold(I)-catalyzed asymmetric intramolecular cyclization of prochiral 1,3-dihydroxymethyl-2-alkynylbenzene or 1,3-bis(carbamate)-2-alkynylbenzene tricarbonylchromium complexes with axially chiral diphosphine ligand gave planar chiral tricarbonylchromium complexes of 1H-isochromene or 1,2-dihydroisoquinoline with high enantioselectivity. An enantiomeric excess of the planar chiral arene chromium complexes was largely affected by a combination of axially chiral diphosphine(AuCl)2 precatalysts and silver salts. In the case of 1,3-dihydroxymethyl-2-alkynylbenzene chromium complexes, a system of segphos(AuCl)2 with AgBF4 resulted in the formation of the corresponding antipode.

A successful DFT calculation of carbon-13 NMR chemical shifts and carbon–fluorine spin–spin coupling constants in (η6-fluoroarene)tricarbonylchromium complexes

Carbon-13 isotropic shielding constants and C–F spin–spin coupling constants for fluorobenzene, 3- and 4-dimethylaminofluorobenzene as well as for their tricarbonylchromium complexes have been calculated using DFT methods.

Gold(I)-Catalyzed Asymmetric Induction of Planar Chirality by Intramolecular Nucleophilic Addition to Chromium-Complexed Alkynylarenes: Asymmetric Synthesis of Planar Chiral (1H-Isochromene and 1,2-Dihydroisoquinoline)chromium Complexes

Gold(I)-catalyzed asymmetric intramolecular cyclization of prochiral 1,3-dihydroxymethyl-2-alkynylbenzene or 1,3-bis(carbamate)-2-alkynylbenzene tricarbonylchromium complexes with axially chiral diphosphine ligand gave planar chiral tricarbonylchromium complexes of 1H-isochromene or 1,2-dihydroisoquinoline with high enantioselectivity. An enantiomeric excess of the planar chiral arene chromium complexes was largely affected by a combination of axially chiral diphosphine(AuCl)2 precatalysts and silver salts. In the case of 1,3-dihydroxymethyl-2-alkynylbenzene chromium complexes, a system of segphos(AuCl)2 with AgBF4 resulted in the formation of the corresponding antipode.

Molecular polarizability of the organic substances and their complexes: LX. Molecular volume and spatial structure of the series of heterocycles, their structurally nonrigid derivatives, and chromium tricarbonyl π-complexes in solutions

We have analyzed the molar volumes and structures in solutions of a series of azines, azoles, conformationally nonrigid bis(2-substituted benzimidazol-1-yl)methanes, and chromium tricarbonyl complexes of arenes. For most of the compounds, the rules of molar volume additivity with respect to the bonds and groups increments hold. Molecules of bis(2-substituted benzimidazol-1-yl)methanes exist in the form of conrotatory comformers with aryl fragments being out of the plane of bridging NCN bond angle. Strong linear correlations between the molar volume and molar refraction have been revealed within the studied compounds classes. In the case of chromium tricarbonyl complexes of arenes, the coordination bond polarity has increased with growing π-donor ability of the ligand, the molar volume increment of Cr(CO)3 has increased as well, due to transfer of π-electron density from the ligand. The simplification of dipole moment and Kerr constant determination has been demonstrated.

Disila‐Galaxolide and Derivatives: Synthesis and Olfactory Characterization of Silicon‐Containing Derivatives of the Musk Odorant Galaxolide

A series of silicon-containing derivatives of the polycyclic musk odorant galaxolide (4 a) was synthesized, that is, disila-galaxolide ((4RS,7SR)-4 b/(4RS,7RS)-4 b), its methylene derivative rac-9, and its nor analogue rac-10. The tricyclic title compounds with their 7,8-dihydro-6,8-disila-6 H-cyclopenta[g]isochromane skeleton were prepared in multistep syntheses by using a cobalt-catalyzed [2+2+2] cycloaddition of the mono- yne H2C=CHCH2 OCH2 C≡CB(pin) (B(pin)=4,4,5,5-tetramethyl-1,3,2-di- oxaborolan-2-yl) with the diynes H2C=C[Si(CH3 )2 C≡CH]2 or H2C- [Si(CH3)2 C≡CH]2 as the key step. Employing [Cr(CO)3 (MeCN)3 ] as an auxiliary, the disila-galaxolide diastereomers (4RS,7SR)-4 b and (4RS,7RS)-4 b could be chromatographically separated through their tricarbonylchromium(0) complexes, followed by oxidative decomplexation. The identity of the title compounds and their precursors was established by elemental analyses and multinuclear NMR spectroscopic studies and in some cases additionally by crystal structure analyses. Compounds (4RS,7SR)-4 b, (4RS,7RS)-4 b, rac-9, and rac-10 were characterized for their olfactory properties, including GC-olfactory studies of the racemic compounds on a chiral stationary phase. As for the parent galaxolide stereoisomers 4 a, only one enantiomer of the silicon compounds (4RS,7SR)-4 b, (4RS,7RS)-4 b, rac-9, and rac-10, smelt upon enantioselective GC-olfactometry, which according to the elution sequence is assumed to be also (4S)-configured as in the case of the galaxolide stereoisomers. The disila-analogues (4S,7R)-4 b and (4S,7S)-4 b were, however, about one order of magnitude less intense in terms of their odor threshold than their parent carbon compounds (4S,7R)-4 a and (4S,7S)-4 a. The introduction of a 7-methylene group in disila-galaxolide (4 b→rac-9) improved the odor threshold by a factor of two. With the novel silicon-containing galaxolide derivatives, the presumed hydrophobic bulk binding pocket of the corresponding musk receptor(s) could be characterized in more detail, which could be useful for the design of novel musk odorants with an improved environmental profile.

1,3-Dipolar cycloaddition reaction of nitrone η6-(arene)chromium tricarbonyl complexes with styrene and η6-(styrene)chromium tricarbonyl

The products of 1,3-dipolar cycloaddition of the nitrone-type η6-(arene)chromium tricarbonyl complexes (CO)3CrC6H5CH=N+(O−)R, where R = Me, Ph, But, with styrene and η6-(styrene)chromium tricarbonyl were obtained and characterized by a combination of physicochemical methods. This type of reactions proceeded with very high regio- and stereoselectivity to exclusively form cis-2,3,5-tri-substituted isoxazolidines.

Synthesis of tricarbonylchromium complexes of 4-aryl-1,4-dihydropyridines

Tricarbonylchromium complexes of 4-aryl-1,4-dihydropyridines have been synthesized both under standard thermodynamic conditions using Cr(CO)6 and under milder complexation conditions using more labile [Cr(CO)3(NH3)3] and (η6-naphthalene)Cr(CO)3. Selective complexation of the Cr(CO)3 on the aryl ring in the presence of a 1,4-dihydropyridine ring was achieved.

Stoichiometric C–H arylation of tricarbonyl(arene)chromium complexes bearing pyridine directing groups

Differentially substituted Cr(CO)3-complexed aryl pyridines have been shown to readily undergo stoichiometric palladation and subsequent arylation using boronic acid nucleophiles. The positioning of the aryl substituents has been shown to be key in governing substrate reactivity, whereby sterically congested compounds prevent the geometry required for cyclometallation.

Synthesis of new η6-(arene) chromium tricarbonyl complexes of isoxazolidines by 1,3-dipolar cycloaddition

The 1,3-dipolar cycloaddition products of C,N-disubstituted nitrones and different in situ prepared mono-N-substituted nitrones to η6-(styrene) chromium tricarbonyl and η6-(ethyl cynnamate) chromium tricarbonyl were synthesized and characterized by HPLC, IR, 1H NMR spectroscopy, and mass spectrometry. The resulted isoxazolidines were produced with a full regioselectivity and high stereoselectivity reached 100% in most cases.

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.

Synthesis and structure of tricarbonyl(η6-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

A series of 15 glycoside-derived tricarbonyl(η6-arene)chromium complexes were prepared in 19–87% yield by heating fully acetylated or methylated aryl O-, S-, N- and C-glycosides of D-glucopyranose and D-mannopyranose with hexacarbonylchromium. All tricarbonylchromium complexes were fully characterized. The structures of nine crystalline complexes were determined by X-ray diffraction, revealing unusual intra- and intermolecular nonclassical hydrogen bonds.

Attempts Directed towards the Synthesis of Intermediate (Aryne)chromium Complexes from Aryl Triflates and from (Haloarene)chromium Complexes

AbstractThe generation of (η6‐aryne)chromium complexes as reactive intermediates was investigated in two ways. Although earlier attempts directed towards triflate eliminations from a variety of tricarbonyl(phenyl triflate)chromium complexes had failed, more electron‐rich phenyl triflate complexes were considered. This was accomplished either by substitution with two methoxy groups in the arene ligand or by replacement of one of the three carbonyl ligands of the tricarbonylchromium complex with triphenylphosphane. However, the attempted elimination still did not take place; in spite of the increased electron densities in the aromatic ligands, anionic thia‐Fries rearrangements were observed in high yields at –78 °C. As an alternative, elimination of lithium fluoride was tested. Tricarbonyl(2‐lithiofluorobenzene)chromium(0) was generated by tin/lithium exchange. After hydrolytic workup, tricarbonyl(fluorobenzene)chromium was obtained as the main product, indicating that the lithiation step had been successful. A dimeric side product provided evidence for the intermediacy of (benzyne)tricarbonylchromium.

The First Benzo[1,2:4,5]dicyclobutenones and Their Tricarbonylchromium Complexes

AbstractTreatment of 1,4‐dibromo‐2,5‐dimethoxybenzene (6) with NaNH2 followed by 1,1‐dimethoxyethene (7) afforded the bi‐ and tricyclic acetals such as 8 and 9 as the products of [2+2] cycloadditions of the intermediate arynes. After chromatographic separation and acetal hydrolysis the title compounds 15 and 16 were obtained in high yields as the first representatives of their class. Complexation of the acetals with Cr(CO)6 gave the corresponding tricarbonylchromium complexes in excellent yields. Subsequent deacetalization afforded the diketone complexes 18 and rac‐20, which underwent stereoselective nucleophilic diadditions at –78 °C.

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.

ChemInform Abstract: Condensation Reactions of Planar Chiral Tricarbonyl‐chromium‐complexed Benzylic Alcohols and Acetates with Reactive Arenes.

AbstractCondensation reactions of planar chiral tricarbonyl chromium complexes containing one or two reactive benzylic sites with various aryl compounds under mild reaction conditions using BF3·OEt2 as catalyst are presented.

Intra- and inter-ring haptotropic rearrangements in (naphthalene and anthracene)nickel complexes: a DFT study

Density functional quantum chemical calculations of the mechanisms of metallotropic η2,η2-intra- and η2,η2-inter-ring haptotropic rearrangements (HRs) in 16e zero-valent η2-(naphthalene and anthracene)nickel complexes involving migration of the organometallic group within the same ring or from one aromatic ring to the other were carried out. The structures of the initial complexes, transition states, and intermediates were determined. The intra-ring HRs in these systems proceed via low-energy η4-cis-butadiene transition states. The inter-ring HRs proceed along the periphery of the naphthalene and anthracene ligands via high-energy η3-allylic transition states. In contrast to well-investigated η6,η6-inter-ring HRs in (naphthalene and anthracene)tricarbonylchromium complexes, the activation barriers to the η2,η2-inter-ring HRs in the corresponding nickel complexes are much lower. Transition states of these processes are characterized by higher hapticity compared to the initial complexes. This also distinguishes the nickel complexes from the corresponding Cr(CO)3 complexes for which the hapticities of transition states of the η6,η6-inter-ring HRs are lower than those of the initial complexes. The calculated activation barriers to the η2,η2-intra-ring HRs in the (naphthalene and anthracene)nickel complexes as well as the barrier to rotation of the organonickel group in the naphthalene complex are in good agreement with the experimental data. The calculated barriers to the η2,η2-inter-ring HRs in the naphthalene and anthracene complexes are 3–5 kcal mol−1 lower than the experimental values. This is probably due to the competition between two mechanisms of this process, a low-energy intramolecular mechanism and a high-energy intermolecular dissociative mechanism.