Xue-Zhong Zheng

Syntheses, structures and catalytic activity for Friedel-Crafts reactions of substituted indenyl rhenium carbonyl complexes

Abstract The complexes [(η5-C9H6R)Re(CO)3] [R = nBu (8), tBu (9), CH(CH2)4 (10), Ph (11), Bz (12), 4-methoxyphenyl (13), 4-chlorophenyl (14)] were synthesized by refluxing substituted indenyl ligands [C9H7R] [R = nBu (1), tBu (2), CH(CH2)4 (3), Ph (4), Bz (5), 4-methoxyphenyl (6), 4-chlorophenyl (7)], and Re2(CO)10 in decalin. The molecular structures of 9, 10, 12, and 13 were determined by X-ray diffraction analysis. These four crystals have similar molecular structures of the mononuclear carbonyl complex. In each of these molecules, Re is η5-coordinated to the five-membered ring of the indenyl group. Complexes 8–14 have catalytic activity for Friedel-Crafts reactions of aromatic compounds with a variety of alkylation and acylation reagents. Compared with traditional catalysts, these mononuclear metal carbonyl complexes have obvious advantages such as high activities, mild reaction conditions, high selectivity, and environmentally friendly chemistry.

Reactivity of a trinuclear ruthenium complex involving C–H activation and insertion of alkene

A novel pyridyl-substituted indenyl trinuclear ruthenium complex, {μ2-η5:η1-(C5H3N-6-Br)(C9H5)}Ru3(CO)9 (1), was synthesized by thermal treatment of 1-(6-bromo-2-pyridyl)indene with Ru3(CO)12 (1 : 1 mol ratio) in refluxing heptane and its reactivity with pyridine derivatives, toluene, indene, fluorene, phenylethylene and divinylbenzene was studied. The reaction of 1 with 5-fold excess of 1-(6-bromo-2-pyridyl)indene gave two products, complex {η5-(C5H3N-6-Br)(C9H5)}{η1-(C5H3N)(C9H6)}Ru2(CO)4 (2) and substituted dibenzfulvalene (3). Reaction of 1 in refluxing toluene afforded an unexpected complex {μ3-η6:η3:η1-(C5H3N-6-Br)(C9H5)}Ru3(CO)7 (4), via the loss of two CO groups. Reaction of 1 with indene in refluxing heptane afforded a known complex [{(η5-C9H7)Ru(CO)2}2] (5). The reaction of 1 with fluorene in refluxing heptane afforded complex {μ3-η6:η3:η1-(C5H3N-6-Br)(C9H5)}Ru3(CO)7 (4), fluorene was not involved in the reaction, indicating that the reactivity of fluorene is low. The reactions of 1 with phenylethylene or divinylbenzene in refluxing toluene gave the dinuclear ruthenium complexes {η5-(C5H3N-6-Br)(C9H5CHCH2Ph)}Ru2(CO)5 (6) and {η5-(C5H3N-6-Br)(C9H5CHCH2PhCHCH2)}Ru2(CO)5 (7), respectively. These complexes have been characterized by elemental analysis, IR, and 1H NMR spectroscopy. The molecular structures of 1–6 were determined by X-ray diffraction. The density functional theoretical calculations on the electronic structure of complex 1 give an illustration to its high reactivity.

Synthesis and structures of bridged biscyclopentadienyl diiron complexes

Three diiron carbonyl complexes, namely [(η5-C5H4)(η3-C(CH2)2)]Fe2(CO)5 (1), [(C2H5)2C(η5-C5H4)2]Fe2(μ-CO)2(CO)2 (2), and [(CH2)4C(η5-C5H4)(η5-C5H3)(C5H9)]Fe2(μ-CO)2(CO)2 (3), have been synthesized by the reactions of C5H4C(Me)2, C5H4C(Et)2, and C5H4C(CH2)4, respectively, with Fe(CO)5 in refluxing xylene. The complexes have been characterized by elemental analysis, IR, and 1H NMR spectra. The molecular structures of the complexes have been determined by single-crystal X-ray diffraction. The structures of the complexes indicate that fulvenes can be bound to transition metal centers by diverse modes.

Five dinuclear iron carbonyl complexes based on substituted tetramethylcyclopentadienyl ligands: synthesis and crystal structures

Thermal treatment of the substituted tetramethylcyclopentadienes [C5Me4HR] [R = n-propyl (1), i-propyl (2), cyclopentyl (3), cyclohexyl (4), and 4-NMe2Ph (5)] with Fe(CO)5 gave five new substituted tetramethylcyclopentadienyl dinuclear iron carbonyl complexes, [η5-C5Me4CH2CH2CH3]2Fe2(CO)4 (6), [η5-C5Me4CH(CH3)2]2Fe2(CO)4 (7), [η5-C5Me4CH(CH2)4]2Fe2(CO)4 (8), [η5-C5Me4CH(CH2)5]2Fe2(CO)4 (9), and [(η5-C5Me4)(4-NMe2Ph)]2Fe2(CO)4 (10). The new complexes were characterized by elemental analysis, IR, and 1H NMR spectra. The molecular structures of 6, 8, 9, and 10 were determined by X-ray single crystal diffraction. Graphical Abstract

Efficient aerobic oxidation of alcohols to aldehydes and ketones using a ruthenium carbonyl complex of a tert -butyl-substituted tetramethylcyclopentadienyl ligand as catalyst

Tert-butyl-substituted tetramethylcyclopentadiene [C5HMe4tBu] was reacted with Ru3(CO)12 to prepare [(η5-C5Me4tBu)Ru(CO)(μ-CO)]2. The complex was characterized by IR, 1H NMR, 13C NMR, elemental analysis, and single-crystal X-ray diffraction. The complex was investigated as a catalyst in the aerobic oxidation of alcohols to the corresponding aldehydes and ketones in the presence of 2,2’,6,6’-tetramethylpiperidine N-oxide (TEMPO) as co-oxidant. The combination of [(η5-C5Me4tBu)Ru(CO)(μ-CO)]2 and TEMPO afforded an efficient catalytic system for the aerobic oxidation of a variety of primary and secondary alcohols, giving the corresponding carbonyl compounds in good-to-excellent yields.

Syntheses, Structures and Catalytic Activity of p-Phenylene-or p -Biphenylene-Bridged Biscyclopentadienyl Dinuclear Rhenium Carbonyl Complexes

Thermal treatment of two p -phenylene-and p -Biphenylene-bridged biscyclopentadienes (C 5 Me 4 H)E(C 5 Me 4 H) (E=C 6 H 4 , (C 6 H 4 ) 2 ) with Re 2 (CO) 10 in refluxing mesitylene gave the corresponding complexes (E)[( η 5 -C 5 Me 4 )Re(CO) 3 ] 2 (E=C 6 H 4 ( 1 ), (C 6 H 4 ) 2 ( 2 )), which were separated by chromatography, and characterized by elemental analysis, IR, 1 H NMR and 13 C NMR spectroscopy. The molecular structures of complexes 1 and 2 were characterized by X-ray crystal diffraction analysis, showing both them are monobridged biscyclopentadienyl dinuclear rhenium carbonyl complexes. In addition, the catalytic performance of complexes 1 and 2 was also tested, and it was found that both complexes were obviously active for Friedel-Crafts acylation reactions.

CCDC 1481418: Experimental Crystal Structure Determination

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Crystal structures of dimolybdenum carbonyl complexes containing the cyclopentadienyl-thienyl ligand

Reactions of thienyl side-chain-functionalized cyclopentadienyl ligands C5H5C(R1R2)C4H3S [R1 = R2 = CH3 (1); R1 = CH3, R2 = C2H5 (2); R1 = R2 = C2H5 (3); R1, R2 = (CH2)5 (4)] with Mo(CO)6 in refluxing xylene gave the corresponding cyclopentadienyl dimolybdenum carbonyl complexes: [(η5-C5H4)C(R1R2) × (C4H3S)Mo(CO)3]2 [R1 = R2 = CH3 (5); R1 = CH3, R2 = C2H5 (6); R1 = R2 = C2H5 (7); R1, R2 = (CH2)5 (8)]. They are characterized by elemental analysis, IR and 1H NMR spectra. The molecular structures of (5) and (8) are determined by single crystal X-ray diffraction.