Ji-Tao Wang

Indium(III) bromide-catalyzed preparation of dihydropyrimidinones: improved protocol conditions for the Biginelli reaction

Abstract Indium(III) bromide efficiently catalyzes the three-component coupling of β-keto esters, aldehydes and urea (or thiourea) to afford the corresponding dihydropyrimidinones. This new protocol for the Biginelli reaction includes the following important features: produces excellent yields, allows the recycling of catalyst with no loss in its activity, and leads to zero-discharge during the process. The reaction of ethyl acetoacetate, salicylaldehyde and thiuourea produced 13-ethoxycarbonyl-9-methyl-11-thioxo-8-oxa-10,12-diazatricyclo [7.3.1.02,7]-trideca-2,4-6-triene, which had its crystal structure determined by X-ray crystallography.

Novel five- and six-coordinate diorganotin(IV) complexes with bis(triazol-1-yl)alkanes: linkage coordination polymers

Abstract A novel poly(triazol-1-yl)alkane ligand, bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane CH2(3,5-Me2Tz)2, has been synthesized under phase transfer catalytic conditions. This ligand as well as bis(1,2,4-triazol-1-yl)methane CH2Tz2 and 1,2-bis(1,2,4-triazol-1-yl)ethane (CH2)2Tz2 reacts with diphenyltin(IV) halides to yield novel five- and six-coordinate diorganotin complexes. The crystal structure of (CH2Tz2)SnPh2Br2 determined by X-ray analysis shows that bis(triazol-1-yl)methane coordinates to the tin atom through exodentate nitrogen atoms on the 4-position of triazole rings to form linkage coordination polymers, which leads to a bridging instead of a general chelating metal coordination. Possibly owing to the hindrance of methyl groups in the triazole ring of CH2(3,5-Me2Tz)2, this ligand is a weaker donor to an organotin acceptor than CH2Tz2. In the hydrolysis product [SnPh2Br2(H2O)]·(CH2(3,5-Me2Tz)2), the tin atom is five-coordinate with a trigonal bipyramid geometry, and the aqua ligand is simultaneously connected to the exonitrogen atoms of two adjacent CH2(3,5-Me2Tz) molecules through hydrogen bonding.

Indium(III) halides-catalyzed preparation of ferrocene-dihydropyrimidinones

Abstract Indium(III) halides (chloride and bromide) catalyse the three-component Biginelli coupling of ferrocenyl-1,3-diketones, aldehydes and urea (or thiourea) to give 5-ferrocenoyl-3,4-dihydropyrimidinones. 4-Ferrocenyl-3,4-dihydropyrimidinones were obtained from alkyl-acetoacetates, formylferrocene and urea. The tricyclic compound, 13-ferrocenecarbonyl-9-methyl-11-oxo-8-oxa-10,12-diazatricyclo [7.3.1.0 2,7 ]trideca-2,4-6-triene, was synthesized from 1-ferrocenyl-1,3-butanedione, salicilaldehyde and urea.

Syntheses and molecular structures of complexes formed in the reaction of dichlorobis[π-cyclopentadienyl)-dicarbonyliron]tin(IV) with polydentate o-(nuclear substituted α-hydroxybenzylidenehydrazonomethyl)phenols

Abstract Eleven complexes having the general formula, [π-C 5 H 5 Fe(CO) 2 ] 2 [RC 6 H 4 C(O)N 2 -CHC 6 H 4 O]Sn (R = H, p -NO 2 , p -Cl, p -Br, p -I, p -CH 3 , p -OCH 3 , m -NO 2 , m -OCH 3 , and 3,5-dinitro) have been synthesized. These complexes have been characterized by 1 H NMR, IR and MS, and by elemental analysis. A single crystal X-ray diffraction study (R = o -NH 2 ) confirmed their molecular structures and revealed that the o -(nuclear substituted α-hydroxybenzylidenehydrazonomethyl)phenols are tridentate planar ligands. The crystals are monoclinic, space group P 2 1 / n with a 13.495(4), b 13.058(2), c 18.311(3) A, β 94.90(2)°, V 3214.9 A 3 , Z = 4, D c 1.66 g/cm 3 . Final discrepancy factors of R = 0.033 and R w = 0.039 were obtained for 3075 observed independent reflections. The tin atom has a distorted trigonal bipyramidal coordination. SnFe bond lengths are 2.5421 and 2.5242 A (av. 2.5332 A). In these complexes, the ligands exist in the enol-form.

Synthesis of diorganotin derivatives containing asymmetric disubstituted bis(pyrazol-1-yl)methanes: X-ray crystal structures of (3-isopropylpyrazol-1-yl-5′-isopropylpyrazol-1-yl)methane diphenyltin(IV) dibromide and bis(5-isopropylpyrazol-1-yl)methane diphenyltin(IV) dibromide

Abstract The reaction of 3- tert -butylpyrazole with dibromomethane under phase-transfer catalytic conditions afforded a new ligand, bis(3- tert -butylpyrazol-1-yl)methane [CH 2 (3-Bu t Pz) 2 ]. However, the reaction of 3-isopropylpyrazole with dibromomethane under the same conditions yielded three isomers: bis(5-isopropylpyrazol-1-yl)methane [CH 2 (5-iPrPz) 2 ], (3-isopropylpyrazol-1-yl-5′-isopropylpyrazol-1-yl)methane [CH 2 (3-iPrPz-5′-iPrPz)] and bis(3-isopropylpyrazol-1-yl)methane [CH 2 (3-iPrPz) 2 ]. Although CH 2 (5-iPrPz) 2 suffered the greatest degree of steric hindrance, this ligand was obtained in highest yield. Upon treating the isomeric mixture with diorganotin halides in petroleum ether (60–90°C), the isomers were isolated in the form of diorganotin derivatives of bis(pyrazol-1-yl)methanes. The crystal structures of CH 2 (3-iPrPz-5′-iPrPz)SnPh 2 Br 2 and CH 2 (5-iPrPz) 2 SnPh 2 Br 2 determined by X-ray crystallography indicated that the isopropyl group in the 3-position of the pyrazole ring decreased the coordination ability of CH 2 (3-iPrPz-5′-iPrPz), and the average Sn–N distance in CH 2 (3-iPrPz-5′-iPrPz)SnPh 2 Br 2 (2.52 A) was longer than that in CH 2 (5-iPrPz) 2 SnPh 2 Br 2 (2.435 A).

Synthesis and structure of pentacoordinate tin(IV) complexes

Ten complexes formulated as Ph2SnL, where L is RC6H4C(O)N2CHC6H4O with R = H, p-NO2, p-Cl, p-Br, p-CH3, p-OCH3, o-NH2, m-NO2, m-OCH3, and 3,5-dinitro, have been prepared and were characterized by 1H NMR, IR, and mass spectroscopy and elemental analyses. A single crystal X-ray diffraction study of the complex with R=o-NH2 confirms the molecular structure. The crystals are triclinic, space group P1 with a 9.608(2), b 11.826(4), c 21.478(6) A, α 76.17(2), β 76.53(2), γ 88.91(2)°, V 2302.7(4) A3, Z = 4, Dc 1.52 g/cm3. The final discrepancy factors are R = 0.050 and Rw = 0.057 for 3129 observed independent reflections. The tin atom has a distorted trigonal bipyramidal coordination. The two SnO bonds of 2.073(6) and 2.116(6) A, respectively and one SnN bond (of 2.143(7) A)1 are shorter than those found in related complexes. A comparison of the IR spectra of the ligands with those of the corresponding complexes, reveals that the disappearance of the bands assigned to carbonyl unambiguously confirms that the ligands coordinate with the tin in the enol form.

Preparation and structural characterization of [RSFe2(CO)6]2S. A novel route to FeS cluster compounds containing a sulfur atom coordinated to four metal atoms

Abstract The reaction of monoanions derived from (μ-S2)Fe2(CO)6 and RMgBr (R  CH3, C2H5, C6H5CH2, p-CH3C6H4, C6H5CC) with di-acid chlorides at room temperature unexpectedly produced tetranuclear complexes of general formula [RSFe2(CO)6]2S in high yield. These complexes have been characterized by proton NMR, IR and elemental analysis. A single crystal X-ray study (for R  C2H5) has unambiguously confirmed the composition and revealed that there is a pseudotetrahedral sulfur atom bridging the four iron atoms and so joins together the two identical [RSFe2(CO)6] fragments. This compound (R  C2H5) crystallizes in the space group P212121 with a 11.875(2), b 12.920(3), c 17.020(3) A, Z = 4; Dc 1.754 g cm−3. Intensity data of 3550 independent reflections were collected in the range 2° 3σ (I)) being used in the structure refinement. When the reaction was stopped at lower temperature, the diacyl groups were found to have bridged the two monoanions.

Synthesis and reactivity of Group 6 metal carbonyl complexes containing bis(triazol-1-yl)methane: linkage coordination polymers

Abstract The reaction of bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane, CH2(3,5-Me2Tz)2, with M(CO)6 (M=Cr, Mo or W) in refluxing DME produces CH2(3,5-Me2Tz)2M(CO)4 in moderate yield. The crystal structures determined by X-ray analysis show that bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane acts as a chelating bidentate ligand with two endodentate nitrogen atoms in these complexes. Reactions of complexes CH2(3,5-Me2Tz)2M(CO)4 (M=Mo or W) with R2SnX2 (R=Ph or Me; X=Cl or Br) in a 1:1 or 1:2 ratio, respectively, only yield 1:1 adducts. In these adducts, bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane may coordinate to tin atom through exodentate nitrogen atoms on the 4-position of triazole rings to form linkage coordination polymers. Possibly owing to weak donors of 4-position exonitrogen atoms on triazole rings to organotin acceptors, the dissociation of these adducts in solution could exist. Adduct of CH2(3,5-Me2Tz)2W(CO)4·SnPh2Br2 absorbs one water molecule while crystals are growing and becomes the hydrolysis product [SnPh2Br2(H2O)]·(CH2(3,5-Me2Tz)2W(CO)4), which is characterized by X-ray crystallography, indicating that tin atom is five coordinate with a trigonal bipyramid geometry, the water molecule coordinates to the tin atom, and is simultaneously connected to the exonitrogen atoms on the 4-position of triazole rings of two adjacent CH2(3,5-Me2Tz)2W(CO)4 units through hydrogen bonds to form linkage coordination polymers, in which two coordination modes are observed.

Synthesis, structures and electrochemical properties of Group 6 metal carbonyl complexes containing ferrocenylpyrazole ligands

Abstract A series of carbonylchromium, molybdenum and tungsten complexes containing ferrocenylpyrazole ligands, (M(CO)5L) (M=Cr, Mo or W; L represents ferrocenyl pyrazole), have been prepared by the photochemical reactions of ferrocenylpyrazole ligands with M(CO)6. Their electrochemical behaviors have also been investigated by cyclic voltammetry, indicating that chromium complexes exhibit two one-electron reversible or quasi-reversible couples, while molybdenum and tungsten complexes have one reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for the molybdenum or tungsten center. The crystal structures of 3-ferrocenylpyrazole pentacarbonyltungsten (3) and 3-methyl-5-ferrocenylpyrazole pentacarbonyltungsten (6) are determined by X-ray diffraction method, indicating that both 3(5)-ferrocenylpyrazole and 3(5)-methyl-5(3)-ferrocenylpyrazole act as a monodentate ligand, and the central metal of W is six-coordinate with a quasi-octahedral coordination geometry in both complexes. Complex 3 is linked into a one-dimensional chain in solid through intermolecular hydrogen bonds formed by metal carbonyl as hydrogen bond acceptors, while complex 6 forms a dimer by similar intermolecular hydrogen bond interactions. The N–H⋯O distances in complexes 3 and 6 are 2.932(11) and 2.900 A, respectively. All new compounds have been characterized by elemental analyses, IR, 1H-NMR. 13C-NMR spectra of molybdenum and tungsten complexes have also been determined.

Synthesis and crystal structures of Group 6 metal carbonyl complexes containing S-rich bis(pyrazol-1-yl)methane ligands

Abstract The reaction of 3(5)-methylthio-5(3)-phenylpyrazole with dibromomethane under phase-transfer catalytic conditions only affords a new ligand, bis(3-phenyl-5-methylthiopyrazol-1-yl)methane. However, the reaction of 3(5)-methylthio-5(3)-p-methoxyphenylpyrazole or 3(5)-methylthio-5(3)-tert-butylpyrazole with dibromomethane under the same conditions yields three isomers, respectively, indicating that the substituents significantly affect the steric and electronic properties of pyrazole ring during the formation of ligands. Treatment of these potential polydentate ligands with M(CO)6 (M=Cr, Mo or W) under UV irradiation at room temperature affords (NN)M(CO)4 derivatives, in which some complexes contain asymmetric substituted bis(pyrazol-1-yl)methane ligands. The X-ray crystal structure analyses indicate that the sulfur atoms in these complexes do not take part in the coordination to the metal centers, and S-rich bis(pyrazol-1-yl)methanes actually act as bidentate chelating ligands by two nitrogen atoms. It is also interesting that in order to reduce the repulsion of methyl groups with carbonyls, the methyl groups in these complexes are oriented away from the metal centers.