Jui-Hsien Huang

Monomeric, Dimeric, and Trimeric Calcium Compounds Containing Substituted Pyrrolyl and Ketiminate Ligands: Synthesis and Structural Characterization

A series of monomeric, dimeric, and trimeric calcium compounds containing substituted pyrrolyl or ketiminate ligands were synthesized, and characterized by NMR spectroscopy and single crystal X-ray diffractometry. The reaction of Ca[N(SiMe(3))(2)](2)(THF)(2) with 1 equiv of [C(4)H(3)NH(2-CH(2)NEt(2))] in toluene generates the dimeric complex, [Ca{N(SiMe(3))}[mu-eta(1):eta(5)-{C(4)H(3)N(2-CH(2)NEt(2))}]](2) (1) in which two substituted pyrrolyl ligands bind two Ca centers in a eta(1) and eta(5) fashion. The reaction between Ca[N(SiMe(3))(2)](2)(THF)(2) and 2 equiv of [C(4)H(3)NH(2-CH(2)NEt(2))] in THF yields a monomeric calcium compound Ca[C(4)H(3)N(2-CH(2)NEt(2))](2)(THF)(2) (2) that exhibits a facial octahedral geometry on the central Ca atom. Similarly, the reactions of Ca[N(SiMe(3))(2)](2)(THF)(2) with 1 and 2 equiv of OCMeCHCMeNHAr (Ar = 2,6-diisopropylphenyl) generate [Ca(OCMeCHCMeNAr){N(SiMe(3))(2)}](2) (3) and [Ca(mu-OCMeCHCMeNAr)(OCMeCHCMeNAr)](2) (4), respectively. In 3, the Ca atom possesses a distorted tetrahedral geometry where as in 4, a square plane is developed by the two calcium atoms with the bridging participation of two oxygen atoms from two ketiminate ligands. The in situ reaction of OCMeCHCMeNHAr, Ca[N(SiMe(3))(2)](2)(THF)(2), and isopropyl alcohol results in a trimeric calcium alkoxide compound Ca(3)(mu-OCMeCHCMeNAr)(2)(OCMeCHCMeNAr)(mu(3)-O-(i)Pr)(2)(mu(2)-O-(i)Pr) (5). Compounds 1, 2, and 5 showed good catalytic activity in the ring-opening polymerization of epsilon-caprolactone and l-lactide.

A New Type of Asymmetric Tridentate Pyrrolyl-Linked Pincer Ligand and Its Aluminum Dihydride Complexes

The new pyrrolyl-linked pincer-type ligand, [C(4)H(2)NH(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))] (1), that has been employed conveniently in high yield by treatment of (2-t-butylaminomethyl)pyrrole with 1 equiv of formaldehyde and dimethylamine hydrochloride each in diethylether and its corresponding aluminum derivative, [C(4)H(2)N(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))]AlH(2) (2), that has been generated from Me(3)N.AlH(3) using diethylether as a solvent are described. Furthermore, reactions of 2 with 2 equiv of either 1,3-diphenylpropane-1,3-dione in diethylether or phenyl thioisocyanate in dichloromethane interestingly formed [C(4)H(2)N(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))]Al(PhCOCHCOPh)(2) (3) and [C(4)H(2)N(2-CH(2)NH(t)Bu)(5-CH(2)NMe(2))]Al(SCHNPh)(2) (4), respectively, following deprotonation or hydroalumination reaction kinetics under a dry nitrogen environment. All of the compounds have been subjected to the X-ray diffraction technique in the solid state as well as characterized by NMR spectra.

Aluminium complexes containing bidentate and symmetrical tridentate pincer type pyrrolyl ligands: synthesis, reactions and ring opening polymerization.

A series of aluminium derivatives containing substituted bidentate and symmetrical tridentate pyrrolyl ligands, [C(4)H(3)NH(2-CH(2)NH(t)Bu)] and [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)], in toluene or diethyl ether were synthesized. Their reactivity and application for the ring opening polymerization of ε-caprolactone have been investigated. The reaction of AlMe(3) with one equiv. of [C(4)H(3)NH(2-CH(2)NH(t)Bu)] in toluene at room temperature affords [C(4)H(3)N(2-CH(2)NH(t)Bu)]AlMe(2) (1) in 70% yield by elimination of one equiv. of methane. Interestingly, while reacting AlMe(3) with one equiv. of [C(4)H(3)NH(2-CH(2)NH(t)Bu)] in toluene at 0 °C followed by refluxing at 100 °C, [{C(4)H(3)N(2-CH(2)N(t)Bu)}AlMe](2) (2) has been isolated via fractional recrystalliztion in 30% yield. Similarly, reacting AlMe(3) with two equiv. of C(4)H(3)NH(2-CH(2)NH(t)Bu) generates [C(4)H(3)N(2-CH(2)NH(t)Bu)](2)AlMe (3) in a moderate yield. Furthermore, complex 1 can be transformed to an aluminium alkoxide derivative, [C(4)H(3)N(2-CH(2)NH(t)Bu)][OC(6)H(2)(-2,6-(t)Bu(2)-4-Me)]AlMe (4) by reacting 1 with one equiv. of HOC(6)H(2)(-2,6-(t)Bu(2)-4-Me) in toluene via the elimination of one equiv. of methane. The reaction of AlR(3) with one equiv. of [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)] in toluene at room temperature affords [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)]AlR(2) (5, R = Me; 6, R = Et) in moderate yield. Surprisingly, from the reaction of two equiv. of [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)] with LiAlH(4) in diethyl ether at 0 °C, a novel complex, [C(4)H(2)N(2-CH(2)N(t)Bu)(5-CH(2)NH(t)Bu)](2)AlLi (7) has been isolated after repeating re-crystallization. Furthermore, reacting one equiv. of C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2) with AlH(3)·NMe(3) in diethyl ether generates an aluminium dihydride complex, [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)]AlH(2) (8), in high yield. Additionally, treating 8 with one equiv. of HOC(6)H(2)(-2,6-(t)Bu(2)-4-Me) in methylene chloride produces [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)][OC(6)H(2)(-2,6-(t)Bu(2)-4-Me)]AlH (9) with the elimination of one equiv. of H(2). The aluminium alkoxide complex 4 shows moderate reactivity toward the ring opening polymerization of ε-caprolatone in toluene.

Zinc and copper coordination polymers with 4,4′-bipyridine and 2-sulfoterephthalate: infinite polypseudorotaxane and unprecedented (3,4,4)-connected trinodal topology

The work presents the first example of employing a template group in a bifunctional ligand to construct an infinite polypseudorotaxane, in which 2D undulated sql anionic sheets are penetrated by 1D linear cationic chains. The bifunctional ligand also leads to the formation of an unprecedented 3D (3,4,4)-connected network with {4.72}2{4.73.8.9}2{72.93.11} topology.

Aluminum Compounds Containing η1- and/or η5-Bidentate Dianionic Pyrrolyl–Methylamide Ligands

A series of dialuminum compounds have been synthesized and their reactivity and application for lactide polymerization have been studied. The reaction of AlH3 x NMe3 with [C4H3NH(2-CH2NHtBu)] in diethyl ether generated a dimeric aluminum hydride compound, [[[C4H3N(2-CH2NtBu)]AlH]2] (1). The structure of 1 was confirmed by spectroscopy of a deuterated analogue of 1 with an Al--D function. Direct treatment of [C4H3NH(2-CH2NHtBu)] with LiAlH4 in diethyl ether resulted in colorless crystals of [[Li[micro-eta1:eta5-C4H3N(2-CH2NtBu)]2Al]2] (2) in 80 % yield after recrystallization from a toluene solution. The micro-eta1:eta5-pyrrolyl protons exhibit high-field shifts at delta=5.73, 6.15, and 6.72 comparable to a similar eta5-bonding mode in the literature. Treatment of 1 with 1 equiv acetone oxime or acetone in dichloromethane gave [[[C4H3N(2-CH2NtBu)]Al[varkappaO,varkappaN-(ON==CMe2)]]2] (3) and [[[C4H3N(2-CH2NtBu)]Al(O--CHMe2)]2] (4) in 67 % and 60 % yield, respectively. Compounds 1-4 have been characterized by X-ray diffractometry and were used as catalysts for epsilon-caprolactone polymerization.

End-to-End Thiocyanato-Bridged Helical Chain Polymer and Dichlorido-Bridged Copper(II) Complexes with a Hydrazone Ligand: Synthesis, Characterisation by Electron Paramagnetic Resonance and Variable-Temperature Magnetic Studies, and Inhibitory Effects on Human Colorectal Carcinoma Cells

The reactions of the tridentate hydrazone ligand, N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide (HL), obtained by condensation of 2-acetylpyridine with acetic hyadrazide, with copper nitrate trihydrate in the presence of thiocyanate, or with CuCl2 produce two distinct coordination compounds, namely a one-dimensional helical coordination chain of [CuL(NCS)]n (1) units, and a doubly chlorido-bridged dinuclear complex [Cu2L2Cl2] (2) (where L=CH3C(O)=N–N=CCH3C5H4N). Single-crystal X-ray structural determination studies reveal that in complex 1, a deprotonated hydrazone ligand L− coordinates a copper(II) ion that is bridged to two neighbouring metal centres by SCN− anions, generating a one-dimensional helical coordination chain. In complex 2, two symmetry-related, adjacent copper(II) coordination entities are doubly chlorido-bridged, producing a dicopper entity with a Cu⋅⋅⋅Cu distance of 3.402 (1) Å. The two coordination compounds have been fully characterised by elemental analysis, spectroscopic techniques including IR, UV–vis and electron paramagnetic resonance, and variable-temperature magnetic studies. The biological effects of 1 and 2 on the viability of human colorectal carcinoma cells (COLO-205 and HT-29) were evaluated using an MTT assay, and the results indicate that these complexes induce a decrease in cell-population growth of human colorectal carcinoma cells with apoptosis.

Deprotonation and reductive addition reactions of hypervalent aluminium dihydride compounds containing substituted pyrrolyl ligands with phenols, ketones, and aldehydes

The reactivities of [C4H2N(CH2NMe2)2]AlH2 (1) with primary and secondary amines, phenols, ketones, and phenyl isothiocyanate were examined. Reactions of 1 with one or two equivalents of 2,6-dichloroaniline in methylene chloride generated [C4H2N(CH2NMe2)2]AlH(NHC6H3-2,6-Cl2) (2) and [C4H2N(CH2NMe2)2]Al(NHC6H3-2,6-Cl2)2 (3), respectively, following hydrogen elimination. Similarly, the reactions of 1 with one or two equivalents of carbazole afforded [C4H2N(CH2NMe2)2]AlH(NC12H8) (4) or [C4H2N(CH2NMe2)2]Al(NC12H8)2 (5) by deprotonating the acidic N-H of carbazole. Reacting 1 with one equivalent of 2,6-diisopropylphenol in diethyl ether formed an aluminium phenoxo compound [C4H2N(CH2NMe2)2]AlH(OC6H3-2,6-iPr2) (6), by deprotonation of phenol as well with the elimination of one equivalent hydrogen. Further reaction of 6 with one equivalent of 2,4,6-trimethylacetophenone in methylene chloride generated [C4H2N(CH2NMe2)2]Al(OC6H3-2,6-iPr2)[OC(=CH2)(C6H2-2,4,6-Me3)] (7) by deprotonating the methyl proton of the acetophenone. Similar deprotonation occurred when 1 reacted with two equivalents of 2,4,6-trimethylacetophenone in methylene chloride to generate [C4H2N(CH2NMe2)2]Al[OC(=CH2)(C6H2-2,4,6-Me3)]2 (8). Compounds [C4H2N(CH2NMe2)2]Al(OCHPh2)2 (9), and [C4H2N(CH2NMe2)2]Al(SCHNPh)2 (10) could also be obtained by reacting 1 with two equivalents of benzophenone and phenyl isothiocyanate, respectively through hydroalumination. The 1H NMR spectra of 10 showed broad signals for the CH2N and NMe2 groups, which represent dynamical fluctuations of the molecules in solution state. The estimated energy barrier (DeltaG(c)(double dagger)) from the coalescence temperature for the fluctuation was estimated at 17.1 Kcal mol(-1). The solid-state structures of compounds 2, 3, 5, 7, 9, and 10 have been determined.

Synthesis and characterization five-coordinate molybdenum compounds bearing bi- or tridentate substituted pyrrole ligands: molecular structures of {Mo(NC6H3Pri2-2,6)2R[NC4H3(CH2NMe2)-2]} and {Mo(NC6H3Pri2-2,6)2Cl[NC4H2(CH2NMe2)2-2,5]}, where R=Cl, Me, Bu

Reacting [Mo(NC6H3Pri2-2,6)2Cl2(dme)] with 1 equiv. of Li [NC4H3(CH2NMe2)-2] in diethyl ether at −78 °C yields a red crystalline solid of {Mo(NC6H3Pri2-2,6)2Cl[NC4H3(CH2NMe2)-2]} 1 in 86% yield. Alkylation of 1 with RLi in diethyl ether generates {Mo(NC6H3Pri2-2,6)2R[NC4H3(CH2NMe2)-2]} (2a, R=Me; 2b, R=Bu) in high yield. Similarly, reacting [Mo(NC6H3Pri2-2,6)2Cl2(dme)] with 1 equiv. of Li[NC4H2(CH2NMe2)2-2,5] in diethyl ether at −78 °C affords dark red crystals of {Mo(NC6H3Pri2-2,6)2Cl[NC4H2(CH2NMe2)2-2,5]} 3 in 92% yield, in which one NMe2 unit of the pyrrole ligand of 3 coordinates to molybdenum whilst the other one dangles outside the coordination sphere. Variable-temperature 1H NMR study of 3 reveals fluxional behavior of the two NMe2 units of the pyrrole ligand. The activation energy of the fluxionality has been determined as ΔG≠=10.5 kcal mol−1. Compounds 1, 2a, 2b and 3 have been characterized by NMR spectroscopy and X-ray crystallography.

Dichlorido{N′-[1-(2-pyridin-2-yl)ethyl­idene]acetohydrazide-κ2N′,O}copper(II)

In the title compound, [CuCl2(C9H11N3O)], the CuII atom is in a distorted square-pyramidal CuCl2N2O coordination geometry. The tridentate acetohydrazide ligand chelates in a meridional fashion. The chloride ligand in the axial position forms a long Cu—Cl distance of 2.4892 (9) Å. In contrast, the Cu—Cl distance from the equatorial chloride ligand is much shorter [2.2110 (7) Å]. Intermolecular N—H⋯Cl and C—H⋯Cl hydrogen bonds link the complexes into a three-dimensional network.

Discrete and polymeric complexes formed from cobalt(II), 4,4′-bipyridine and 2-sulfoterephthalate: synthetic, crystallographic and magnetic studies

A series of five coordination compounds, namely, {[Co3(stp)2(bipy)(H2O)4]·2H2O}n, (1), {[Co3(stp)2(bipy)5(H2O)6]·4H2O}n, (2), [Co3(stp)2(bipy)4(H2O)10]·8H2O, (3), [Co(Hstp)2(Hbipy)2], (4) and {[Co(stp)2(H2O)2][Co(bipy)2(H2O)4]}·2Hbipy·2H2O, (5) have been synthesised hydrothermally, through the reaction of different molar ratios of 2-sulfoterephthalic acid monosodium salt, Na(H2stp), cobalt(II) nitrate hexahydrate and the N-donor ancillary co-ligand 4,4′-bipyridine (bipy). Due to the combination of the multiple potential coordination modes of the stp ligand and the bipy co-ligand, the products are structurally and topologically diverse with the connectivities of the materials dependent on the ratios of starting materials employed. Single-crystal X-ray diffraction studies show that compound 1 is a three-dimensional coordination polymer, compound 2 consists of infinite one-dimensional zig-zag chains, compound 3 is a discrete trinuclear complex, compound 4 is a discrete mononuclear complex and compound 5 is an ionic solid consisting of both cobalt containing cations and anions. Magnetic studies show that the Co(II) ions in 1 are strongly coupled, while 2, 3 and 5 show insignificant coupling due to larger metal–metal separations. Modelling required the introduction of zero field splitting parameters due to orbital angular momentum contributions in these cases.