Synthesis, Characterization, Structure And Catalytic Capability Of Chiral Transition Metal Schiff-base Complexes

Transition metal Schiff-base complexes had a wide application in the field of catalytic asymmetric synthesis. In particular, the Jacobsen-Katsuki epoxidation system, marked by (salen*)Mn(III) structure (salen*=N,N'-bis(salicylidene)-(chiral)ethylenediamine dianion), had emerged as a highly reactive and a highly enantioselective catalytic system for the asymmetric epoxidation of unfunctionalized alkenes. To get a better insight into the relation between the catalyst structure and its catalytic activity, four series of chiral Schiff-base ligands and their transition metal complexes were designed and synthesized, and the Mn(III) and Ni(II) complexes were then employed in the catalytic asymmetric epoxidation of unfunctionalized alkenes. Four series of chiral Schiff-base ligands included: (1) the salen ligands featuring two tertiary ammonium units on the 5,5'- positions of their salen matrix; (2) the salen ligands featuring two alkoxy chains with different length on the 3,3'-positions of their salen matrix; (3) linear dimeric chiral salen ligands with different length; (4) linear hybrid trimeric salen ligands. The catalytic results indicated (1) Manganese and Nickel catalysts featuring two tertiary ammonium units on the 5,5'- positions of their salen matrix had certain inherent phase-transfer capability. After the loading of iodomethane, the quaternary ammonium units formed, and the phase-transfer capability of the catalysts become more obvious, (2) the enantioselectivity is sensitively effected by the 3,3'- substituents of the salen rings, (3) the enantioselectivity of linear dimeric (salen)Mn(III) catalysts is always lower than that of their monomeric counterparts. However, the linear dimeric (salen)Mn(III) catalysts with longer lengths could afford comparatively better enantioselectivities. To optimize the catalytic reaction conditions, a new chiral ionic liquid and a new porous coordination polymer was introduced into this catalytic system, and the catalytic results also indicated that (1) the presence of ionic liquid and porous coordination polymer could obviously accelerate the reaction, respectively, and (2) the synergetic effect of chiral ionic liquid with chiral catalysts in the catalytic reaction does actually exist.There are six parts in this thesis:1. The recent advance in the catalytic asymmetric epoxidation and its corresponding structural studies were reviewed.2. Eight chiral salen ligands featuring two tertiary ammonium units on the 5,5'-positions of their salen rings (H₂L^A) were prepared and fully characterized: (R,R)-N,N'-[2,2'-bis(nitrilomethyli-dyne)]bis[4-(methylene-N,N'-dibutylamino)-6-(1,1-dimethyl)phenolato]-1,2-cyclohexanediamine (H₂L¹), (R,R)-N,N'-[2,2'-bis(nitrilomethylidyne)]bis[4-(methylene-N,N'-dibutylamino)-6-(1,1 -dimethyl)phenolato]-1,2-diphenyldiamine (H₂L²), (R,R)-N,N'-[2,2 '-bis(nitrilomethylidyne)]bis [4-(methylene-N,N'-dibutylamino)-6-( 1,1 -dimethylethyl)phenolato]-1,2-cyclohexan-ediamine (H₂L³), (R,R)-N,N'-[2,2'-bis(nitrilomethylidyne)]bis[4-(methylene-N,N'-dibutylamino)-6-(1,1-dimethylethyl)phenolato]-1,2-diphenyldiamine (H₂L⁴), (R,R)-N,N'-[2,2'-bis (nitrilomethylidyne)] bis[4-(methylene-N-morpholino)-6-( 1,1 -dimethylethyl)phenolato]-1,2-cyclohexanediamine (H₂L⁵), (R,R)-N,N'-[2,2'-bis(nitrilomethylidyne)]bis[4-(methylene-N-morpholino)-6-(1,1-dimethylethyl)phenolato]-1,2-diphenyldiamine (H₂L⁶), (R,R)-N,N'-[2,2'- bis(nitrilomethylidyne)] bis[ 1 -(benzo-1,2-dioxolane-4-methylenepiperazine)-6-(1,1 -dimethylethyl)phenolato]-1,2-cyclohe xanediamine (H₂L⁷), (R,R)-N,N'-[2,2'-bis(nitrilomethylidyne)] bis[1-(benzo-1,2-dioxolane-4-methylenepiperazine)-6-( 1,1 -dimethylethyl)phenolato]-1,2-diphenyldiamine (H₂L⁸). The Mn(III) and Ni(II) complexes of these salen ligands were also prepared and fully characterized by FT-IR, UV-Vis, EA, molar conductance and polarimetric analysis. The composition of these transition metal complexes seems to be MnL^ACl·nH₂O (n=0～4.7, A=1～8), Ni(II)L^A·nH₂O (n=0～3.5, A=1～4). Based on the research on the Mannich reaction, an improved method was employed to synthesize an important intermediate (3-tert-butyl-5-chloromethyl-2-hydroxybenzaldehyde), and its single-crystal structure was also determined by X-ray crystallography. The single-crystal structure analysis revealed that the 0-H...0 hydrogen bond does exist between the formoxy group and phenol hydroxyl group. Possibly, this 0-H...0 hydrogen bond protected the formoxy group in the modification reaction of salicylaldehyde derivatives.3. Eight chiral salen ligands featuring two aloxy chains derived from the 3,3'-positions of salen matrixes (H₂L^B), including (R,R)-N,N'-(3-((2'-oxopropyl)-5-methylsalicylidene)-1,2-cyclohexanediamine (H₂L⁹), (S,S)-N,N'-(3-((2'-oxopropyl)-5-methylsalicylidene)-1,2-diphenyldiamine(H₂L¹⁰), (R,R)-N,N'-(3-((2'-oxobutyl)-5-methylsalicylidene)-1,2-cyclohexanediamine(H₂L¹¹), (S,S)-N,N'-(3-((2'-oxobutyl)-5-methylsalicylidene)-l,2-diphenyldiamine (H₂L¹²),(R,R)-N,N'-(3-((2' -oxopentyl)-5-methylsalicylidene)-1,2-cyclohexanediamine(H₂L¹³), (S,S)-N,N'-(3-((2'-oxopentyl)-5-methylsalicylidene)-1,2-diphenyldiamine(H₂L¹⁴), (R,R)-N,N'-(3-((2'-oxohexyl)-5-methylsalicylidene)-1,2-cyclohexanediamine(H₂L¹⁵)) (S,S)-N,N'-(3-((2'-oxohexyl)-5-methylsalicylidene)-1,2-diphenyldiamine(H₂L¹⁶), were prepared and fully characterized. Their Mn(III), Ni(II), Zn(II) and Cu(II) complexes were also synthesized and characterized by FT-IR, UV-Vis, EA, molar conductance, thermography and polarimetric analysis. The composition of these transition metal complexes seems to be Ni(II)L^B·nH₂O (n=0～2.2), MnL^BCl·nH₂O (n=0～2.1). The single-crystal structure of complex Ni(II)L¹⁰ was determined by X-ray crystallography. The single-crystal structure analysis revealed that the two nitrogen atoms and two phenol oxygen atoms of L¹⁰ coordinated to Ni(II) ion and form a twisted tetra-plane, therefore, two diastereoisomers (S, S, P)- and (S, S, M)- occurred in one unsymmetrical crystal unit. The subsequent CD analysis clearly indicated that this isomerization does exist in its analogous complexes with long aloxy chains of various lengths.4. Twelve linear dimeric salen ligands (H₄L^C), including 5,5-methylene di-[(R,R)-{N-salicylidine-N'-(3',5'-di-tert-butylsalicylidene)}-1,2-cyclohexanediamine] (H₄L¹⁷), 5,5-methylenedi-[(R,R)- {N-salicylidine-N'-(3' ,5'-di-tert-butylsalicylidene)}-1,2-diphenyldiamine] (H₄L¹⁸), 5,5-methylenedi-[(R,R)-{N-salicylidine-N'-(3',5'-di-tert-butylacetylphenone)}-1,2-diphenyldiamine] (H₄L¹⁹), 5,5-methylene di-[(R,R)-{N-(3-methylsalicylidine)-N'-(3',5'-di-terf-butylsalicylidene)}-1,2-cyclohexanediamine] (H₄L²⁰), 5,5-methylenedi-[(R,R)-{N-(3-methylsalicylidine)-N'-(3',5'-di-tert-butylsalicylidene)}-1 ,2-diphenyldiamine] (H₄L²¹), 5,5-methylenedi-[(R,R)-{N-(3-methylsalicylidine)-N'-(3',5'-di-tert-butylacetylphenone)}-1,2-diphenyldiamine] (H₄L²²), 5,5-methylene di-[(R,R)-{N-(3-tert-butylsalicylidine)-N'-(3',5'-di-tert-butylsalicylidene)}-1,2-cyclohexanediamine] (H₄L²³), 5,5-methylenedi-[(R,R)-{N-(3-tert-butylsalicylidine)-N'-(3',5'-di-tert-butylsalicylidene)}-1,2-diphenyldiamine] (H₄L²⁴),5,5-methylenedi-[(R,R)-{N-(3-tert-butylsalicylidine)-N'-{3',5'-di-tert-butylacetylphenone)}-1,2-diphenyldiamine] (H₄L²⁵), 5,5-(1,4-dimethylene)piperazine di-[(R,R)-{N-(3-tert-butyl salicylidine)-N'-(3',5'-di-tert-butylsalicylidene)}-1 ,2-cyclohexanediamine] (H₄L²⁶), 5,5-(1,4-dimethylene)piperazine di-[(R,R)-{N-(3-tert-butylsalicylidine)-N'-(3',5'-di-tert-butylsali cylicdene)}-1,2-diphenyldiamine](H₄L²⁷), and 5,5-(1,4-dimethylene)piperazinedi-[(R,R){N-(3-tert-butylsalicylidine)-N'-(3',5'-di-tert-butylacetylphenone)}-1,2-diphenyldiamine](H₄L²⁸) were synthesized and fully characterized. Their Mn(III), Ni(II), Cu(II) and Zn(II) complexes were also prepared and characterized by FT-IR, UV-Vis, EA, molar conductance, and polarimetric analysis. The composition of these transition metal complexes seems to be ML^C·nH₂O (M=Ni(II), Cu(II), Zn(II), n=0～4), MnL^C·nH₂O (n=0～5), and Mn₂L¹⁹Cl₂·3C₂H₅OH. 5. Two linear hybrid trimeric salen ligands (H₆L^D), including (R,R)-di-N-(3-tert-butyl-5-methylene-bis-N'-salicylidene-(N'-(2-aminoethyl)ethane-1,2-diamine)salicylidene-1,2-cyclohexa nediamine(H₆L²⁹),(R,R)-di-N-(3-tert-butyl-5-methylene-bis-N'-salicylidene-(N'-(2-amino ethyl)ethane-1,2-diamine)salicylidene-1,2-diphenyldiamine (H₆L³⁰), were synthesized and fully characterized. Their Mn(III) and Ni(II) complexes was also prepared and characterized by FT-IR, EA and other methods. The composition of these transition metal complexes seems to be Mn₃L²⁹Cl₃·7H₂O and Mn₃L³⁰Cl₃·C₂H₅OH.6. The (salen)Mn(III) and (salen)Ni(II) complexes were used as epoxidation catalysts, and three terminal oxidants were selected herein, including aqueous NaClO solution, PhIO and m-CPBA. In the aspect of optimizing reaction media, a novel chiral ionic liquid and a porous coordination polymer was loaded in the catalytic reaction, respectively. The catalytic results clearly indicated that the presence of ionic liquid and coordination polymer could accelerate the catalytic reaction, and the synergetic effect of chiral ionic liquid with chiral catalysts does exist.