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New titanium complexes, TiLCl2(THF) and TiL2, containing the tridentate chiral Schiff-base ligand, L, prepared from the condensation reaction of 2,4-pentadione and (1R,2S)-(−)-1-aminoindanol, were synthesized and characterized by various analytical methods including X-ray crystallography. Ligand L acted as a dianionic tridentate ligand and, owing to a chiral center in the aminoindanol part, imparted chirality to its titanium complexes. The newly synthesized titanium complexes and previously reported analogous Ti complexes were used as catalysts in the cycloaddition of CO2 to propylene oxide as the first representatives of titanium complexes with tridentate Schiff base ligands to have been used for this purpose. These complexes provided high selectivity toward cyclic propylene carbonate (>99%) and showed considerable activities with TOF values up to 131 h−1 in comparison with the previously reported catalyst systems.

Herein, the selective formation of dinuclear and hexagonal disk-shape heptanuclear metal cluster complexes is reported. The reaction of 4-tert-butyl-2,6-diformylphenol (L) and M(ClO4)2, where M is Zn (II), Co (II), or Ni (II), in the presence of a strong base resulted in the formation of heptanuclear metal cluster complexes. Treatment of M(ClO4)2·6H2O (M = Zn, and Ni) in the presence of NaOCH3 in MeOH at the elevated temperature afforded [Zn2(L)2(CH3O)4].ClO4 (1) and [Ni2(L)2(CH3O)2].ClO4 (2). Furthermore, treatment of M(ClO4)2·6H2O (M = Zn, Co, and Ni) in the presence of NaOH in MeOH at the elevated temperature yielded heptanuclear metal cluster complexes [Zn7(L)6(µ3-CH3O)6]·2ClO4 (3), [Co7(L)6(µ3-CH3O)6]·2ClO4 (4), and [Ni7(L)6(µ3-OH)6]·2ClO4 (5). These were characterized using elemental analysis, infrared spectroscopy, and X-ray crystallography. Zinc complexes 1 and 3 were also characterized using 1H NMR spectroscopy. In the crystal structures of heptanuclear cluster complexes 3–5, six ligand molecules were aligned to hold six metal centers that were in hexagonal positions. The central metal atom was connected by the bridging of the oxygen atom of methoxy and hydroxy groups with the remaining metal atoms. The photophysical properties of complexes were studied and zinc complexes 1 and 3 showed strong fluorescence in PL spectra. Themetal cluster complexes 1, 3 and 4 were employed as catalysts in the cycloaddition reaction of CO2 to epoxide, exhibiting moderate activities.

The reaction of three equivalents of 5-(2,4-dihydroxyphenyl)-1H-tetrazole (H3dhptz) with iron(III) perchlorate in the presence of potassium hydroxide afforded the metallascorpionate framework. By simple recrystallization, an interesting coordination polymer, [K4.5Fe(dhptz)1.5(Hdhptz)1.5DMF7(H2O)3.5]n, was obtained. It possesses two potassium ions with either κ3-O or κ3-N binding modes, resulting in an array of K–Fe–K metal ions and a short Fe–K distance (3.427 A). One scorpionate ligand possesses 4.5 potassium ions at six different positions in the solid state by means of the bridging oxygen atoms of the DMF solvent. Further coordination modes between the potassium ions and water/DMF provide a one-dimensional (1-D) metallascorpionate array and allow the formation of a 3-D hexagonal coordination network.

The complexes [Py(Pz)2]Zn(OC( O)Me)2 (1) and [Py(Me2Pz)2]Zn(OC( O)Me)2 (2), where ligands Py(Pz)2 and Py(Me2Pz)2 are tridentate 2,6-bis(pyrazol-1-yl)pyridine and 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine, respectively, have been synthesized and characterized. The single crystal X-ray diffraction analysis confirmed compound 2 to be monomeric with six-coordinate zinc center. In addition to tridentate ligand Py(Me2Pz)2, both κ1-acetate and κ2-acetate ligands are ligated to zinc metal atom in 2. The synthesized complexes 1 and 2 were used as effective catalysts for the cycloaddition between CO2 and epoxides in the presence of various kinds of cocatalysts such as n-Bu4PBr, n-Bu4NI, n-Bu4NBr, n-Bu4NCl, PPNCl, and DMAP under the condition of 75 °C, 10 bar CO2 pressure, 0.1 mol% catalyst loading, and 24 h. The reaction temperature, CO2 pressure, and catalyst loading ratio applied in this study are somewhat milder condition than those for other reported zinc-based catalysts. In addition, 1/n-Bu4PBr system showed the best catalytic activity for the cycloaddition of CO2 to propylene oxide, which showed the highest reactivity among seven other kinds of epoxides.

Herein, we report various metal complexes containing {5-(2-hydroxy)phenyl}tetrazolyl (H2hptz) which form various high-dimensional coordination polymers in a crystalline solid state. A reaction of metal perchlorates, 2,2′-bipyrimidine (bpym), KOH, and tetrazolyl ligand (H2hptz) in H2O or N,N-dimethylmethanamide (DMF) yield 2-D [Cu(hptz)(bpym)]n (1), [Zn(hptz)(bpym)]n (2) and 3-D [K(bpym)2Ni(hptz)(H2O)2.5(OH)]n (3) coordination complexes with a high synthetic yield. These compounds were characterized by elemental analysis, IR spectroscopy, and single crystal X-ray crystallography. Cu2+ and Zn2+ complexes showed 2-D infinite network systems, forming coordination polymers (caused by extra bonding between metal ions and tetrazolyl). The environment of the Cu and Zn metal centers are quite similar; however, Zn2+ complexes have significantly shorter Zn–O bond distances with the hydroxyl group of other [Zn(hptz)(bpym)] unit. The Ni2+ complex 3 showed a completely different composition from that of complexes 1–2. Complex 3 showed 3-D structure based on octahedral units, which were composed of two hptz2− and one bpym ligands around the Ni center. These units infinitely repeat with K ions and water molecules along the a-, b-, and c-axes of the unit cells. Their magnetic behaviors were also studied.

Cobalt complexes containing a salen-type pyridoxal ligand with pyridine were synthesized as a new Co(III) catalytic system for the cycloaddition of carbon dioxide. Two cobalt(III) complexes possessing a salen-type pyridoxyl ligand were synthesized by the reaction of pyridoxal ligands (pyr2en = (N,N′-bis(pyridoxylideneiminato)ethylene) and pyr2cy = (N,N′-bis(pyridoxylideneiminato)cyclohexane)) and Co(OAc)2 and characterized by various analytical methods, including infrared spectroscopy and high-resolution mass analysis. Single-crystal X-ray crystallography analysis confirmed that the cobalt pyr2en complex had a distorted octahedral structure: the tetradentate Schiff base ligand binds the cobalt metal in one plane, and the metal center adopts an octahedral geometry by the additional coordination of acetate and dimethyl sulfoxide. The synthesized complexes were used as catalysts in the cycloaddition of carbon dioxide (CO2) to propylene oxide. The catalysts showed high activity for cycloaddition between CO2 and epoxides, even at a low loading (0.5 mol%), in the presence of various cocatalysts.

Dimeric iron(III) complexes bearing acetylacetonate (acac) ligands and tridentate chiral Schiff base ligands, which were synthesized from condensation reactions between salicylaldehyde and amino-indanol, were prepared and characterized by various methods, including infrared spectroscopy and mass spectrometry. X-ray analysis revealed that two iron centers are each coordinated octahedrally within the complexes, but are situated in different coordination environments; one is attached to two tridentate ligands with meridional isomerization, while the other is coordinated to two acac molecules and two of the oxygen atoms of the indanol moieties of the Schiff bases. The complexes showed higher activity than Fe(acac)3 for the ring opening polymerization of lactide.

The selective syntheses of titanium complexes containing the 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4,6-di-tert-pentylphenol (LH) ligand, namely [LTiCl2(μ-Cl)]2 (1), LTiCl3(THF) (2), L2Ti(NMe2)2 (3), L2TiCl2 (4) and L2Ti(O-i-Pr)2 (5), were achieved by changing the solvents or metal precursors. The solid state structures of 1–5 were revealed by single-crystal X-ray analyses. Complexes 2 and 5 showed a fast thermal exchange process of the benzotriazole ligand L. Among 1–5, complex 5 was proven as a highly effective catalyst for the controlled ring opening polymerization (ROP) of lactide (LA), as shown by the linearity of the molecular weight versus [LA]/[Ti] ratio as well as very narrow PDI values of the PLA polymers obtained.

Tris(4-hydroxy-3,5-diisopropylbenzyl)amine (LH3) was synthesized by the reaction of 2,6-diisopropylphenol and hexamethylenetetramine in the presence of p-toluenesulfonic acid or paraformaldehyde. Its solid state structure was determined by single crystal X-ray diffraction. Its fully deprotonated specie, (4-O-3,5-i-Pr2PhCH2)3N (L), was used to form novel trinuclear half-sandwich titanocene complexes, namely [(η5-C5Me5)TiCl2]3L (1) and [(η5-C5Me5)Ti(OMe)2]3L (2), which were then tested for the syndiospecific polymerization of styrene in the presence of methylaluminoxane (MAO) cocatalyst. Their catalytic properties were directly compared with those of trichloro(pentamethylcyclopentadienyl)titanium(IV) (3) and dichloro(2,6-diisopropylphenolato)(pentamethylcyclopentadienyl)titanium(IV) (4). 1/MAO and 2/MAO systems showed higher activities towards styrene polymerization than the mononuclear catalytic systems 3/MAO and 4/MAO, giving syndiotactic polystyrene of high molecular weight.

Three monomeric boratranes B[(OCH2CH2)nN(CH2CMe2O)3−n] (n = 0, 1; n = 1, 2; n = 2, 3) have been synthesized by the reaction of B(OMe)3 with a series of triethanolateamines such as [(OCH2CH2)nN(CH2CMe2O)3−n]3− (n = 0, L1; n = 1, L2; n = 2, L3), where the number of CMe2 groups adjacent to the OH functionality varied from 3 (L1H3) to 2 (L2H3) to 1 (L3H3). These boratranes 1–3 have been characterized by solution 1H, 13C{1H} and 11B NMR, and the crystal structures of 1 and 2 have been determined by single crystal X-ray diffraction.

Treatment of CpZrCl 3 with 1 equiv of 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4,6-di- tert -pentylphenol ( LigH ) in THF or toluene affords the monomeric complex C 31 H 41 Cl 2 N 3 O 2 Zr ( 1 ) or the dimeric complex C 54 H 66 Cl 4 N 6 O 2 Zr 2 ( 2 ), respectively. THF can transform the dimeric 2 into monomeric 1 within a few minutes at room temperature. The reaction between LigH and 2 equiv of CpZrCl 3 gave the novel dinuclear complex C 32 H 38 Cl 5 N 3 OZr 2 ( 3 ), linked by three bridging chlorides. The monomeric complex C 44 H 56 Cl 2 N 6 O 2 Zr ( 4 ), containing two Lig and two Cl ligands, could be obtained by the reaction between 2 equiv of LigH and Zr(NMe 2 ) 4 in toluene and subsequent addition of Me 3 SiCl. The molecular structures of the complexes were determined by the single crystal X-ray crystallographic method. In the presence of methylalumoxane (MAO) as a cocatalyst, the four complexes synthesized were highly active for the polymerization of ethylene.

Monomeric titanatrane i-PrOTi(OCMe2CH2)3N (1) and dimeric titanatranes [i-PrOTi(OCH2CH2)nN(CH2CMe2O)3−n]2 (n = 1, 2; n = 2, 3) were synthesized by the reaction of Ti(O-i-Pr)4 with a series of triethanolateamines such as (OCH2CH2)nN(CH2CMe2O)3−n3− (n = 0, Lig1; n = 1, Lig2; n = 2, Lig3), which vary by the number of CMe2 groups adjacent to a OH functionality from 3 (Lig1H3) to 2 (Lig2H3) to 1 (Lig3H3). The resultant titanatranes 1–3 have been characterized by solution 1H and 13C{1H} NMR and their solid state structures have been determined by X-ray crystallography. Whereas compound 1 is monomeric in the solid state, compounds 2 and 3 are dimeric, due to the reduction of the steric congestion in the vicinity of the Ti.

The TFA-catalyzed condensation of 5-(thienyl)dipyrromethane with thiophene carboxaldehyde allows for the formation of the thienyl meso-substituted 5,10,15-tris(2-thienyl)corrole H3(T2TC) (1) and the 5,10,15-tris(3-thienyl)corrole H3(T3TC) (2). These ligands undergo metalation with copper and cobalt acetate to yield the four respective metallocorroles. Single-crystal X-ray crystallographic solutions for Cu(T2TC) (3), Co(T2TC)(Py)2 (5) and Co(T3TC)(Py)2 (6) have been obtained, confirming the direct pyrrole–pyrrole link and axial pyridine groups in the case of the cobalt structures. Cyclic voltammetry data indicated the 2-thienyl derivatives are more difficult to oxidize when compared to trispentafluorophenyl corroles (TPFC). Both metal complex isomers are comparably stable towards the formation of dinuclear products resulting from intermolecular C–C coupling. Soret bands for both ligands and complexes have been obtained and variable temperature 1H NMR studies (−50–60 °C) for 3 and 4 reveal a fluxional rotational behavior for the three thienyl substituents believed to impart a less electron withdrawing effect on the corrole core, opposed to the TPFC’s.