A series of novel aluminium complexes containing cyclic β-ketiminato ligands of type Me2Al{O-[(ArNCHC4H4(C6H4))]} (3a, Ar = 2,6-iPr2C6H3; 3b, Ar = C6H5; 3c, Ar = C6F5) have been prepared in high yields. These complexes were identified by 1H, 13C NMR spectroscopy and elemental analysis. X-ray structural analyses for 3a–c revealed that these complexes have a distorted tetrahedral geometry around Al, and both bond distances and bond angles were considerably influenced by the ligand structure. These complexes were tested as catalyst precursors for ring-opening polymerisation of ε-caprolactone (ε-CL) and L-lactide (L-LA) in the presence of 2-propanol as an initiator. Complex 3a could polymerize ε-CL in a controlled manner with high efficiency. Based on the living characteristics, the preparation of well-defined block copolymers PCL-b-PLLA via sequential addition of monomers was performed by 3a. Note that complex 3c exhibited rather high catalytic activity for the ROP of L-LA with narrow molecular weight distribution. The monomer conversion reached completion only in 4 h when the L-LA/Al molar ratio was 100 at 80 °C. PLLA-b-PCL copolymers were thus easily produced by 3c.

A series of novel half-zirconocenes containing phosphine-(thio)phenolate chelating ligands of the type Cp′Zr(thf)Cl2[X-2-R1-4-R2-6-(PPh2)C6H2] (Cp′ = C5Me5, 2a: X = O, R1 = Ph, R2 = H; 2b: X = O, R1 = tBu, R2 = H; 2c: X = O, R1 = R2 = tBu; 2d: X = O, R1 = SiMe3, R2 = H; 2e: X = S, R1 = SiMe3, R2 = H; Cp′ = C5H5, 3b: X = O, R1 = tBu, R2 = H; 3c: X = O, R1 = R2 = tBu; 3d: X = O, R1 = SiMe3, R2 = H; 3e: X = S, R1 = SiMe3, R2 = H) have been synthesized in high yields (74–85%). These complexes were identified by 1H, 13C and 31P NMR as well as elemental analyses. Structural analysis for 2a–b and 2d revealed that these complexes adopt six-coordinate, distorted octahedral geometry around the zirconium center. These novel half-zirconocenes possessed high catalytic performance for ethylene polymerization at high temperature in the presence of MMAO. The phosphine-phenolate-based Cp* complexes produced high molecular weight polymers (MW > 400000), while the Cp analogues displayed much higher activities at high temperature. Complex 3c with MMAO showed a maximum ethylene polymerization activity of 17580 kg molZr−1 h−1 at 75 °C. In addition, the Cp based complexes 3b–e could promote ethylene and 1-hexene copolymerization with high activities.

A series of novel binuclear phenoxyimino organoaluminum complexes of the type [(RNCH)C6H3OAlMe2]2 [R = C6H5 (2a), 2,6-iPr2C6H3 (2b), 2,6-Ph2C6H3 (2c), adamantyl (2d), tBu (2e)] have been prepared in high yields, and these complexes were identified by 1H, 13C NMR and elemental analysis. Structural analysis for 2a–e revealed that these complexes have a distorted tetrahedral geometry around Al and both the Al–O and the Al–N bond distances were considerably influenced by substituents in the imino groups. The complexes were tested as catalyst precursors for ring-opening polymerisation (ROP) of ε-caprolactone (CL) in the presence of BnOH, and their catalytic activities were strongly affected by the catalyst structures and polymerisation conditions. An efficient living ROP has been achieved using the 2b/BnOH system.

A series of novel monochloro half-zirconocene complexes containing phosphine oxide-(thio)phenolate chelating ligands of the type, ClCp′Zr[X-2-R1-4-R2-6-(Ph2PO)C6H2]2 (Cp′ = C5H5, 2a: X = O, R1 = Ph, R2 = H; 2b: X = O, R1 = F, R2 = H; 2c: X = O, R1 = tBu, R2 = H; 2d: X = O, R1 = R2 = tBu; 2e: X = O, R1 = SiMe3, R2 = H; 2f: X = S, R1 = SiMe3, R2 = H; Cp′ = C5Me5, 2g: X = O, R1 = SiMe3, R2 = H), have been synthesized in high yields. These complexes were identified by 1H {13C} NMR and elemental analyses. Structures for 2b, 2c and 2f were further confirmed by X-ray crystallography. Structural characterization of these complexes reveals crowded environments around the zirconium. Complexes 2b and 2c adopt six-coordinate, distorted octahedral geometry around the zirconium center, in which the equatorial positions are occupied by three oxygen atoms of two chelating phosphine oxide-bridged phenolate ligands and a chlorine atom. The cyclopentadienyl ring and one oxygen atom of the ligand are coordinated on the axial position. Complex 2f also folds a six-coordinate, distorted octahedral geometry around the Zr center, consisting of a Cp–Zr–O (in PO) axis [177.16°] and a distorted plane of two sulfur atoms and one oxygen atom of two chelating phosphine oxide-bridged thiophenolate ligands as well as a chlorine atom. When activated by modified methylaluminoxane (MMAO), all the complexes exhibited high activities towards ethylene polymerization at high temperature (75 °C), giving high molecular weight polymers with unimodal molecular weight distribution. The formation of 14-electron, cationic metal alkyl species might come from the Zr–O (in phenol ring) bond cleavage based on the DFT calculations study.

A series of novel half-sandwich-type chromium complexes bearing phenoxy-phosphine [O,P] ligands (3a–3f) or phenoxy-phosphine oxide [O,P═O] ligands (4b–4e) were synthesized in high yields from CpCrCl2(thf) with corresponding ligands in THF. X-ray structure analyses for 3b, 3c, 3e, and 4c revealed that these complexes adopt a three-legged piano stool geometry. When activated by modified methylaluminoxane, complexes 3a–3f exhibited moderate to high activities toward ethylene polymerization, giving high molecular weight polymers with unimodal molecular weight distributions. Excitingly, complex 3c could efficiently promote ethylene/NBE copolymerization, therefore, high molecular weight copolymers with high NBE content could easily be obtained under optimized conditions. The [O,P═O] complexes showed higher catalytic activities than [O,P] analogues but produced much lower molecular weight polymers. The difference in polymerization behavior might be caused by the change of both the steric bulk and the electronic effect around the metal center.

A series of novel titanium complexes bearing tridentate β-enaminoketonato chelating ligands of type, [R2NC(CF3)C(H)CR1O]TiCl3 (2a: R1 = Ph, R2 = −C6H4OMe(o); 2b: R1 = Ph, R2 = −C9H6N; 2c: R1 = Ph, R2 = −C6H4SMe(o); 2d: R1 = Ph, R2 = −C6H4SPh(o); 2e: R1 = tBu, R2 = −C6H4SPh(o)) and [R2NC(R1)C(H)C(CF3)O]TiCl3 (2f: R1 = Ph, R2 = −C6H4PPh2(o)) were prepared from TiCl4 by treating with one equiv of deprotonated ligands in toluene. The reaction of 1a with equivalent of TiCl4 in THF afforded another complex, C6H4OMeNC(CF3)C(H)CPhO]TiCl3(thf) (3a), in addition to formation of the dichloride complex 4a, [C6H4(OMe)NC(CF3)C(H)CPhO]2TiCl2. After deprotonation by alkali-metal hydride at −78 °C in diethyl ether, ligand 1a could react with 0.5 equiv of TiCl4 to form the exclusive and clean dichloride complex 4a in high yield. These complexes were identified by NMR and mass spectra as well as elemental analyses. X-ray diffraction studies on these new trichloride complexes revealed a distorted octahedral coordination of the central metal with three chlorine atoms in a mer disposition. Dichloride complex 4a also adopted a distorted octahedral geometry around the titanium center. Two chlorine atoms are situated in the cis position, as seen in the bond angles for Cl(1)–Ti–Cl(2) (92.64(7)°). The O atom on the heterocyclic group was not coordinated with Ti. When activated by modified methylaluminoxane (MMAO), complexes 2a–e exhibited moderate to high activity towards ethylene (co)polymerization, giving relatively high molecular weight polymers with unimodal molecular weight distribution.

A series of new titanium complexes with two asymmetric bidentate β-enaminoketonato [N,O] ligands (2b–t), [PhNC(CF3)CHC(Ar)O]2TiCl2 (2b, Ar = –C6H4F(o); 2c, Ar = –C6H4F(m); 2d, Ar = –C6H4F(p); 2e, Ar = –C6H4Cl(p); 2f, Ar = –C6H4OMe(p); 2g, Ar = –C6H4CF3(p); 2h, Ar = –C6H4CF3(m); 2i, Ar = –C6H4CF3(o); 2j, Ar = –C6H4Cl(o); 2k, Ar = –C6H4Br(o); 2l, Ar = –C6H4I(o); 2m, Ar = –C6H3F2(2,4); 2n, Ar = –C6H3F2(2,6); 2o, Ar = –C6H3F2(3,4); 2p, Ar = –C6H3F2(3,5); 2q, Ar = –C6F5; 2r, Ar = C6F4OMe; 2s, Ar = –C6H3Cl2(2,6); 2t, Ar = –C6H3Cl2(2,5)), have been synthesized based on substituted acetophenones. X-Ray analyses reveal that complexes 2h, 2k, 2m, and 2n adopt distorted octahedral geometry around the titanium center, in which the two chloride ligands are situated in the cis-orientation. 2s also adopts distorted octahedral geometry, but the two chloride ligands in it are situated in the trans-orientation due to the increase of the steric effect of the phenyl derived from the acetophenone. The influence of the substituent effects on catalyst performance, including catalytic activities and the molecular weight distribution of the polymers obtained, was investigated in detail. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 2b–r and 2t are active catalysts for ethylene polymerization at room temperature, and produce high molecular weight polymers. It is observed that the catalytic activities are significantly enhanced by introducing some electron-withdrawing groups, such as –F, –Cl and –CF3, into the suitable positions of the phenyl ring close to the oxygen donor. It should be noted that complexes 2c–i, 2p, 2n and 2t are also capable of promoting the living copolymerization of ethylene with norbornene at room temperature, yielding high molecular weight copolymers with narrow molecular weight distributions (PDI = 1.05–1.30).

A series of novel half-metallocene-type titanium complexes CpTiCl2[PhNC(R2)CHC(R1)O] (2a, R1 = Cy, R2 = CF3; 2b, R1 = tBu, R2 = CF3; 2c, R1 = Ph, R2 = CF3; 2d, R1 = Ph, R2 = CH3) have been synthesized by treating CpTiCl3 with the corresponding bidentate β-enaminoketonato ligands PhNC(R2)CHC(R1)OH in the presence of triethylamine. Single crystal X-ray diffraction revealed that complex 2b adopts distorted square-pyramid geometry around the titanium center. The complexes 2a–d were investigated as the catalysts for ethylene polymerization and the copolymerization of ethylene with norbornene. All the complexes were active towards ethylene (co)polymerization in the presence of modified methylaluminoxane, and produced high molecular weight (co)polymers. The catalytic activity and the norbornene incorporation were highly dependent upon catalyst and reaction conditions employed. Among four complexes, 2c exhibited both high catalytic activity and efficient norbornene incorporation under the same conditions, affording high molecular weight copolymers with unimodal molecular weight distributions.

Several non-metallocene-type titanium(IV) complexes containing phenoxy-phosphine or thiophenoxy-phosphine ligands of type, (2-R1-4-R2-6-PPh2-C6H2X)2TiCl2 (2a: X = O, R1 = R2 = t-Bu; 2b: X = O, R1 = R2 = cumyl; 2c: X = S, R1 = SiMe3, R2 = H) have been synthesized by treating TiCl4 with the corresponding ligands 2-R1-4-R2-6-PPh2-C6H2XH in the presence of n-BuLi. The complexes 2a–c were investigated as the catalysts for ethylene with 1-hexene and/or polar alkenes copolymerizations. The catalytic activity and the comonomer incorporation were highly dependent upon catalyst and reaction conditions employed. Among these complexes, 2a can not only promote ethylene/1-hexene living copolymerization at room temperature, but also can utilize ethylene with methyl 10-undecenoate copolymerization.

A series of novel titanium complexes bearing tridentate β-enaminoketonato chelating ligands of type, [R2NC(CF3)C(H)CR1O]TiCl3 (2a: R1 = Ph, R2 = −C6H4OMe(o); 2b: R1 = Ph, R2 = −C9H6N; 2c: R1 = Ph, R2 = −C6H4SMe(o); 2d: R1 = Ph, R2 = −C6H4SPh(o); 2e: R1 = tBu, R2 = −C6H4SPh(o)) and [R2NC(R1)C(H)C(CF3)O]TiCl3 (2f: R1 = Ph, R2 = −C6H4PPh2(o)) were prepared from TiCl4 by treating with one equiv of deprotonated ligands in toluene. The reaction of 1a with equivalent of TiCl4 in THF afforded another complex, C6H4OMeNC(CF3)C(H)CPhO]TiCl3(thf) (3a), in addition to formation of the dichloride complex 4a, [C6H4(OMe)NC(CF3)C(H)CPhO]2TiCl2. After deprotonation by alkali-metal hydride at −78 °C in diethyl ether, ligand 1a could react with 0.5 equiv of TiCl4 to form the exclusive and clean dichloride complex 4a in high yield. These complexes were identified by NMR and mass spectra as well as elemental analyses. X-ray diffraction studies on these new trichloride complexes revealed a distorted octahedral coordination of the central metal with three chlorine atoms in a mer disposition. Dichloride complex 4a also adopted a distorted octahedral geometry around the titanium center. Two chlorine atoms are situated in the cis position, as seen in the bond angles for Cl(1)–Ti–Cl(2) (92.64(7)°). The O atom on the heterocyclic group was not coordinated with Ti. When activated by modified methylaluminoxane (MMAO), complexes 2a–e exhibited moderate to high activity towards ethylene (co)polymerization, giving relatively high molecular weight polymers with unimodal molecular weight distribution.

A series of new titanium complexes with two asymmetric bidentate β-enaminoketonato [N,O] ligands (2b–t), [PhNC(CF3)CHC(Ar)O]2TiCl2 (2b, Ar = –C6H4F(o); 2c, Ar = –C6H4F(m); 2d, Ar = –C6H4F(p); 2e, Ar = –C6H4Cl(p); 2f, Ar = –C6H4OMe(p); 2g, Ar = –C6H4CF3(p); 2h, Ar = –C6H4CF3(m); 2i, Ar = –C6H4CF3(o); 2j, Ar = –C6H4Cl(o); 2k, Ar = –C6H4Br(o); 2l, Ar = –C6H4I(o); 2m, Ar = –C6H3F2(2,4); 2n, Ar = –C6H3F2(2,6); 2o, Ar = –C6H3F2(3,4); 2p, Ar = –C6H3F2(3,5); 2q, Ar = –C6F5; 2r, Ar = C6F4OMe; 2s, Ar = –C6H3Cl2(2,6); 2t, Ar = –C6H3Cl2(2,5)), have been synthesized based on substituted acetophenones. X-Ray analyses reveal that complexes 2h, 2k, 2m, and 2n adopt distorted octahedral geometry around the titanium center, in which the two chloride ligands are situated in the cis-orientation. 2s also adopts distorted octahedral geometry, but the two chloride ligands in it are situated in the trans-orientation due to the increase of the steric effect of the phenyl derived from the acetophenone. The influence of the substituent effects on catalyst performance, including catalytic activities and the molecular weight distribution of the polymers obtained, was investigated in detail. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 2b–r and 2t are active catalysts for ethylene polymerization at room temperature, and produce high molecular weight polymers. It is observed that the catalytic activities are significantly enhanced by introducing some electron-withdrawing groups, such as –F, –Cl and –CF3, into the suitable positions of the phenyl ring close to the oxygen donor. It should be noted that complexes 2c–i, 2p, 2n and 2t are also capable of promoting the living copolymerization of ethylene with norbornene at room temperature, yielding high molecular weight copolymers with narrow molecular weight distributions (PDI = 1.05–1.30).

A series of novel binuclear phenoxyimino organoaluminum complexes of the type [(RNCH)C6H3OAlMe2]2 [R = C6H5 (2a), 2,6-iPr2C6H3 (2b), 2,6-Ph2C6H3 (2c), adamantyl (2d), tBu (2e)] have been prepared in high yields, and these complexes were identified by 1H, 13C NMR and elemental analysis. Structural analysis for 2a–e revealed that these complexes have a distorted tetrahedral geometry around Al and both the Al–O and the Al–N bond distances were considerably influenced by substituents in the imino groups. The complexes were tested as catalyst precursors for ring-opening polymerisation (ROP) of ε-caprolactone (CL) in the presence of BnOH, and their catalytic activities were strongly affected by the catalyst structures and polymerisation conditions. An efficient living ROP has been achieved using the 2b/BnOH system.

A series of novel monochloro half-zirconocene complexes containing phosphine oxide-(thio)phenolate chelating ligands of the type, ClCp′Zr[X-2-R1-4-R2-6-(Ph2PO)C6H2]2 (Cp′ = C5H5, 2a: X = O, R1 = Ph, R2 = H; 2b: X = O, R1 = F, R2 = H; 2c: X = O, R1 = tBu, R2 = H; 2d: X = O, R1 = R2 = tBu; 2e: X = O, R1 = SiMe3, R2 = H; 2f: X = S, R1 = SiMe3, R2 = H; Cp′ = C5Me5, 2g: X = O, R1 = SiMe3, R2 = H), have been synthesized in high yields. These complexes were identified by 1H {13C} NMR and elemental analyses. Structures for 2b, 2c and 2f were further confirmed by X-ray crystallography. Structural characterization of these complexes reveals crowded environments around the zirconium. Complexes 2b and 2c adopt six-coordinate, distorted octahedral geometry around the zirconium center, in which the equatorial positions are occupied by three oxygen atoms of two chelating phosphine oxide-bridged phenolate ligands and a chlorine atom. The cyclopentadienyl ring and one oxygen atom of the ligand are coordinated on the axial position. Complex 2f also folds a six-coordinate, distorted octahedral geometry around the Zr center, consisting of a Cp–Zr–O (in PO) axis [177.16°] and a distorted plane of two sulfur atoms and one oxygen atom of two chelating phosphine oxide-bridged thiophenolate ligands as well as a chlorine atom. When activated by modified methylaluminoxane (MMAO), all the complexes exhibited high activities towards ethylene polymerization at high temperature (75 °C), giving high molecular weight polymers with unimodal molecular weight distribution. The formation of 14-electron, cationic metal alkyl species might come from the Zr–O (in phenol ring) bond cleavage based on the DFT calculations study.

A series of novel half-zirconocenes containing phosphine-(thio)phenolate chelating ligands of the type Cp′Zr(thf)Cl2[X-2-R1-4-R2-6-(PPh2)C6H2] (Cp′ = C5Me5, 2a: X = O, R1 = Ph, R2 = H; 2b: X = O, R1 = tBu, R2 = H; 2c: X = O, R1 = R2 = tBu; 2d: X = O, R1 = SiMe3, R2 = H; 2e: X = S, R1 = SiMe3, R2 = H; Cp′ = C5H5, 3b: X = O, R1 = tBu, R2 = H; 3c: X = O, R1 = R2 = tBu; 3d: X = O, R1 = SiMe3, R2 = H; 3e: X = S, R1 = SiMe3, R2 = H) have been synthesized in high yields (74–85%). These complexes were identified by 1H, 13C and 31P NMR as well as elemental analyses. Structural analysis for 2a–b and 2d revealed that these complexes adopt six-coordinate, distorted octahedral geometry around the zirconium center. These novel half-zirconocenes possessed high catalytic performance for ethylene polymerization at high temperature in the presence of MMAO. The phosphine-phenolate-based Cp* complexes produced high molecular weight polymers (MW > 400000), while the Cp analogues displayed much higher activities at high temperature. Complex 3c with MMAO showed a maximum ethylene polymerization activity of 17580 kg molZr−1 h−1 at 75 °C. In addition, the Cp based complexes 3b–e could promote ethylene and 1-hexene copolymerization with high activities.

A series of novel aluminium complexes containing cyclic β-ketiminato ligands of type Me2Al{O-[(ArNCHC4H4(C6H4))]} (3a, Ar = 2,6-iPr2C6H3; 3b, Ar = C6H5; 3c, Ar = C6F5) have been prepared in high yields. These complexes were identified by 1H, 13C NMR spectroscopy and elemental analysis. X-ray structural analyses for 3a–c revealed that these complexes have a distorted tetrahedral geometry around Al, and both bond distances and bond angles were considerably influenced by the ligand structure. These complexes were tested as catalyst precursors for ring-opening polymerisation of ε-caprolactone (ε-CL) and L-lactide (L-LA) in the presence of 2-propanol as an initiator. Complex 3a could polymerize ε-CL in a controlled manner with high efficiency. Based on the living characteristics, the preparation of well-defined block copolymers PCL-b-PLLA via sequential addition of monomers was performed by 3a. Note that complex 3c exhibited rather high catalytic activity for the ROP of L-LA with narrow molecular weight distribution. The monomer conversion reached completion only in 4 h when the L-LA/Al molar ratio was 100 at 80 °C. PLLA-b-PCL copolymers were thus easily produced by 3c.