A cobalt(III) complex (1) of a salcy-type ligand tethering 4 quaternary ammonium salts, which is thought to act as a highly active catalyst for CO2/propylene oxide (PO) copolymerization, also shows high activity (TOF, 25,900 h(-1); TON, 518,000; 2.72 kg polymer per g cat) and selectivity (>98%) for CO2/ethylene oxide (EO) copolymerization that results in high-molecular-weight polymers (M(n), 200,000-300,000) that have strictly alternating repeating units. The related cobalt(III) complexes 11-14 were prepared through variations of the ligand framework of 1 by replacing the trans-1,2-diaminocyclohexane unit with 2,2-dimethyl-1,3-propanediamine, trans-1,2-diaminocyclopentane, or 1,1'-binaphthyl-2,2'-diamine or by replacing the aldimine bond with ketimine. These ligand frameworks are thought to favour the formation of the cis-β configuration in complexation, and the formation of the cis-β configuration in 11-14 was confirmed through NMR studies or X-ray crystallographic studies of model complexes not bearing the quaternary ammonium salts. Complexes 11, 13, and 14, which adopt the cis-β configuration even in DMSO did not show any activity for CO2/PO copolymerization. Complex 12, which was constructed with trans-1,2-diaminocyclopentane and fluctuated in DMSO between the coordination and de-coordination of the acetate ligand as observed for 1, showed fairly high activity (TOF, 12,400 h(-1)). This fluctuating behaviour may play a role in polymerization. However, complex 12 did not compete with 1 in terms of activity, selectivity, and the catalyst cost.

The synthesis and characterization of dinuclear aluminum complexes bearing multidentate aliphatic aminoethanol-based ligands are presented. Single-crystal X-ray analyses, NMR data, and mass data reveal that four aluminum complexes synthesized are all dimeric in the solid, solution, and gas states. Especially, 27Al NMR spectra have demonstrated that they exist as both five-coordinate Al(III) species in benzene-d 6 solution. All aluminum complexes are effective catalysts for the cycloaddition of CO2 to propylene oxide in the presence of n-Bu4NI as a cocatalyst. Complexes 1 and 3, which have two methyl groups per aluminum center, are better catalytic systems than the corresponding complexes 2 and 4 with a mono methyl group per aluminum. In addition, complexes 3 and 4 containing a pendant −CH2CH2­NMe2 group attached to nitrogen showed the higher activity than those 1 and 2 with a pendant −CH2CH2­OMe group did. As expected, the catalytic activity for 3 increases as the reaction temperature increases up to 130 °C. In addition, compound 3 showed the highest activity for the cycloaddition of CO2 with propylene oxide in the presence of tetrabutylphosphonium bromide as a cocatalyst.

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An ansa-zirconocene bearing methyl substituents at all positions adjacent to the bridgehead [(-C(Ph)HC(Ph)H-)(η(5)-2,5-Me2C5H2)2ZrCl2] (4) was prepared in high yields (78%) through the reductive dimerization of 1,4-dimethyl-6-phenylfulvene utilizing ZrCl2·DME generated in situ. The structure of 4 was subsequently confirmed using X-ray crystallography. 4 exhibited excellent catalytic performance with regard to 1-decene oligomerization, which was carried out with the intention of preparing lubricant base stocks. High activities (21 × 10(6) g mol(-1) Zr h(-1) activity; TON = 150 000; TOF = 42 s(-1)) were observed at temperatures as high as 120 °C and the oligomer distribution was appropriate for lubricant application. The simulated distillation (SIMDIS) data confirmed that a wide range of oligomers were formed, ranging from the dimer (2-mer) to 20-mer. A minimal amount of the dimer and oligomers larger than the 10-mer was formed (13 and 25 wt%, respectively). Alternatively, a typical unbridged complex such as (η(5)-nBuC5H4)2ZrCl2 primarily produced dimers (54 wt%), whereas the ansa-zirconocene (EBI)ZrCl2 primarily produced oligomers larger than 10-mer (62 wt%). The methyl substituents at the positions adjacent to the bridgehead in 4 played a significant role in the catalytic performance.

Aniline (N-R-C 6 H 5 NH) and 1,2,3,4-tetrahydroquinoline (2-R-C 9 H 9 NH) derivatives were ortho-lithiated via conversion of the respective −NH groups to −N(COOLi), followed by treatment with tBuLi. The resulting ortho-lithiated compounds were transformed to ortho-Ph 2 P-substituted derivatives on treatment with Ph 2 P(OPh). Further reaction of the resulting compounds with M(CH 2 Ph) 4 (M = Zr, Hf) afforded a series of Hf and Zr complexes: (2-R-8-Ph 2 PC 9 H 9 N)Hf(CH 2 Ph) 3