Rare-Earth-Metal Mixed Hydride/Aryloxide Complexes Bearing Mono(cyclopentadienyl) Ligands. Synthesis, CO₂ Fixation, and Catalysis on Copolymerization of CO₂ with Cyclohexene Oxide

Abstract

Hydrogenolysis of mono(cyclopentadienyl)-ligated rare-earth-metal bis(alkyl) complexes Cp′Ln(CH2SiMe3)2(THF) (Ln = Y (1a), Dy (1b), Lu (1c); Cp′ = C5Me4SiMe3) with PhSiH3 afforded the mixed hydride/alkyl complexes [Cp′Ln(μ-H)(CH2SiMe3)(THF)]2 (Ln = Y (2a), Dy (2b), Lu (2c)). The overall structure of complexes 2a−c is a C 2-symmetric dimer containing a planar symmetric Ln2H2 core at the center of the molecule. Deprotonation of ArOH (Ar = C6H2- t Bu2-2,6-Me-4) by the metal alkyl group of 2a−c led to formation of the mixed hydride/aryloxide derivatives [Cp′Ln(μ-H)(OAr)]2 (Ln = Y (3a), Dy (3b), Lu (3c)), which adopt the dimeric structure through hydride bridges with trans-accommodated terminal aryloxide groups. Complexes 3a−c swiftly reacted with CO2 to generate the mixed formate/carbonate complexes [Cp′Ln(μ-η1:η1-O2CH)(μ-η1:η1-O2COAr)]2 (Ln = Y (4a), Dy (4b), Lu (4c)). The two Cp′Ln fragments in these complexes are bridged by the formate and carbonate species, respectively, to form two square-pyramidal geometries around the metal centers. Furthermore, complexes 3a−c initiated the copolymerization of CO2 and cyclohexene oxide (CHO) under mild conditions to afford polymers with modest molecular weights and high carbonate linkages (92−99%).

Synthesis and Electrochemistry of Schiff Base Cobalt(III) Complexes and Their Catalytic Activity for Copolymerization of Epoxide and Carbon Dioxide

“…Several efficient catalyst systems, such as zinc, aluminum, cadmium, manganese, cobalt, chromium, and rare-earth-metal complexes, in combination with other reagents for the copolymerization of CO 2 and alicyclic epoxides such as propylene oxide have been developed. [3][4][5][6][7] Recently, salentype catalysts have become the focus of many groups. The chemical structures of the complexes as catalysts are related to the overall catalytic copolymerization performance of CO 2 with an epoxide.…”

Reactivity of lanthanocene hydroxides toward carbodiimide and CO2: Synthesis and characterization of lanthanide ureido and carbonate complexes

“…Table 1 Bond lengths (Å) and angles (deg) for complexes 1. The absorption at ca 1565 cm À1 in the IR spectra of complexes 4-Yb and 4-Er may be assigned to the carbonate group [51]. The structures of 4 are shown in Fig.…”

Dinuclear Metal Complex-Mediated Formation of CO2-Based Polycarbonates

“…Subsequently, research has focussed on well-defined singlesite catalysts of the stoichiometry (LMX), where L is an ancillary ligand, M is the Lewis acidic metal centre and X is the co-ligand or initiating group. Metal centres (M) with a strong precedent in this field include Zn(II), Co(III) and Cr(III), although successful complexes of metals including Ti(IV) [50,51], Zr(IV) [50], Sn(IV) [50], Ge(IV) [50], Mn(II) [52], Mn(III) [52][53][54], Fe(III) [55,56], Lu(III) [57], Y(III) [57,58], Sc(III) [58], Dy(III) [57,58], Lu(III) [57,58], Al(III) [59][60][61][62], Mg(II) [63,64], Co(II) [38,65], Cu(II) [66] and Ni(II) [67] have all been reported and will be highlighted herein. Whilst a range of ancillary ligands (L) have been explored and will be the described in more detail subsequently, it is possible to identify some common and successful ligand classes (Fig.…”

“…In 2005, a series of dimeric rare-earth metal complexes for CHO/CO 2 copolymerisation were reported [57,58]. Hou and co-workers showed that halfsandwich bis(alkyl) lutetium complexes underwent CO 2 insertion leading to dimeric compounds, as depicted in Fig.…”