Date of Award

4-19-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Lothar Stahl

Abstract

Treatment of an array of bis(phenol)s H2Lx {Lx = [(-OC6H2(2,4-R)(6-CH 2))2 NCH2CH2X], where X = CH2 NMe2, NMe2, NEt2, OMe and R= Bu t, Pet where Pe t = C(CH3)2Et} with [Ln(N(SiMe 3)2)2(THF)2] (Ln = Yb, Sm) in a 1:1 molar ratio in hexanes afforded a multitude of new divalent lanthanide bis(phenolate) complexes: [L5Yb]2 (X = NMe2, R = Bu t) 11, [L6Yb]2 (X = OMe, R = But) 12, [L 4Yb]2 (X = NEt2, R = But) 13, [L7Yb]2 (X = CH2NMe2 , R = But) 14, [L 9Yb]2 (X = NMe2, R = Pet) 15, [L8Yb]2 (X = OMe, R = Pe t) 16, [L4Sm] (X = NEt2 , R = But) 19, [L 10Yb] (X = NEt2, R = Pet) 17, [L10Sm] (X = NEt2, R = Pe t) 18. X-Ray crystallographic analyses of compounds 11, 13 and 15 reveal dimeric, centrosymmetric structures with 5-coordinate ytterbium centers. Metathesis from YbI2 and K 2L6 reproducibly afforded the surprising oxidized product [(L6)2YbK(dme)2] (20). Both 11 and 12 have been oxidized by a variety of oxidants (AgX, ROH) to form heteroleptic ytterbium(III) bis(phenolate) complexes: [(L5)Yb][PF6] (21), [(L 5)YbOSO2CF3(THF)] (22), [(L 5)YbOBut] (23), [(L 5)YbOPh] (24), [(L6)YbOPh] (25). Compound 22 has been structurally characterized as having a quasi-octahedral environment around ytterbium. A pair of neutral binuclear heterobimetallic complexes are defined with ytterbium(III), with phenol, as sodium salts, of the form [Yb(LX)(OPh) 2Na(DME)(HOPh)] (30: R=NMe2, 31: R = OMe). A further complex, [Na(DME)3][Yb(*Lpy) 2] (35), results from an unusual ligand reduction by a ytterbium(II) species to give a new dianionic Schiff base ligand which is coordinated to ytterbium(III) {*Lpy = -OC 6H2(2,4-But)(CH=N-CH-C6H5 N)}. A selection of divalent compounds (11, 12, 13, 16, 18, 19, 26, and 27) were tested as catalyst precursors in the polymerization of ϵ-caprolactone and/or L-lactide which resulted in high molecular weight polymers with PDIs of 1.11–2.81 and 1.13–1.56 for ϵ-caprolactone and L-lactide respectively. All polymerization studies were performed in either toluene or THF and at room temperature (ϵ-caprolactone) or 70°C (L-lactide) at a variety of catalyst:monomer ratios (1:100–1:400). Kinetics analyses of the polymerization of L-lactide by compounds 13 and 19 indicated pseudo-first order response with respect to L-lactide.

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