Synthesis, structures and reduction chemistry of monophthalocyanine scandium hydroxides

The preparation and structural characterization of a pair of scanditun(III) phthalocyanine hydroxide complexes were achieved by reaction of PcScCl with alkali metal alkoxides, likely via hydrolysis of soluble PcSc-alkoxide intermediates. A Sc2Li2 (mu(3)-OH)(4) cubane supported by two distorted Pc rings of the form (PcSc)(2)(mu(3)-OH)(4)Li-2 (THF)(DME) was isolated from the reaction of PcScCl with (LiOPr)-Pr-i, while a simpler alkali-metal-free [Pc2Sc2(mu(2)-OH)(2)(THE)] was obtained from addition of (NaOBu)-Bu-i; both structures are reminiscent of bent metallocenes, with dihedral angles between the two Pc rings of 50.8 and 37.7 degrees respectively. A soluble PcScOH material can also be obtained directly via hydrolysis of insoluble PcScCl in approximately 95:5 THF:water. Reduction of the Pc ring of PcScCl using KC8 is reversible and generates Pc3- and Pc4--containing materials that were characterized via UV-vis spectroscopy and, where appropriate EPR and H-1 NMR spectroscopy; analogous reductions of the PcScOH-based species were irreversible. Exposure of the air-sensitive, reduced PcScCl-based species to ambient atmosphere generated PcScOH materials analogous to the direct hydrolysis route

Precise Microstructure Control in Poly(hydroxybutyrate- co-lactic Acid) Copolymers Prepared by an Yttrium Amine Bis(phenolate) Complex

A diamino-bis(phenolate) yttrium amide complex, 1, was used as an initiator in the ring-opening copolymerization of rac-lactide (rac-LA) and rac-β-butyrolactone (rac-β-BL) in toluene at ambient temperature. Copolymers were prepared across a wide composition range (10-89% LA content), and the copolymer composition closely matched the monomer feed ratio. The copolymers had Tg values ranging from 3.8 °C (for a copolymer with 10% LA content) to 44.0 °C (for a copolymer with 89% LA content). Tm ranged from 132 to 144 °C for copolymers with LA composition 48-10%. The copolymer microstructure was determined using 1H and 13C{1H} NMR spectroscopy of copolymers and through reaction monitoring by NMR spectroscopy. This revealed that no BB diads are formed in the copolymer in the presence of any rac-LA monomer, even at very high concentrations of rac-β-BL. However, when [LA] = 0, rac-β-BL is rapidly polymerized. The copolymers thus have a microstructure consisting of two distinct regions, one containing both LA and BL units in an even distribution and one containing solely BL or LA units, depending on the monomer feed ratio