Dinesh C. Aluthge

Role of aggregation in the synthesis and polymerization activity of SalBinap indium alkoxide complexes.

The reaction of racemic SalBinap ligand, (±)-H2(ONN*OMe), with InCl3 and excess NaOEt generated a mixture of two dinuclear compounds [(μ-κ(2)-ONN*OMe)In(μ-OEt)]2 (1a) and [κ(4)-ONN*OMe)In(μ-OEt)]2 (1b), which were isolated and fully characterized. Polymerization of racemic lactide with 1a and 1b was slow in refluxing THF and showed only modest stereoselectivity. Catalyst 1b displayed better control than 1a, with the experimental molecular weights of the resulting poly(lactic acid) in agreement with the expected values. The higher-than-expected molecular weights observed in polymers formed by 1a were due to partial initiation of the catalyst. The reaction of (±)-H2(ONN*OtBu) with InCl3 yielded (κ(4)-ONN*OtBu)InCl (2); however, further reactivity of the compound formed a mixture of products. An attempt to prevent aggregation by reacting (±)-H2(ONN*OMe) with InCl3 and excess NaO(i)Pr yielded an intractable mixture, including [(μ-κ(2)-ONN*OMe)In]2(μ-Cl)(μ-OH) (3). The thermal stabilities of compounds 1a and 1b under polymerization conditions were investigated. Examination of the polymerization behavior of complexes 1a and 1b and the reaction equilibrium between the two illustrates the importance of aggregation in indium salen complexes compared to their aluminum counterparts.

Probing the Role of Secondary versus Tertiary Amine Donor Ligands for Indium Catalysts in Lactide Polymerization

The role of the central amine donor in a previously reported dinuclear indium catalyst, [N(Me2)N(H)O)InCl]2(μ-Cl)(μ-OEt) (1), for the polymerization of lactide was investigated through experimental methods. The solid state structural data of a series of dimeric complexes related to 1, including the previously reported bromide derivative [(N(Me2)N(H)O)InBr](μ-Br)(μ-OEt) (2) and the newly synthesized methylated derivative [(N(Me2)N(Me)O)InCl]2(μ-Cl)(μ-OEt) (6), showed that weak hydrogen bonding may be present within some of these complexes in the solid state. The polymerization of rac-lactide with 2, 6, and a related achiral complex [(L(H))InCl]2(μ-Cl)(μ-OEt) (8) synthesized for this study indicates that hydrogen bonding may not influence the reactivity of these compounds. The nature of the central amine donor may play a role in tuning the reactivity of these types of catalysts. Catalysts with central secondary amine donors, such as complexes 1, 2, and 8, are 2 orders of magnitude more reactive than those with central tertiary amine donors, such as complex 6.

Dinucleating Ligand Platforms Supporting Indium and Zinc Catalysts for Cyclic Ester Polymerization

The synthesis of the first alkoxide-bridged indium complex supported by a chiral dinucleating ligand platform (1), along with its zinc analogue (2), is reported. Both complexes are synthesized in a one-pot reaction starting from a chiral dinucleating bis(diamino)phenolate ligand platform, sodium ethoxide, and respective metal salts. The dinucleating indium analogue (7) based on an achiral ligand backbone is also reported. Indium complexes bearing either the chiral or achiral ligand catalyze the ring-opening polymerization of racemic lactide (rac-LA) to afford highly heterotactic poly(lactic acid) (PLA; Pr > 0.85). The indium complex bearing an achiral ligand affords essentially atactic PLA from meso-LA. The role of the dinucleating ligand structure in catalyst synthesis and polymerization activity is discussed.

Coupling of Epoxides and Lactones by Cationic Indium Catalysts To Form Functionalized Spiro-Orthoesters

We prepared a cationic indium catalyst for the conversion of epoxides and lactones into spiro‐orthoesters (SOEs), a family of expanding monomers. The cationic indium alkyl complexes [(NNiO)In(CH2SiMe3)(S)][B{3,5‐(CF3)2C6H3}4] (2⋅Solv; H(NNiO)=2,4‐dicumyl‐6‐({[2‐(dimethylamino)cyclohexyl]imino}methyl)phenol, S=OEt2 or THF) were synthesized and fully characterized. The reaction of ϵ‐caprolactone with 1,2‐epoxy‐7‐octene resulted in the formation of 2‐(hex‐5‐en‐1‐yl)‐1,4,6‐trioxaspiro[4.6]undecane (SOE1) with full conversion of both components. We extended the substrate scope to five‐ and six‐membered lactones as well as to a number of functionalized epoxides. The reactivity of the SOEs was explored.

CCDC 1492149: Experimental Crystal Structure Determination

Related Article: Tannaz Ebrahimi, Dinesh Aluthge, Savvas Hatzikiriakos, Parisa Mehrkhodavandi|2016|Macromolecules|49|8812|doi:10.1021/acs.macromol.6b01908

CCDC 1492151: Experimental Crystal Structure Determination

Related Article: Tannaz Ebrahimi, Dinesh Aluthge, Savvas Hatzikiriakos, Parisa Mehrkhodavandi|2016|Macromolecules|49|8812|doi:10.1021/acs.macromol.6b01908

CCDC 1492150: Experimental Crystal Structure Determination

Related Article: Tannaz Ebrahimi, Dinesh Aluthge, Savvas Hatzikiriakos, Parisa Mehrkhodavandi|2016|Macromolecules|49|8812|doi:10.1021/acs.macromol.6b01908

CCDC 1492148: Experimental Crystal Structure Determination

Related Article: Tannaz Ebrahimi, Dinesh Aluthge, Savvas Hatzikiriakos, Parisa Mehrkhodavandi|2016|Macromolecules|49|8812|doi:10.1021/acs.macromol.6b01908