Dinuclear Indium Research Articles

Preparation and structure of an enantiomeric water-bridged dinuclear indium complex containing two homochiral N atoms and its performance as an initiator in polymerization of rac-lactide

Abstract A novel dinuclear indium complex (1) containing a sole water bridge was prepared from the reaction of InCl3 with an unsymmetric N2O2-ligand and the molecular structure of the complex 1 was determined. The X-ray crystallography data show that the dinuclear complex possesses two homochiral N atoms, namely, N(R)N(R) and N(S)N(S) enantiomers. Complex 1 was used as initiator for ring-opening polymerization of rac-lactide, giving heterotactic-rich polylactide (Pr = 0.63–0.69) with narrow polydispersities (1.13–1.31).

Synthesis and Structural Studies of Chiral Indium(III) Complexes Supported by Tridentate Diaminophenol Ligands

Indium(III) dimethyl, dihalide, and alkoxy-bridged complexes bearing a chiral diaminophenoxy tridentate ligand [NN(H)O](-) were synthesized. The dimethyl complex (NN(H)O)InMe(2) (1) was unreactive toward ethanol and 2-propanol and only partially reactive toward the more acidic phenol. The dihalide complexes (NN(H)O)InX(2) (X = Cl (3), Br (4), I (5)) reacted with NaOEt to form robust alkoxy-bridged complexes with the formula {[(NN(H)O)InX](2)(mu-X)(mu-OEt)} (X = Cl (6), Br (7), I (8)). The reaction of the alkoxy-bridged complexes with water produced hydroxy-bridged dinuclear indium compounds. The hydroxy-bridged complex bearing a chloride ligand [(NN(H)O)InCl(mu-OH)](2) (9) was significantly more reactive toward dissociation and formation of a pyridine adduct than the iodo analogue [(NN(H)O)InI(mu-OH)](2) (10). All compounds were fully characterized in solution by NMR spectroscopy and in the solid state by single-crystal X-ray diffraction. In addition, DFT calculations were used to help explain the reactivity trends observed.

A Dinuclear Indium(III) Complex with Two Pyrazolate Bridging Ligands

The crystal structure of bis[μ-3-(2-pyridyl)-1H-pyrazolato]-1κ 2 N', N 2 :2κN 1 ;1κN 1 :2κN',N 2 -bis[dichloro(dimethylformamide-O)indium]-dimethylformamide (1/2), [In 2 Cl 4 L 2 (dmf) 2 ].2dmf [where HL is 3-(2-pyridyl)-pyrazole, C 8 H 7 N 3 , and dmf is dimethylformamide, C 3 H 7 NO], contains pairs of [InCl 2 (dmf)] fragments linked by two pyrazolate bridges from the deprotonated bridging ligand 3-(2-pyridyl)pyrazolate (L-). This ligand acts as a bidentate N-donor chelate to one metal centre using the pyridyl N and pyrazolyl N 2 atoms, and bridges to the other metal using the (deprotonated) pyrazolyl N 1 atom. Each In III centre, therefore, has an N 3 Cl 2 O donor set.

Synthesis and Structure of Novel Bridged Dinuclear Indium Complexes.

The unique, lantern-type structure of 1 has two In centers in unusual square-based pyramidal environments consisting of the four formamidinate N atoms with a terminal chloride occupying the apical position. Two routes for the formation of 1 and a stepwise pathway for the preparation of the dimethyl analogue are presented. Without the possibility of In−In interactions it would appear that steric features are the primary cause for the formation of these compounds.