Preparation and Structural Properties of In^III-H Complexes

The use of the tripodal ligands tris[(N'-tert-butylureaylato)-N-ethyl]aminato ([H₃buea]^3-) and the sulfonamide-based N,N',N"-[2,2',2"-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzene-sulfonamidato) ([MST]^3-) has led to the synthesis of two structurally distinct In(III)-OH complexes. The first example of a five-coordinate indium(III) complex with a terminal hydroxide ligand, K[In^IIIH₃buea(OH)], was prepared by addition of In(OAc)₃ and water to a deprotonated solution of H₆buea. X-ray diffraction analysis, as well as FTIR and ¹H NMR spectroscopic methods, provided evidence for the formation of a monomeric In(III)-OH complex. The complex contains an intramolecular hydrogen bonding (H-bonding) network involving the In(III)-OH unit and [H₃buea]^3- ligand, which aided in isolation of the complex. Isotope labeling studies verified the source of the hydroxo ligand as water. Treatment of the [In^IIIMST] complex with a mixture of 15-crown-5 ether and NaOH led to isolation of the complex [15-crown-5⊃Na^I-(μ-OH)-In^IIIMST], whose solid-state structure was confirmed using X-ray diffraction methods. Nuclear magnetic resonance studies on this complex suggest it retains its heterobimetallic structure in solution.