Evidence on ligand strengths from the crystal structures of [InCl3(dmf)3], [InCl3(dma)3], [{InCl3(PhCHO)3}2]·PhCHO and [InCl3(PhCOMe)2] from dimethylformamide (dmf), dimethylacetamide (dma), benzaldehyde and acetophenone

Abstract

X-Ray crystal structure determinations have been made for the fac octahedral complexes [InCl₃(dmf)₃]1, [InCl₃(dma)₃]2 and [{InCl₃(PhCHO)₃}₂]·PhCHO 3, from dimethylformamide (dmf), dimethyl-acetamide and benzaldehyde and the trigonal-bipyramidal complex [InCl₃(PhCOMe)₂]4 from acetophenone. The average In–O bond length for 3 is ca. 0.07 Å greater than for 1 or 2. In 4, In–O is 0.07 Å longer than that known for [InCl₃(tmu)₂] from tetramethylurea (tmu). An extension of the comparison to structures involving other ligands shows there to be a general correspondence between In–O bond lengths and ligand donor values. By contrast with the weak co-ordination of aldehydes and ketones, co-ordination of an amide is enhanced through polarisation. In the crystal of 3, individual [InCl₃(PhCHO)₃] molecules are paired, almost centrosymmetrically, with intermeshing of their PhCHO ligands.