Spectroscopic and crystallographic studies of phosphino adducts of indium(III) iodide

Abstract

Indium(III) iodide forms both 1:1 and 1:2 adducts with triphenylphosphine, depending on the reaction conditions, and especially on the solvent used. The complex InI3•PPh3 involves four-coordination at indium; the structure is trigonal, with a = 15.105(4) Å, c = 16.769(7) Å, V = 3313(2) Å3, Z = 6, and space group [Formula: see text]. Crystals were also obtained in which InI3•PPh3 and InI3(PPh3)2 are present in a 1:1 ratio; these are also trigonal, a = 15.473(4) Å, c = 41.701(7) Å, V = 8646.1(1.8) Å3,Z = 3 + 3 and space group [Formula: see text]. The 1:2 adduct has approximately D3h symmetry in the InI3P2 kernel. The bond distances and angles are discussed; in particular, the In—P bonds are extremely weak in the 1:2 adduct. This compound has been shown by 31P NMR to undergo complete dissociation in solution to InI3•PPh3 and PPh3. The addition of R4NI (R = n-C3H7, n-C4H9) causes quantitative conversion to InI4− and free Ph3P. Similar experiments are reported for the compound InI3(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane), whose structure is an infinite chain of InI3 units linked through In-P-C2H4-P-In coordination. The crystal structure showed that InI3(dppe) cocrystallizes with an equimolar quantity of dppe; these crystals are cubic, a = 41.445(14) Å, b = 15.944(8) Å, c = 16.533(11) Å, p = 102.02(4)°, V = 10 685(9) Å3, Z = 4 + 4, space group C2/c, Solid state and solution phase results are discussed in terms of the coordination chemistry of indium(III). Key words: indium, phosphorus, coordination chemistry, multinuclear NMR, X-ray crystallography.