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

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 . PPh(3) involves four-coordination at indium; the structure is trigonal, with a = 15.105(4) Angstrom, c = 16.769(7) Angstrom(3), V = 3313(2) Angstrom(3), Z = 6, and space group <R(3)over bar>. Crystals were also obtained in which InI3 . PPh(3) and InI3(PPh(3))(2) are present in a 1:1 ratio; these are also trigonal, a = 15.473(4) Angstrom, c = 41.701(7) Angstrom, V = 8646.1(1.8) Angstrom(3), Z = 3 + 3 and space group <R(3)over bar>. The 1:2 adduct has approximately D-3h 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 P-31 NMR to undergo complete dissociation in solution to InI3 . PPh(3) and PPh(3). The addition of R(4)NI (R = n-C3H7, n-C4H9) causes quantitative conversion to InI4- and free Ph(3)P. Similar experiments are reported for the compound Inl(3)(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) Angstrom, b = 15.944(8) Angstrom, c = 16.533(11) Angstrom, beta = 102.02(4)degrees, V = 10 685(9) Angstrom(3), Z = 4 + 4, space group C-2/c. Solid state and solution phase results are discussed in terms of the coordination chemistry of indium(III).