Dimethyl sulfoxide solvates of the aluminium(III), gallium(III) and indium(III) ions. A crystallographic, EXAFS and vibrational spectroscopic study

摘要

The isostructural hexakis( dimethyl sulfoxide)-aluminium(III),ud-gallium(III) and -indium(III) iodides crystallise in the trigonaludspace group R(3) over bar ( no. 148), Z = 3, at 295 +/- 1 K. The metaludions are located in a (3) over bar symmetry site with M-O bonduddistances of 1.894(4), 1.974(4) and 2.145(3) Angstrom, and M-O-S bondudangles of 127.1(3), 124.1(3) and 123.1(2)degrees, for M = Al, Ga andudIn, respectively. The unit cell parameters are a = 10.762(2), c =ud24.599(3) Angstrom, V = 2467.2(5) Angstrom(3) forud[Al(OS(CH3)(2))(6)]I-3, a = 10.927(2), c = 23.868(4) Angstrom, V =ud2468.1(6) Angstrom(3) for [Ga(OS(CH3)(2))(6)]I-3, and a = 11.358(2), cud= 21.512(4) Angstrom, V = 2403.5(7) Angstrom(3) forud[In(OS(CH3)(2))(6)]I-3. The increasing compression of the octahedraludMO6 coordination entities along one three-fold axis for M = Al, Ga andudIn, respectively, explains why the largest ion indium(III) has theudsmallest unit cell volume. EXAFS measurements on the dimethyl sulfoxideudsolvated gallium(III) and indium(III) ions in solution and in the solidudperchlorate and trifluoromethanesulfonate salts, show similar bonduddistances as in the solid iodide solvates. Raman and infrared spectraudhave been recorded for the hexakis( dimethyl sulfoxide) metal(III)udiodides and the nature of the metal-sulfoxide bond has been evaluatedudby normal coordinate methods. The symmetric and asymmetric M-Oudstretching modes correspond to the vibrational frequencies 465 and 540udcm(-1) for [Al(OS(CH3)(2))(6)]I-3, 491 and 495 cm(-1) forud[Ga(OS(CH3)(2))(6)]I-3, and 444 and 440 cm(-1) forud[In(OS(CH3)(2))(6)]I-3, respectively.