Citation:
Abstract:
The crystal structure of [Ph3PH](2)[Ga2Br6], previously described as having a disordered anion in the space group R (3) over bar, has been re-determined in the correct space group P (3) over bar, where it is fully ordered. Interestingly, two-thirds of the [Ga2Br6](2-) dianions have an intermediate conformation with a Br-Ga-Ga-Br torsion angle of 36.91 (1)degrees, while the remaining is staggered as required from adopting a site with inversion symmetry. In the lattice, [Ph3PH](+) ions lie along the same threefold axes as the dianions and are oriented such that the P-H bond is directed towards a gallium atom. The phosphonium ions lie back-to-back and interact with relatively strong T-interactions between phenyl rings on adjacent cations. DFT calculations at the B3LYP/6-311+ G(fd,) level have been used to determine the barriers to rotation in [Ga2X6](2-) ions. For X = Cl and X = Br, the barriers are found to be very small, with values of 4.3 and 5.1 kJ mol(-1) for the two halogens.