SPECTROSCOPIC STUDIES OF GALLIUM COMPLEXES IN SOLUTION - MULTINUCLEARNMR AND RAMAN-SPECTRA OF MIXED-LIGAND HALIDETHIOCYANATE AND HALIDE ETHERATE COMPLEXES

High-field Ga-71 NMR spectra at 122.03 MHz of aqueous Ga3+ solutions c ontaining NCS- ions show the progressive replacement of the sharp sign al of [Ga(H2O)(6)](3+) by a broad up-field resonance due a mixture of gallium thiocyanate complexes. Solvent extraction into diethyl ether o r methyl isobutyl ketone phases is employed to prepare and identify a series of four-coordinate gallium complexes, including [Ga(NCS)(4)](-) , [GaX(n)(NCS)(4 - n)](-) (X = Cl, Br or I) and [GaX(m)Y(n)(NCS)(4 - m - n)](-) (in which X and Y are different halide ligands). The method of pairwise interactions is used to calculate the chemical shifts and lends support to the assignments. Vibrational frequencies derived from Raman spectra and the Ga-71, N-14 and C-13 NMR chemical shifts of the se species are reported. [Ga(NCS)(4)](-) is characterized by a Ga-71 r esonance at 125 ppm, N-14 resonance at -257 ppm (MeNO(2) scale) and v( Ga-NCS)(sym) = 318 cm(-1). Two of the species, [GaCl3NCS](-) and [GaCl 2(NCS)(2)](-), exhibit Ga-N coupling which is observed in both Ga-71 a nd N-14 NMR spectra as (1)J(Ga-N-14) = 97 and 112 Hz, respectively. Th e Ga-71 NMR spectra of gallium halide etherates, GaX(n)Y(3 - n).OEt(2) (X and Y = Cl, Br or I; n = 0-3), have been observed in the range 242 to -220 ppm and consist of much broader signals than those of the com plex anions, reflecting the low symmetry and other influences of the d ifferent kinds of ligands.