EFFECT OF POLYETHER LIGANDS ON STABILITIES AND MASS-TRANSPORT PROPERTIES OF A SERIES OF GADOLINIUM(III) BETA-DIKETONATE COMPLEXES

The reaction of [Gd(tmhd)(3)](2) (1) (tmhd-H = 2,2,6,6-tetramethylheptane-3,5-dione) with a selected range of chelating O-donors such as, mono- {CH3OCH2CH2OCH3}, di- {CH3(OCH2CH2)(2)OCH3}, tri- {CH3(OCH2CH2)(3)OCH3}, tetra- {CH3(OCH2CH2)(4)OCH3), and heptaglyme {CH3(OCH2CH2)(7)OCH3} in n-hexane at room temperature yielded the compounds [Gd(tmhd)(3)(monoglyme)] (2), [Gd(tmhd)(3)(diglyme)] (3), [{Gd(tmhd)(3)}(2)(triglyme)] (4). [{Gd-(tmhd)(3)}(2)(tetraglyme)] (5), and [(Gd(tmhd)(3)}(2)(heptaglyme)] (6), respectively. The complexes are either monomers (2, 3) or dimers (1, 4-6) and have been characterized by microanalyses, solution cryoscopy in benzene, FT IR, mass spectrometry, and sublimation, TGA, and DSC studies. Complexes 1, 2, 5, and 6 have also been characterized by X-ray crystallography. 1 and 6 both crystallize in the monoclinic space group P2(1)/n, with a = 12.228(2) Angstrom, b = 27.615(2) Angstrom, c = 21.843(11) Angstrom, and beta = 105.37(6)degrees (1) and a = 11.773(2) Angstrom, b = 18.712(3) Angstrom), c = 21.610(3) Angstrom, and beta = 103.53(1)degrees (6). 2 and 5 crystallize in the triclinic space group P $$($) over bar 1 with a = 10.814(2) Angstrom, b = 12.141(3) Angstrom, c = 16.534(2) Angstrom, alpha = 83.90(1)degrees, beta = 88.20(1)degrees, and gamma = 71.85(1)degrees (2) and a = 11.934(2) Angstrom, b = 19.478(4) Angstrom, c = 20.508(10) Angstrom, alpha = 99.25(1)degrees, beta = 106.94(2)degrees, and gamma = 104.76(1)degrees, (5), The gadolinium ion shows a seven-coordinate distorted monocapped trigonal prismatic geometry in 1 and an eight coordinate square antiprismatic geometry in the other compounds. In 2 the monoglyme nets as bidentate chelating ligand. The tetraglyme and heptaglyme molecules in complexes 5 and 6, respectively, act as chelating as well as bridging ligands, utilizing four of their available oxygen atoms for coordination. All these compounds are air and water stable. and those with the longer glymes have good volatilities and thermal stabilities, as demonstrated by sublimation, TGA, and DSC studies.