Synthesis and Structural Properties of Anhydrous Rare Earth Cinnamates, [RE(cinn)₃]

Anhydrous rare earth tris(cinnamates) [RE(cinn)(3)] (RE= La - Lu, Y and Sc and cinnH = trans-cinnamic acid) were prepared by metathesis in water and by direct reaction of the metal with cinnamic acid in a 1,2,4,5-tetramethylbenzene flux at ca. 200 degrees C. X-ray crystal structure determinations and X-ray powder data show that, in the solid state, the larger lanthanoids (La - Dy) form an isomorphous polymeric series consisting of homoleptic ninecoordinate metal centres bonded to three chelating and bridging tridentate cinnamates. The late REIII cinnamate (RE = Dy, Ho - Lu, Y) complexes also form linear one-dimensional polymeric chains with all RE metal atoms being seven-coordinate. The cinnamates are either bound tridentate bridging in a V-T,2:111 fashion, or mu-eta(1):eta(1) syn-syn bidentate bridging. A structural break occurs at dysprosium which has been characterised in both crystallographic forms, and gives solely the late RE form when precipitated at 80 degrees C. Sc-III cinnamate was also isolated as an analytically pure precipitate which was, again, found to be anhydrous in nature. A structural change was identified by powder XRD between the late REIII cinnamates and Sc-III cinnamate.