Coordination number 12 in praseodymium and 11 in neodymium complexes with organofluorotitanate ligands

AbstractThe complexes of [Pr{(C 5 Me 5 ) 2 Ti 2 F 7 } 3 ] 2 and [Nd{(C 5 Me 5 ) 2 Ti 2 F 7 } 3 ] 3 were obtained by the reaction of[Hdmpy] [(C 5 Me 5 ) 2 Ti 2 F 7 ] 1 (dmpy / 2,6 dimethylpyridine, C 5 H 3 NMe 2 ), with praseodymium(III) and neodymium(III) trifluor-omethanesulfonate. The X / ray crystal structures of 2 and 3 exhibit a fluorine environment of 12 at the praseodymium and of 11 atthe neodymium with [(C 5 Me 5 ) 2 Ti 2 F 7 ] acting as well as a tetra- and as a three-fluorodentate ligand. Both complexes retained theirstructures in solution. Complex 2 is the first molecular compound containing Pr / F bonds.# 2003 Elsevier Science Ltd. All rights reserved. Keywords: Fluoride; Praseodymium; Neodymium; X-ray structure; Titanium 1. IntroductionLanthanide (Ln) contraction, a decrease of bonddistances (d(Ln / X)) with an increase of the lanthanideatom number, was observed in ionic (a shrinking of theionic radii), covalent, and coordination compounds [1].Moreover, lanthanide contraction affects the coordina-tion number at the central atom and the geometry of thecomplexes [2], the mechanism and consequently the rateof ligand exchange [3]. This property was used for theoptimization of the catalytic behavior of lanthanidecatalysts [4]. The coordination number 12 in lanthanidecomplexes was achieved with small atoms, such asoxygen and in a few cases with nitrogen [2,5]. Recentlywe prepared the complex [La{(C