Structural studies of some mono- and bi-nuclear heteroleptic trispyrazolyborate complexes containing eight-co-oordinated europium and gadolinium

Abstract

The X-ray crystal structures of two heteroleptic dimeric carboxylate complexes, [Eu(HBpz₃)₂(μ-O₂CPh)]₂ and [Eu(HBpz₃)(μ-O₂CPh)₂]₂ have been determined, together with those of the known mononuclear complexes [Eu(HBpz₃)₂{OC(Me)CHC(Me)O}] and [Eu(HBpz₃)₂{OC(Ph)CHC(Ph)O}]. A fifth complex, [{Gd(HBpz₃)₂}₂{μ-1,4-(O₂C)₂C₆H₄}] whose structure has also been determined, contains two gadolinium centres linked by a ditopic 1,4-benzenedicarboxylate ligand. The solid angle sum (s.a.s.) values of complexes within the series [Ln(HBpz₃)₂(dik)] [dik = OC(Me)CHC(Me)O, Ln = Ce, Eu, Yb; dik = OC(Ph)CHC(Ph)O, Ln = Eu; dik = 1-O-2-(OCH)-4-(OMe)C₆H₃, Ln = Eu; dik = 2-O₂CC₅H₄NO, Ln = Tb] vary linearly with Ln³⁺ ionic radius. In structures containing a non-bridging κ² carboxylate ligand, the s.a.s. values fall below the trend line for [Ln(HBpz₃)₂(dik)]. However, for the two binuclear complexes containing bridging carboxylate ligands the s.a.s. values lie above this trend line.