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

The X-ray crystal structures of two heteroleptic dimeric carboxylate complexes, [Eu(HBpz(3))(2)(mu -O2CPh)](2) and [Eu(HBpz(3))(mu -O2CPh)(2)](2) have been determined, together with those of the known mononuclear complexes [Eu(HBpz(3))(2){OC(Me)CHC(Me)O}] and [Eu(HBpz(3))(2){OC(Ph)CHC(Ph)O}]. A fifth complex, [{Gd(HBpz(3))(2)}(2){mu -1,4-(O2C)(2)C6H4}] 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(HBpz(3))(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 Ln(3+) ionic radius. In structures containing a non-bridging kappa (2) carboxylate ligand, the s.a.s. values fall below the trend line for [Ln(HBpz(3))(2)(dik)]. However, for the two binuclear complexes containing bridging carboxylate ligands the s.a.s. values lie above this trend line.