Abstract:
The bulk magnetic susceptibilities of the binuclear nickel(11) complexes of the 1,3,5- triketonates from diethyl (2-oxocyclopentane-1,3-diy1)bisglyoxylate (H2ecg) (1) and diethyl 2,4,6-trioxoheptanedioate (H2decg) (2) have been measured over the temperature range 6-300 K. Antiferromagnetic spin-spin coupling is observed in each case with Nee1 temperatures in the range 45-65 K. The X-ray crystal structure of [ N i ( e ~ g ) ( p y ) ~ ] ~ . ( p y ) has been solved. The complex crystallize! with one pyridine of solvation in the space group PT [ a 10.507(1), b 13.384(1), c g q 9 9 2 ( 1 ) A, a 103.004(9), /3 115.867(9), y 86.857(10)", Z = 11. The molecule is binuclear with two coplanar triketonate dianions bridging the two six-coordinate nickel atoms through a di-p-0x0 linkage [Ni-Ob-Ni angle 102.0(1)"]. Two pyridine molecules and four triketonate oxygen atoms are bound to each nickel atoms. Magnetostructural correlations are presented in comparison with binuclear copper(11) 1,3,5- triketonates. The marked decrease in spin-spin interaction in the nickel complexes is attributed to increasing metal-bridging oxygen bond lengths that decrease the efficacy of the u antiferromagnetic pathway xyllOb 1 x y and contributions from the ferromagnetic xyllOb / / z2 pathway.
