Complexes of the heavier alkaline earth metals containing β-diketiminato and iodide ligand sets

Treatment of [(2,6-iPr(2)C(6)H(3))NC(tBu)CH2C(tBu)N(2,6-iPr(2)C(6)H(3))]((LH)-H-Ar') with potassium hydride in etrahydrofuran afforded K(eta(1)-L-Ar')(THF)(3) (89%) as a yellow crystalline solid after workup. The crystal structure of K(eta(1)-L-Ar')(THF)(3) revealed an open monomeric molecule in which the potassium ion is bonded to three tetrahydrofuran ligands and one eta(1)-beta-diketiminato ligand through one of the nitrogen atoms. Treatment of K(eta(1)-L-Ar')(THF)(3) with equimolar amounts of MI2 (M = Ca, Ba) afforded [Ca(eta(5)-L-Ar')(mu-I)(THF)](2) (62%) and [Ba(eta(2)-L-Ar')(mu-I)](2) (27%) as yellow crystalline solids. Treatment of M(eta(5)-L-tBu)(2) (M = Ca, Sr, Ba, L-tBu = tBuNC(CH3)CHC(CH3)NtBu(-)) with the corresponding metal iodide in tetrahydrofuran afforded [Ca(eta(5)-L-tBu)- (mu-I)(THF)](2) (68%), [Sr(eta(5)-L-tBu)(mu-I)(THF)](2) (53%), and [(eta(5)-L-tBu)Ba(mu-I)(mu-eta(2):eta(5)-L-tBu)Ba(eta(5)-L-tBu)](2)(24%). Structural assignments for these complexes were based on spectral and analytical data as well as X-ray crystallography. [Ca(eta(5)-L-tBu)(mu-I)(THF)](2) and [Sr(eta(5)-L-tBu)(mu-I)(THF)](2) are dimers that are held together by bridging iodide ligands, while [Ba(eta(5)-L-tBu)(mu-I)(mu-eta(2):eta(5)-L-tBu)- Ba(eta(5)-L-tBu)](2) is a tetramer containing two symmetrical dimeric units that are linked by two bridging iodide ligands. In benzene-d(6) solution, [Ca(eta(5)-L-Ar')(mu-I)(THF)](2) and [Ba(eta(2)-L-Ar')(P-I)](2) are stable toward ligand redistribution. [Ca(eta(5)-L-tBu)(mu-I)(THF)](2) exists as mixtures of three species in toluene-d8, but the mixed ligand complex is strongly favored under the conditions studied. At 31.3 degrees C, the equilibrium constant for ligand redistribution of [Sr(eta(5)-L-tBu)(mu-I)(THF)](2) to Sr(eta(5)-L-tBu)(2) and SrI2(THF)(2) in toluene-d(8) was 5.3 x 10(-5) M. (c) 2005 Elsevier Ltd. All rights reserved.