Exploring the Nuclearity and Structural Motifs ofPhenoxyimine Alkaline Earth Complexes

The nuclearity and structural motifs of alkaline earth complexes supported by bidentate phenoxyimine ligands has been explored by modulation of the stereoelectronic profile of the ligand, the atomic number of the metal, and the synthetic protocol. Changing the size of the <i>N</i>-imine substituents was found to have no effect on protonolysis reactions between [MgN″₂]₂ or CaN″₂(thf)₂ (N″ = N(SiMe₃)₂) and H^{<i>^t</i>Bu₂,Ar}L (1-OH-2-CH = NAr-4,6-<i>^t</i>Bu-C₆H₂; Ar = 2,6-ⁱPr–C₆H₃ = Dipp or 2,6-CHPh₂-4-Me-C₆H₂ = Ar*) regardless of reaction stoichiometry, with homoleptic <i>bis</i>(ligand) complexes (^{<i>^t</i>Bu₂,Dipp}L)₂Mg (<b>1</b>), (^{<i>^t</i>Bu₂,Ar*}L)₂Mg (<b>2</b>), (^{<i>^t</i>Bu₂,Dipp}L)₂Ca(thf) (<b>3</b>) and (^{<i>^t</i>Bu₂,Ar*}L)₂Ca(thf) (<b>4</b>) isolated. The importance of reaction protocol was demonstrated by the facile isolation of heteroleptic complex (^{<i>^t</i>Bu₂,Ar*}L)MgI(OEt₂) (<b>5</b>) from the reaction of equimolar amounts of H^{<i>^t</i>Bu₂,Ar*}L and MeMgI. Importantly, no subsequent ligand redistribution was observed when complex <b>5</b> readily reacted with KN” or KODipp to form (^{<i>^t</i>Bu₂,Ar*}L)Mg{N(SiMe₃)₂}(OEt₂) (<b>6</b>) and (^{<i>^t</i>Bu₂,Ar*}L)Mg(ODipp)(thf) (<b>7</b>). When small 4,6-phenoxide substituents were considered (H^H₂,DippL), multimetallic clusters were afforded: (^H₂,DippL)₃Ca₂(N″)(thf) (<b>8</b>) and (^H₂,DippL)₆Sr₃ (<b>9</b>).