Organoaluminates with Three Terminal Phenylethynyl Groups and Their Interactions with Alkali Metal Cations

The synthesis of [K + ·THF(2,6- i Pr 2 C 6 H 3 N(SiMe 3 )Al(C⋮CPh) 3 ) - ] 2 ( 1 ), [Na + ·THF (2,6- i Pr 2 C 6 H 3 N(SiMe 3 )Al(C⋮CPh) 3 ) - ] 2 ( 2 ), and [Li + ·dioxane (2,6- i Pr 2 C 6 H 3 N(SiMe 3 )Al(C⋮CPh) 3 ) - ] 2 ·2dioxane ( 3 ) respectively by the reaction of [2,6- i Pr 2 C 6 H 3 N(SiMe 3 )AlCl 2 ] 2 ( 4 ) with the corresponding phenylethynyl alkali metal salt is reported. In compound 1 the potassium ( 2, sodium) interacts with the C⋮C bonds of four phenylethynyl groups. A further coordination site of the potassium (sodium) is occupied by a THF molecule. Thus, the cation therein acts as a bridging moiety to form the dimer. In compound 3 each of the lithium cations is 2-fold coordinated by phenylethynyl ligands and two dioxane molecules. One of the dioxane molecules in 3 functions as a bridge forming the dimer. The herein described compounds are the first structurally characterized species having three terminal phenylethynyl groups bound to the aluminum atom.