Calcium stilbene complexes: structures and dual reactivity

Addition of a calcium hydride complex to diphenylacetylene gave a complex in which the stilbene dianion symmetrically bridges two Ca²⁺ions. With H₂, this complex reacts as a double Brønsted base. In reaction with I₂it provides two electrons.

Exploiting σ/π coordination isomerism to prepare homologous organoalkali metal (Li, Na, K) monomers with identical ligand sets

Tetraamine Me(6)TREN has been used as a scaffold support to provide coordinative saturation in the complexes PhCH(2)M⋅Me(6)TREN (M=Li, Na, K). The Li derivative displays a Li−−C σ interaction with a pyramidalized CH(2) both in the solid state and in solution, and represents the first example of η(4) coordination of Me(6)TREN to lithium. In the sodium derivative, the metal cation slips slightly towards the delocalized π electrons whilst maintaining a partial σ interaction with the CH(2) group. For the potassium case, coordinative saturation successfully yields the first monomeric benzylpotassium complex, in which the anion binds to the metal cation exclusively through its delocalized π system resulting in a planar CH(2) group.