Peculiar binding modes of a ligand with two adjacent beta-diiminato binding sites in alkali and alkaline-earth metal chemistry.
Reaction of the diprotic ligand [Xanthdim]H(2) (a ligand system where two adjacent beta-dialdimine units are linked by a xanthyl backbone) with 2 equiv of potassium hydride or benzylcesium gave access to bimetallic alkali metal complexes. These complexes were structurally characterized by X-ray diffraction, which showed that the beta-diiminato units are orientated in a W-conformation. Treatment with 2 equiv of Mg[N(SiMe(3))(2)](2)(THF)(2) led to the formation of the heteroleptic complex [Xanthdim][MgN(SiMe(3))(2)(THF)](2), that crystallized as a highly strained monomer. The heteroleptic Mg complex is remarkably stable against ligand exchange but is not active in CO(2)/cyclohexene oxide copolymerization. Reaction with Ca[N(SiMe(3))(2)](2)(THF)(2) gave the homoleptic complex [Xanthdim][Ca(THF)]. Both alkaline-earth metal complexes display considerable distortions in their solid state structure.
Piesik
Dirk F-J
DF
Anorganische Chemie, Universität Duisburg-Essen, 45117 Essen, Germany.
Haack
Peter
P
Harder
Sjoerd
S
Limberg
Christian
C