On the way to ferrocene-based multiple-decker sandwich complexes

Abstract

Three ferrocene derivatives, Li[FcBH 3], Li 2[1,1 ′-fc(BMe 3) 2] and Li 2[1,1 ′-fc(BMe 2pz) 2] [Fc=(C 5H 5)Fe(C 5H 4), fc=(C 5H 4) 2Fe, pz=pyrazolyl], have been synthesized and structurally characterized to investigate the interaction of the negatively charged sandwich complex with its Li + counterion(s) in the solid state. Single crystals of Li[FcBH 3] · (12-crown-4), obtained from a THF solution after addition of 12-crown-4, contain hexacoordinated Li + ions, which are bonded to one molecule of crown ether and to two hydrogen atoms of the BH 3 fragment. The compound Li 2[1,1 ′-fc(BMe 3) 2] crystallized from THF as solvent-separated ion pairs with each Li + being encapsulated by four THF molecules. Single crystals of Li 2[1,1 ′-fc(BMe 2pz) 2] were grown from diethyl ether. In this compound, the lithium ions are coordinated by two solvent molecules, the pyrazolyl side-arm and the cyclopentadienyl ring. Thus, Li 2[1,1 ′-fc(BMe 2pz) 2] can be regarded as a trinuclear segment of the polymeric structure [–(C 5H 4R)Li(C 5H 4R)Fe–] ∞ with R=BMe 2pz.