Preparation of η 2-acetylene- and η 1-vinylidene-manganese complexes from p-diethynylbenzene and cymantrene. X-ray crystal and molecular structure of Cp(OC) 2MnCCHC 6H 4CBrCH 2

Abstract

Cp(OC) 2Mn(THF) reacts with p-diethynylbenzene (Deb), yielding Cp(OC) 2Mn(Deb) (I) and [Cp(OC) 2Mn] 2(Deb) (II) with the η 2-acetylene coordination of Deb (to both Mn atoms in II). Under the action of PhLi, I and II are isomerized into Cp(OC) 2MnCCHC 6H 4CCH (III) and [Cp(OC) 2MnCCH] 2C 6H 4 (VI). Treatment of I with PhLi, LiBr and an excess of HCl in ether, as well as direct interaction of III with LiBr and HCl/Et 2O, gives Cp(OC) 2MnCCHC 6H 4CBrCH 2 (IV), which has been characterized by an X-ray single-crystal diffraction study. III adds PPh 3, yielding a zwitterionic complex, Cp(OC) 2Mn −C(P +Ph 3)CHC 6H 4CCH (V).