Bulky group 2 octaphenylmetallocenes and direct access to calcium and ytterbium pseudo-grignard complexes

The reaction between Mg(nBu)2 and C5Ph4H2 in toluene at 100-110 ?C yielded octaphenylmagnesocene, [Mg(C5Ph4H)2], which has two parallel Cp rings despite the steric bulk of the ligands. The redox-transmetalation/protolysis (RTP) reaction between calcium metal, HgPh2, and C5Ph4H2 in thf afforded the bent calcium sandwich complex [Ca(C5Ph4H)2(thf)]. Two rare calcium and ytterbium pseudo-Grignard complexes, [M(C5Ph4H)(?-Br)(thf)2]2, were prepared from RTP reactions of the corresponding metal, PhHgBr, and C5Ph4H2 in thf. Reduction of the calcium bromide complex by KC8 in the presence of 18-crown-6 afforded the charge-separated potassium compound [K(18-crown-6)(thf)2][C5Ph4H], but no CaI species were detected.