-effects in alkaline earth metal octaphenylmetallocenophanes and a derived -ferrocene.

The synthesis and structural characterisation of a series of alkaline earth -octaphenylmetallocenes (Mg, Ca, Sr, Ba) bearing an ethylene bridge are described. The complexes [AE(CPhCH)(thf)] (AE = Mg (1), Ca (2) = 1; AE = Sr (3), Ba (4), = 2) were obtained through reductive dimerisation of 1,2,3,4-tetraphenylfulvene, facilitated by zero-valent metals and fully characterised by NMR spectroscopy. Single-crystal XRD studies reveal distinct binding differences of the Cp ligands to Mg in complex 1 compared to the heavier analogues (η η). Complex 3 is the first structurally characterised -metallocene complex of Sr. An -effect was observed for the Ba complex 4 which showed good stability at room temperature in contrast to the previously described non-bridged analogue. Efficient transmetallation from the Ca complex 2 to FeCl provided the new -ferrocene complex [Fe(CPhCH)] (5). Structural, spectroscopic and electrochemical properties of this bent ferrocenophane complex were compared to those of the known unbridged octaphenylferrocene.