Synthesis, structures and reactions of doubly bridged biscyclopentadienyl diruthenium complexes (CR2)(EMe2)[(η5-C5H3)Ru(CO)2]2 (R = Me, H; E = Si, Ge)

► Title compounds contain the longest Ru-Ru bonds among all di-Cp di-Ru analogues. ► Structurally novel products (CMe2)(SiMe2)[(η5-C5H3)2Ru2(CO)3(X)](μ-X) are obtained. ► Ru3(CO)12 has different reactivity from Fe(CO)5 towards double-bridged di-Cp ligands. ►Reactivity of title compound with non- or singly bridged analogues was compared. ► Molecular structures of 7 compounds were determined by X-ray diffraction.