Half-way coordination state of a butadienyl group on ruthenium. η3-Allylic bonding with η1-character or vice versa.

Article abstract of DOI:10.1016/0022-328X(92)83276-N

The butadienyl complexes formed by the reaction of trans-(R¹)CH=CHC<*>CR² (R¹, R²=SiMe3, t-Bu, Me, Et) with RuCl(CO)H(PPh3)3 exhibit unique structures: instead of taking the 18-electron configuration of the metal by conventional η³-coordination of the butadienyl ligand, they shift significantly to the 16-electron η¹-coordination state.