Two coordination modes of TCNE in the ruthenium amidinates: The first example providing experimental evidence for κ1-N to η2-C rearrangement

A stable ruthenium amidinate having a “κ1-N”-coordinated TCNE, Cp∗Ru(κ2-N(tBu)C(Mes)NtBu)(κ1(N)-TCNE) (2c), is synthesized by treatment of Cp∗Ru(κ2-N(tBu)C(Mes)NtBu) (1c) with TCNE, and the charge transfer nature is supported by ESR analysis. Close analogy in IR and UV–Vis spectroscopy of 2c with the intermediary species formed from the Ph analogue of 1c suggests that this intermediary product is “κ1-N TCNE” ruthenium amidinate, which is rearranged to the “η2-C TCNE” complex.