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Abstract:Deprotonation of [(2-C 5 The complex also has a bent metallocene geometry, with average Ca-C and Ca-O distances are 2.670(6) and 2.407(3) Å respectively; the ring centroid-Ca-ring centroid angle is 136.6°.

The reaction of KCpni (Cpni = (C3H7) n C5H5 - n ; n = 3, 4) with MnCl2 in THF produces the metallocenes (Cp3i)2Mn or (Cp4i)2Mn in good yield. Solid-state magnetic susceptibility measurements indicate that orange-red (Cp3i)2Mn is in high-spin/low-spin equilibrium at room temperature. In the solid-state, it has a centrosymmetric sandwich structure with an average Mn−C bond length (2.130(6) Å) typical of low-spin manganocenes. (Cp3i)2Mn reduces tetracyanoethylene (TCNE) to generate the TCNE radical anion. Despite the presence of additional electron-donating isopropyl groups, pale yellow (Cp4i)2Mn is entirely high-spin from room temperature to 10 K. The crystal structure of (Cp4i)2Mn reveals a bent metallocene structure, with a centroid−Mn−centroid angle of 167.4° and an average Mn−C distance of 2.42(2) Å. This structure is consistent with its high-spin electron configuration; the longer Mn−C bonds provide relief from the steric strain that would be present in a low-spin complex. The reaction of (Cp4i)2Mn with TCNE produces a tricyanovinylation product, C5(i-Pr)4HC(CN)C(CN)2, which was characterized by X-ray diffraction.