Zwitterionic Ring-Borylated <i>a</i><i>nsa</i>-Chromocene Complexes

Ring borylation of [Me4C2(η5-C5H4)2CrCO] by B(C6F5)3 affords the zwitterionic complex {Me4(η5-C5H4)(η5-C4H3B(C6F5)3)}CrH(CO) (1), the first structurally characterized bent-metallocene complex of Cr(4+). This species decomposes thermally to the zwitterionic species {Me4(η5-C5H4)(η5-C4H3B(C6F5)3)}Cr (2) and the ionic species [Me4C2(η5-C5H4)2CrCO][HB(C6F5)3] (3). The molecular structure of 2 is also described.