Trapping an unprecedented Ti(3)C(3) unit inside the icosahedral C(80) fullerene: a crystallographic survey

The sub-nanometer cavity of fullerene cages is an ideal platform to accommodate otherwise unstable species for accurate structural characterization with, for example, rather accurate single crystal X-ray diffraction (XRD) crystallography. Herein, we report the successful entrapment of an isolated Ti(3)C(3) moiety inside the icosahedral-C(80) cage to form Ti(3)C(3)@I(h)-C(80)via an arc-evaporation process in the gas phase. The single crystal XRD crystallographic results unambiguously reveal that the C(3)-unit adopts an unprecedented cyclopropane-like structure which coordinates with the three titanium atoms in an unexpected fashion where the triangular C(3)-unit is nearly perpendicular to the Ti(3)-plane. The intercalation of a cyclopropanated C(3)-unit into the titanium layer is thus unambiguously confirmed. The theoretical results reveal that the Ti(3)C(3) cluster transfers six electrons to the I(h)-C(80) cage so that each titanium atom has a positive charge slightly above +2 and the C(3)-unit is negatively charged with about –1. It is noteworthy that this is the first observation of the cyclopropane-coordination fashion in any reported organometallic complex, providing new insights into coordination chemistry.