Synthesis and Characterization of a Rhodium(I) sigma-Alkane Complex in the Solid State

Transition metal-alkane complexes-termed sigma-complexes because the alkane donates electron density to the metal from a sigma-symmetry carbon-hydrogen (C-H) orbital-are key intermediates in catalytic C-H activation processes, yet these complexes remain tantalizingly elusive to characterization in the solid state by single-crystal x-ray diffraction techniques. Here, we report an approach to the synthesis and characterization of transition metal-alkane complexes in the solid state by a simple gas-solid reaction to produce an alkane sigma-complex directly. This strategy enables the structural determination, by x-ray diffraction, of an alkane (norbornane) sigma-bound to a d(8)-rhodium(I) metal center, in which the chelating alkane ligand is coordinated to the pseudosquare planar metal center through two sigma-C-H bonds.