Methyl Iodide as a Source of CH2: Two Routes for Generating 1,1‐Disubstituted Butatrienes in the Coordination Sphere of a Transition Metal

The addition of a CH2 group to the α-carbon atom of the metallacumulene unit RhCCC(R)Ph occurs with CH2N2 (1 → 2) and, surprisingly, also with CH3I (1 → 3). The free butatriene H2CCCC(tBu)Ph is generated from 2 (R = tBu) and CO. Analogously, the allenes H2CCCRPh (R = Ph, CF3) are accessible from the allene complexes trans-[RhCl{(1,2-η-H2C1C2C3(R)Ph}(PiPr3)2], which are formed by hydrogenation of 1 (R = Ph, CF3), and CO. L = iPr3.