Starting from commercially available 4,4′-di-tert-butyldiphenylmethane the pincer ligand bis­(4-tert-butyl-2-(diphenylphosphino)­phenyl)­methane (PCP) was prepared in two steps in moderate yield. Treatment of a solution of RhCl3·3H2O in a mixture of isopropyl alcohol and toluene with equimolar amounts of PCP gave the dimeric rhodium complex 1. In an electrophilic metalation a facially coordinated pincer complex is formed. When PCP is treated with [CODRhCl]2 in a solution of pyridine, the square-pyramidal complex 2 is generated where the bis-phosphine PCP acts as bidentate ligand that coordinates in a cis fashion. SnCl2 inserts into the Rh–Cl bond of 2, which results in an oxidative addition of one of the methylene C–H bonds to form the Rh­(III) complex 3, where the PCP ligand coordinates in a meridional way. A 2 equiv portion of PCP reacts with 1 equiv of [CODRhCl]2 in the presence of the electron-donating ligands HPhPC6H4NMe2, PPh2Py, and PPh3, respectively, as well as with stanna- and germa-closo-dodecaborate to give the octahedral Rh­(III) complexes 4–8. Attempts to remove the HCl with KOtBu from complexes 4–6 produces the planar Rh­(I) compounds 9 and 10. No carbene formation has been observed.

The protonation of the benzo annulated cycloheptatriene PCP pincer ruthenium hydrido dicarbonyl complex using the superacid [H(Et2O)2][BArF24] launches a cascade of hydride shifts which lead to the hydrogenation of the ligand backbone.