Na[cyclo-((P5Bu4)-Bu-t)] (1) reacts with [RhCl(PPh3)(3)] (1:1) to give the first rhodium(l) complex With a tetra-tert-butylcyclopentaphosphanide ligand, [Rh{cylco-((P5Bu4)-Bu-t)}(PPh3)(2)] (2). 2 was characterized by NMR (H-1, C-13, P-31), MS, IR, and X-ray structure determination.