The chromium phenylcarbyne complexes (η 5 -C 5 R 5 )(CO) 2 Cr CPh (2a: R = H; 2b: R = Me) have been prepared and their structure, cyclic voltammetry and reactions with PMe 3 are reported. The compounds 2a and 2b are obtained as red and purple thermolabile solids respectively after treatment of cis-Br(CO) 2 (pic) 2 Cr CPh (pic = 4-methylpyridine) (1) with NaCp (Cp = C 5 H 5 ) and KCp * (Cp * = C 5 Me 5 ) respectively. Complex 2a adds PMe 3 at the carbyne-carbon atom to give the green α-phosphoniocarbene complex Cp(CO) 2 Cr=C(PMe 3 )Ph (3), whereas 2b undergoes with PMe 3 a carbyne-carbonyl coupling reaction to afford the green η 2 ketenyl complex Cp * (CO)(PMe 3 )Cr[C(Ph)CO] (4). Cyclic voltammetry studies show the phenylcarbyne complexes 2a and 2b and the carbene complex 3 to undergo a reversible one-electron oxidation in CH 2 Cl 2 at E 1 2 = 0.39 V, E 1 2 = 0.20 V and E 1 2 = -0.52 V respectively (potentials vs. the ferrocene/ferrocenium redox couple). In comparison, the ketenyl complex 4 is electrochemically inactive in the potential range of -1.5 to 1.0 V. The crystal structures of 2a and 3 are reported.