Hydroformylations of cyclopentene and 3,3-dimethylbut-1-ene were performed using both Rh-4(CO)(12) and (eta(5)-C5H5)Mo(CO)(3)H as precursors in n-hexane at 298 K. Both stoichiometric and catalytic hydroformylations were conducted as well as isotopic labeling experiments. Six organometallic pure component spectra were recovered from the high-pressure FTIR experiments, namely the known species Rh-4(CO)(12), (eta(5)-C5H5)Mo(CO)(3)H, RCORh(CO)(4), and the new heterobimetallic complexes RhMo(CO)(7)(eta(5)-C5H5), a weak hydrogen bonded species (eta(5)-C5H5)Mo(CO)(3)H-C5H9CORh(CO)(4), and a substituted RhMo(CO)(7-y)(eta(5)-C5H5)L-y, where y=1 or 2 and L = (pi-C5H8). The main findings were (1) catalytic binuclear elimination (CBER) occurs between (eta(5)-C5H5)Mo(CO)(3)H and RCORh(CO)(4) resulting in aldehyde and RhMo(CO)(7)(eta(5)-C5H5), and this mechanism is responsible for ca. 10% of the product formation; (2) molecular hydrogen is readily activated by the new heterobimetallic complex(es); (3) FTIR and DFT spectroscopic evidence suggests that the weak hydrogen bonded species (eta(5)-C5H5)Mo(CO)(3)H-C5H9CORh(CO)(4) has an interaction of the type eta(5)-C5H4-H center dot center dot center dot O=C; and (4) independent physicochemical experiments for volumes of interaction confirm that significant solute-solute interactions are present. With respect to the efficiency of the catalytic cycle, the formation of a weak (eta(5)-C5H5)Mo(CO)(3)H-C5H9CORh(CO)(4) complex results in a significant decrease in the measured turnover frequency (TOF) and is the primary reason for the inhibition observed in the bimetallic catalytic hydroformylation. Such hydrogen bonding through the eta(5)-C5H5 ring might have relevance to inhibition observed in other catalytic metallocene systems. The present catalytic system is an example of concurrent synergism and inhibition in bimetallic homogeneous catalysis.