Remarkable Stability of (η5-C5H5)Re(CO)2L (L = n-Heptane, Xe, and Kr): A Time-Resolved Infrared Spectroscopic Study of (η5-C5H5)Re(CO)3 in Conventional and Supercritical Fluid Solution

Employing fast time-resolved infrared (TRIR) spectroscopy we have characterized CpRe(CO) 2 ( n -heptane), CpRe(CO) 2 (Xe), and CpRe(CO) 2 (Kr) (Cp = η 5 -C 5 H 5 ) at or above room temperature in n -heptane, supercritical Xe, and Kr solution. The reactivity of CpRe(CO) 2 ( n -heptane) with CO ( k 2 = 2.1 (±0.5) × 10 3 mol - 1 dm 3 s - 1 ) shows this complex to be the least reactive of the reported organometallic alkane complexes. We report a trend in reactivity of the early transition metal alkane complexes. CpRe(CO) 2 (Xe) and CpRe(CO) 2 (Kr) are also shown to have significant stability. CpRe(CO) 2 (Xe) is less reactive toward CO than all of the reported alkane complexes except CpRe(CO) 2 ( n -heptane).