PENTAMETHYLCYCLOPENTADIENYL DERIVATIVES OF TRANSITION-METALS .6. CARBONYLATION OF METAL-METAL TRIPLE BONDS - HIGH-PRESSURE INFRARED SPECTROSCOPIC STUDY

Reactions of appropriate metal carbonyl derivatives with pentamethylcyclopentadiene in boiling n-decane provide improved routes to the metalmetal triple bond compounds [(CH3)5C5M(CO)2]2 (M Cr, Mo, and W) as well as (CH3)5C5M(CO)3 (M Mn and Re) and [(CH3)5C5Ru(CO)2]2. Infrared spectroscopic studies at elevated pressures indicate that the ease of CO addition in n-tetradecane solution to the metalmetal triple bond in the analogous compounds [(CH3)5C5M(CO)2]2 (M Cr, Mo, and W) to form the corresponding [(CH3)5C5M(CO)3]2 derivatives increases in the sequence Cr < W < Mo. These carbonylations have also been carried out on the preparative scale leading to the isolation of the three metalmetal single bonded [(CH3)5C5M(CO)3]2 derivatives (M Cr, Mo, and W) in the solid state. The chromium derivative [(CH3)5C5Cr(CO)3]2, reported here for the first time, is the least stable of these compounds and is red-purple in contrast to the green [C5H5Cr(CO)3]2. © 1979.