Abstract
The intramolecular carbonyl exchange processes which occur in metal carbonyl complexes of the cyclic polyenes, azulene, guaiazulene, and 7-H-indene have been examined by carbon-13 NMR spectroscopy. These polyenes form dinuclear complexes with M₂(CO)₄L (M=Fe, Ru; L=Co, PEt₃) fragments in which the polyene bridges the two metal atoms. A unique pathway for internuclear carbonyl exchange is observed in (7-H-indene) Fe₂(CO)₄PEt₃. This process involves the transfer of one carbonyl ligand from the M(CO)₂PEt₃ fragment to the M(CO)₂ group with a concomitant rearrangement of the pi-electron density in 7-H-indene. Local scrambling may then take place on the newly formed M(CO)₃ group leading to selective scrambling of only three CO groups. Two carbonyl exchange processes are observed in (7-H-indene)- Fe₂(CO)₅, (azulene) Ru₂(CO)₅, and the two isomers of (guaiazulene) Ru₂(CO)₅. First, local exchange is observed on the M(CO)₃ fragment. This process occurs with a low activation barrier. Second, internuclear exchange occurs at temperatures greater than 25°. The internuclear process is postulated to occur via the same mechanism proposed for (7-H-indene)- Fe₂(CO)₄PEt₃. To help elucidate the carbonyl exchange mechanism in these molecules the crystal structure of (7-H-indene) Fe₂(CO)₅ has been determined. Crystals belong to the orthorhombic system, space group Pbca. Unit cell parameters are a=14.968(5), b=13.576(5), and c=13.124(7)A. The Fe-Fe bond length is 2.782(1)A..
Hanson, Brian Ernest (1978). Pathways for intramolecular carbonyl exchange in some metal carbonyl complexes. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -261105.