Synthesis of Cyclopentadienyl‐Based Tricarbonyl Rhenium Complexes and Some Unusual Reactivities of Cyclopentadienyl Substituents

Abstract

Cyclopentadienyl-based (Cp-based) tricarbonyl rhenium complexes [Cp′Re(CO) 3 ] are convenient precursors for the corresponding Cp-based trioxorhenium complexes (Cp′ReO 3 ), which are potential catalysts for the deoxydehydration (DODH) of diols to olefins. To evaluate the influence of different Cp substituents in Cp′ReO 3 complexes in DODH, a series of alkyl-substituted Cp′Re(CO) 3 complexes (1a-8a) were synthesized. High yields (86-98 %) were obtained from the reactions of Re 2 (CO) 10 with the corresponding Cp′H ligands (1-8). The C-O infrared absorptions of 1a-8a indicate that the electron-donating character of the Cp ligand increases with the number of substituents attached directly to the Cp ring. Analogous aryl-substituted complexes 10a-12a containing bulky phenyl groups were accessed through the salt metathesis of ReBr(CO) 5 with [a] The alkyl-appended Cp′H ligands were either obtained commercially (2, 5, 6, and 8) or synthesized through literature pro-Eur. J. Inorg. Chem. 2017, 741-751 www.eurjic.org 742 Figure 3. Molecular crystal structure of 9a, drawn at the 50 % probability level. Hydrogen atoms are omitted for clarity.Scheme 3. Proposed mechanism for the formation of 9a through the [6+4] cycloaddition of fulvene species B with 1,2,3,4-tetramethylcyclopentadiene 8.