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| Theoretical studies predict the lowest energy structures of the binuclear cyclopentadienylrhenium hydrides Cp2Re2Hn (Cp = 5-cyclopentadienyl ligand; n = 4, 6, 8) to have a central doubly bridged Re2(μ-H)2 unit with terminal ?5-Cp rings and the remaining hydrides as terminal ligands. However, the lowest energy Cp2Re2H2 structure by more [less] than 12 kcal/mol has one terminal ?5-Cp ring, a bridging ?3 ,?2-Cp ring, and two terminal hydride ligands bonded to the same Re atom. The lowest energy hydride-free Cp2Re2 structure is a perpendicular structure with two bridging ?3,?2-Cp rings. The previously predicted bent singlet Cp2Re2 structure with terminal ?5-Cp rings and a formal Re-Re sextuple bond lies ~37 kcal/mol above this lowest energy (?3,?2-Cp)2Re2 structure. The thermochemistry of the CpReHn and Cp2Re2Hn systems is consistent with the reported synthesis of the permethylated derivatives Cp*ReH6 and Cp*2Re2H6 (Cp* = ?5-Me5C5) as very stable compounds. |
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| Keywords:physical chemistry; binuclear cyclopentadienylrhenium hydrides; thermochemistry; density functional theory |
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