Binuclear hexafluorocyclopentadiene iron carbonyls: bis(dihapto) versus trihapto-monohapto bonding in iron-iron bonded structuresElectronic supplementary information (ESI) available: Tables S1-S6: coordinates of (C5F6)Fe(CO)n (n = 4, 3, 2); Tables S7-S22: coordinates of (C5F6)Fe2(CO)n (n = 8, 7, 6, 5); Tables S23-S28: harmonic vibrational frequencies (cm−1) and IR intensities (km mol−1) of (C5F6)Fe(CO)n (n = 4, 3, 2); Tables S29-S44: harmonic vibrational frequencies (cm−1) and IR intensities (km

• Main Authors: Deng, Jianming, Li, Qian-shu, Xie, Yaoming, King, R. Bruce, Schaefer, III, H. F
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c3nj00311f

Binuclear organometallic systems incorporating free cyclopentadiene (C 5 H 6 ) as a ligand rather than the ubiquitous cyclopentadienyl ligand (C 5 H 5 ) have never been reported in the literature. However, the hexafluorocyclopentadiene ligand (C 5 F 6 ) is known to form the stable binuclear carbonyl derivatives (η 2 ,η 2 -C 5 F 6 )Fe 2 (CO) 8 and trans -(η 3 ,η 1 -C 5 F 6 )Co 2 (CO) 7 . The related hexafluorocyclopentadiene iron carbonyl systems (C 5 F 6 )Fe(CO) n ( n = 4, 3, 2) and (C 5 F 6 )Fe 2 (CO) n ( n = 8, 7, 6, 5) have now been explored using density functional theory. The hexafluorocyclopentadiene ligand is found to use one or both of its C&z.dbd;C double bonds to bind either as a dihapto η 2 -C 5 F 6 monoolefin or a tetrahapto η 4 -C 5 F 6 diolefin in mononuclear (C 5 F 6 )Fe(CO) n structures. In binuclear iron carbonyl structures lacking direct iron-iron bonds, such as the lowest energy trans - and cis -(η 2 ,η 2 -C 5 F 6 )Fe 2 (CO) 8 structures as well as higher energy trans -(η 2 ,η 2 -C 5 F 6 )Fe 2 (CO) n ( n = 7, 6, 5) structures, the hexafluorocyclopentadiene ligand binds as a bis(dihapto) diolefin. However, the lowest energy (C 5 F 6 )Fe 2 (CO) n ( n = 7, 6, 5) structures have cis stereochemistries with direct iron-iron bonds of orders ranging from one to three. In such lowest energy structures the hexafluorocyclopentadiene ligand is bonded to the Fe 2 unit as a trihapto-monohapto η 3 ,η 1 -C 5 F 6 ligand. The structures and energetics of the hexafluorocyclopentadiene iron carbonyls (C 5 F 6 )Fe 2 (CO) n ( n = 8, 7, 6, 5) are explored using density functional theory.