Synthesis, structure and hapticity interconversion reactions of pentahapto-bonded cyclooctadienyl complexes of molybdenumElectronic supplementary information (ESI) available: 1H and 13C NMR data for [Mo(CO)2(L′)(L2)(η3-C8H11) 8a, 9a 11a, 12a, 3b, 8b, 9b, 10b, 11b, 12b. See http://www.rsc.org/suppdata/dt/b2/b209975f/

FeI 2 (thf) 2 ] was sequentially treated with Li(C 5 Me 5 ) and the potassium salt of the phenylmethallyl ("open indenyl") ligand oInd Me , leading to selective formation of the half-open ferrocene [(η 5 -C 5 Me 5 )Fe(η 5 -oInd Me )] (1). A variable-temperature NMR study revealed a barrier of ca. 12 kcal mol −1 for the rotation of the phenyl group. The apparent lability and susceptibility of the oInd Me ligand in 1 to undergo η 5 −η 3 interconversion allowed the preparation of the complexes [(η 5 -C 5 Me 5 )Fe(η 3 -oInd Me )(L)] (2, L = CO; 3, L = IMe; 4, L = PMe 3 ) by addition of carbon monoxide, 1,3,4,5tetramethylimidazolin-2-ylidene (IMe), and trimethylphosphine, respectively. The η 3 -bound phenylmethallyl ligand in these complexes initially adopts an anti orientation with regard to the relative positions of the phenyl and methyl substituents, followed by anti-to-syn isomerization. For L = CO, both isomers could be isolated, and the conversion of anti-2 into syn-2 was monitored by NMR spectroscopy at 35, 50, 65, and 80 °C, affording an enthalpy of activation of ΔH ⧧ = 24(1) kcal mol −1 for this equilibrium reaction. On the basis of DFT calculations, a mechanism is proposed that proceeds via consecutive η 3 −η 1 −η 3 interconversions and involves η 3 -benzyl intermediates. In contrast, rapid equilibration was observed for L = IMe and PMe 3 . Addition of 1,2-bis(dimethylphosphino)ethane (dmpe) to 1 gave [(η 5 -C 5 Me 5 )Fe(η 1 -oInd Me )(dmpe)] (5), containing the oInd Me ligand bound in an η 1 -allyl fashion. η 5 -to-η 3 hapticity interconversion was also observed upon reaction of 1 with methyl iodide and CH 2 Cl 2 , which formed the Fe(III) complexes [(η 5 -C 5 Me 5 )Fe(η 3 -oInd Me )(X)] (6, X = I; 7, X = Cl); solid-state magnetic susceptibility measurements on 6 revealed an S = 1/2 ground state. The mixed indenyl−open indenyl complex [(η 5 -Ind″)Fe(η 3 -oInd Me )(CO)] (9, Ind″ = 1,3-di(tert-butyl)indenyl) was isolated from the stepwise reaction of [FeI 2 (thf) 2 ] with Na(Ind″), K(oInd Me ), and CO. The molecular structures of 1, anti-2, syn-2, syn-3, 5, syn-6, syn-7, and syn-9 were established by single-crystal X-ray diffraction.

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References 19 publications

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