A study of dynamic behavior of transition metal complexes with fullerene C60 using density function theory

Dynamic processes in the complexes of a general formula of [M(NO)Hn(PPh3)2(η2-C60)] (M = Co, Rh, n = 0; 1, 2, respectively, and Ru, n = 1; 3) were studied theoretically by means of density functional theory (DFT). Earlier two distinct dynamic processes were established for 1–3, namely a low barrier of organometallic group (OMG) rotation around the axis of C60 double bond with the metal ( Δ G exp #  = 9, 10, 14 kcal/mol, respectively) and η2,η2-haptotropic rearrangements (HR) consisting of a metal shifting over the whole surface of C60 with activation barrier approximately 2–4 kcal/mol higher than the corresponding barriers for rotation ( Δ G exp # were not measured quantitatively). Mechanisms of these both experimentally observed dynamic processes were theoretically modeled in our paper and activation barriers for rotation (ΔG = 8.5, 10.5, 15.1 kcal/mol) and HR (ΔG = 12.2, 12.2, 18.2 kcal/mol) for 1–3, respectively, were calculated, discussed and compared with experimental barriers from 13C EXCY and dynamic NMR at variable temperatures. Rotation of OMG for 1 and 2 has quite a straightforward mechanism and proceeds through η2-transition states TSrot(1, 2). For 3 the process of rotation is much more complicated and involves the intermediate IMrot(3) and two non-equivalent transition states, TS1rot(3) and TS2rot(3), with all stationary states on potential energy surface (PES) possessing η2-hapticity. HR rearrangements proceed via consequent intra- and inter-ring shifts of OMG over the whole surface of C60. Process occurs through the structurally similar for 1–3 η2-intermediates (IM) in which OMG coordinated to buckminsterfullerene at 6-5 ring fusion and η1-transition states (TS), respectively.