Al. Chistyakov et Iv. Stankevich, PHYSICAL-CHEMISTRY - ON THE POSSIBILITY OF EXISTENCE OF ETA(5)-PI-COMPLEXES OF C-60 FULLERENE - PI-COMPLEXES WITH SILICON, Russian chemical bulletin, 45(10), 1996, pp. 2294-2301
Qualitative estimates of possibility of the formation of fullerene eta
(5)-pi-complexes have been carried out by the MNDO/PM3 method. It was
shown, as exemplified by the C-60 cluster, that the introduction of fi
ve univalent functional groups R (R = H, Cl, Br) to alpha-positions of
a separate pentagon of C-60 with the formation of [R(5)C(60)](-) anio
ns results in a pronounced increase in the pi-electron density on the
atoms of this five-membered cycle and more favorable conditions for th
e formation of pi-bonds with the eta(5)-ligand. The nature of the inte
raction between the atoms of the separate cycle in [R(5)C(60)](-) anio
n and eta(5)-ligand was analyzed by the example of hypothetical sandwi
ch systems R(5)C(60)SiCp. Half-sandwich complexes R(5)C(60)SiX (X = H,
CI) were also investigated. The local energy minima were found on the
potential energy surfaces (PES) of systems R(5)C(60)SiCp and R(5)C(60
),SiX with C-5v symmetry. These systems transform barrirlessly into et
a(5)-pi-complexes with the angular structure if the symmetry restricti
ons are removed. The most favorable conditions for eta(5)-pi-complexes
of R(5)C(60) to form are realized for R = H. The results obtained wer
e compared to those of semiempirical and nonempirical calculations of
bis (cyclopentadienyl) silicon.