π-Backbonding on Group 9 Metal Complexes Bearing an η²-(H₂O@C₆₀) Ligand

Abstract

As a measure of d-π* back-donation, IR stretching modes are, in general, used for metal carbonyl compounds. Once the ligand is replaced with olefins (metal−arene complexes), it can be analyzed crystallographically unless otherwise the C−C bond length falls into values within standard deviation. Herein, we propose a novel measure using an η 2 -(H 2 O@C 60 ) ligand in group 9 metal− fullerene complexes, in which the stronger d-π* backbonding causes enhanced sp 3character on the coordinated olefinic bond and consequently leads to the restricted rotation for the H 2 O molecule as detectable by the 1 H NMR relaxation time. The π-backbonding strengths were, therefore, found to follow the ascending order of atomic numbers (Co < Rh < Ir) in CpM(CO)(η 2 -H 2 O@C 60 ) (Cp = cyclopentadienyl), associated with the anodic shift on oxidation potentials and hypsochromic shift on absorption edges.

Chiral Open-[60]Fullerene Ligands with Giant Dissymmetry Factors

“…The calculated oscillator strengths f and rotatory strengths R of f,s A - 1 , f,s C - 2 , and f,s A - 3 were shown as stick bands. The transition energies were calibrated with a factor of 0.72 . (b) HPLC profiles of 1 – 3 and reaction mixtures (CHIRALPAK IF, toluene, 1 mL/min).…”

C2-insertion into a fullerene orifice

“…Thus, a spin-rotation mechanism contributes to the proton relaxation as a primal contributor. 11 At 300 K, the T 1 values of H 2 O@ 1a and H 2 O@ 2a were recorded to be 3.12 and 2.11 s, respectively, demonstrating the 48% increase in relaxivity by the C2-insertion into the rim. Upon assuming the relaxation described solely by the spin-rotation mechanism, the T 1 profile obeys the Arrhenius-type thermal activation process.…”

The coordination chemistry of oxide and nanocarbon materials

“…For example, orbital misalignment in fullerenes prevents formation of (η 6 -C n ) 2 M interconnects described above. [181][182][183][184][185]…”