Synthetic, electrochemical, and theoretical studies of tetrairidium clusters bearing mono- and bis[60]fullerene ligands.
Heating a mixture of Ir(4)(CO)(9)(PPh(3))(3) (1) and 2 equiv of C(60) in refluxing chlorobenzene (CB) affords a "butterfly" tetrairidium-C(60) complex Ir(4)(CO)(6){mu(3)-kappa(3)-PPh(2)(o-C(6)H(4))P(o-C(6)H(4))PPh(eta(1)-o-C(6)H(4))}(mu(3)-eta(2):eta(2):eta(2)-C(60)) (3, 36%). Brief thermolysis of 1 in refluxing chlorobenzene (CB) gives a "butterfly" complex Ir(4)(CO)(8){mu-k(2)-PPh(2)(o-C(6)H(4))PPh}{mu(3)-PPh(2)(eta(1):eta(2)-o-C(6)H(4))} (2, 64%) that is both ortho-phosphorylated and ortho-metalated. Interestingly, reaction of 2 with 2 equiv of C(60) in refluxing CB produces 3 (41%) by C(60)-assisted ortho-phosphorylation, indicating that 2 is the reaction intermediate for the final product 3. On the other hand, reaction of Ir(4)(CO)(8)(PMe(3))(4) (4) with excess (4 equiv) C(60) in refluxing 1,2-dichlorobenzene, followed by treatment with CNCH(2)Ph at 70 degrees C, affords a square-planar complex with two C(60) ligands and a face-capping methylidyne ligand, Ir(4)(CO)(3)(mu(4)-CH)(PMe(3))(2)(mu-PMe(2))(CNCH(2)Ph)(mu-eta(2):eta(2)-C(60))(mu(4)-eta(1):eta(1):eta(2):eta(2)-C(60)) (5, 13%) as the major product. Compounds 2, 3, and 5 have been characterized by spectroscopic and microanalytical methods, as well as by single-crystal X-ray diffraction studies. Cyclic voltammetry has been used to examine the electrochemical properties of 2, 3, 5, and a related known "butterfly" complex Ir(4)(CO)(6)(mu-CO){mu(3)-k(2)-PPh(2)(o-C(6)H(4))P(eta(1)-o-C(6)H(4))}(mu(3)-eta(2):eta(2):eta(2)-C(60)) (6). These cyclic voltammetry data suggest that a C(60)-mediated electron transfer to the iridium cluster center takes place for the species 3(3)(-) and 6(2)(-) in compounds 3 and 6. The cyclic voltammogram of 5 exhibits six well-separated reversible, one-electron redox waves due to the strong electronic communication between two C(60) cages through a tetrairidium metal cluster spacer. The electrochemical properties of 3, 5, and 6 have been rationalized by molecular orbital calculations using density functional theory and by charge distribution studies employing the Mulliken and Hirshfeld population analyses.
Park
Bo Keun
BK
Department of Chemistry and School of Molecular Science (BK 21), Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701, Korea.
Lee
Gaehang
G
Kim
Kyoung Hoon
KH
Kang
Hongkyu
H
Lee
Chang Yeon
CY
Miah
Md Arzu
MA
Jung
Jaehoon
J
Han
Young-Kyu
YK
Park
Joon T
JT
D018360:Crystallography, X-Ray; D004563:Electrochemistry / Q000379:methods*; D037741:Fullerenes / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular
D037741:Fullerenes; D008024:Ligands; D007495:Iridium; C069837:fullerene C60