1258937-64-2Relevant articles and documents
Synthesis, structure, and reductive elimination in the series Tp′Rh(PR3)(ArF)H; Determination of rhodium-carbon bond energies of fluoroaryl substituents
Tanabe, Taro,Brennessel, William W.,Clot, Eric,Eisenstein, Odile,Jones, William D.
, p. 10495 - 10509 (2011/01/10)
A series of complexes of the type Tp′Rh(PR3)(Ar F)H, where PR3 = PMe3 (3) and PMe2Ph (9), ArF = C6F5 (a), 2,3,4,5-C 6F4H (b), 2,3,5,6-C6F4H (c), 2,4,6-C6F3H2 (d), 2,3-C6F 2H3 (e), 2,5-C6F2H3 (g), and 2-C6FH4 (h) and Tp′ = tris(3,5- dimethylpyrazolyl)borate, has been synthesized as stable crystalline compounds by the reactions of the [Tp′Rh(PR3)] fragment with the corresponding fluorinated aromatic hydrocarbons, and their structures were characterized by NMR spectroscopy and elemental analysis together with X-ray crystallography. The kinetics of the reductive eliminations of fluoroarenes from complexes 3a-h in benzene-d6 solutions at 140 °C were investigated, but were complicated by the formation of the rhodium(i) bisphosphine complex, Tp′Rh(PMe3)2 (4). On the other hand, thermal reactions of (9) in THF-d8 solutions at 120 °C resulted in the formation of an intramolecular C-H bond activated complex of the phenyl group on the phosphorus atom, Tp′Rh(κ2-C 6H4-2-PMe2)H (7), which prevents the formation of the corresponding bisphosphine complex. The experimentally determined rates of the reductive eliminations of fluoroarenes from the complexes 9a-h and their kinetic selectivities for formation in competition with the metallacycle have been used to determine relative Rh-CArF bond energies. The Rh-CArF bond energy is found to be dependent on the number of ortho fluorines. A plot of Rh-CArFvs. C-H bond strengths resulted in a line with a slope RM-C/C-H of 2.15 that closely matches the DFT calculated value (slope = 2.05).
