959934-28-2Relevant academic research and scientific papers
One-electron oxidations of the methyldiphenylphosphonium cyclopentadienylide complexes M(η5-C5H 4PMePh2)(CO)3 (M = Cr, Mo, W): Formation and dimerization of the 17-electron, metal-centered radicals [M(η5- C5H4PMePh2)(CO)3]+
Brownie, John H.,Baird, Michael C.,Laws, Derek R.,Geiger, William E.
, p. 5890 - 5901 (2007)
Electrochemical oxidations of the group 6 metal complexes M(η5-C5H4PMePh2)(CO) 3 (M = Cr (1), Mo (2), W (3)) occur via one-electron processes at potentials that are highly positive of the values previously observed for the analogous 18-electron anions [M(η5-C5H 5)(CO)3]-. A value of +0.44 V was determined for the electronic effect of the R = [PMePh2]+ group compared to R = H in a C5H4R ligand, making it one of the most strongly electron-withdrawing substituents known. On the basis of the experimentally determined oxidation potentials and observations that the oxidized species were long-lived, bulk oxidations of 1, 2, and 3 by [FeCp 2][B(C6F5)4] were carried out to give the crystalline, dimeric products [M(η5-C5H 4PMePh2)(CO)3]2[B(C 6F5)4]2 (M = Cr (12 2+), Mo (222+), and W (32 2+)). These were isolated analytically pure and were characterized by IR (solid state and solution) and NMR (1H, 13C, 19F, 31P) spectroscopy, high-resolution mass spectrometry, and crystallographically. The dimers all contain metal-metal bonds that are comparable in length with or longer than the metal-metal bonds in the isoelectronic, neutral η5-C5H5 and η5-C5Me5 analogues, and the metal-metal bond in 122+ is the longest nonbridged Cr-Cr bond known. As a result of the apparent weakness of its Cr-Cr bond, 12 2+ dissociates significantly in solution to the paramagnetic radical cation 1+; the 1H NMR spectrum of this complex in THF at 298 K exhibits characteristic C5H4 resonances at δ26.08 and 13.62.
