Synthesis and properties of [CoCp*(2,5-PC4tBu2H2)]: the first monophosphacobaltocene.

Journal article

The reduction of the phosphacobaltocenium salt [CoCp*(2,5-PC(4)tBu(2)H(2))](+)[BPh(4)](-) (3; Cp*=pentamethylcyclopentadienyl) by magnesium in tetrahydrofuran (THF) furnishes the stable air-sensitive phosphacobaltocene [CoCp*(2,5-PC(4)tBu(2)H(2))] (4) in yields of up to 80 %. The crystal structure of 4 shows long Co-C(alpha) and short C(alpha)-C(beta)bonds in the phospholyl ligand, consistent with a semi-occupied molecular orbital (SOMO) having a" symmetry. A combined Amsterdam density functional (ADF)/photoelectron spectroscopic study, which confirms this assignment, gives ionisation energies (IE) of 5.02 eV from the SOMO and 8.89 eV from the phosphorus "lone pair". A comparison of cyclovoltammograms for 3 and the corresponding cyclopentadienyl complex [CoCp*(1,3-C(5)tBu(2)H(3))](+) [BPh(4)](-)(5) shows that replacing a CH group by an sp(2) phosphorus atom results in an anodic first reduction potential shift of 0.29 V.

Authors: Burney, C; Carmichael, D; Forissier, K; Green, J; Mathey, F

• Publication status: Published
• Journal: Chemistry (Weinheim an der Bergstrasse, Germany)
• Volume: 9
• Issue: 11
• Pages: 2567-2573
• Publication date: 2003-06-01
• DOI: 10.1002/chem.200204421
• EISSN: 1521-3765
• ISSN: 0947-6539
• Language: English
• Keywords: redox chemistry; cobalt; electronic structure; photoelectron spectroscopy; phosphametallocenes