title: Synthesis and properties of [CoCp*(2,5-PC4tBu2H2)]: the first monophosphacobaltocene.
abstract: 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.affiliation: Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 9QR, UK.
authors.forename: Claire
authors.initials: C
authors.lastname: Burney
authors.forename: Duncan
authors.initials: D
authors.lastname: Carmichael
authors.forename: Kareen
authors.initials: K
authors.lastname: Forissier
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Green
authors.forename: François
authors.initials: F
authors.lastname: Mathey
authors.forename: Louis
authors.initials: L
authors.lastname: Ricard