Josephine A McKeon

Facile and stereoselective condensation of acetone with ammonia ligands on cobalt(III): structure of a N-bonded cyanate complex containing the 2-methyl-2-amino-4-imino-pentane ligand

The complex [(NH(3))(5)CoO(3)SCF(3)](CF(3)SO(3))(2) reacts with excess NaNCO in warm acetone solution to give, stereoselectively, a Schiff base complex (40%) which has been characterized by standard NMR techniques as one of the six isomers of [Co{NH(2)C(CH(3))(2)CH(2)C(CH(3))=NH}(2)(NH(3))NCO](ClO(4))(2). H(2)O, confirmed by a single crystal X-ray structural analysis. Schiff base formation in non-basic conditions for kinetically inert Co(III) complexes is unprecedented. Also, this is only the second cyanate complex of pentaaminecobalt(III) to be structurally characterized (CoNCO: Co-N, 1.908 Angstrom; N-C, 1.152 Angstrom; C-O, 1.206 Angstrom; Co-N-C, 170 degrees; N-C-O, 177 degrees)

The rediscovery of Alfred Werner's second hexol

A compound originally prepared by Alfred Werner but structurally misassigned has been shown by three independent X-ray structural analyses to be a hexanuclear species which can now be regarded as Werners second hexol, his first being that famous for being the first non-carbon containing species to be optically resolved.

Deactivation of the chlorosulfonate ion coordinated to pentaamminecobalt(III)

The synthesis and properties of [(NH 3 ) 5 CoOSO 2 Cl](ClO 4 ) 2 are described. This complex is one of the most reactive cobalt(III) species ever isolated ( t 1/2 10 s; 25°C; 0.1 M HClO 4 ). In water it yields [(NH 3 ) 5 CoOSO 3 ] + , [(NH 3 ) 5 CoOH 2 ] 3+ and [(NH 3 ) 5 CoCl] 2+ . The first two of these products come from the expected direct S-Cl and Co-O cleavages. The chloro complex arises via intramolecular linkage isomerisation to the transient [(NH 3 ) 5 Co-ClSO 3 ] 2+ species which then cleaves the S-Cl bond. Considerable attention is given to the characterisation of the Co-O 3 SCl species, including reaction in 17 O-H 2 O where the NMR spectra confirm Co- 17 OSO 3 , Co- 17 OH 2 and free 17 OSO 3 2 m products. The reactions have been studied also in aqueous base, 0.1 M HClO 4 and Me 2 SO where the same reactions are observed but in quite different proportions. In liquid ammonia, with or without added NH 4 + , no O-bonded sulphamate complex [(NH 3 ) 5 CoOSO 2 NH 2 ] 2+ arising from direct S-Cl clea...