US EPA

1110225 

Journal Article 

Extending the coordination chemistry of cobalt with the metalloligand [Pt-2(mu-S)(2)(PPh3)(4)]: Synthesis of the first cobalt(III) derivatives 

Clarke, HM; Henderson, W; Nicholson, BK 

2011 

1 

Inorganica Chimica Acta
ISSN: 0020-1693
EISSN: 1873-3255 

376 

1 

446-455 

10.1016/j.ica.2011.07.006 

WOS:000295592700060 

The coordination chemistry of the metalloligand [Pt-2(mu-S)(2)(PPh3)(4)] towards cobalt(II) and cobalt(III) centres has been explored using an electrospray ionisation mass spectrometry (ESI MS)-directed methodology. Reaction of [Pt-2(mu-S)(2)(PPh3)(4)] with CoCl2 center dot 6H(2)O in methanol gave a green-yellow suspension of the known adduct [Pt-2(mu-S)(2)(PPh3)(4)CoCl2], and the CoBr2 adduct could be similarly prepared. When in situ-generated [Pt-2(mu-S)(2)(PPh3)(4)CoCl2] is reacted with 8-hydroxyquinoline (HQ) and base, the initial product is the cobalt(II) adduct [Pt-2(mu-S)(2)(PPh3)(4)CoQ](+), which is then converted in air to the cobalt(III) adduct [Pt-2(mu-S)(2)(PPh3)(4)CoQ(2)](+), isolated as its hexafluorophosphate salt. The corresponding picolinate (Pic) derivative [Pt-2(mu-S)(2)(PPh3)(4)Co(Pic)(2)](+) was similarly prepared, however reaction of [Pt-2(mu-S)(2)(PPh3)(4)], CoCl2 center dot 6H(2)O and 8-(tosylamino)quinoline (HTQ) produced only the cobalt(II) adduct [Pt-2(mu-S)(2)(PPh3)(4)CoTQ](+). Reactions of [Pt-2(mu-S)(2)(PPh3)(4)], CoCl2 center dot 6H(2)O and dithiocarbamates gave cobalt(III) complexes [Pt-2(mu-S)(2)(PPh3)(4)Co(S2CNR2)(2)](+) [R = Et or R-2 = (CH2)(4)], and proceeded much more rapidly, consistent with the known ability of the dithiocarbamate ligand to stabilize cobalt in higher oxidation states. A study of the fragmentation of cobalt(III) adducts by positive-ion ESI mass spectrometry indicated that [Pt-2(mu-S)(2)(PPh3)(4)CoQ(2)](+) fragments to form the radical cation [Pt-2(mu-S)(2)(PPh3)(4)](center dot+), which could also be generated by ESI MS analysis of [Pt-2(mu-S)(2)(PPh3)(4)] in methanol-NaOH solution. In contrast, the corresponding indium(III) derivative [Pt-2(mu-S)(2)(PPh3)(4)InQ(2)](+), and the cobalt(III) dithiocarbamate [Pt-2(mu-S)(2)(PPh3)(4)Co(S2CN(CH2)(4))(2)](+) are much more reluctant to fragment under analogous conditions, and the differences are discussed in terms of cobalt(III) redox chemistry. (C) 2011 Elsevier B.V. All rights reserved. 

Platinum complexes; Cobalt complexes; Electrospray ionisation mass spectrometry; X-ray crystal structure