Synthesis, characterisation and NMR study of paramagnetic heteropolynuclear anionic Pt-Co species. Crystal structures of [NBu4](2)[{cis-Pt(C6F5)(2)(C CSiMe3)(2)}CoCl2]center dot 0.5(CH3)(2)CO and [NBu4](2)[{Pt(C(CBu)-Bu-t)(4)}{CoCl2}(2)]center dot 1.5(CH3)(2)CO

The reactions of [NBu4](2)[cis-Pt(C6F5)(2)(C=CR)(2)] (R = Bu-t or SiMe3) with CoCl2 . 6H(2)O in a 1:1 molar ratio yielded the paramagnetic binuclear species [NBu4](2)[(cis-Pt(C6F5)(2)(mu-C=CR)(2))CoCl2] (R=Bu-1 (1a), SiMe3 (1b)) in which the cobalt(II) chloride is coordinated eta(2)-side on to both alkynyl ligands of the platinum fragment. Similar treatment of [NBu4](2)[Pt(C=CR)(4)]. 2H(2)O (R=Bu-1 or SiMe3) with CoCl2 . 6H(2)O in a 1:2 molar ratio gave the corresponding trinuclear 1:2 adducts [NBu4](2)[{Pt(mu-C=CR)(4)}{CoCl2}(2)] (2). The compounds were characterised by analytical and spectroscopic data and, in addition, the crystal structures of a representative complex of each category were determined: 1b.acetone and 2a.acetone. Surprisingly, whilst in the binuclear anion [{Pt(C5F5)(2)(C=CSiMe3)(2)}CoCl2](2-) the cobalt atom is well embedded by the alkynyl fragments giving a precisely planar PtC4Co core and a very long Pt ... Co separation (3.446(3) Angstrom), in the trinuclear derivative [{Pt(C=(CBu)-Bu-t)(4)}{CoCl2}(2)](2-) the PtC4Co cores are hinged imposing significantly shorter Pt ... Co distances(3.077(3) Angstrom). (C) 1997 Elsevier Science S.A.