Platinum carbonyl clusters stabilized by Sn(ii)-based fragments: syntheses and structures of [Pt6(CO)6(SnCl2)2(SnCl3)4]4−, [Pt9(CO)8(SnCl2)3(SnCl3)2(Cl2SnOCOSnCl2)]4− and [Pt10(CO)14{Cl2Sn(OH)SnCl2}2]2−

Abstract

The reaction of [Pt₁₅(CO)₃₀]²⁻ with increasing amounts of SnCl₂ affords [Pt₈(CO)₁₀(SnCl₂)₄]²⁻ (2), [Pt₁₀(CO)₁₄{Cl₂Sn(OH)SnCl₂}₂]²⁻ (5), [Pt₆(CO)₆(SnCl₂)₂(SnCl₃)₄]⁴⁻ (3), [Pt₉(CO)₈(SnCl₂)₃(SnCl₃)₂(Cl₂SnOCOSnCl₂)]⁴⁻ (4) and [Pt₅(CO)₅{Cl₂Sn(OR)SnCl₂}₃]³⁻ (R = H, Me, Et, and ⁱPr) (1-R). 1-R and 2 have been previously described, whereas 3–5 are herein reported for the first time. The species 1–3 are the main products of the reaction under different experimental conditions, whereas 4 and 5 are by-products of the synthesis of 3 and 2, respectively. From a structural point of view, the clusters 1–5 all show a perfect segregation of the two metals, which are composed of a low valent Pt core decorated on the surface by Sn(II) fragments such as SnCl₂, [SnCl₃]⁻, [Cl₂Sn(OH)SnCl₂]⁻ and [Cl₂SnOCOSnCl₂]²⁻. These fragments behave as two electron donor ligands via each Sn-atom (and also the C-atom in the case of [Cl₂SnOCOSnCl₂]²⁻). The [Cl₂SnOCOSnCl₂]²⁻ ligand is rather unique and may be viewed as a bis-stannyl-carboxylate, a carbon dioxide μ₃:k³-C,O,O′-CO₂ or a carbonite ion [CO₂]²⁻ stabilized by coordination to metal atoms. Compounds 1–5 have been fully characterised via IR spectroscopy, X-ray crystallography and DFT calculations.