Facilitation of the substitution reactions of triangular platinum cluster compounds and the structural characterisations of [Pt3(µ-SO2)3{P(C6H11)3}3] and [NEt4][Pt3(µ-Br)(µ-SO2)2{P(C6H11)3}3] by single-crystal X-ray techniques

Abstract

Trimethylamine N-oxide has been used to facilitate the substitution reactions of the triangulo-triplatinum clusters [Pt₃(µ-SO₂)₃(PR₃)₃](R = cyclo-C₆H₁₁ or Ph) with CO, halide, and azide anions. In the absence of Me₃NO a benzene solution of [Pt₃(µ-SO₂)₃{P(C₆H₁₁)₃}₃] gives only partially substituted products with CO, but the addition of Me₃NO leads to a high-yield conversion to [Pt₃(CO)₃{P(C₆H₁₁)₃}₃]. Me₃NO has also been used to synthesise some unusual 44-eletron anionic clusters of the general type [Pt₃(µ-X)(µ-SO₂)₂(PR₃)₃]^–[X = Cl, Br, or N₃; PR₃= P(C₆H₁₁)₃, PPh₃, or PMe₂Ph]. The compounds have been characterised by i.r. spectroscopy and ³¹P-{¹H} and ¹⁹⁵Pt-{¹H} n.m.r. studies. Single-crystal X-ray crystallographic investigations of the related 42- and 44-valence electron clusters [Pt₃(µ-SO₂)₃{P(C₆H₁₁)₃}₃] and [NEt₄][Pt₃(µ-Br)(µ-SO₂)₂{P(C₆H₁₁)₃}₃] have demonstrated that the additional electron pair causes an expansion of the Pt₃ triangle, with the average Pt–Pt distance increasing from 2.814(1) to 2.885 4(15)Å.