The synthesis and reactions of some cyclopentadienylpiatinum complexes. Crystal structure of [Pt2{µ-C(Ph)C(Ph)C(O)}(η-C5H5)2]

Abstract

Treatment of di-µ-chloro-dichlorobis(η-ethylene)diplatinum with Mg(C₅H₅)₂ affords the compounds [Pt(η-C₂H₄)(σ-C₅H₅)(η-C₅H₅)] and [Pt₂(µ-C₁₀H₁₀)(η-C₅H₅)₂]. Reaction between [NBuⁿ₄]₂[Pt₂Cl₄(CO)₂] and Mg(C₅H₅)₂ affords [Pt₂(CO)₂(η-C₅H₅)₂] in good yield, as well as the compound [Pt(CO)(σ-C₅H₅)(η-C₅H₅)]. Protonation of [Pt(η-C₂H₄)(σ-C₅H₅5)(η-C₅H₅)] yields the salt [Pt(η-C₂H₄)(η²-C₅H₆)(η-C₅H₅)][BF₄]. Reaction of [Pt(η-C₂H₄)(σ-C₅H₅)(η-C₅H₅)] with PhCCPh affords (η-cyclopentadienyl)(σ: 2–3-η-2,3-diphenylbicyclo[2.2.1 ] hepta-2,5-dien-7-yl) platinum. The compound [Pt₂(CO)₂(η-C₅H₅)₂] on treatment with PhCCPh in the presence of Me₃NO gives [Pt₂{µ-C(Ph)C(Ph)C(O)}(η-C₅H₅)₂], and on similar treatment with Bu^tCCBu^t and Me₃NO affords [Pt₂(µ-Bu^tC₂Bu^t)(η-C₅H₅)₂]. The complex [Pt₂{µ-C(Ph)C(Ph)C(O)}(η-C₅H₅)₂] was structurally characterised by a single crystal X-ray diffraction study. The metal–metal bond [Pt–Pt 2.590(1)Å] is bridged by the C(Ph)C(Ph)–C(O) ligand, in such a manner that the terminal carbon atoms are each σ-bonded to one platinum centre, while the C(Ph)C(Ph) fragment is η²-co-ordinated to the other. Both metal atoms carry C₅H₅ ligands, but one is asymmetrically bound. The n.m.r. data (¹H, ³¹C-{¹H}, and ¹⁹⁵Pt-{¹H}) for the new compounds are reported and discussed, and this information used to suggest mechanisms for the dynamic behaviour of [Pt(η-C₂H₄)(σ-C₅H₅)(η-C₅H₅)], [Pt₂(CO)₂(η-C₅H₅)₂], and [Pt(η-C₂H₄)(η²-C₅H₆)(η-C₅H₅)]⁺.