Occurrence of a µ-SiF interaction in bimetallic trifluorosilyl complexes

Abstract

With the aim of inducing a µ-SiF interaction between two metal centres, MeO was replaced by F on the silicon atom involved in µ-SiO bonding with a bimetallic unit by the reaction of mer-[(OC)₃[graphic omitted]dCl)]1(dppm = Ph₂PCH₂PPh₂) with BF₃. However, the desired complex mer-[(OC)₃[graphic omitted]dCl]3 could only be characterised in solution. From the solution structure of the reaction intermediate mer-[(OC)₃[graphic omitted]dCl]2 where a MeO→Pd interaction in preference to F→Pd is suggested on the basis of spectroscopic data, it appears that the dative F→Pd interaction is weaker than the corresponding MeO→Pd one. In the presence of an excess of BF₃, rupture of the Fe–Si bond of 3 eventually occurred in CH₂Cl₂, resulting in the formation of [(OC)₃[graphic omitted]dCl]4a. When the complex mer-[{(MeO)₃Si}(OC)₃[graphic omitted]tH(PPh₃)]5 was treated with BF₃·Et₂O, the trifluorosilyl derivative mer-[(F₃Si)(OC)₃[graphic omitted]tH(PPh₃)]6 was obtained and isolated in 87% yield. The structure of its benzene solvate 6·0.5C₆H₆ was determined by X-ray diffraction: triclinic, space group P, a= 17.692(7), b= 13.084(5), c= 11.031(5)Å, α= 112.16(1), β= 91.31(2), γ= 101.71(1)° and Z= 2. It has been solved by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.0408 for 5870 observed reflections. The Fe and Pt atoms are at a distance of 2.661(1)Å, consistent with a metal–metal bond. The nearly square-planar co-ordination of Pt involves also one P atom from dppm, one PPh₃ and a hydride. The co-ordination of Fe is completed by three carbonyl groups, a P atom of the dppm ligand, and the SiF₃ ligand. Noteworthy are the weak intramolecular interactions between the hydride and two F atom from the SiF₃ ligand [H ⋯ F 2.39(7) and 2.50(6)Å]. The IR and NMR (¹H, ³¹P-{¹H} and ¹⁹F-{¹H}) spectra of the new complexes are reported and discussed.