Synthesis, characterisation and reactivity of ruthenium bis-bifluoride, ruthenium hydride bifluoride and ruthenium hydride fluoride complexes

Abstract

Bifluoride complexes, trans-[Ru(depe)₂H(FHF)] (1), trans-[Ru(dppe)₂H(FHF)] (2), trans-[Ru(dppp)₂H(FHF)] (3) and cis-[Ru(PMe₃)₄(FHF)₂] (4) (depe = Et₂PCH₂CH₂PEt₂, dppe = Ph₂PCH₂CH₂PPh₂, dppp = Ph₂PCH₂CH₂CH₂PPh₂) were synthesised from the reactions of the corresponding cis-dihydride complexes with NEt₃·3HF in THF. The characteristic features of the low temperature NMR spectra of the bifluoride complexes include ¹⁹F resonances at ca.δ −300 for the proximal fluorine and ca.δ −165 for the distal fluorine. The acidic protons resonate at ca.δ 13. The value of J(HF) for the distal fluorine lies in the range 300–400 Hz. The bifluoride ligands exhibit characteristic vibrations at ca. 2300 cm⁻¹ and ca. 2430 cm⁻¹ in the IR spectrum. All the complexes exhibit dynamic exchange processes, probably due to dissociation of FHF⁻. In addition, complex 3 undergoes a ring flipping process that is suppressed at low temperature. The X-ray crystal structure of 3 has been obtained. The bifluoride ligand is disordered over two positions about the inversion centre. The Ru–F distance is 2.351(5) Å and the F ⋯ F distance is 2.290(8) Å, the Ru–F ⋯ F angle is 149.7°. The X-ray crystal structure for 4 reveals that the Ru–F distances are 2.149(5) Å and 2.150(4) Å, the F ⋯ F bond lengths are 2.323(8) Å and 2.329(8) Å, with Ru–F ⋯ F angles of 128.5(3)° and 138.4(3)°. The two bifluoride ligands are cis to each other. Reaction of 1 and 3 with [NMe₄]F yields trans-[Ru(depe)₂(H)F] 5 and trans-[Ru(dppp)₂(H)F] 6. Reaction of 2 with Me₃SiX (X = N₃, OTf) yields trans-[Ru(dppe)₂(H)N₃] and [Ru(dppe)₂(H)]OTf. Reactions with several halo-organic compounds yields trans-[Ru(dppe)₂(H)X] (X = Cl, Br and I). The organic products from CH₃I, CH₃COCl and C₆H₅COCl were identified as CH₃F, CH₃COF and C₆H₅COF respectively.