Complexes with functional phosphines. Part 8. Interconversion study of [RuCl2{Ph2PCH2C(O)OEt}L2], [RuCl2(CO){Ph2PCH2C(O)OEt}L], and [RuCl2(CO)2L2][L = Ph2PCH2C(O)OEt] under CO. Synthesis and X-ray structure of mer-[RuCl3{Ph2PCH2C(O)OEt}L]

Abstract

The complex trans-[[graphic omitted]O)OEt}L₂](1)[L = Ph₂PCH₂C(O)OEt] undergoes a reversible one-electron oxidation at +0.77 V vs. a saturated calomel electrode (s.c.e.) on a Pt electrode in 1,2-dichloroethane containing 0.1 mol dm^–3 NBu₄ClO₄. A cyclic voltammetric study establishes that under a CO atmosphere, (1) is quantitatively converted into trans,trans,trans-[RuCl₂(CO)₂L₂](3)(E_½=+1.65V)via trans-[[graphic omitted])OEt}L](2)(E_½= 1.35 V). Complex (2) interconverts with (3)via reversible CO co-ordination. Regeneration of (1) from (3) requires u.v. irradiation in the presence of excess L. The reversible one-electron reduction of mer,trans-[[graphic omitted])OEt}L](4) occurs at –0.22 V. The structure of complex (4) was established by a single-crystal X-ray diffraction study. Crystals are orthorhombic, space group P2₁2₁2₁(no. 1 9), with Z= 4 in a unit cell of dimensions a= 9.1 04(2), b= 15.511(2), and c= 24.1 90(2)Å. The structure has been refined to R 0.034 (R′ 0.046). The Ru atom has a distorted octahedral environment with the three chlorine atoms in a mer relationship. The chelating ligand is characterized by a Ru–P(2) distance of 2.368(2)Å and a relatively short Ru–O(3) distance of 2.1 43(5)Å. The distance between Ru and the chlorine atom [Cl(1)]trans to the co-ordinated ester oxygen is 2.31 2(2)Å whereas Ru–Cl(2) and Ru–Cl(3) are 2.323(2) and 2.362(2)Å, respectively.