85709-91-7Relevant academic research and scientific papers
Complexes of functional phosphines. 5. Rhodium (III) and ruthenium(II) complexes of ethyl (diphenylphosphino)acetate. Synthesis, dynamic behavior, and crystal structure of trans-RuCl2[Ph2PCH2C(O)OC2H 5][Ph2PCH2C(O)OC2H5] 2. Reversible CO coordination on a ruthenium(II) complex
Braunstein, Pierre,Matt, Dominique,Dusausoy, Yves
, p. 2043 - 2047 (2008/10/08)
The coordination properties of Ph2PCH2C(O)OC2H5 (P O) have been investigated toward Rh(III) and Ru(II) centers. Displacement of a nitrile ligand of RuCl3(o-CH3C6H4CN)3 by P O leads to the complex trans,trans,trans-RuCl2(o-CH3C6H 4CN)2(P O)2 (1) in which P O behaves as a monodentate ligand through the phosphorus. Reaction of RhCl3(P O)2 (2) with AgPF6 in acetone converts a monodentate P O into a bidentate P O, affording [RhCl2(Ph2PCH2C(O)OC2H 5)2]PF6 (3). Whereas 2 exhibits stereodynamic behavior on the NMR time scale, 3 does not. Reaction of P O with ruthenium trichloride in hot ethanol leads to trans-RuCl2[Ph2PCH2C(O)OC2H 5][Ph2PCH2C(O)OC2H5J 2 (4). The molecular structure of 4 has been determined by X-ray diffraction: triclinic, space group P1 with Z = 2, a = 11.829 (4) ?, b = 12.896 (2) ?, c = 16.909 (7) ?, α = 91.43 (2)°, β = 93.74 (3)°, γ = 112.26 (2)°, d(calcd) = 1.37 g/cm3. The structure was solved by using 8342 reflections with I > σ(I) and refined to conventional R = 0.043. The Ru atom has a distorted octahedral environment with trans Cl atoms (Ru-Cl = 2.419 (1) ?) and mer P atoms. The two monodentate P O ligands (Ru-P(1) = 2.403 (1), Ru-P(3) = 2.266 (1) ?) are cis to each other, and the chelating P O has P(2) trans to P(1) (Ru-P(2) = 2.363 (1) ?) and O(3) trans to P(3). The long Ru-O(3) distance (2.230 (3) ?), together with the short Ru-P(3) bond, is consistent with the weak trans influence of the ester oxygen donor atom. The hemilabile character of P O in this complex is evidenced by its stereodynamic behavior, resulting from the easy rupture of the Ru-O(3) bond. In the 31P NMR, coalescence of the signals due to P(1) and P(2) occurred at 315 K (ΔG* = 13.3 kcal/mol). Another coalescence phenomenon was observed at 193 K resulting from conformational changes within the organic backbones of the ligands (ΔG* = 8.5 kcal/mol). Bubbling CO through a solution of 4 in CH2Cl2 under ambient conditions affords trans,trans,trans-RuCl2(CO)2(P O)2 (5), in which the remaining P O ligands are both monodentate through the phosphorus. Chelation of one of these P O ligands occurs by removal of one coordinated CO. This is facilitated by bubbling nitrogen through a solution of 5 in CH2Cl2, affording RuCl2(CO)[Ph2PCH2C(O)OC2H 5][Ph2PCH2C(O)C2H5] (6). Conversely, 6 will take up CO under ambient conditions and regenerate 5. The ease with which 6 reversibly binds CO is related to the electronic and structural properties of the P O ligand. All complexes were characterized by elemental analysis and IR, 1H NMR, and 31P{1H} NMR spectroscopy.
