The red complex RuCl2(PO)2 (1) (PO = o-(diphenylphosphino)anisole) crystallizes from dichloromethane/hexane as a solvate, RuCl2(PO)2·CH2Cl2, and has been characterized by a single-crystal X-ray structural analysis. The crystals have space group P21/n with a = 11.194 (1) Å, b = 28.294 (4) Å, c = 12.458 (1) Å, β = 95.50 (1)°, Z = 4, ρobsd = 1.40 g/cm3. and ρcaled = 1.40 g/cm3. The complex is six-coordinate with trans chlorine and cis phosphorus donor atoms. The Ru-P distances of 2.217 (1) and 2.219 (1) Å, are similar to those found for apical phosphines in square-pyramidal ruthenium(II) complexes. The Ru-O distances of 2.299 (3) and 2.257 (3) Å are greater than that of the sum of the respective covalent radii, consistent with a weak Ru-O bond. 1 undergoes reversible electrochemical oxidation in acetone at 0.778 V vs. Ag/AgCl and chemical oxidation with NOBF4 to afford the paramagnetic complex [RuCl2(PO)2](BF4) (2), characterized by its ESR spectrum. The room-temperature reaction of 1 with CO gives initially a fluxional monomeric complex, RuCl2(PO)2(CO) (4), and then all-trans-RuCl2(PO)2(CO)2 (3), via dissociation of the Ru-O bonds. Reaction of 1 with CO at elevated temperatures gives a new cis-dicarbonyl isomer. RuCl2(PO)2(CO)2 (5), which has trans phosphines. Unlike 4, complex 5 does not readily lose CO thermally; however, it is photochemically converted to a mixture of 3 and 4. Closely related reactions are observed when 1 is treated with tert-butyl isocyanide and the species RuCl2(PO)2(t-BuNC)2 (6) and RuCl2(PO)2(t-BuNC) (7) were identified spectroscopically (and isolated for 6). A reaction scheme rationalizing the formation of 3, 4, 5, 6, and 7 is presented and the results are discussed in light of the known work on phosphinoanisole-transition-metal complexes.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry