METAL-COMPLEXES OF HEMILABILE LIGANDS - REACTIVITY AND STRUCTURE OF DICHLOROBIS(ORTHO-(DIPHENYLPHOSPHINO)ANISOLE)RUTHENIUM(II)

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) υ,b=28.294 (4) υ, c=12.458 (1) υ,=95.50 (1)°, Z=4, pobsd =1.40 g/cm3, and pcaicd=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) υ, 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) υ 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(;-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. © 1979, American Chemical Society. All rights reserved.