Spectroscopic and structural characterization of ruthenium(II) carbonyl-porphine complexes

Reaction of Ru₃(CO)₁₂ with tetraphenylporphine and tetra-p-isopropylphenylporphine affords ruthenium(II) carbonyl-porphine complexes which in past investigations have been formulated as the monocarbonyls Ru(CO)(TPP) and Ru(CO)(i-Pr-TPP), respectively. A recent X-ray study of the tetraphenylporphine reaction product recrystallized from chloroform-ethanol has led to reformulation of this product as the dicarbonyl Ru(CO)₂(TPP), containing markedly bent (154°) Ru-C-O bonds. The nature of these compounds after recrystallization from chloroform-ethanol has been reinvestigated. Chemical and spectroscopic experiments show (i) no CO evolution when monopyridinates are formed with excess pyridine, (ii) no mass spectral peaks due to dicarbonyl ions such as Ru(CO)₂TPP⁺, (iii) an ABCD pattern of phenyl o-H and m-H pmr signals (z-Pr-TPP complex) which collapses to an AA′BB′ pattern at elevated temperatures, (iv) methyl and methylene pmr signals (z-Pr-TPP complex) whose chemical shifts are indicative of axially coordinated ethanol. These observations are incompatible with the dicarbonyl description but are consistent with the formulations Ru(CO)(TPP)(EtOH) and Ru(CO)(z-Pr-TPP)(EtOH). The composition and structure of the TPP reaction product has been confirmed by an X-ray determination. The compound Ru(CO)(TPP)(EtOH) crystallizes in space group [formula omitted] of the triclinic system in a cell of dimensions a = 10.078 (4), b = 11.819 (5), c = 8.883 (4) Å α = 101.37 (5), β = 106.12 (4), and y = 65.91 (3)°. A density of 1.416 g cm-3 calculated for one molecule in the unit cell agrees with that of 1.39 (1) g cm^-3 observed by flotation of the crystals in aqueous ZnCl₂. The structure has been solved and refined by standard methods, based on 2906 unique reflections collected by counter methods using monochromatized Mo Kα radiation. The final agreement index is 7.5%. The molecule has crystallographically imposed [formula omitted] symmetry and hence the CO and EtOH groups are disordered and the RuN₄ portion of the molecule is planar. The overall deviations from planarity of the porphinato core are very small. The distances within the porphinato core are in good agreement with those reported for other metalloporphyrins. The Ru-O(Et) distance is 2.21 (2) Å, and the EtOH group has its expected geometry. The Ru-C (of CO) distance is 1.77 (2)Å and the Ru-C-O bond is essentially linear, the bond angle being 175.8 (1.9)°.