121575-22-2Relevant academic research and scientific papers
Pentaammineruthenium(II), pentaammineosmium(II), and (N-(hydroxyethyl)ethylenediammetriacetato)ruthenate(II) complexes of styrenes
Elliott, Michael G.,Zhang, Songsheng,Shepherd, Rex E.
, p. 3036 - 3043 (2008/10/08)
[M(NH3)5(styrene)2+] and [M(NH3)5(olefin)2+] (M = RuII, OsII) and the related Ru(hedta)(styrene)- and Ru(hedta)(olefin)- complexes have been prepared and characterized by 1H and 13C NMR spectroscopy and by cyclic voltammetry and differential-pulse polarography. Complexes in these series include styrene, 4-vinylbenzoic acid, dimethyl acetylenedicarboxylate (DMAD), 1,3-cyclohexadiene, and 3-cyclohexene-1,1-dimethanol (CHDM). Preferential coordination of the metal centers to the exo vinylic substituent of the styrenes rather than η2 ring coordination was observed. The chemical shifts and electrochemical behavior were found to be similar to those of linear olefin analogues such as propylene and 1,3-butadiene. 1H NMR upfield shifts of protons of the coordinated vinylic group of styrene are virtually the same as those of the M(NH3)5(1,3-butadiene)2+ analogues; the greater effect of OsII vs RuII is maintained. E1/2 values for the styrene complexes were found to be 0.98 V for (NH3)5Ru(styrene)2+, 0.49 V for (NH3)5Os(styrene)2+ and 0.64 V for (hedta)Ru(styrene)- complexes, again similar to those for linear olefin analogues. E1/2 values for substituted styrenes with para substituents -CO2H and -CO2- were virtually the same (±0.02 V) as those for the parent styrene complexes. A plot of ΔE1/2 = (E1/2[Ru(NH3)5L] - E1/2[Ru(hedta)L]) vs the π-acceptor power of L (ESCA scale) was shown to be linear with a slope of 0.325 ± 0.073 V and an intercept of 0.106 ± 0.044 V, including points for L = H2O, CH3CN, py, pz, olefins, styrenes, CO, and CH3pz+. DMAD was shown to deviate from the line, which is attributed to the π-donor character of the second π lone pair available with acetylenes. The ammine environment is better than hedta3- in stabilizing RuII complexes with strong π-acceptor ligands. The 13C NMR spectra reveal an opposite influence of the coordination of Ru(NH3)52+ and Os(NH3)52+ moieties. The aromatic carbon attached to the vinylic substituent shifts downfield 12 ppm for RuII and upfield 8 ppm for OsII. A greater involvement of the ring carbon in a "allylic-like" coordination to (NH3)5Os2+ is suggested by this result.
