Trigonal field splitting in tris(ethylenediamine) complexes. Evidence from the electron paramagnetic resonance spectrum of Ru(en)33+

Abstract

related with steric interaction between the released chloride and the number of axial methyl groups,26 while the rate increase due to ring expansion has been attributed to steric interaction of boat or twist-boat ring conformations.' 327 The rate increase in the primary hydrolysis of trans-Co(en)-(tmd)Cl2+ relative to trans-Co(en)2Clz+ can also be accounted for on this basis and the positive value for the entropy of activation supports Tobe's t h e~r y , '~ as considerable stereochemical change is observed. Registry No. [Cr(en)(tmd)Clz] C104, 36904-25-3; cis-[Cr-(26) M. D. Alexander,Inorg. Chem., 5, 2084 (1966). (27) M. C. Couldwell and D. A. House, Znorg. Nucl. Chem. L e t t , 7,947 (1971). Stanko, et al. (en)aClz]The epr spectrum of the tris(ethylenediamine)ruthenium(III) complex, Ru(en), 3+, was measured at 4"K, diluted in single crystals of [Rh(en),C1,],.NaCl.6H2O and in powders of [Co(en),] Br3.3H2O, and employing K-band and X-band frequencies, respectively. The spectrum in both media can be described by an axial spin Hamiltonian with gl= 2.640 * 0.022 andgll= 0.330 f 0.007, defined with respect to the threefold symmetry axis of the complex. Interpretation of these g factors in terms of the theory of axial distortions for a low-spin d5 electronic configuration shows the ground electronic state t o be E'(2A,) and yields a value of the trigonal field splitting parameter, K , of -413 cm-'. The observed magnitude and sign of this latter quantity are discussed in terms of the known structure of the complex, crystal field theory predictions, and a comparison with the value for the same quantity in other tris(ethy1enediamine) complexes. IntroductionFor a transition metal ion immersed in a crystal field of predominantly octahedral symmetry, but with a superimposed component of trigonal ( D 3 ) symmetry, the lower lying,

Experimental evidence for trapped valences in the mixed-valence complex .mu.-pyrazine-bis(pentaammineruthenium) tosylate. Electron paramagnetic resonance, magnetic susceptibility, and nuclear magnetic resonance results

“…As we shall see later, the g¡| signal is not observed because g|i is less than 0.66, and can only be detected using magnetic fields in excess of the maximum field of 10 000 G attainable on our EPR instrumentation. The EPR signal reported in the literature for Ru(en)33+ 14 is almost identical with that seen here for the Rumpyr monomer and the [3,3]pyr dimer. The gj_ resonance for Ru(en)33+ centered at g = 2.65 shows the same asymmetric shape seen here.…”

Probing α−RuCl3 Beyond Magnetic Order: Effects of Temperature and Magnetic Field

“…In the calculations we used g c * = 1.3 and g ab = 2.3; these values are consistent with the range of previous theoretical estimates for α-RuCl 3 [25,45], and experimental values for similar compounds [46][47][48]. We note that this simplified model underestimates the zero-field gap for excitations [16,31,32], which may be related to a weak breaking of C 3 symmetry in actual samples [23], or small additional interactions [25,26].…”

Catalytic oxidation of alkanes and alkenes by polymer-anchored amino acid–ruthenium complexes

“…No hyperfine splitting is noticed at this temperature. Interestingly, the spectral features have been ascribed to the presence of mixed valent Ru (III)/(II) species for dimeric ruthenium complexes [21,[24][25][26]. The ESR spectra of high-spin Ru +2 (4d 6 ) ion would be difficult to observe and are not consistent with the spectrum in this study.…”