EPR Insensitivity of the Metal‐Nitrosyl Spin‐Bearing Moiety in Complexes [L_nRu^II‐NO^·]^k

Abstract

A survey of 18 paramagnetic species [L n Ru(NO)] k , including seven new examples studied by in situ electrolysis, reveals a surprisingly narrow range of EPR parameters despite a wide variety of ligands such as pyridine, polypyridines, imines, amines, nitriles, phosphanes, carbonyl, cyclopentadienides, halides, hydride, hydroxide, thiocyanate or cyanide: g 1 = 2.015 ± 0.02, g 2 = 1.990 ± 0.015, g 3 = 1.892 ± 0.03, g av = 1.968 ± 0.02, ∆g = g 1 − g 3 = 0.122 ± 0.037, A 2 ( 14 N) = 3.3 ± 0.5 mT. This rather small variability, smaller still if the organometallic compounds are excluded, differs from the wider range of EPR data reported for nitrosyliron species with S = 1/2; appar-

Electronic structures and reactivity aspects of ruthenium–nitrosyls

“…The presence of strongly p-acidic pap ligand along with the weakly p-acidic tpm as ancillary ligands in the complex framework of 4 3+ has been reflected in the high m(NO) frequency which in turn signifies the nitrosonium character of the coordinated NO [42]. On the other hand the reduced nitrosyl bent geometry (138.0°, sp 2 -hybridization) in 4 2+ as observed earlier in analogous complexes [42][43][44][45][46][47][48][49][50][51][52][87][88][89][90][91]. The one-electron reduced radical species [Ru II (tpm)(pap)(NO Å )] 2+ (4 2+ ) exhibits the EPR spectrum with g = 1.989 (Fig.…”

Complete and Partial Electron Transfer Involving Coordinated NOx

“…For complexes of the general formula [M(NO)L], the spin may be also localized on the coordinating metal, M (12), or on the ancillary ligands, L (8,(14)(15)(16). The EPR characteristics and the underlying spin distribution in complexes [M(NO • )L] were found as rather invariant within series such as [M(NO)(CN) 5 ] 3À , M¼ Fe, Ru, Os (17), or [Ru(NO • )L] k , L ¼ N-heterocycles, imines, amines, PR 3 , CO, RCN, CN À , SCN À , OH À , H À , Hal À , Cp À (13). The EPR parameters for the latter series with…”

“…Similar values have been observed for iron (6) compounds. The large number and variety of Ru II (NO • ) complexes has allowed for an analysis of the correlation between EPR data and coligand characteristics (13). The variation is not as large as one might anticipate, suggesting a relatively inert {RuNO} 7 configuration.…”

“…Nitric oxide with a + II oxidation state of nitrogen is a weak base which dimerizes to ONNO at low temperatures (11). In the absence of additional magnetic interactions, the spin of NO • may be detected by EPR and yield information on the bonding situation (12,13).…”

Four-component relativistic density functional theory with the polarisable continuum model: application to EPR parameters and paramagnetic NMR shifts

“…Such a solvent shift corresponds to ca. a 25% contribution to the overall g 11 value and it is larger than the e↵ect of Hartree-Fock exchange admixture or the variation of the g 11 values in Ru nitrosyl complexes upon ligand substitution [117]. Note that the g 11 axis lies in the M-N-O plane and it is nearly parallel to the N-O bond; cf.…”