Single-crystal EPR study and DFT structure of the [Mo(CO)5PPh3]+· radical cation

Abstract

a b s t r a c tA radical species characterized by a large g-anisotropy and a clearly resolved hyperfine structure with 95/97 Mo and 31 P nuclei is formed, at 77 K, by radiolysis of a single crystal of Mo(CO) 5 PPh 3 . The corresponding EPR signals disappear irreversibly with increasing temperature and the angular dependence of the various coupling constants imply a spin delocalization of $60% and $4% on the molybdenum and the phosphorus atoms, respectively and are, a priori, consistent with the trapping of a one-electron deficient centre. The ability of DFT to predict the EPR tensors for a 17-electron Mo (I) species is verified by calculating the g-tensor and the various 14 N and 13 C coupling tensors previously reported by Hayes for [Mo(CN) 5 NO] 3À . Calculations at the B3LYP/ZORA/SOMF level of theory show that, in contrast to Mo(CO) 5 PH 3 , one-electron oxidation of Mo(CO) 5 PPh 3 causes an appreciable change in the geometry of the complex. The g-tensor and the 95/97 Mo and 31 P isotropic and anisotropic coupling constants calculated for [Mo(CO) 5 PPh 3 ] + Á confirm the trapping of this species in the irradiated crystal of Mo(CO) 5 PPh 3 ; they also show that the conformational modifications induced by the electron release are probably hindered by the nearby complexes.

EPR detection and characterisation of a paramagnetic Mo(iii) dihydride intermediate involved in electrocatalytic hydrogen evolution

“…As often reported for paramagnetic complexes containing phosphorous atoms, the predicted isotropic 31 P couplings are underestimated compared to experimental ones. 22 Thus a factor of ∼1.44, which is in agreement with previous DFT studies of Mo-P complexes, 22 has been used to scale the P Fig. 2 EPR spectra of A o (a) and its deuterated form (b).…”

Electronic structure predictions of the properties of non-innocent P-ligands in group 6B transition metal complexes

“…The results for the R″ = CH 3 and Ph complexes agree with previous computational and experimental studies. 38,39 A number of the PnR 3 radical anions do not form a M-L bond on optimization and essentially dissociate. There are fewer stable [M(CO) 5 PnR 3 ] − complexes with nitrogen ligands as compared to those with phosphorus ligands (Table 1).…”