The single-crystal e.s.r. parameters for [AsPh,] [CrCI,O] giving gil2.006 * 0.002 and g l 1.979 f 0.002 are reported (where Q ~J coincides with the Cr-0 direction). Solution measurements in CH2C12 give g 1.988 f 0.001 and a 18.1 x 1 0-4 cm-l. and the addition of excess of [NEt,]CI to these solutions results in an additional e.s.r. signal a t 1.970 f 0.001 which is attributed t o the [CrC1,0I2-species. The e.s.r. parameters have been interpreted using an ab initio molecular-orbital approach as well as the more conventional molecular-orbital approach. The results of these two approaches are critically compared.structures of the dl mono-oxo-chromo-[CrOj3+, and [Mo0I3+ have received considerable attention in recent years.1-23 Except for a small number of examples in the case of vanadium, very few data are available for definitely characterised compounds of a known crystal structure. Our recent e.s.r. studies 23 of chloro-complexes of the [Mo0I3+ cation suggest that many previous solution and dilute singlecrystal measurements could be of doubtful value since the species present may not be known for certain. In view of this lack of data we have undertaken a systematic study of compounds in this area and now report the single-crystal e.s.r. spectrum of [AsPh,] [CrCl,O]. We also include a detailed discussion of the interpretation of the e.s.r. data in conjunction with the recently reported single-crystal polarised electronic spectrum and ab irtitio molecular-orbital (m.0.) calculations of the above compound.22 EXPERIMENTAL Single crystals of [AsPh,] [CrCl,O] were prepared as described earlier. 22 E.S.R. Spectra.-Single-crystal and solution e.s.r. spectra were obtained a t room temperature on equipment and by methods described p r e v i o ~s l y . ~~ Single crystals were mounted on quartz rods such that spectra could be obtained in a plane containing gll (parallel to the crystal c axis) and gL and also in a plane perpendicular to gll. t These measurements gave g 2.006 f 0.002 and g 1.979 f 0.002. No chromium hyperfine splittings were observed a t any t Crystals of this compound have been shown t o possess the tetragonal space group P,/iz, and to contain the [CrC140]-unit with all the Cr-0 vectors parallel to the unique crystallographic axis (A.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.