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High-Field EPR Determines the Bond Order in a Palladium (Pd 2 ) 5+ Complex Saritha Nellutla, Narpinder Kaur, Naresh S. Dalal, Johan van Tol (NHMFL and FSU) ; F. Albert Cotton and Carlos Murillo (Texas A&M).
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High-Field EPR Determines the Bond Order in a Palladium (Pd2)5+ Complex Saritha Nellutla, Narpinder Kaur, Naresh S. Dalal, Johan van Tol (NHMFL and FSU) ; F. Albert Cotton and Carlos Murillo (Texas A&M) Palladium (Pd) compounds are of fundamental and industrial importance (e.g. catalysts, H-storage). Of the known Pd-paddle wheel compounds, only two contain paramagnetic (Pd2)+5 (s = ½) core. However, there are conflicting reports regarding the location of the unpaired electron. EPR is the technique of choice for such structural elucidation, but the resolution of commercially available EPR spectrometers is often not adequate. Single isotropic EPR peak around g = 2.01 was observed for the investigated (Pd2)5+ complex at 9.6 GHz, which does not help to identify the type of molecular orbital containing unpaired electron. However, increasing the frequency from 34 GHz to 105.6 GHz to 211.2 GHz (see figure on the right) provides complete resolution of g-tensor components. A g-tensor spread of ~0.03 at these high frequencies implies that the unpaired electron is in a metal-based molecular orbital, in contrast to the earlier low-field results that suggested the orbital to be ligand-based. High frequency EPR spectra of [Pd2(DAniF)4]+. 1 J. F. Berry, E. Bill, E. Bothe, F. A. Cotton, N. S. Dalal, S. A. Ibragimov, N. Kaur, C. Y. Liu, C. A. Murillo, S. Nellutla, J. M. North andD. Villagr, J. Am. Chem. Soc.129, 2007, 1393.