Oxovanadium(IV) Thiocarboxylate Paddlewheels Containing Ancillary Group 10 Metals: A Comparative Study on Pd and Pt Derivatives

Vanadyl-containing paddlewheel structures have recently joined the pool of molecular spin systems showing respectable coherence times (<i>T</i>_m). We extended the investigation of [PtVO(SOCR)₄] (R = Me, Ph) by synthesizing the corresponding Pd derivatives. Crystals of [PdVO(SOCMe)₄] and [PdVO(SOCPh)₄]·DCM are isomorphous to their Pt analogues and comprise staggered and square dimers, respectively. For both Group 10 metals, M···M' contacts in staggered dimers promote a stronger antiferromagnetic coupling than M···S' contacts in square dimers, with Pd complexes showing a slightly more effective interaction consistent with DFT predictions. In solution, the paddlewheels exist in monomeric form and undergo a quasi-reversible one-electron reduction, more favorable for M = Pd than Pt and for R = Ph than Me. X-band EPR spectra in frozen CD₂Cl₂/toluene-<i>d</i>₈ show the eight-line hyperfine pattern characteristic of ⁵¹V (<i>I</i> = 7/2), with identical spin-Hamiltonian parameters across the series. Unlike the interaction with ¹⁹⁵Pt (<i>I</i> = 1/2, 34%), the superhyperfine coupling with ¹⁰⁵Pd (<i>I</i> = 5/2, 22%) is unresolved. <i>T</i>_m values are essentially the same for Pt and Pd derivatives and follow the same substituent dependence (Ph > Me). Therefore, the ancillary Group 10 metal affects redox potentials and, to a lesser extent, solid-state magnetic properties, but leaves quantum coherence unchanged.