As mentioned in the introduction, the isomerization of olefins is a critical step of alkane metathesis protocols. Within this context, an in-depth computational and experimental study conducted by Brookhart, Krogh-Jespersen and Goldman in 2012 showed that olefin isomerization mediated by [Ir I (POCOP)] requires high temperatures (125 °C). In order to evaluate whether our Ir II complexes were superior catalysts, we selected the isomerization of 1hexene as a benchmark reaction. For convenience, the Ir II catalyst 3•BF4 was generated in situ from the equimolar mixture of 1 and AgBF4, observing the corresponding immediate color change from yellow to dark green, characteristic of 3•BF4. Our preliminary experiments already revealed a higher catalytic activity of Ir II compared to its Ir I counterpart: even under mild operating conditions (25 °C, 1 mol% [Ir]), the Ir II metalloradical 3•BF4 was capable of isomerizing the olefin (20% conversion after 18 h; Table , entry 2), while complex 1 was completely inactive (no conversion even after 7 days, entry 1). Performing the same experiment starting from an isolated sample of the Ir II catalyst led to the same results (entry 3). Additionally, a control experiment with AgBF4 in the absence of 1 led to no conversion (entry 4). It is important to remark that monitoring a catalytic run with 3•BF4 by 1 H and 31 P{ 1 H} NMR did not manifest the appearance of any diamagnetic resonances, further speaking in favor of an active open-shell paramagnetic catalyst that clearly outperforms the traditional Ir I system. Next, we analyzed the effect of the counteranion, particularly important having already observed that its coordinating capacity may lead to divergent reactivity in terms of substrate binding (Figure ). Considering the higher stability of the Ir I precursor and the fact that Ir II derivatives are readily produced, we decided to continue our exploration by generating the Ir II catalysts in situ. Under mild heating (50 °C) the Ir I precursor exhibited minimal activity (5%, entry 5), being clearly surpassed by Ir II complexes 3 . In fact, as discussed below, there seems to be a qualitative correlation between the weakness of the coordinating anion and the conversion of 1-hexene. In this vein, Ir II catalyst 1•BAr F , bearing the least coordinating [BAr F ] - anion presented the best results, revealing quantitative conversion of the olefin under the same conditions at which its Ir I precursor was barely active. Therefore, the open-shell Ir II complex 1•BAr F is ca. 20 times more active than its isostructural Ir I analogue 1. Besides, warming-up to 70 °C allowed us to quantitatively isomerize the olefin in only two hours, conditions that we selected for substrate screening, as described later.