Substrate-Dependent Hydridic and Radical Reactivity of Triiron Hydride Clusters

The reactivity of iron clusters with one of more μ-hydrides and in the weak field pertains to catalysis on surfaces and biological metal cluster cofactors. As a model, then, a reactivity survey of the weak-field ligated iron hydride clusters Fe₃H₃<b>L</b> (<b>1</b>) and (FeCO)₂Fe(μ₃-H)<b>L</b> (<b>2</b>) (where <b>L</b>^<b>3-</b> is a tris(β-diketiminate)cyclophanate) with Brønsted acids, organochlorides, acetyl chloride, boron trihalides, and titanium electrophiles is reported. Complex <b>1</b> reacts with Brønsted acids H₂O and [Et₃NH][Cl] to afford Fe₃(OH)₃<b>L</b> (<b>3</b>) and Fe₃H₂Cl<b>L</b> (<b>4</b>), respectively, consistent with hydridic reactivity. Clusters <b>1</b> and <b>2</b> react readily with organochlorides, such as CCl₄, CHCl₃, and CH₂Cl₂, with identified intermediates supporting a radical pathway. Complex <b>1</b> reacts with trityl chloride (2 equiv) to selectively afford Fe₃HCl₂<b>L</b> (<b>5</b>) with reductive elimination of dihydrogen observed. Mixed-valent complex <b>2</b> reacts with AcCl to afford (FeCO)Fe₂HCl<b>L</b> (<b>9</b>). The scope of reactivity displayed implicates possible pathways accessible to larger clusters in biology or on metal surfaces.