Light-Driven Ring Slippage in [Re(η7‑C7H7)(η5‑C7H9)]+ and the Inertness of Its Technetium Homologue

Here, we present the light-driven reactions of [Re­(η7-C7H7)­(η5-C7H9)]+ (1 +) with nitriles, phosphines, and isocyanides, which are added to 1 + via a ring slippage of the tropylium cation from η7 to η3, forming [Re­(η3-C7H7)­(η5-C7H9)­(L)2]+ (L= acetonitrile 2 + ; 2-phenylacetonitrile 3 +; 1,3,5-triaza-5-phosphoadamantane (PTA) 4 + ; tert-butyl isocyanide 6 +; benzyl isocyanide 7 +) and [Re­(η3-C7H7)­(η5-C7H9)­(L)]+ with L = (ethane-1,2-diyl)­bis­(diphenylphosphane) (dppe) 5 +. To compare the reactivities of rhenium and technetium, we also investigated the synthesis of [99Tc­(η6-C10H8)2]+, its substitution of naphthalene with cyclohepta-1,3,5-triene to obtain [99Tc­(η7-C7H7)­(η5-C7H9)]+, and its reactivity (or lack thereof) with light.