Photolysis of Tricarbonyl(η5-cyclohexadienyl)manganese in Tetrahydrofuran, Reactions with Cumulated Dienes

Abstract

[Mn(η5‐C6H7)(CO)3] (1) forms highly reactive [Mn(η5‐C6H7)(CO)2(THF)] (2) upon UV irradiation in THF at 208 K. Solvent complex 2 reacts between 208 and 293 K with 1,1‐disubstituted allenes C3H2RR′ [R, R′ = CH3, CH3 (A); CH3, C6H5 (B); C2H5, C6H5 (C); C6H5, C6H5 (D); OCH3, Si(CH3)3 (E)] to four different types of complexes: The [5+2] cycloadduct [Mn(η3:2‐C9H9RR′)(CO)3] (3E), rearranged [5+2] cycloadducts [Mn(η3:2‐C9H9RR′)(CO)3] (4B, 4C, 4D), 1:2 adducts [Mn(η3:2‐C12H11R2R′2)(CO)3] (5A–5E), and the 1:3 adduct [Mn{η3:2:2‐C15H13(CH3)6}(CO)2] (6A). The constitutions of the products were established by IR and NMR spectroscopy, as well as by C,H elemental analysis and mass spectrometry. The crystal and molecular structure of 6A was determined by X‐ray structure analysis. A formation mechanism for the complexes is proposed.