Assembly of Functionalized Organic Fragments via Reductive Activation and (Cross)‐Coupling of C ₂ H ₄ , CO, CO ₂ and/or H ₂ Using a Magnesium‐Dinitrogen Complex

Abstract Reactions of 1,2‐dimagnesioethane compound [{K( TCHP NON)Mg} 2 (μ‐C 2 H 4 )] ( TCHP NON = 4,5‐bis(2,4,6‐tricyclohexylanilido)‐2,7‐diethyl‐9,9‐dimethyl‐xanthene), formed by the two‐electron reduction of ethene with a dimagnesium/dipotassium complex of reduced N 2 , viz. [{K( TCHP NON)Mg} 2 (μ‐N 2 )], with CO and CO 2 have been explored. In the case of the reaction with CO, cross‐coupling of the reduced ethene fragment with two molecules of CO gave a heterobimetallic complex of the parent cyclobutenediolate dianion, [{K( TCHP NON)Mg} 2 (μ‐O 2 C 4 H 4 )], which when exposed to THF gave adduct [{K( TCHP NON)Mg} 2 (μ‐O 2 C 4 H 4 )(THF)]. Treating [{K( TCHP NON)Mg} 2 (μ‐C 2 H 4 )] with CO 2 led to the insertion of CO 2 into both Mg─C bonds and all Mg─N bonds, yielding a magnesium succinate complex, [{K( TCHP NON‐C 2 O 4 )Mg} 2 (μ‐O 4 C 4 H 4 )], in which the diamide ligands have been converted to xanthene bridged dicarbamates. The reaction of [{K( TCHP NON)Mg} 2 (μ‐N 2 )] with CO 2 , proceeded via reductive coupling of the heterocumulene to give the oxalate dianion, in addition to the insertion of CO 2 into all Mg─N bonds of the magnesium‐dinitrogen complex, forming dimeric [{K( TCHP NON‐C 2 O 4 )Mg} 2 (μ‐O 4 C 2 )] 2 . When treated with THF this yields monomeric [{K(THF)( TCHP NON‐C 2 O 4 )Mg(THF)} 2 (μ‐O 4 C 2 )]. Related chemistry results from the reaction of a dianionic magnesium(I) compound with CO 2 . In contrast, C─C bond formation was not observed in the reaction of [{K( TCHP NON)Mg} 2 (μ‐N 2 )] with a CO 2 analog, i.e., the carbodiimide CyNCNCy (Cy = cyclohexyl). Instead, H abstraction by a proposed radical intermediate gave polymeric formamidinate complex [K( TCHP NON)Mg{(CyN) 2 CH}] ∞ . Reaction of CO 2 with the magnesium hydride complex [{K( TCHP NON)Mg(μ‐H)} 2 ] gave the unusual trimeric magnesium formate complex [{K( TCHP NON‐CO 2 )Mg}(μ‐O 2 CH)] 3 in which CO 2 has inserted into only one Mg─N bond of each TCHP NON ligand. This study highlights the capacity of [{K( TCHP NON)Mg} 2 (μ‐N 2 )] to act as a masked dimagnesium(I) diradical in reductive coupling or cross‐coupling of the simple gaseous reagents, C 2 H 4 , CO, CO 2 and H 2 , to give value‐added organic fragments.