Synthesis of Bench-Stable (CO)₅Mn(I)-Aryl Compounds by Transmetalation of Arylboronic Esters

To explore arylboron transmetalation at manganese(I), reactions of 4-fluorophenylborates with pentacarbonylmanganese(I) hexafluorophosphate cation (CO)₅Mn(MeCN)(PF₆) were evaluated for the formation of 4-fluorophenylmanganese(I) pentacarbonyl (CO)₅Mn(4-F-C₆H₄). The optimal reagent was neopentylglycol 4-fluorophenylboronic ester activated with n-butyllithium, which reacted with (CO)₅Mn(MeCN)(PF₆) to give (CO)₅Mn(4-F-C₆H₄) in 58% yield. These conditions were extrapolated to reactions involving other neopentylglycol esters to yield a scope of seven (CO)₅Mn(I)-aryls with varied substitutions on the aryl ring. The bench-stable, diamagnetic (CO)₅Mn(I)-aryl compounds were purified by flash column chromatography on silica and were characterized by IR spectroscopy and by ¹H, ¹³C, ¹⁹F, and ⁵⁵Mn NMR spectroscopies, with solid-state molecular structures verified by X-ray crystallography. Finally, (CO)₅Mn(4-F-C₆H₄) was explored as a synthetic arylating reagent in reactions with various electrophiles and nucleophiles, with organic products including those from aryl C(sp²)-X and aroyl C(sp²)CO-X bond formation.