Synthesis of Bench-Stable (CO)Mn(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)Mn(MeCN)(PF) were evaluated for the formation of 4-fluorophenylmanganese(I) pentacarbonyl (CO)Mn(4-F-CH). The optimal reagent was neopentylglycol 4-fluorophenylboronic ester activated with -butyllithium, which reacted with (CO)Mn(MeCN)(PF) to give (CO)Mn(4-F-CH) in 58% yield. These conditions were extrapolated to reactions involving other neopentylglycol esters to yield a scope of seven (CO)Mn(I)-aryls with varied substitutions on the aryl ring. The bench-stable, diamagnetic (CO)Mn(I)-aryl compounds were purified by flash column chromatography on silica and were characterized by IR spectroscopy and by H, C, F, and Mn NMR spectroscopies, with solid-state molecular structures verified by X-ray crystallography. Finally, (CO)Mn(4-F-CH) was explored as a synthetic arylating reagent in reactions with various electrophiles and nucleophiles, with organic products including those from aryl C(sp)-X and aroyl C(sp)CO-X bond formation.