Activating Robust Covalent Bonds with Cobalt and Iron Carbonyls

Metal carbonyls are a class of organometallic compounds characterized by the presence of transition metals bonded to one or more carbonyl (CO) ligands. These compounds exhibit great ability to activate and transform small molecules (like carbon monoxide and hydrogen) by coordinating and activating their robust bonds. This property gives metal carbonyls substantial importance in industrial (production of fuels and chemicals) and medical applications. My research is focused on carbonyls of iron and cobalt. In contrast to the commonly employed noble metals, such as Pd, Ru, Rh, and Pt, first-row transition metals offer a more cost-effective and environmentally friendly alternative. I demonstrated that Fe carbonyl anion KCpFe(CO)2 can activate C-F bonds of aryl fluorides for: 1. The synthesis of aryliron(II) complexes CpFe(CO)2Ar (FpAr) in the absence of any catalyst; 2. Subsequent coupling with alkenes in Heck-type reactions; 3. Performing one-pot C-F/C-H functionalization with alkynes, giving indene derivatives as major products. Fe carbonyl-based heterobinuclear complex Ldipp(Me)Al-FeCp(CO)2 (Ldipp = HC{(CMe)(2,6-iPr2C6H3N)}2) was found to activate CO2 and epoxides through cooperative behavior of two radical intermediates. The Al-Fe bond dissociates homolytically at room temperature to generate formally AlII and FeI metalloradicals, which then add to substrates in a pairwise fashion initiated by O-coordination to Al. This “radical pair” pathway represents an unprecedented mechanism for CO2 activation. On the other hand, I also discovered that unprecedently Co carbonyl, cheap and commercially available Co2(CO)8, can catalyze hydrogermylation of terminal alkynes. Subsequently, a selective, accessible method was developed to synthesize E-(β)-vinyl(trialkyl)germanes, crucial synthetic building blocks, from various terminal alkynes with high yields. The newly developed is compatible with alkynes bearing both aryl and alkyl substituents, providing unrivaled selectivity for previously challenging primary alkyl-substituted alkynes. Despite the significant advances in the field, there is always room for improvement, and it is likely metal carbonyls will continue to play a vital role in industrial processes and academic research in the future.