Functional Al/Cd Heterometallics - From Controlled Al(I) Transfer to Nucleophilic Transfer of Cadmium Ions

Low-valent cadmium compounds have remained largely unexplored as electron reservoirs, with no precedent for their use in reduction or bond activation chemistry. Here, we address this gap by integrating low-valent aluminum into the cadmium coordination sphere. Aluminylene insertion into Cd{N(TMS)₂}₂ affords bi- and trimetallic cadmium aluminyls 1 and 2, featuring covalent yet tunable Al–Cd bonding. While 1 is irreversibly formed, 2 exhibits dynamic reactivity, enabling reversible [AlCp*]⁰ transfer─a rare and previously undocumented feature in heterobimetallic aluminum chemistry. Acting as a thermodynamically stable yet chemically reactive surrogate for free Al(I), 2 enables selective Al(I) shuttling to B, Cd, Zn, and Ag substrates (compounds 1ᶻⁿ, 3–5). The cooperative Al–Cd framework in 1 and 2 further promotes bond activation of heterocumulenes such as carbodiimides and CO₂, with 1 serving as a source of nucleophilic cadmium─an unprecedented reactivity mode for this element (compounds 6–8). Detailed quantum chemical calculations elucidate the electronic structures of 1 and 2 as well as the mechanism for both Al(I) transfer and heterocumulene insertion. These findings establish a platform for bimetallic cooperativity in small-molecule activation and lay the groundwork for Al(I)-based multimetallic systems relevant to future catalysis and main group/transition-metal synergy.