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 <b>1</b> and <b>2</b>, featuring covalent yet tunable Al-Cd bonding. While <b>1</b> is irreversibly formed, <b>2</b> 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), <b>2</b> enables selective Al(I) shuttling to B, Cd, Zn, and Ag substrates (compounds <b>1</b>^<b>Zn</b>, <b>3</b>-<b>5</b>). The cooperative Al-Cd framework in <b>1</b> and <b>2</b> further promotes bond activation of heterocumulenes such as carbodiimides and CO₂, with <b>1</b> serving as a source of nucleophilic cadmium─an unprecedented reactivity mode for this element (compounds <b>6</b>-<b>8</b>). Detailed quantum chemical calculations elucidate the electronic structures of <b>1</b> and <b>2</b> 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.