Reactions of Laser-Ablated Aluminum Atoms with Cyanogen: Matrix Infrared Spectra and Electronic Structure Calculations for Aluminum Isocyanides Al(NC)_1,2,3 and Their Novel Dimers

Laser-ablated Al atoms react with (CN)₂ in excess argon during condensation at 4 K to produce AlNC, Al­(NC)₂, and Al­(NC)₃, which were computed (B3LYP) to be 27, 16, and 28 kJ/mol lower in energy, respectively, than their cyanide counterparts. Irradiation at 220–580 nm increased absorptions for the above molecules and the very stable Al­(NC)₄^– anion. Annealing to 30, 35, and 40 K allowed for diffusion and reaction of trapped species and produced new bands for the Al­(NC)_1,2,3 dimers including a rhombic ring core (C)­(AlN)₂(C) with C’s attached to the N’s, a (NC)₂Al­(II)–Al­(II)­(NC)₂ dimer with a computed Al–Al length of 2.557 Å, and the dibridged Al₂(NC)₆ molecule with a calculated <i>D</i>_2<i>h</i> structure and rhombic ring core like Al₂H₆. In contrast, the Al­(NC)₄^– anion was destroyed on annealing presumably due to neutralization by Al⁺. B3LYP calculations also show that aluminum chlorides form the analogous molecules and dimers. In our search for possible new products, we calculated Al­(NC)₄ and found it to be a stable molecule, but it was not detected here