ABSTRACTWe present the results of a combined experimental and computational study of the structures of gas-phase M
+(N
2O)
n (M?=?Li, Al) complexes. Infrared spectra were recorded in the region of the N
2O asymmetric (N?=?N) stretch using photodissociation spectroscopy employing the inert messenger technique. Unlike in our previous studies on M
+(N
2O)
n (M?=?Cu, Ag, Au and M?=?Co, Rh, Ir) complexes, N– and O–bound isomers in this case are near isoenergetic and are not distinguished spectroscopically at this resolution. In the case of Li
+ complexes, there is, however, evidence for the presence of bound N
2 moieties, indicating the presence of inserted, OLi
+N
2(N
2O)
n–type structures. The weak N
2 band lies to the blue of the signature of molecularly N– and O–bound ligands and is well–reproduced in the simulated spectra of energetically low-lying structures computed from density functional theory. No such inserted isomers are observed in the case of Al
+(N
2O)
n complexes whose infrared spectra can be understood on the basis of molecularly-bound N
2O ligands. The differences in M
+(N
2O)
n structures observed for these closed–shell,
ns2, metal centres relative to other metal cations are discussed in terms of the likely bonding motifs.
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