Alkali ion carbonyls: sequential bond energies of Li +(CO) x ( x = 1−3), Na +(CO) x ( x = 1, 2) and K +(CO)

Abstract

The sequential bond dissociation energies for Li +(CO) x ( x = 1−3), Na +(CO) x ( x = 1,2), and K +(CO) are determined by examining the collision-induced dissociation reactions with argon in a guided ion beam mass spectrometer. Analysis of the kinetic energy dependent cross sections yield values for the (CO) x−1 M +CO bond dissociation energies (BDEs) of 0.57 ± 0.13, 0.37 ± 0.04 and 0.36 ± 0.04 eV for M  Li ( x = 1–3, respectively), 0.33 ± 0.08 and 0.25 ± 0.03 eV for M  Na ( x = 1 and 2, respectively), and 0.19 ± 0.05 eV for K +CO. In addition, the M +Ar BDEs are determined by examining the ligand exchange reaction of M +(CO) with Ar and are found to be 0.34 ± 0.14, 0.16 ± 0.09 and 0.14 ± 0.07 eV for M  Li, Na and K, respectively. The trends in BDEs can be explained readily in terms of electrostatic bonding interactions. A comparison of the alkali metal ion—CO BDEs with those of transition metal ion carbonyls reveals the contributions of s-dσ hybridization and d-π ∗ back-donation in the chemical bonding of the latter systems.