Growth dynamics and intracluster reactions in $Ni+(CO2)n$ complexes via infrared spectroscopy Available to Purchase

$Ni+(CO2)n,$ $Ni+(CO2)nAr,$ $Ni+(CO2)nNe,$ and $Ni+(O2)(CO2)n$ complexes are generated by laser vaporization in a pulsed supersonic expansion. The complexes are mass-selected in a reflectron time-of-flight mass spectrometer and studied by infrared resonance-enhanced photodissociation (IR-REPD) spectroscopy. Photofragmentation proceeds exclusively through the loss of intact $CO2$ molecules from $Ni+(CO2)n$ and $Ni+(O2)(CO2)n$ complexes, and by elimination of the noble gas atom from $Ni+(CO2)nAr$ and $Ni+(CO2)nNe.$ Vibrational resonances are identified and assigned in the region of the asymmetric stretch of $CO2.$ Small complexes have resonances that are blueshifted from the asymmetric stretch of free $CO2,$ consistent with structures having linear $Ni+–O=C=O$ configurations. Fragmentation of larger $Ni+(CO2)n$ clusters terminates at the size of $n=4,$ and new vibrational bands assigned to external ligands are observed for $n⩾5.$ These combined observations indicate that the coordination number for $CO2$ molecules around $Ni+$ is exactly four. Trends in the loss channels and spectra of $Ni+(O2)(CO2)n$ clusters suggest that each oxygen atom occupies a different coordination site around a four-coordinate metal ion in these complexes. The spectra of larger $Ni+(CO2)n$ clusters provide evidence for an intracluster insertion reaction assisted by solvation, producing a metal oxide-carbonyl species as the reaction product.