Interaction of molecular SiS with silver atoms in an argon matrix: IR spectrum and ab initio rationalization

Co-condensation of silver atoms and SiS in an argon matrix leads to the formation of Ag(SiS). The IR spectrum can be interpreted in two different ways: Isotopic shifts (28Si/29Si, 28Si/30Si, 32S/34S) imply a side-on coordination of SiS to silver. On the other hand, the SiS frequency and the isotopic shifts can be assigned to an isolated SiS− molecule. The SiS force constant is reduced from 5.0 mdyn/A in free SiS to 3.9 mdyn/A in AgSiS. Ab initio investigations confirm the formation of an ion pair Ag+(SiS)−, admitting some electron delocalization.