IR Structural Identification of Oxocumulene···HCl Complexes Generated in Cryogenic Matrixes. The Product-like Transition State of the Corresponding Electrophilic Addition

Abstract

The structure and energy properties of the 1:1 complex formed between HCl and carbon suboxide C3O2 (3) have been investigated using FTIR matrix isolation spectroscopy and ab initio calculations at the MP2/6-31G** level. Investigations have been extended to other oxocumulenes such as H2CCO (1), and (CH2)2CCO (2) complexed by HCl. Trapped in argon matrixes, these complexes are characterized by a large shift of the νHCl stretching mode to lower frequencies (191, 135, and 150.5 cm-1 for 1−3, respectively). The similarity of IR spectra of the complexes generated in the gas or in the solid phase is indicative of a similar inclusion site. Concordance between experimental and calculated νHCl shifts is obtained with T-shaped complexes. These complexes describe the interaction between hydrogen and the Cβ carbon atom of the ketene moiety. The geometrical modifications of the ketene subunit suggest that the complex is the product-like transition state of the corresponding electrophilic addition to the carbon atom.