The heavier pnictogen and chalcogen analogues of isocyanic and cyanic acids and their dimers: A high level ab initio study |
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| Authors: | Zhong Zhang Chencheng Liu Ge Tian Zuqing Chen Liang Pu Robert Bruce King |
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| Institution: | 1. College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi, People's Republic of China;2. Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia |
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| Abstract: | The CCSD(T)/cc-pVTZ//CCSD/cc-pVTZ method is used to determine the geometries and energetics of the isomers HX?C?Y vs HY─C?X (X?N, P, As; Y?O, S) and their dimers from chain dimerizations and head-to-head or head-to-tail 2 + 2] cyclodimerizations. The HO─C?X structures with C?X triple bonds lie at energies at least 18.5 kcal/mol above their HX?C?O isomers. However, the energy differences between the HX?C?S and HS─C?X isomers are found to be particularly small, especially in the H,P,C,S] and H,As,C,S] systems. For (HNCY)2, the lowest energy dimers are the chain isomers, which lie ~11 kcal/mol below the lowest energy cyclic dimers aNO containing a NCNC ring and cNS containing a NCSC ring. Formation of the remaining dimers through dimerization from two monomers is predicted to be endothermic and thus thermodynamically disfavored. However, the energies of the chain isomers in the other (HXCY)2 (X?P, As; Y?O, S) series are higher than those of the corresponding isomeric lowest energy cyclodimers. For (HXCO)2 (X?P, As), the lowest energy structures are the head-to-head dimers hPO and hAsO containing a C─C─X?X ring. For (HXCS)2 (X?P, As), the lowest energy structures are the head-to-head dimers gPS and gAsS with a CCXS ring. |
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| Keywords: | dimerisation pnictogen analogue chalcogen analogues cyanic acid cyclodimerisation |
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