Pnicogen bonds in complexes with CO and CS: differentiating properties |
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Authors: | Janet E Del Bene José Elguero |
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Institution: | 1. Department of Chemistry, Youngstown State University, Youngstown, Ohio, USAjedelbene@ysu.edu https://orcid.org/0000-0002-9037-2822;3. Instituto de Química Médica (IQM-CSIC), Madrid, Spain https://orcid.org/0000-0002-9213-6858 |
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Abstract: | ABSTRACTAb initio MP2/aug’-cc-pVTZ calculations have been performed on pnicogen-bonded complexes with CO and CS as electron-pair donors to PH2X, for X?=?F, NC, OH, CN, CCH, and H. CO:PH2X and OC:PH2X complexes are stabilised by traditional pnicogen bonds. CS is an electron-pair donor through its in-plane π system to four PH2X molecules. It forms C···?P phosphorus-shared bonds with some ion-pair character with PH2F, PH2(OH-Z), and PH2(OH-E), and traditional pnicogen bonds with all PH2X except PH2F. C-O and C-S stretching frequencies are blue-shifted for C···P pnicogen bonds, and red-shifted for O···P and S···P bonds. EOM-CCSD spin-spin coupling constants 1pJ(P-C) for OC:PH2X and 1pJ(P-O) for CO:PH2X are characteristic of complexes stabilised by traditional pnicogen bonds. Coupling constants 1pJ(P-C) as a function of the P-C distance for SC:PH2X illustrate the evolution of the C···P pnicogen bond. They increase as the P-C distance decreases in complexes with traditional bonds, reach a maximum for SC:PH2OH transition structures as the P-C distance further decreases and the bonds gain phosphorus-shared character, and then change sign and continue to decrease as the P-C distance further decreases and the phosphorus-shared pnicogen bonds gain ion-pair character. They approach the values of 1J(P-C) for the cation (H2PCS)+. |
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Keywords: | Pnicogen bonds geometry energy shared bonds spin-spin coupling constants |
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