Del Bene Janet E, Alkorta Ibon, Elguero José
Department of Chemistry, Youngstown State University , Youngstown, Ohio 44555, United States.
J Phys Chem A. 2014 May 8;118(18):3386-92. doi: 10.1021/jp502667k. Epub 2014 Apr 24.
Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate the pnicogen-bonded complexes H2YP:X(-), for X,Y = Cl, NC, F, CCH, and CH3. Of the 36 possible complexes, only 21 are unique equilibrium structures. All substituents form (H2XPX)(-) complexes with symmetric X-P-X bonds. The P-A ion-molecule pnicogen bonds in these and some additional complexes have partial covalent character, while some P-A' covalent bonds have partial ion-molecule character. A and A' are the atoms of X and Y, respectively, which are directly bonded to P. Complexes with these types of bonds include the symmetric complexes (H2XPX)(-), H2(CH3)P:F(-), H2(CCH)P:F(-), H2FP:NC(-), H2FP:Cl(-), H2FP:CN(-), and H2(NC)P:Cl(-). Charge transfer from A to the P-A' σ* orbital stabilizes H2YP:X(-) complexes and leads to a reduction of the negative charge on X. For fixed X, the smallest negative charge occurs in the symmetric complex. Then, for a given X, the order of decreasing negative charge with respect to Y is CH3 > CCH > CN (bonded through C) > F > NC (bonded through N) > Cl, which is also the order of decreasing P-A distance. EOM-CCSD spin-spin coupling constants (1p)J(P-A) differentiate between shorter ion-molecule pnicogen bonds with partial covalent character and longer P···A ion-molecule pnicogen bonds. Similarly, coupling constants (1)J(P-A') differentiate between longer covalent P-A' bonds with partial ion-molecule character and shorter P-A' covalent bonds.
已开展从头算MP2/aug'-cc-pVTZ计算，以研究氮族元素键合的配合物H2YP:X(-)，其中X、Y = Cl、NC、F、CCH和CH3。在36种可能的配合物中，只有21种是独特的平衡结构。所有取代基均形成具有对称X-P-X键的(H2XPX)(-)配合物。这些配合物以及一些其他配合物中的P-A离子-分子氮族元素键具有部分共价特征，而一些P-A'共价键具有部分离子-分子特征。A和A'分别是直接与P键合的X和Y的原子。具有这些键型的配合物包括对称配合物(H2XPX)(-)、H2(CH3)P:F(-)、H2(CCH)P:F(-)、H2FP:NC(-)、H2FP:Cl(-)、H2FP:CN(-)和H2(NC)P:Cl(-)。从A到P-A' σ*轨道的电荷转移使H2YP:X(-)配合物稳定，并导致X上负电荷减少。对于固定的X，对称配合物中负电荷最小。然后，对于给定的X，相对于Y，负电荷递减的顺序为CH3 > CCH > CN（通过C键合）> F > NC（通过N键合）> Cl，这也是P-A距离递减的顺序。EOM-CCSD自旋-自旋耦合常数(1p)J(P-A)区分具有部分共价特征的较短离子-分子氮族元素键和较长的P···A离子-分子氮族元素键。同样，耦合常数(1)J(P-A')区分具有部分离子-分子特征的较长共价P-A'键和较短的P-A'共价键。
