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The Structures of [X 2 YNYX 2 ] + Cations (X F, Cl; Y S, Se). A Comparison of X‐ray and ab Initio Studies [1]
Author(s) -
Schulz Axel,
Broschag Matthias,
TornieporthOetting Inis C.,
Klapötke Thomas M.,
Buzek Peter,
Schleyer Paul Von Ragué,
White Peter S.
Publication year - 1995
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19951280106
Subject(s) - chemistry , crystallography , ab initio , isostructural , natural bond orbital , lone pair , crystal structure , ab initio quantum chemistry methods , bond length , lattice energy , antibonding molecular orbital , chalcogen , electron , computational chemistry , atomic orbital , molecule , density functional theory , physics , organic chemistry , quantum mechanics
The structures of cationic species of the series [X 2 YNYX 2 ] + (X F, Cl; Y S, Se) have been computed ab initio using all electron treatments for first‐row elements and sulfur and quasi‐relativistic pseudopotentials for Se and Cl. Splitvalence basis sets with polarization and diffuse functions were employed. The MP2 results for the (non‐isostructural!) cations [Cl 2 SeNSeCl 2 ] + ( 1 : C s ) and [F 2 S NSF 2 ] + ( 2 : C 2 v ) are in excellent agreement with the experimental (X‐ray) observations. Both structures represent local minima. A deeper minimum for either of the cations is represented by another C 2 v isomer which for crystal lattice energy reasons is stable in the isolated state only. The geometries of the hitherto unknown species [Cl 2 SNSCl 2 ] + ( 3 ) and [F 2 SeNSeF 2 ] + ( 4 ) have been assessed by ab initio HF calculations. In analogy to 2 , cations 3 and 4 are predicted to prefer C 2 v symmetry. Therefore, 1 exhibits unusual structural features. According to strictly localized natural bond orbital analysis (NBO), the central nitrogen atoms in 1 and 2 possess two lone pairs of electrons (LP: one sp hybrid and one p orbital). The relatively short SeN and SN bond distances in 1 (1.741–1.760 Å) and 2 (1.551 Å) can best be attributed to LP(N)→s̀*(YX) negative hyperconjugation ( 1 : Y Se, X Cl; 2 : Y S, X F).