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Sandwich‐like Compounds Based on the All‐Metal Aromatic Unit Al 4 2− and the Main‐Group Metals M (M=Li, Na, K, Be, Mg, Ca)
Author(s) -
Yang LiMing,
Ding YiHong,
Sun ChiaChung
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601223
Subject(s) - bimetallic strip , crystallography , counterion , transition metal , metal , density functional theory , chemistry , aromaticity , formula unit , main group element , group (periodic table) , molecule , computational chemistry , materials science , stereochemistry , crystal structure , ion , organic chemistry , catalysis
Inspired by the pioneering experimental characterisation of the all‐metal aromatic unit Al 4 2− in the bimetallic molecules MAl 4 − (M=Li, Na, Cu) and by the very recent theoretical design of sandwich‐type transition‐metal complexes [Al 4 MAl 4 ] q − ( q =0–2; M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W), we used density functional theory (DFT) calculations (B3LYP/6‐311+G(d) to design a series of novel non‐transition‐metal sandwich complexes based on the all‐metal aromatic unit Al 4 2− and the main‐group metals M (M=Li, Na, K, Be, Mg, Ca). The traditional homo‐decked sandwich compounds [Al 4 MAl 4 ] q − (without counterions) and ( n M) q + [Al 4 MAl 4 ] q − (with counterions M) ( q =2–3, M=Li, Na, K, Be, Mg, Ca), although some of them are truly energy minima, have a much higher energy than many fused isomers. We thus concluded that it seems unlikely for Al 4 2− to sandwich the main‐group metal atoms in the homo‐decked sandwich form. Alternatively, we proposed a new type of sandwich complex, namely hetero‐decked sandwich compounds [CpMAl 4 ] q − , that are the ground‐state structures for each M both with and without counterions. It was shown that with the rigid Cp − partner, the all‐metal aromatic unit Al 4 2− might indeed act as a “superatom”. These new types of all‐metal aromatic unit‐based sandwich complexes await future experimental verification.