Structures of XH32+ (X = C, Si and Ge) and isoelectronic XH3+ (X = B, Al and Ga) [1]

Ab initio calculations at the MP2/6-31G** and QCISD(T)/6-311G** levels were carried out to calculate the structures of XH32+ (X = C, Si and Ge) and XH 3+ (X = B, Al and Ga). Energy comparison shows that the global minimum stru ctures of XH32+ (X = Si and Ge) and XH3+ (X = Al and Ga) are not of C-2v sy mmetry (2-3a and 5-6a) but of C-s symmetry (2-3b and 5-6b) with 3c-2e bonds . As we move to higher analogs of a given series, the 3c-2e bonded structur es are increasingly more favorable than the corresponding C-2v structures. (C) 1998 Elsevier Science B.V. All rights reserved.