Theoretical study on a class of organometallic complexes based on all-metal aromatic Ga-3(-) through sandwiching stabilization

摘要

We report the theoretical study on a class of organometallic complexes containing the all-metal aromatic unit Ga-3(-) on the basis of density functional theory calculations on a series of model sandwich-like compounds [DM(Ga-3)](q-) as well as those of the saturated compounds [DM,(Ga3)] [D = Ga-3(-) Cp- (C5H5-); M = Li, Na, K, Be, Mg, Ca] and extended compounds (Cp-)(m)(Li+)(n)(Ga-3(-))(o) (m, n, and o are integers). For the six metals, the all-metal aromatic Ga-3(-) can only be assembled and stabilized in the "heterodecked sandwich" scheme (e.g. [CpM(Ga-3)](q-)) so as to avoid cluster fusion. Moreover, we designed a novel class of all-metal aromatic "metalloid" compounds. The ground state heterodecked sandwich species (Cp)(-)(M)(q+)(Ga-3)(-) (M = Li, Na, K, q = 1; M = Be, Mg, Ca, q = 2) and the extended sandwich species (Cp-)(m)(Li+)(n)(Ga-3(-))(o) are mainly ionic bonded, cluster- assembled "polyatomic molecule", grown from the combination of Cp-, M atoms, and Ga-3(-). As a prototype for ionic bonding involving intact Ga-3(-) subunits, [CpM(Ga-3)](q-) may be a stepping stone toward forming ionic, cluster-assembled all-metal aromatic Ga-3-based bulk solids or materials. Additionally, our results for the first time showed that the electronic, structural, and aromatic properties of the all-metal aromatic Ga-3(-) could be well retained during cluster assembly, which is indicative of "building block" character. Bearing the significant difference in bonding patterns between our designed metalloid compounds and the known metalloid species, synthesis of these novel species might present an attractive challenge to experimental chemists. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).