Triple-decker sandwich complexes bonding

Triple-decker sandwich complexes, in which the heteroarene rings are simultaneously and equivalently bonded to two transition metal atoms lying opposite to each other, are rare. Jonas has reported... 

Following the preparation of 4.79, a number of other cyclic mercury crown compounds have been synthesised, which do exhibit halide complexation behaviour. Compound 4.80, forms a 1 1 polymer with bromide in the solid state in which the Hr anions perch above the Hg3 plane. The Hg—Br distances of 3.07-3.39A are considerably longer than normal Hg—Br covalent bonds (about 2.54A).61 The compound also binds SCN- with similarly long bonds as shown in Figure 4.34.60 The analogous chloride complex has a 3 2 stoichiometry suggesting a triple-decker sandwich of type [4.80 Cl 4.80 Cl 4.80]2. ... 

Cyclic triene (nonaromatic) and tetraene reactions form a series of new complexes. While some cyclotrienes yield mostly unstable species, heating or hgand trapping can generally lead to stable, isolable compounds. Hydrogen transfer also plays an important role in the synthesis ofrf-rf sandwich complexes. With cot and Cr atoms a Ci Cr bonded Cr2(CgH8)3 complex is formed, while in the case of Ti-cot, a novel Triple Decker Sandwich is obtained. ... 

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