Trinuclear halide complexes of Re

Rhenium forms a variety of ions and molecules based on a triangular unit of three Re atoms, for example, Re3Cl9(pyr)3, Re3Cl3(NCS)8 and Re3Cl3(NCS)9, R 3 io and Re3Xij, (X = Cl, Br), the ions being isolated as salts of 

Trinuclear halide complexes of Re (a) (ReaCUj). (b) crystalline ReCla, (c) bridge in ReCls, (d) crystalline Resig. 

The compounds to be discussed here are formed by certain metals of the second and third transition series, 

A limited number of B subgroup metals also form halides in which there is metal-metal bonding, notably Hg and Bi. We shall refer briefly to the Bi compounds for mercurous compounds see Chapter 26, and for Cu4l4(AsEt3)4 see Chapter 25. 

Metal cluster complexes (a) MjXs (or MjXs.Xs), (b) MjXia, (c) crystalline 

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