Trigonal bipyramidal clusters Zintl ions

Fig. 9.3 The Zintl ion [Sn5p has a trigonal bipyramidal cluster structure.

The Sn6[M(CO)5]6 clusters (M = Cr, Mo, W) [51] are not prepared from Zintl anions, but the Siig octahedral cores can be viewed as a closo 2n+2 member of the deltahedral Zintl anion series and are similar to the cZoso-trigonal bipyramidal Sns ion. The Sn chemical shifts of the Sn6[M(CO)5]6 complexes are in the range 198-561 ppm and are somewhat downfield of the anionic Zintl clusters. Large one-bond Sn-Sn couplings of 1,800 Hz are suggestive of nonfluxional compounds. 

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