Cycloarsines, -stibines and -bismuthines

6-(CH2NMe2)2], initially produces the tricyclic compound Ar3Sb5 with a trigonal bipyramidal arrangement of five Sb atoms.  

The lability of the E-E and E-C bonds in cyclostibines and cyclobismuthines is readily evident in reactions of these homocycles with metal carbonyls. Under mild conditions, complexes in which the antimony ligand acts as a two-electron donor towards the metal centres may be isolated, e.g. cyclo-( BuSb)4[W(CO)5] (n=l,2) cf. metal complexes of cyclophosphines, see Section 7.1.1). In boiling solvents, however, rupture of the inorganic homocycle and/or the E-C bonds 

In contrast to the simple adduct formation observed in the reaction of cyclostibines with [W(CO)5(THF)], the treatment of cyclobismuthines (RBi) (t7 = 3, 5 R = Me3SiCH2) with this labile reagent produces a binuclear complex of the dibismuthene RBi=BiR [eqn (11.19)].  

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