Cations bismuth

As is well known, simple stoichiometry of a compound is not a good guide to the coordination number of the central atom. This is well shown in (BiCl3)3-7tu (tu = thiourea), where bismuth is octahedrally coordinated to thiourea via the sulfur atom.240 The structure was found to consist of bismuth cations and anions, [Bi2Cl4tu6]2+[BiCl5tu]2- (82). 

This stabilization may also be interpreted in terms of oxygen anions, which, due, to the vacancy, are initially double bonded to Mo. One electron is transferred to the catalyst in this reaction step. To form acrolein, a second hydrogen atom is transferred (to form water) and an oxygen atom is bonded to the allyl radical. In this (rather complex) process, another three electrons are transferred to the catalysts and doubtless distributed over several Mo ions. Reoxidation takes place at the bismuth cations, where oxygen molecules are attracted by the free electron pair. The intermediate result is a surface bismuth with an oxygen coordination similar to that in the bulk, viz. 

There has been little reported study of preparation of polyatomic cations of metals in superacids. The very limited experience with Bij+ in weakly acidic HF suggests that this may be a fertile field for research. For example, Hg +, which was found to disproportionate in S02 [51], should be stable in protonic superacids or in acidic media such as neat SbFs. Similarly, bismuth cations other than Bij+ should be stable in media of controlled acidity. 

Ether bismuth halide adducts also exist. Structural work on bismuth chloride diethyl ether or THF complexes show that, at low temperature, polymeric chains of BiXs linked by hahde bridges exist and that the bismuth atoms may be coordinated by one or two ether molecules. Bismuth(ni) bromide coordinates three THF molecules. These solvent molecules are readily removed under vacuum. The polyethers diglyme and diethylcarbitol give dimeric adducts with Bids. In the presence of cyclic polyethers, simple coordination, or formation of polyether-coordinated bismuth cations... 

Since these homopolyatomic ZiniD anions and cations are devoid of ligands, they are sometimes referred to as naked" clusters. In general there is a good correlation between electronic structure and geometry as predicted by Wade s rules for the.se clusters, though some exceptions are known. Thus whereas Sn " and Bi are isoelectronic. they have different structures, the latter violating the rules. Only a small distortion of the bismuth cation, however, would convert it to the geometry ob.served for the tin cluster. 

C24H2( Bi Tetraphenylbismuthonium diphenylbis(trifluoroacetato-0)bismuthate (cation part) 6.6-20 ... 

Some studies of BaBi03 accept two different charges on the two crystallographically distinct bismuth cations. Howeverf they prefer to write Ba2Bi4 Bi4+ and speak of a charge density wave instead of disproportionation. 

There continues to be great confusion about the meaning of formal oxidation states vs. real charges on ions. As expected this is more of a problem in the physics communityf but it is unfortunately also a problem in parts of the chemistry community. When one writes Ba2BiIIIBiv0 f there is no implication that the real charges on bismuth cations should resemble +3 and +5. 

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