Q:

How does bismuth's lone pair affect its properties as a metal and alloy?

Bismuth is really the only metal to exhibit a lone pair in its outermost shell, this means that it and its salts should be a Lewis base. As bismuth can act as a Lewis base, how does this affect its properties as a metal specifically in regards to alloying? For instance, if I have a 1:1 mole ratio of aluminum and bismuth in an alloy, will the aluminum and bismuth form dative bonds?

A:

If you look at the chemistry of lead(II) and the work by Tony F. Hill (and others) on platinum group metals you will see that bismuth is clearly not the only metal to have lone pairs.
What Tony Hill did was rather clever, normally metal-ligand coordination is all about the donation of lone pairs to the metal and sometimes the retrodonation of electron density onto pi acidic ligands such as carbon monoxide and cyanide.
What Tony did was to get a borane to bind to a lone pair on a low valent metal such as ruthenium, osmium or rhodium. Here is a diagram of an example of one of his compounds.

The synthesis of this rhodium compound can occur from [RhCl2(Ph)(PPh3)2], this rhodium complex can react with Na[HB(mt)3] (mt = methimazolyl) to form an intermidate (mt)B(H)(mt)2Rh(Ph)Cl(PPh3)2 which then decomposes to lose a molecule of benzene to form B(mt)3RhCl(PPh3). (Chem. Comm., 2005, page 221).
I am sure that tin has a stereochemcially active lone pair, if we consider the strcuture of Cp2Sn, this is not quite like ferrocene. Instead of the two Cp rings being parallel. They are not. So I think that bismuth is not the only metal to have lone pairs on it. Even the bis Cp* complex of lead(II) (bis(h5-Pentamethyl-cyclopentadienyl)-lead) is bent away from the ferrocene type strcutre suggesting that the lead has a stereochemically active lone pair.

