Ligands may bridge two or more centres. The prefix μ is used to specify a bridging ligand in both the formula and the name. For example the dimeric form of aluminium trichloride:
: AlCl(μ-Cl)
: di-μ-chlorido-tetrachlorido-1κCl,2κCl-dialuminium
This example illustrates the ordering of bridging and non bridging ligands of the same type. In the formula the bridging ligands follow the non bridging whereas in the name the bridging ligands precede the non bridging. Note the use of the kappa convention to specify that there are two terminal chlorides on each aluminium.