Ligand Displacement Reactions Utilizing Group 13 Diyls, RM

2 Ligand Displacement Reactions Utilizing Group 13 Diyls, RM 

Two prototypical examples of alkene displacement are the displacement of cyclooctene (COE) from Cr(CO)5(COE) by Cp Ga to yield Cr(CO)5(GaCp ), and that of cycloheptatriene (CHT) in 66 from 

In) [279,281]. This is a result of the lack of competing x-acceptor CO Ugands in the coordination sphere of the transition metal [282]. 

The coordination chemistry of heterocycles featuring the Group 13 element in the +1 oxidation state and supported by an -chelating substituent has been developed in the last decade. Monomeric heterocycles of types VI-VIII have been isolated and used as ligands the neutral four and six-membered heterocycles are isolobtil to NHCs in that they bear a singlet lone pair and a formaUy vacant p-orbital at the metal center, and the anionic five-membered heterocycles are valence isoelectronic to NHCs. 

Only two six-membered aluminum heterocydes, Al (NDippCMe)2CH] (78) and Al (NDippC Bu)2CH (79) have been isolated these compounds represent rare examples of two-coordinate aluminum [299, 302]. Their coordination chemistry is limited to that of 78 with palladium [17, 183, 200, 201, 303, 304]. Accordingly, reaction with lequiv. of Pd2(dvds)j forms a 1 2 complex in which the aluminum heterocyde bridges two ptJladium centers reaction with an excess of 78 generates (dvds)PdAl (NDippCMe)2CH, featuring a rare example of a three-coordinate aluminum center in the coordination sphere of a transition metd [305, 306]. 

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