An unusual monomeric alkenyl-substituted pyrazolato aluminum dichloride and its derivatives with both terminal and eta(2)-pyrazolato ligands

The facile formation of the unusual monomeric alkenyl-substituted pyrazolat o aluminum dichloride [(3,5-Bu-t(2)-N-CH=C(SiMe3)-pz)AlCl2] (2; 3,5-(t)Bu(2 )pz = 3,5-di-tert-butylpyrazolato) was achieved in high yield by reacting d imeric pyrazolato aluminum dichloride [eta (1)-eta (1)-3,5-(t)Bu(2)pz(mu -A l)Cl-2](2) (1) with 2 equiv of trimethylsilylethine. The addition of 1 and 2 equiv of K[3,5-(t)Bu(2)pz] to 2, respectively, resulted in the formation of two novel complexes, [(3,5-Bu-t(2)-N-CH=C(SiMe3)-pz)AlCl(3,5-(t)Bu(2)pz) ] (3) and [(3,5-Bu-t(2)-N-CH=C(SiMe3)-pz)Al(eta (1)-3,5-(t)Bu(2)pz)(eta (2) -3,5-(t)Bu(2)pz)] (4), for which crystallographic data are presented. The c oordination of the pyrazolato ligand in 3 represents an extreme example of a "slipped" eta (2)-coordination.