Synthesis and characterization of HC{C(Me)N(C6H3-2,6-i-Pr-2)}(2)MX2 (M = Al, X = Cl, I; M = Ga, In, X = Me, Cl, I): Sterically encumbered beta-diketiminate group 13 metal derivatives

series of group 13 metal complexes featuring the beta -diketiminate ligand [((C6H3-2,6-i-Pr-2)NC(Me))(2)CH](-) (i.e., [Dipp(2)nacnac](-), Dipp = C6H3- 2,6-i-Pr-2) have been prepared and spectroscupically and structurally chara cterized. The chloride derivatives Dipp(2)nacnacMCl(2) (M = Al (3), Ga (5), In (8) were isolated in good yield by the reaction of 1 equiv of Dipp2nacn acLi . Et2O (2) and the respective metal halides. The iodide derivatives Di pp(2)nacnacMI(2) (M = Al (4), Ga (6), In (9)), which are useful for reducti on to afford M(I) species, were made by a variety of routes. Thus, 4 was ob tained by treatment of the previously reported Dipp(2)nacnacAlMe(2) with I- 2, whereas the gallium analogue 6 was obtained as a product of the reaction of "GaI" with Dipp(2)nacnacLi . Et2O, and 9 was obtained by direct reactio n of InI3 and the lithium salt. The methyl derivatives Dipp(2)nncnacMMe(2) (M = Ga (7), In (10)), which are analogous to the previously reported Dipp( 2)nacnacAlMe(2), were synthesized by the reaction of GaMe3 with Dipp(2)nacn acH (1) or by reaction of the indium chloride derivative 8 with 2 equiv of MeMgBr in diethyl ether. The compounds 3-10 exist as colorless, air- and mo isture-sensitive crystalline solids. Their X-ray crystal structures feature nearly planar C3N2 arrays in the Dipp(2)nacnac ligand backbone with short C-C and C-N distances that are consistent with a delocalized structure. How ever, there are large dihedral angles between the C3N2 plane and the N2M me tal coordination plane which have been attributed mainly to steric effects. The relatively short M-N distances are consistent with the coordination nu mbers of the metals and the normal/dative character of the nitrogen ligands . The compounds were also characterized by H-1 and C-13 NMR spectroscopy. 1 H NMR data for 7 revealed equivalent methyl groups whereas the spectrum of 10 displayed two In-Me signals which indicated that ring wagging was slow o n the H-1 NMR time scale.