HALIDES OF o-SUBSTITUTED ARYL-ALUMINUM COMPOUNDS WITH COORDINATION NUMBERS FOUR AND FIVE Christian Böker, Mathias Noltemeyer, Heinz Gornitzka, Boris O. Kneisel, Markus Teichert, Regine Herbst-lrmer and Anton Meiler* Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany ABSTRACT The THF adduct of dichloro(2,4,6-triisopropylphenyl)aluminum (1) was prepared. Dehalogenation of 1 with Na/K alloy gave a tricyclic compound with a dioxonia-dialuminata central unit (2). The reaction of 2,6-bis{[(dimethylamino)methyl]phenyl}lithium with AIX 3 (X = CI, Br, I), EtAICI 2 or Et 2 AICI (in 1:1 ratio) yielded compounds Β and 3-6 containing penta- coordinated aluminum atoms. From 2-[(dimethylamino)methyl]phenyllithium and AICI 3 , AIBr 3 , EtAICI 2 or Et 2 AICI (1:1) the tetracoordinated Al-species 7, 8, C and D were obtained while with the same reactants in 2:1 ratio the pentacoordinated species 9, 10 and Ε are formed. The reaction of 3 equivalents of 2-[(dimethylamino)methyl]phenyllithium with AICI 3 gave 11 (coordination number five, fluxional behaviour in solution). From 8- (dimethylamino)naphthyllithium, AICI 3 , AIBr 3 and EtAICI 2 the tetracoordinated species 12 - 14 were synthesized. By treating the dibromo species 6 and C with lithiated 2,6-dimethyl-N- (trimethylsilyl)aniline the correspondingly substituted monobromo species 15 and 16 were obtained. The compounds are characterized by NMR ( 1 H, 13 C and 29 Si) and mass spectrome- try, most of them also by 27 AI NMR and elemental analyses. X-ray structure analyses are provided for 2, 4, 6, 7, 11 and 16. INTRODUCTION It is generally known that the coordination of metal atoms can be governed as well by the steric requirement of the substituents as by inter- and specially intramolecular donor stabilization. Aryl substituted aluminum atoms did not find much interest in the past, compared to their alkyl substituted analogs. Research activity, however, did increase considerably within the last years. Stimulated by the isolation of the first monomeric aluminum dihalide with coordination number three, Mes*AIBr 2 (Mes*= 2,4,6-f-Bu 3 C 6 H 2 ) 1 and our own results about supermesityl substituted halides of gallium and indium 2 " 4 , we wanted to extend our research to halides of aluminum stabilized either by inter- or by intramolecular coordination. The aim was primarily to compare the influence of different substituents on NMR and structural data. With o-substituted aromatic groups, Mes*AICI 2 6 with the coordination number three as well as MesAICI 2 THF 5 (Mes = mesityl), Mes*AICI 2 THF 6 , and TripAIBr 2 OEt 2 1 (Trip = 2,4,6-triisopropylphenyl) with the coordination number four are already known. Furthermore arylaluminumhalides stabilized by intramolecular coordination with the coordination numbers four and five should be included. The 2-[(dimethylaminomethyl)- phenyl]-, (Q), the 2,6-bis[(dimethylaminomethyl)phenyl]-, (R), and the 8-[(dimethylamino- methyl)naphthyl]-ligand, (X), were applied. So far the following halides of aluminum with the ligands (Q and R) have been described: QAICI 2 7 , QAIBr 2 8,9 , QAI(Me)CI 7 , QAI(t-Bu)CI 9 , QAI(CSiMe 3 ) 3 CI 7 and RAICI 2 8 " 10 . Ligand (X) was not used before. RESULTS AND DISCUSSION Bis(2,4,6-triisopropylphenyl)magnesium · 2 THF (A) 11 was prepared by a Grignard reaction from the corresponding bromide in THF followed by a Schlenk-dismutation with dioxane. 565