Unusual dicationic trimetallic aluminum chelates  S. Liu, M.-A. Munoz-Hernandez, P. Wei, D.A. Atwood * Department of Chemistry, The University of Kentucky, Lexington, KY 40506-0055, USA Received 15 October 1999; accepted 17 November 1999 Abstract The bimetallic compounds, L(AlMeCl) 2 with L  Salpen(tBu) (N,N 0 -1,3-propylenenebis(3,5-di-tert-butylsalicylidenei- mine), Salben(tBu) (N,N 0 -1,4-butylenebis(3,5-di-tert-butylsalicylideneimine)) and Salhen(tBu) (N,N 0 -1,6 hexylenebis(3,5-di- tert-butylsalicylideneimine)) form the unusual trimetallic dicationic complexes, {[Salpen( t Bu)  ] 2 (AlCl) 3 ]} 2+ [GaCl 4 ] - GaMe 2 Cl 2  - (1), {Salben t Bu   2 AlCl 3 } 2+ GaCl 4  - GaMe 2 Cl 2  - (2) and {Salhen t Bu   2 AlCl 3 } 2+ GaCl 4  - [GaMe 2 Cl 2 ] - (3) when combined with GaCl 3 in toluene. In their formation, the ligands of the compounds undergo a unique dealkylation reaction to lose one tBu group from each ligand (marked with an asterisk). These compounds are a new and unique class of aluminum cations. The compounds were characterized by Mp, analyses, IR, 1 H NMR, and in the case of 1 and 2, by single-crystal X-ray diffractometry.  2000 Elsevier Science B.V. All rights reserved. Keywords: Aluminum chelates; X-ray diffractrometry; Dealkylation; Trigonal bipyramidal; Cation; Structure 1. Introduction The Salen 1 class of ligands (Fig. 1) have been of proven utility in the isolation of higher-coordinate monometallic group 13 complexes. Some examples include those incorporating aluminum [1,2], gallium [3] and indium [4,5] alkyls and halides and aluminum amides [6], alkoxides [7], siloxides [8] and cations [9–11]. Bimetallic derivatives are also available. The first one to be structurally characterized was Salpen (GaMe 2 ) 2 [12]. Later, other derivatives, including mixed-metal derivatives like Salen(GaMe 2 )(AlMe 2 ) [13], and boron derivatives, Salen{(BOR) 2 } 2 (R  alkyl) [14,15] were reported. In view of the growing awareness that cationic aluminum can be used in cata- lysis [9–11,16–18], we had hoped to use the bimetallics of formula, L(AlRCl) 2 (where L  Salen ligand) as starting materials for the formation of the bimetallic, dicationics, [L{AlR(solvent)} 2 ] 2+ X - . We were surprised to discover that the expected bimetallic dica- tions could not be formed, but rather a new and unusual type of trimetallic dicationic compound was discovered (for a survey of the know types of group 13 cations, see Ref. [19]). In the present paper, we wish to report on the structural features of this unique class of aluminum cation. 2. Experimental section 2.1. General considerations All manipulations were conducted using Schlenk Journal of Molecular Structure 550–551 (2000) 467–472 0022-2860/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0022-2860(00)00506-8 www.elsevier.nl/locate/molstruc  Dedicated to Professor James R. Durig on the occasion of his 65th birthday. * Corresponding author. Tel.: +1-606-257-4741; fax: +1-606- 323-1069. E-mail address: datwood@pop.uky.edu (D.A. Atwood). 1 Salen is the name that has historically been used to describe the entire class of such ligands possessing various diamino backbones. However, it is also the specific name of the ethyl derivative, SalenH 2 .