Successful extrapolation of an f-element synthetic method to the pseudo light lanthanoid, aluminium Jacinta M. Bakker a , Leonard J. Barbour b , Glen B. Deacon a , Peter C. Junk a, * , Gareth O. Lloyd a, c , Jonathan W. Steed c a School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia b Department of Chemistry, University of Stellenbosch, 7602, Matieland, South Africa c Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom article info Article history: Received 8 July 2010 Received in revised form 4 August 2010 Accepted 6 August 2010 Available online 12 August 2010 Dedicated to Professor Herbert Schumann the Father of German Organolanthanoid Chemistry, a valued colleague and friend. Keywords: Redox transmetallation/ligand exchange Aluminium complexes Pyrazole and pyrazolates High Z 0 Crystallography abstract A redox transmetallation/ligand exchange reaction between Al metal, Hg(C 6 F 5 ) 2 and 3,5-di-tert-butyl- pyrazole (tBu 2 pzH) in tetrahydrofuran (thf) yields [Al(tBu 2 pz) 3 (thf)] in which the six coordinate aluminium atom has two h 2 - and one h 1 -tBu 2 pz ligands. By contrast an analogous reaction in 1,2-dimethoxyethane (dme) gives the organoaluminium complex [Al 2 (tBu 2 pz) 3 (C 6 F 5 ) 2 (OCH 2 CH 2 OCH 3 )] in which each aluminium atom has an h 2 -pyrazolate and a C 6 F 5 ligand and the Al atoms are bridged by an h 1 :h 1 -tBu 2 pz ligand and a 2-methoxyethoxide ligand. In addition, [Al(tBu 2 pz) 3 ] was isolated from the reaction mixture in a different form from that previously reprinted. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction The coordination chemistry of pyrazolate anions and pyrazoles has become a mainstay of inorganic chemistry.[1] Prior to 1997 the coordination modes established for pyrazolates by crystallographic means consisted of just the simple meh 1 :h 1 , h 1 and h 2 modes [1a,p,2]. However, post-1997, the possible modes of coordination have increased substantially to over 20, resulting in such extreme cases as meh 1 :h 2 :h 1 (to K þ and Tl þ ) and h 5 (to Ru 2þ ) [1a,3,4a]. The synthesis of homoleptic pyrazolate complexes of d-block [4aec], f- block [4def] and main group metals has also been achieved [2,3c,g]. 3,5-Di-tert-butylpyrazole (tBu 2 pzH) is an archetypal ligand when it comes to the coordination chemistry of the pyrazolates [1a,2,3a,c,d,g,4bee,5]. Due to its simplicity in structure and it being the bulkiest of the simple pyrazolates, it forms many types of complexes with different metals [2,3c,4,5b]. We have previously synthesised the homoleptic [Al(tBu 2 pz) 3 ] (Compound 1; a trigonal crystal structure was determined.) using a metathesis method [2]. In this study, we report developments in the coordination chem- istry of aluminium with tBu 2 pz through the use of a different synthetic route, namely, the redox transmetallation/ligand exchange reaction [6]. Such reactions (e.g. Scheme 1) have hitherto been used to synthesise particularly f-element, but also Group 2 complexes [6], derivatives of elements more electropositive than aluminium. Nevertheless, Al is a highly reactive metal and the common oxidation state is the same as that of the f-element complexes. It could thus be regarded as the lightest rare earth metal. Further, the well-known preparations of homoleptic aluminium alkyls and aryls from metallic aluminium and HgR 2 species at elevated temperatures [7] suggested that aluminium metal should participate in redox transmetallation/ligand exchange reactions. 2. Results and discussion Carrying out the redox transmetallation/ligand exchange reac- tion shown in Scheme 1 using thf as the solvent resulted in a complex of formula [Al(tBu 2 pz) 3 thf]$thf (2). The best yields of ca. * Corresponding author. Fax: þ61 03 9905 4597. E-mail address: peter.junk@monash.edu (P.C. Junk). Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem 0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2010.08.007 Journal of Organometallic Chemistry 695 (2010) 2720e2725