Published: September 08, 2011 r2011 American Chemical Society 9564 dx.doi.org/10.1021/ic2013123 | Inorg. Chem. 2011, 50, 9564–9570 ARTICLE pubs.acs.org/IC Multimetallic Synergic Sedation of a Labile Sodium Atrane: Synthesis and Characterization of a Tetranuclear Sodium Atrane Cation Complex Jinfeng Zhang, † Ai Liu, † XiaoBo Pan, Lihui Yao, Lei Wang, Jianguo Fang, and Jincai Wu* Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People’s Republic of China b S Supporting Information 1. INTRODUCTION Multimetallic coordination chemistry has attracted consider- able interest due to some special synergic effects. The enzyme of nitrogenase, for example, includes heterometallic complexes (e.g., Fe, Mo, and Co) at the active site in which the multimetallic synergic effect plays a key role in the fixation of atmospheric nitrogen gas. 1 Some heterobimetallic complexes applied as asymmetric catalysts can efficiently promote many reactions through a synergetic cooperation between two different metals, 2 and the heterobimetallic complex of “iBu 3 Al(TMP)Li” (TMP(H) = 2,2,6,6-tetramethylpiperidine) exhibits high chemo- and regios- electivity in proton abstraction reactions of functionalized aro- matic substrates because of alkali-metalÀaluminum synergic effects. 3 Recently, Mulvey et al. published extensive and excellent work on the applications of mixed-metal molecular synergy, such as the extraordinary synergic sedation of sensitive cyclic ether and ethene anions by alkali-mediated zincation 4 and the quantitative regioselective tetramagnesiation of ferrocene, ruthenocene, and osmocene (which cannot be directly magnesiated by any known conventional organomagnesium reagent by an alkali-metal-mediated magnesiation approach). 5 They have also reported the activation of arene by multimetallic inverse crown complexes 6 and the self- deprotonation/metalation of the TMP anion in a KÀAl hetero- bimetallic complex, which is unlikely to be reproduced in a homometallic system under a controlled manner. 7 Recently, our research has focused on the development of multimetallic catalysts for the ring-opening polymerization of cyclic esters. Thus, some multimetallic complexes have been synthesized, and some interesting synergic effects were observed. 8 Here, we report a new synergic effect in the stabilization of a special tetrasodium atrane cation with tripodal aminetris(phenol) as the ligand. An atrane is tricyclic molecule with three five- or six-mem- bered rings and a transannular bond. Atranes have attracted the interest of many chemists because they can be used to stabi- lize unusual metal coordination geometries, 9 unusual inorganic functionalities, 10 and catalytically active species. 11 The tripodal aminetris(phenol), when acting as an atrane ligand with one nitrogen and three oxygen coordination atoms, usually binds to a metal in a tetradentate manner to give the settled coordinating environment; five-coordinate trigonal bipyramidal complexes are most commonly observed with another simple coordinated ligand at the apical position. Because of the ease with which steric and electronic modulation are induced by changes in the substituents on the aryl rings, tripodal aminetris(phenol) ligands have been widely used to synthesize many kinds of atranes such as silicon, 12 phosphorus, 13 titanium, 14 tantalum, 15 indium, 16 vanadium, 17 iron, 18 and germanium 19 atranes. Among the known atranes, sodatrane remains relatively unexplored. To the best of our knowledge, the sodium complexes of aminetriethanol re- ported by Verkade et al. are the only examples of sodatranes, 20 Received: June 17, 2011 ABSTRACT: A series of sodium and aluminum atrane complexes of Na 3 L(THF) 5 (1), [AlLMe][Na 4 L(THF) 6 ](2), AlL(THF) (3), AlNaLMe(THF) 2 (4), and AlNaLOBn- (THF) 2 (5), wherein L = tris(2-oxy-4,6-di-tert-butyl-benzyl)amine, were synthesized and characterized by NMR, X-ray crystallography, and elemental analysis. The trinuclear sodium atrane complex of Na 3 L(THF) 5 (1) is labile at room temperature; however, the tetranuclear sodium atrane cation in complex 2 can be stabilized by a multimetallic synergetic effect due to a firm interaction ring of À[NaÀOÀbenzene] 3 À. Complex 2 is also the first example of a sodatrane and alumatrane ion-paired complex in which both the cationic and anionic moieties contain an atrane ligand.