Paper The ‘globule–globule’ hybrid dicarbaborane–polyoxometallate salt, [C 2 B 10 H 11 CH 2 NHCH(CH 3 ) 2 ] 4 [W 10 O 32 ][H 2 O] 2 [(CH 3 ) 2 CO] 4 Ramo ´n Macı ´as,* a,b { John D. Kennedy, a Mark Thornton-Pett a and Pascual Roma ´n b a Department of Chemistry, University of Leeds, Leeds, UK LS2 9JT b Departamento de Quı ´mica Inorga ´nica, Universidad del Paı ´s Vasco, Apartado 644, E-48080 Bilbao, Spain Received 28th February 2003, Accepted 26th March 2003 First published as an Advance Article on the web 9th April 2003 The ‘globule–globule’ salt, [C 2 B 10 H 11 CH 2 NHCH(CH 3 ) 2 ] 4 [W 10 O 32 ][H 2 O] 2 [(CH 3 ) 2 CO] 4 , contains new iminium dicarbaborane cluster cations, [C 2 B 10 H 11 CH 2 NHLCH(CH 3 ) 2 ] 1 , and decatungstate cluster anions, [W 10 O 32 ] 42 , linked by hydrogen bonded H 2 O and (CH 3 ) 2 CO solvent molecules to form a hydrophilic/hydrophobic lamellar structure. Polyoxoanions of early transition elements on one hand, 1 and polyhedral boron-containing compounds on the other, 2 con- stitute two extensive classes of cluster compounds with a wide range of useful and/or interesting structures and properties. Both types of compounds can be functionalized with organic and organometallic groups, either by the incorporation of such groups into the cluster, or by their attachment to the cluster surface. In the case of boranes and carbaboranes this func- tional chemistry is rich. 3 The known functional chemistry of polyoxometallates is much more limited, although much current research is now directed towards their similar function- alization. 4 The various currently emerging developments in both polyhedral boron and polyoxometallate chemistry offer intrinsic continuities and complementarities among these two branches of chemical science. In this regard, we envisage the synthesis of (a) contiguously covalent borane/polyoxometallate hybrid compounds that would exhibit structural patterns and properties to complement those found in reported organic and organometallic derivatives of polyoxometallates; as well as (b) the synthesis of new types of ionic hybrid salts, in which both the anions and the cations are of large, globular, aspect. In this overall context we here report the synthesis and structure of the first such carbaborane–polyoxometalate ‘globule–globule’ hybrid salt. The dicarbaboranylmethylammonium salt [C 2 B 10 H 11 CH 2 - NH 3 ]Cl was prepared as in the literature, 5 and, thence, based on the procedure used for the preparation of tetrabutylammonium salts of decatungstate(VI), 6 treatment of an acidified solution of Na 2 WO 4 with [C 2 B 10 H 11 CH 2 NH 3 ]Cl in water yielded a white precipitate of formulation [C 2 B 10 H 11 CH 2 NH 3 ] 4 [W 10 O 32 ] [eqn. (1)]. Crystallization of this salt from acetone/hexane afforded crystals of the new globule–globule salt, [C 2 B 10 H 11 - CH 2 NHLCH(CH 3 ) 2 ] 4 [W 10 O 32 ], as its {[H 2 O] 2 [(CH 3 ) 2 CO] 4 } solvate 1. 10Na 2 WO 4 1 16HCl 1 4[C 2 B 10 H 11 CH 2 NH 3 ]Cl A [C 2 B 10 H 11 CH 2 NH 3 ] 4 [W 10 O 32 ] 1 20NaCl 1 8H 2 O (1) The solid-state structure of compound 1 is based on a matrix of dicarbaboranylmethyliminium cations and decatungstate anions (Fig. 1). The generation of the iminium function from the ammonium residue is of interest, and reasonably results from the reaction between acetone and the primary ammonium group of the starting aminomethyl-ortho-dicarbaborane resi- due during the crystallization process. Compound 1 crystallizes in the space group P1 ¯ with two formula units in the unit cell. There are two crystallographi- cally independent dicarbaboranyl cations, of which each bears a pendant organic group that exhibits angles and a C–N distance typical for a double bond, fully in accord with the presence of an iminium function [Fig. 1(a)]. The distances and angles within the deltahedral cluster are within the ranges found for other functionalized closo-dicarbaboranes (Table 1). 7 The molecular structure of the large globular decatungstate ion [Fig. 1 (b)] is known; the interatomic distances and angles of the [W 10 O 32 ] 42 cage found in its new salt 1 conform to values previously reported (Table 1). 8 In compound 1 these anions have D 4h point-symmetry and lie on crystallographic inversion centres at the vertices of the primitive unit cell. They pack in chains along the b vector, their four-fold axes being slightly tilted with respect to the crystallographic axes (Fig. 2). Along the b direction, the shortest interanionic contact distances are 3.38 and 3.37 A ˚ ; these distances are the separation of one of the polar (i.e. axial terminal) oxygen atoms, O1, of an isopoly- tungstate anion with, respectively, an axial terminal oxygen { Present address: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA. E-mail: rmaza@nd.edu Fig. 1 (a) Molecular structure of one of the crystallographically independent [C 2 B 10 H 11 CH 2 NHCH(CH 3 ) 2 ] 1 cations. (b) Molecular structure of the [W 10 O 32 ] 42 anion in 1. DOI: 10.1039/b302341a CrystEngComm, 2003, 5(19), 93–95 93 This journal is # The Royal Society of Chemistry 2003