Ten-vertex {closo-2,1,10-FeC2B7} clusters with intramolecular imidate linkages: anchors for supramolecular construction.

Intramolecular hydroxyl attack upon iron-coordinated nitriles in a {closo-2,1,10-FeC2B7} system forms imidates that allow construction of a tetra-cluster {FeC2B7}-{C2Co2}-{C2Co2}-{FeC2B7} molecule.

Synthesis and reactivity of [closo-1-CB9H9-1-N2]: functional group interconversion at the carbon vertex of the {closo-1-CB9} cluster.

The dinitrogen derivative [closo-1-CB(9)H(9)-1-N(2)] (1) was prepared from amine [closo-1-CB(9)H(9)-1-NH(3)] (2) and reacted with three types of nucleophiles: activated arenes (phenolate and aniline), divalent sulfur compounds (Me(2)S and Me(2)NCHS), and pyridine, giving products of substitution at C(cage). The reaction of 1 with pyridine gave all four isomers 11a-11d, indicating the Gomberg-Bachmann mechanism, which involves radical anion [closo-1-CB(9)H(9)](-*) (26). The radical and also closed-shell electrophilic aromatic substitution mechanisms were probed with the aid of DFT and MP2 computational methods and compared to those of phenylation of pyridine. Overall, experimental results supported by computational analysis suggest two mechanisms for the substitution of the N(2) group in 1: (i) thermal heterolytic cleavage of the C(cage)-N bond and the formation of electrophilic carbonium ylide [closo-1-CB(9)H(9)] (19) and (ii) electron-transfer-induced homolytic cleavage of the C(cage)-N bond and the formation of 26. Decomposition of 1 in MeCN is believed to proceed by the nonradical mechanism involving formation of the ylide 19 as the rate-determining step with experimental activation parameters DeltaH(double dagger) = 38.4 +/- 0.8 kcal mol(-1) and DeltaS(double dagger) = 44.5 +/- 2.5 cal mol(-1) K(-1). The electron-transfer-induced formation of 26 is consistent with the relatively high reduction potential of 1 (E(pc) = -0.54 V), which is more cathodic than that of PhN(2)(+) by 0.38 V. Transformations of the phenol 8a and the Me(2)NCHS adduct 10 were demonstrated by O-methylation of the former and hydrolysis of 10 followed by S-alkylative cyclization. Direct products and their derivatives were investigated by UV-vis spectroscopy and analyzed with the ZINDO computational method.

Formation of intramolecular rings in ferramonocarbollide complexes.

Addition of PPh 2Cl and Tl[PF 6] to CH 2Cl 2 solutions of [N(PPh 3) 2][6,6,6-(CO) 3- closo-6,1-FeCB 8H 9] ( 1) affords the isomeric B-substituted species [6,6,6-(CO) 3- n-(PHPh 2)- closo-6,1-FeCB 8H 8] [ n = 7 ( 2a) or 10 ( 2b)]. Deprotonation (NaH) of the phosphine ligand in 2a, with subsequent addition of [IrCl(CO)(PPh 3) 2] and Tl[PF 6], yields the neutral, zwitterionic complex [6,6,6-(CO) 3-4,7-mu-{Ir(H)(CO)(PPh 3) 2PPh 2}- closo-6,1-FeCB 8H 7] ( 3), which contains a B-P-Ir- B ring. Alternatively, deprotonation using NEt 3, followed by addition of HC[triple bond]CCH 2Br, affords [6,6,6-(CO) 3-7-(PPh 2CCMe)- closo-6,1-FeCB 8H 8] ( 4). Addition of [Co 2(CO) 8] to CH 2Cl 2 solutions of the latter gives [6,6,6-(CO) 3-7-(PPh 2-{(mu-eta (2):eta (2)-CCMe)Co 2(CO) 6})- closo-6,1-FeCB 8H 8] ( 5), which contains a {C 2Co 2} tetrahedron. In the absence of added substrates, deprotonation of the PHPh 2 group in compounds 2, followed by reaction of the resulting anions with CH 2Cl 2 solvent, affords [6,6,6-(CO) 3- n-(PPh 2CH 2Cl)- closo-6,1-FeCB 8H 8] [ n = 7 ( 6a) or 10 ( 6b)] plus [6,6-(CO) 2-6,7-mu-{PPh 2CH 2PPh 2}- closo-6,1-FeCB 8H 8] ( 7, formed from 2a), of which the latter species possesses an intramolecular B-P-C-P- Fe ring. Addition of Me 3NO to CH 2Cl 2 solutions of 2a causes loss of an Fe-bound CO ligand and formation of [6,6-(CO) 2-6,7-mu-{NMe 2CH 2PPh 2}- closo-6,1-FeCB 8H 8] ( 8), which incorporates a B-P-C-N- Fe ring. A similar reaction in the presence of ligands L yields [6,6-(CO) 2-6-L-7-(PPh 2CH 2Cl)- closo-6,1-FeCB 8H 8] [L = PEt 3 ( 9) or CNBu (t) ( 10)], in addition to 8.

Design, synthesis and biological evaluation of dihydronaphthalene and benzosuberene analogs of the combretastatins as inhibitors of tubulin polymerization in cancer chemotherapy.

A novel series of dihydronaphthalene and benzosuberene analogs bearing structural similarity to the combretastatins in terms of 1,2-diarylethene, trimethoxyphenyl, and biaryl functionality has been synthesized. The compounds have been evaluated in regard to their ability to inhibit tubulin assembly and for their cytotoxicity against selected human cancer cell lines. From this series of compounds, benzosuberene analogs 2 and 4 inhibited tubulin assembly at concentrations comparable to that of combretastatin A-4 (CA4) and combretastatin A-1 (CA1). Furthermore, analog 4 demonstrated remarkable cytotoxicity against the three human cancer cell lines evaluated (for example GI(50)=0.0000032 microM against DU-145 prostate carcinoma).

[1,3-Bis(diphenyl-phosphino)propane-κP,P']diiodido(perfluoro-propyl)rhodium(III) dichloro-methane solvate.

The structure of the title compound, [RhI(2)(C(3)F(7))(C(27)H(26)P(2))]·CH(2)Cl(2), at 110 (2) K is an unusual example of a structurally characterized square-based pyramidal alkyl complex of rhodium(III). The Rh-C bond is relatively short at 1.996 (6) Å. This short metal-carbon bond length is typical of perfluoro complexes of transition metals and illustrates the enhanced bond strength in these compounds.

Synthesis and reactivity of fluorinated ferracarborane anions.

The ferracarborane [N(PPh3)2][6,6,6,10,10,10-(CO)6-closo-6,10,1-Fe2CB7H8] reacts in CH2Cl2 with 3 molar equivalents of Ag[PF6] to yield the trifluoro-substituted species [N(PPh3)2][7,8,9-F3-6,6,6,10,10,10-(CO)6-closo-6,10,1-Fe2CB7H5]. Compound undergoes structural rearrangement in toluene at reflux temperatures, forming [N(PPh3)2][8,9,10-F3-6,6,6,7,7,7-(CO)6-closo-6,7,1-Fe2CB7H5]. Alternatively, reaction of either or with a 10-fold excess of Ag[PF6] in CH2Cl2 forms two species: namely, [N(PPh3)2][2,7,9,10-F4-6,6,6,8,8,8-(CO)6-closo-6,8,1-Fe2CB7H4], in which one further B-F substitution has occurred and the {Fe2CB7} cluster core has rearranged, plus a mono-iron co-product, [N(PPh3)2][3,8,9-F3-7,7,7-(CO)3-closo-7,1-FeCB7H5] that is formed by polyhedral contraction. Treatment of with [NO][BF4] in CH2Cl2 results in CO substitution at the 4-connected iron vertex [Fe10], producing the zwitterionic complex [7,8,9-F3-6,6,6,10,10-(CO)5-10-NO-closo-6,10,1-Fe2CB7H5]. Addition of Me3NO to a mixture of and PEt3 in CH2Cl2 also results in CO substitution, forming the isomeric species [N(PPh3)2][7,8,9-F3-6,6,m,10,10-(CO)5-n-PEt3-closo-6,10,1-Fe2CB7H5] [m=6, n=10; m=10, n=6] in a 5:1 ratio. Treatment of with [NO][BF4] and then CNBut in CH2Cl2 allows further, successive CO substitution at Fe10 to yield first a neutral, zwitterionic complex [7,8,9-F3-6,6,6,10-(CO)4-10-NO-10-PEt3-closo-6,10,1-Fe2CB7H5] and then [7,8,9-F3-6,6,6-(CO)3-10-CNBut-10-NO-10-PEt3-closo-6,10,1-Fe2CB7H5]. The molecular structures of compounds and have been established by X-ray diffraction.

Iridium-iron-monocarborane clusters from oxidative insertion reactions of [IrCl(CO)(PPh3)2] with ferracarborane anions.

The nine-vertex ferracarborane salt [N(PPh3)2][7,7,7-(CO)3-closo-7,1-FeCB7H8] (1) reacts with an excess of [IrCl(CO)(PPh3)2] in the presence of Tl[PF6] to form, successively, the bimetallic species [7,7,9,9,9-(CO)5-7-PPh3-closo-7,9,1-IrFeCB6H7] (3), in which one {BH}- vertex has formally been subrogated by an {Ir(CO)2(PPh3)} unit, and the trimetallic complex [6,7,9-{Ir(CO)(PPh3)2}-7,9-(mu-H)2-7,9,9-(CO)3-7-PPh3-closo-7,9,1-IrFeCB6H6] (5), which contains an {FeIr2} triangle. The {FeIrCB6} core in 5 resembles that in 3 with, in addition, the Fe...Ir connectivity being spanned by an {Ir(CO)(PPh3)2} fragment and the consequent Fe-Ir and Ir-Ir bonds bridged by hydrido ligands. In contrast to the above, treatment of the 10-vertex diferracarborane salt [N(PPh3)2][6,6,6,10,10,10-(CO)6-closo-6,10, 1-Fe2CB7H8] (2) with the same reagents yields two very different, trimetallic complexes, namely [8,10-{Ir(mu-PPh2)(Ph)(CO)(PPh3)}-8-(mu-H)-6,6,6,10,10-( CO)5-closo-6,10,1-Fe2CB7H7] (6) and [6,7,10-{Fe(CO)3}-6-(mu-H)-6,10,10,10-(CO)4-6-PPh3-closo-6,10,1-IrFeCB7H7] (7). In 6, an exo-polyhedral {IrPh(CO)(PPh3)} moiety is attached to a {closo-6,10,1-Fe2CB7} framework via a PPh2-bridged Fe-Ir bond and a B-HIr agostic-type linkage, the iridium center formally having inserted into one P-Ph bond of a PPh3 unit. Complex 7 contains an {IrFeCB7} cluster core, with an exo-polyhedral {Fe(CO)3} moiety bridging a {BIrFe} triangular face and with an additional Ir-H-Fe bridge. However, this metal atom arrangement reveals that iridium and iron moieties have exchanged exo- and endo-polyhedral sites with respect to the 10-vertex metallacarborane. X-ray diffraction studies upon 3, 5, 6, and 7 confirmed their novel structural features; some preliminary reactivity studies upon these compounds are also reported.

Polyhedral monocarbaborane chemistry. Some C-phenylated seven, eight, nine, ten, eleven and twelve-vertex species.

Some synthetic and structural systematics for monocarbaboranes, using the C-phenylated motif as the example, are investigated. The 10-vertex [6-Ph-nido-6-CB(9)H(11)](-) anion 1, from reaction of PhCHO with B(10)H(14) in KOH/H(2)O, is a useful entry synthon into C-phenyl monocarbaborane chemistry. Treatment of anion 1 with Na/thf yields the 10-vertex [1-Ph-closo-1-CB(9)H(9)](-) anion 2a, whereas treatment of anion 1 with iodine in alkaline solution yields the isomeric 10-vertex [2-Ph-closo-2-CB(9)H(9)](-) anion 2b, which isomerises quantitatively to 2a on heating under reflux in DME. Thermolysis of anion 1 yields the 9-vertex [4-Ph-closo-4-CB(8)H(8)](-) anion 5, whereas treatment of anion 1 with FeCl(3)/HCl gives neutral 9-vertex [4-Ph-arachno-4-CB(8)H(13)] 3. Compound 3 gives neutral 9-vertex [1-Ph-nido-1-CB(8)H(11)] 4 in refluxing toluene, and gives the 7-vertex [2-Ph-closo-2-CB(6)H(6)](-) anion 7 and the 8-vertex [1-Ph-closo-1-CB(7)H(7)](-) anion 6 in refluxing toluene with NEt(3). Reaction of 1 with [BH(3)(thf)] yields the 11-vertex [7-Ph-nido-7-CB(10)H(12)](-) anion 8 which can be converted to the 12-vertex [1-Ph-closo-1-CB(11)H(11)](-) anion 10 using [BH(3)(SMe(2))]; alternatively, anion 1 yields anion 10 directly on treatment with [BH(3)(NEt(3))]. Treatment of anion 8 with I(2)/KOH yields the 11-vertex [2-Ph-closo-2-CB(10)H(10)](-) anion 9. The structures of anions 1, 2a, 2b, 5, 6, 7, 8, 9 and 10 have been established by single-crystal X-ray diffraction analyses of their [NEt(4)](+) salts, and those of neutral 3 and 4 estimated by DFT calculations at the B3LYP/6-31G* level; similar calculations have also been applied to the new anionic closo species 2a, 2b, 5, 6, 7, 9 and 10. Crystals of the [NEt(4)](+) salt of the [2-Ph-closo-2-CB(6)H(6)](-) anion 7 required synchrotron X-radiation for sufficient diffraction intensity for molecular-structure elucidation. The syntheses are in principle generally applicable to give extensive derivative C-aryl and C-alkyl chemistries.

Carbonyl-metal fragment insertion into eight-vertex [closo-1-CB7H8]-. Facile synthesis of ten-vertex metalladicarbollide complexes [2,2,2-(CO)3-1-OH-closo-2,1,10-MC2B7H8]n-{M = Fe, Ru (n= 0), Mn, Re (n= 1)}.

Insertion of {M(CO)4} fragments (M = Fe, Ru, Mn, Re) into the eight-vertex monocarborane anion [closo-1-CB7H8]- affords ten-vertex metal-dicarbollide complexes.

Ten-vertex iron-monocarbollide complexes: synthesis and reactivity of the anion [4,9-{Fe(CO)4}-9,9,9-(CO)3-arachno-9,6-FeCB8H11]-.

The reagent [arachno-4-CB8H14] reacts with [Fe3(CO)12] in tetrahydrofuran (THF) at reflux temperatures, followed by addition of [N(PPh3)2]Cl, to afford [N(PPh3)2][4,9-{Fe(CO)4}-9,9,9-(CO)3-arachno-9,6-FeCB8H11] (3). In the anion of 3, one iron atom is part of the open CBBFeBB face of a 10-vertex {arachno-9,6-FeCB8} cage, to which the second iron atom is attached via an Fe-Fe bond and an additional exo-polyhedral Fe-B sigma bond. Upon heating 3 in refluxing toluene, the closed 10-vertex species [N(PPh3)2][2,2,2-(CO)3-closo-2,1-FeCB8H9] (4) is obtained, whereas the isomeric compound [N(PPh3)2][6,6,6-(CO)3-closo-6,1-FeCB8H9] (5) is isolated upon heating [closo-4-CB8H9]- and [Fe3(CO)12] in refluxing THF with subsequent addition of [N(PPh3)2]Cl. Protonation of 3 using CF3SO3H in CH2Cl2 gives the charge-compensated compound [4,9-{Fe(CO)4}-4-(mu-H)-9,9,9-(CO)3-arachno-9,6-FeCB8H11] (6), in which the B-Fe sigma bond of the precursor has been converted to a B-H right harpoon-up Fe linkage. In contrast, 3 with {M(PPh3)}+ gives the trimetallic species [1,3,4,9-{MFe(CO)4(PPh3)}-1,3-(mu-H)2-9,9,9-(CO)3-arachno-9,6-FeCB8H9] (M = Cu (7), Ag 8) in which the three metal centers form a V-shaped M-Fe-Fe unit. Compound 6 reacts with PEt3 in the presence of Me(3)NO to yield [4,9-(PEt3)2-9,9-(CO)2-nido-9,6-FeCB8H10] (9). In the latter, the formerly exo-polyhedral {Fe(CO)4} fragment has been replaced by a PEt3 ligand, with a second PEt3 substituting one CO group at the remaining cluster iron vertex. The novel structural features of compounds 3-9 have been confirmed by single-crystal X-ray diffraction studies.

A practical synthesis of isomerically pure 1,10-difunctionalized derivatives of the [closo-1-CB9H10] anion.

The isomer-free [closo-1-CB9H(8)-1-COOH-10-I]- anion was prepared in four steps and 10% overall yield from B10H14. The key step is the skeletal isomerization of the [closo-2-CB9H8-2-COOH-7-I]- anion to a mixture of the 10- and 6-iodo derivatives of [closo-1-CB9H(9)-1-COOH]- formed in up to a 3:1 ratio. The carboxylic acid 4 was converted to the amine [closo-1-CB9H(8)-1-NH(2)-10-I]- using the Curtius reaction. The relative thermodynamic stability of each product was calculated at the DFT and MP2 levels of theory. The regioselectivity of electrophilic substitution in [closo-CB9H10]- derivatives was briefly investigated using the NBO population analysis of the MP2 wave function.

Synthesis of nickel-monocarbollide complexes by oxidative insertion.

Treatment of the 11-vertex carborane anion [closo-2-CB(10)H(11)](-) with Ni(0) reagents in tetrahydrofuran (THF) affords-via oxidative insertion reactions-12-vertex Ni(II) complexes, isolated as the salts [N(PPh(3))(2)][2,2-L(2)-closo-2,1-NiCB(10)H(11)] (L = CO (1a), CNBu(t) (1b), and CNXyl (1c; Xyl = C(6)H(3)Me(2)-2,6); L(2) = cod (1d; cod = 1,2:5,6-eta-cyclo-octa-1,5-diene)). One CO ligand in 1a is readily replaced by donors L' in the presence of Me(3)NO to give the species [N(PPh(3))(2)][2-CO-2-L'-closo-2,1-NiCB(10)H(11)] (L' = PEt(3) (1e), PPh(3) (1f), CNBu(t) (1g), and CNXyl (1h)). The anionic complexes themselves readily react with hydride abstracting reagents in the presence of donor ligands to yield zwitterionic complexes in which boron vertexes bear substituents that are bound through C, N, or O atoms. Thus, for example, 1c with H(+) and CNXyl gives [2,2,7-(CNXyl)(3)-closo-2,1-NiCB(10)H(10)] (2b), while 1f with Me(+) in the presence of OEt(2) affords [2-CO-2,11-{mu-PPh(2)(C(6)H(4)-o)}-7-OEt(2)-closo-2,1-NiCB(10)H(9)] (4), in which an additional cycloboronation of one phosphine phenyl ring has occurred. In contrast, 1f with Me(+) in the presence of NCMe gives a mixture of the isomers [2-CO-2-PPh(3)-7-{(X)-N(Me)=C(H)Me}-closo-2,1-NiCB(10)H(10)] (X identical with E (5c) and Z (5d)). X-ray diffraction analyses of compounds 1a, 2b, 4, and 5c confirmed their important structural features.

Preparation of 1-p-halophenyl and 1-p-biphenylyl substituted monocarbadodecaborate anions [closo-1-Ar-CB11H11]- by insertion of arylhalocarbenes into [nido-B11H14]-.

In the presence of a strong base, benzal chloride (C(6)H(5)CHCl(2)) and its p-substituted derivatives react with [nido-B(11)H(14)](-) to yield [closo-1-p-X-C(6)H(4)-CB(11)H(11)](-) (X = H, F, Cl, Br, I, Ph), presumably by insertion of an arylhalocarbene and oxidation. On a 1-g scale, the yields are 30-40%, except in the case of p-iodobenzal chloride, which yields only 12% of the insertion product.

Monocarbaborane anion chemistry. [COOH], [CH2OH] and [CHO] units as functional groups on ten-vertex monocarbaborane anionic compounds.

B(10)H(14) reacts with para-C(6)H(4)(CHO)(COOH) in aqueous KOH solution to give the [nido-6-CB(9)H(11)-6-(C(6)H(4)-para-COOH)](-) anion 1, which undergoes cage closure with iodine in alkaline solution to give the [closo-2-CB(9)H(9)-2-(C(6)H(4)-para-COOH)](-) anion 2. Upon heating, anion 2 rearranges to form the [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-COOH)](-) anion 3. Similarly, B(10)H(14) with glyoxylic acid OHCCOOH in aqueous KOH gives the [arachno-6-CB(9)H(13)-6-(COOH)](-) anion 4, which undergoes cage closure with iodine in alkaline solution to give the [closo-2-CB(9)H(9)-2-(COOH)](-) anion 5. Upon heating, anion 5 rearranges to give the [closo-1-CB(9)H(9)-1-(COOH)](-) anion 6. Reduction of the [COOH] anions 3 and 6 with diisobutylaluminium hydride gives the [CH(2)OH] hydroxy anions [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CH(2)OH)](-) and [closo-1-CB(9)H(9)-1-(CH(2)OH)](-) 8 respectively. The [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CH(2)OH)](-) anion 7 can also be made via isomerisation of the [closo-2-CB(9)H(9)-2-(C(6)H(4)-para-CH(2)OH)](-) anion 9, in turn obtained from the [nido-6-CB(9)H(11)-6-(C(6)H(4)-para-CH(2)OH)](-) anion 10, which is obtained from the reaction of B(10)H(14) with terephthaldicarboxaldehyde, C(6)H(4)-para-(CHO)(2), in aqueous KOH solution. Oxidation of the hydroxy anions 7 and 8 with pyridinium dichromate gives the aldehydic [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CHO)](-) anion 11 and the aldehydic [closo-1-CB(9)H(9)-1-(CHO)](-) anion 12 respectively, characterised as their 2,4-dinitrophenylhydrazone derivatives, the [closo-1-CB(9)H(9)-1-C(6)H(4)-para-CH=N-NHC(6)H(3)(NO(2))(2)](-) anion 13 and the [closo-1-CB(9)H(9)-1-CH=N-NHC(6)H(3)(NO(2))(2)](-) anion respectively.

Macropolyhedral boron-containing cluster chemistry. Cluster assembly about a molybdenum centre. Formation of the 19-vertex [(CO)2MoB16H15C2Ph2]- anion.

Fusion of nine-vertex [1-Ph-nido-1-CB8H11] with [Mo(CH3CN)3(CO)3] in the presence of tetramethylnaphthalenediamine gives the nineteen-vertex macropolyhedral metallaborane anion [(CO)2MoB16H15C2Ph2]- with a molybdenum(VI) twelve-atom coordination sphere.

Group 1 coordination chains and hexagonal networks of host cyclotriveratrylene with halogenated monocarbaborane anions.

Halogenated carbaborane ions [CB(11)H(6)X(6)](-) in which X=Cl or Br have been combined with the host molecule cyclotriveratrylene (CTV) and Group 1 metal cations to give crystalline materials. The complexes [Na(ctv)(H(2)O)(CB(11)H(6)X(6))](CF(3)CH(2)OH) feature chiral Na-CTV coordination chains with complexation of the [CB(11)H(6)X(6)](-) ion by the Na(+) ion, together with the CTV molecular cavity. The coordination chains are hydrogen bonded together to give a puckered two-dimensional hexagonal grid structure. [K(ctv)(CB(11)H(6)Cl(6))(CF(3)CH(2)OH)(0.5)] is essentially isostructural. Complexes [Rb(ctv)(CB(11)H(6)Br(6))(H(2)O)] and [Cs(ctv)(CB(11)H(6)X(6))(CH(3)CN)] are coordination polymers with related distorted hexagonal grid structures. Use of N,N'-dimethylformamide (DMF) as a solvent results in an entirely different type of assembly, with [Na(2)(dmf)(4)(H(2)O)(2)(ctv)][(dmf)(0.5)(ctv)][CB(11)H(6)Br(6)](2) showing unusual [Na-mu-(dmf)-Na] bridges, and once again forming a distorted hexagonal coordination polymer.

Monocarbaborane anion chemistry. An interesting encapsulation of the Pd2I2(P(C6H(4)-4-Me)3)4]2+ cation by a pair of [PhCB9H4I(C6H4Me)4]- anions.

Reaction of the [1-Ph-closo-1-CB9H(4)-6,7,8,9,10-I5]- anion with 4-MeC6H4MgBr in the presence of [PdCl2(PPh3)2] gives the [Pd2I2(P(C6H(4)-4-Me)3)4]2+ salt of the [1-Ph-closo-1-CB9H(4)-10-I-6,7,8,9-(C6H(4)-4-Me)4]- anion, which exhibits an unusual neutral supramolecular assembly in the solid state, in which the dipalladium dication is encapsulated by two four-armed 'tetrapus' anionic units; the anion also has potentialities for four-fold dendrimer construction.