From nano-balls to nano-bowls.

Pentaphosphaferrocene [Cp*Fe(η5-P5)] in combination with Cu(i) halides is capable of a template-directed synthesis of fullerene-like spheres. Herein, we present the use of a triple decker complex as template that leads to the formation of unprecedented 'nano-bowls'. These spherical domes resemble the truncated fullerenes I h-C80 and represent a novel spherical arrangement in the chemistry of spherical molecules.

Anionic Hosts for the Incorporation of Cationic Guests.

Pentaphosphaferrocene [Cp*Fe(η5 -P5 )] (1 a) represents an excellent building block for the template-directed synthesis of spherical supramolecules. Here, the self-assembly of 1 a with CuI and CuII halides in the presence of the template complexes [FeCp2 ][PF6 ], [CoCp2 ][PF6 ] and [CoCp2 ] is reported, testifying to the redox behavior of the formed supramolecules. The oxidation or reduction capacity of these reactive complexes does not inhibit their template impact and, for the first time, the cationic metallocene [CoCp2 ]+ is enclosed in unprecedented anionic organometallic hosts. Furthermore, the large variety of structural motifs, as icosahedral, trigonal antiprismatic, cuboidal and tetragonal antiprismatic arrangements of 1 a units are realized in the supramolecules [FeCp2 ]@[{1 a}12 (CuBr)17.3 ] (3), [CoCp2 ]+3 {[CoCp2 ]+ @[{1 a}8 Cu24.25 Br28.25 (CH3 CN)6 ]4- } (4), {[Cp2 Co]+ @[{1 a}8 (CuI)28 (CH3 CN)9.8 ]}{[Cp2 Co]+ @[{1 a)}8 Cu24.4 I26.4 (CH3 CN)8 ]2- } (5), and [{1 a}3 {(1 a)2 NH}3 Cu16 I10 (CH3 CN)7 ] (6), respectively.

An Icosidodecahedral Supramolecule Based on Pentaphosphaferrocene: From a Disordered Average Structure to Individual Isomers.

Pentaphosphaferrocenes [CpR Fe(η5 -P5 )] (1) and CuI halides are excellent building blocks for the formation of discrete supramolecules. Herein, we demonstrate the potential of Cu(CF3 SO3 ) for the construction of the novel 2D polymer [{Cp*Fe(µ4 ,η5:1:1:1 -P5 )}{Cu(CF3 SO3 )}]n (2) and the unprecedented nanosphere (CH2 Cl2 )1.4 @[{CpBn Fe(η5 -P5 )}12 {Cu(CF3 SO3 )}19.6 ] (3). The supramolecule 3 has a unique scaffold beyond the fullerene topology, with 20 copper atoms statistically distributed over the 30 vertices of an icosidodecahedron. Combinatorics was used to interpret the average disordered structure of the supramolecules. In this case, only two pairs of enantiomers with D5 and D2 symmetry are possible for bidentate bridging coordination of the triflate ligands. DFT calculations showed that differences in the energies of the isomers are negligible. The benzyl ligands enhance the solubility of 3, enabling NMR-spectroscopic and mass-spectrometric investigations.

cyclo-P4 Building Blocks: Achieving Non-Classical Fullerene Topology and Beyond.

The cyclo-P4 complexes [CpR Ta(CO)2 (η4 -P4 )] (CpR : Cp''=1,3-C5 H3 tBu2 , Cp'''=1,2,4-C5 H2 tBu3 ) turned out to be predestined for the formation of hollow spherical supramolecules with non-classical fullerene-like topology. The resulting assemblies constructed with CuX (X=Cl, Br) showed a highly symmetric 32-vertex core of solely four- and six-membered rings. In some supramolecules, the inner cavity was occupied by an additional CuX unit. On the other hand, using CuI, two different supramolecules with either peanut- or pear-like shapes and outer diameters in the range of 2-2.5 nm were isolated. Furthermore, the spherical supramolecules containing Cp''' ligands at tantalum are soluble in CH2 Cl2 . NMR spectroscopic investigations in solution revealed the formation of isomeric supramolecules owing to the steric hindrance caused by the third tBu group on the Cp''' ligand. In addition, a 2D coordination polymer was obtained and structurally characterized.

The First Coordination Polymers Based on 1,3-Diphosphaferrocenes and 1,1',2,3',4-Pentaphosphaferrocenes.

Phosphaferrocenes in combination with coinage metal salts proved to be excellent building blocks in supramolecular chemistry for the buildup of oligomeric and polymeric assemblies. The synthesis of a series of novel phosphaferrocenes containing the 1,3-P2C3iPr3 and/or the 1,2,4-P3C2iPr2 ligand is described herein. The self-assembly processes of the 1,3-diphospha-, 1,2,4-triphospha-, and 1,1',2,3',4-pentaphosphaferrocenes with CuI halides led to the formation of 1D or 2D polymers. With [Cp*Fe(η5-P2C3iPr3)] (Cp* = η5-C5Me5), infinite chains are formed, whereas with [(η5-P3C2iPr2)Fe(η5-P2C3iPr3)] 1D ladderlike structures are obtained. These are the first polymers containing such a di- and pentaphosphaferrocene, respectively. On the other hand, the use of [Cp*Fe(η5-P3C2iPr2)] leads to the construction of 2D networks with intact sandwich complexes, which is uncommon for this class of complexes.

Progress in Polyarsolyl Chemistry.

The synthesis of heteroatom analogues of the cyclopentadienyl anion Cp- is a fascinating and challenging field of research. The replacement of methine moieties by phosphorus is well investigated for the synthesis of mono-, tri- and pentaphospholyl ligands. On the other hand, arsenic derivatives are rare and 1,2,4-triarsolyl and tetraarsolyl salts are unknown. Herein, we report on the synthesis of Cs[E3 C2 (trip)2 ] (1 a: E=P; 1 b: E=As; trip=2,4,6-triisopropylphenyl) and Cs[E4 C(trip)] (2 a: E=P; 2 b: E=As). Compound 1 b represents the first 1,2,4-triarsolyl and 2 b the first tetraarsolyl anion. All salts are obtained in one-pot syntheses using E(SiMe3 )3 , 2,4,6-triisopropylbenzoyl chloride and CsF. The products 1 a⋅2 C4 H8 O2 , 2 a⋅Et2 O and 2 b⋅3 C4 H8 O2 were characterized by X-ray structural analysis, which revealed planar heterocycles. Nucleus-independent chemical shifts (NICS) confirmed the aromaticity of these anions. Notably, compound 2 a⋅Et2 O is only the second tetraphospholyl ligand which is structurally characterized.

A cyclo-P6 Ligand Complex for the Formation of Planar 2D Layers.

The all-phosphorus analogue of benzene, stabilized as middle deck in triple-decker complexes, is a promising building block for the formation of graphene-like sheet structures. The reaction of [(CpMo)2 (µ,η(6) :η(6)-P6)] (1) with CuX (X=Br, I) leads to self-assembly into unprecedented 2D networks of [{(CpMo)2P6}(CuBr)4 ]n (2) and [{(CpMo)2 P6}(CuI)2]n (3). X-ray structural analyses show a unique deformation of the previously planar cyclo-P6 ligand. This includes bending of one P atom in an envelope conformation as well as a bisallylic distortion. Despite this, 2 and 3 form planar layers. Both polymers were furthermore analyzed by (31)P{(1)H} magic angle spinning (MAS) NMR spectroscopy, revealing signals corresponding to six non-equivalent phosphorus sites. A peak assignment is achieved by 2D correlation spectra as well as by DFT chemical shift computations.

Giant Rugby Ball [{Cp(Bn)Fe(η(5)-P5)}24Cu96Br96] Derived from Pentaphosphaferrocene and CuBr2.

The self-assembly of [Cp(Bn)Fe(η(5)-P5)] (Cp(Bn) = η(5)-C5(CH2Ph)5) with CuBr2 leads to the formation of an unprecedented rugby ball-shaped supramolecule consisting of 24 units of the pentaphosphaferrocene and an extended CuBr framework, which does not follow the fullerene topology. The resulting scaffold of 312 noncarbon atoms reveals three different coordination modes of the cyclo-P5 ligand including a novel π-coordination. The outer dimensions of 3.7 × 4.6 nm of the sphere approach the range of the size of proteins. With a value of 32.1 nm(3), it is 62 times larger in volume than a C60 molecule. Surprisingly, this giant rugby ball is also slightly soluble in CH2Cl2.

1,2,4-Triphospholyl anions - versatile building blocks for the formation of 1D, 2D and 3D assemblies.

The potential of K[P3C2R2] (R = (t)Bu, Mes) as building blocks in metallo-supramolecular chemistry was investigated and self-assembly processes with Cu(i) halides resulted in the formation of a large variety of unprecedented one-, two- and even three-dimensional aggregates. The 3D networks showed an interesting topological similarity to allotropes of carbon: diamond and the theoretically proposed polybenzene. Furthermore, the negative charge of the phospholyl ligand favoured the generation of cationic CuaXb (a > b, X = Cl, Br, I) assemblies, a challenging area within the well-studied coordination chemistry of CuX units. In addition, the 1D strands were also characterized in solution, revealing the presence of oligomeric units.

Unexpected fragmentations of triphosphaferrocene - formation of supramolecular assemblies containing the (1,2,4-P3C2Mes2)(-) ligand.

While reacting the sterically demanding triphosphaferrocene [Cp*Fe(η(5)-P3C2Mes2)] () with Cu(i) halides, the sandwich complex undergoes an unprecedented fragmentation into decamethylferrocene, FeX2 (X = Cl, Br, I) and [P3C2Mes2](-) units. Subsequently, these phospholyl ligands act as versatile, negatively charged building blocks for the formation of supramolecular aggregates representing the monomeric, dimeric and polymeric (1D and 2D) coordination compounds [(P3C2Mes2)2{Cu7(CH3CN)7(µ4-X)(µ3-X)2(µ-X)}{Cu2(µ2-X)2X}{Cu(CH3CN)(µ2-X)}]2·6CH3CN (·6CH3CN: X = Cl, ·6CH3CN: X = Br), [(P3C2Mes2)2{Cu(CH3CN)}6(µ-Br)2(µ3-Br)2{Cu(CH3CN)2Br}2]·CH3CN (·CH3CN), [(P3C2Mes2)4{Cu5(CH3CN)5(µ2-Br)}{Cu(CH3CN)2CuBr2}2{Cu(CH3CN)2}]n(+)[CuBr2]n(-)·2CH3CN (·2CH3CN), [(P3C2Mes2){Cu(CH3CN)(µ-I)}4{Cu(CH3CN)3}]·0.5C7H8·2.5CH3CN (·0.5C7H8·2.5CH3CN), [(P3C2Mes2)Cu7(CH3CN)4(µ4-I)2(µ3-I)2(µ-I)2]x·2C7H8 (·2C7H8), [(P3C2Mes2){Cu(CH3CN)3}2{Cu(µ-I)}6]·0.5CH2Cl2·3CH3CN (·0.5CH2Cl2·3CH3CN) and [Cp*Fe(CH3CN)3]n(+)[(P3C2Mes2)2{Cu(CH3CN)2}{Cu(µ-I)}6]n(-)·0.6CH2Cl2 (·0.6CH2Cl2) with rather non-typical structural motifs within the large varieties of copper halide chemistry. Besides the X-ray structural analyses the obtained assemblies were also characterized in solution in which they undergo fragmentation and re-aggregation processes.

Tunable porosities and shapes of fullerene-like spheres.

The formation of reversible switchable nanostructures monitored by solution and solid-state methods is still a challenge in supramolecular chemistry. By a comprehensive solid state and solution study we demonstrate the potential of the fivefold symmetrical building block of pentaphosphaferrocene in combination with Cu(I) halides to switch between spheres of different porosity and shape. With increasing amount of CuX, the structures of the formed supramolecules change from incomplete to complete spherically shaped fullerene-like assemblies possessing an Ih -C80 topology at one side and to a tetrahedral-structured aggregate at the other. In the solid state, the formed nano-sized aggregates reach an outer diameter of 3.14 and 3.56 nm, respectively. This feature is used to reversibly encapsulate and release guest molecules in solution.

A nano-sized supramolecule beyond the fullerene topology.

The reaction of [Cp(Bn) Fe(η(5) -P5 )] (1) (Cp(Bn) =η(5) -C5 (CH2 Ph)5 ) with CuI selectively yields a novel spherical supramolecule (CH2 Cl2 )3.4 @[(Cp(Bn) FeP5 )12 {CuI}54 (MeCN)1.46 ] (2) showing a linkage of the scaffold atoms which is beyond the Fullerene topology. Its extended CuI framework reveals an outer diameter of 3.7 nm-a size that has not been reached before using five-fold symmetric building blocks. Furthermore, 2 shows a remarkable solubility in CH2 Cl2 , and NMR spectroscopy reveals that the scaffold of the supramolecule remains intact in solution. In addition, a novel 2D polymer [{Cp(Bn) Fe(η(5) -P5 )}2 {Cu6 (µ-I)2 (µ3 -I)4 }]n (3) with an uncommon structural motif was isolated. Its formation can be avoided by using a large excess of CuI in the reaction with 1.

Discrete and extended supersandwich structures based on weak interactions between phosphorus and mercury.

Supersized mercury: Adducts with polymeric (left) or discrete supersandwich structures (right) form from mixtures of the trinuclear mercury complex [(o-C(6)F(4)Hg)(3)] (A) with the triple-decker complex [(CpMo)(2)(µ-η(6):η(6)-P(6))] (B) in the solid state. This arrangement arises from P···Hg interactions between opposing atoms of the P(6) units and the Hg(3) units (see picture; P-purple, Hg-orange, F-green, Mo-red, C-gray).

Size-determining dependencies in supramolecular organometallic host-guest chemistry.

Treatment of the pentaphosphaferrocene [Cp*Fe(η(5)-P(5))] with Cu(I) halides in the presence of different templates leads to novel fullerene-like spherical molecules that serve as hosts for the templates. If ferrocene is used as the template the 80-vertex ball [Cp(2)Fe]@[{Cp*Fe(η(5)-P(5))}(12){CuCl}(20)] (4), with an overall icosahedral C(80) topological symmetry, is obtained. This result shows the ability of ferrocene to compete successfully with the internal template of the reaction system [Cp*Fe(η(5)-P(5))], although the 90-vertex ball [{Cp*Fe(η(5):η(1):η(1):η(1):η(1):η(1)-P(5))}(12)(CuCl)(10)(Cu(2)Cl(3))(5){Cu(CH(3)CN)(2)}(5)] (2 a) containing pentaphosphaferrocene as a guest is also formed as a byproduct. With use of the triple-decker sandwich complex [(CpCr)(2)(µ,η(5)-As(5))] as a template the reaction between [Cp*Fe(η(5)-P(5))] and CuBr leads to the 90-vertex ball [(CpCr)(2)(µ,η(5)-As(5))]@[{Cp*Fe(η(5)-P(5))}(12){CuBr}(10){Cu(2)Br(3)}(5){Cu(CH(3) CN)(2)}(5)] (6), in which the complete molecule acts as a template. However, if the corresponding reaction is instead carried out with CuCl, cleavage of the triple-decker complex is found and the 80-vertex ball [CpCr(η(5)-As(5))]@[{Cp*Fe(η(5)-P(5))}(12){CuCl}(20)] (5) is obtained. This accommodates as its guest [CpCr(η(5)-As(5))], which has only 16 valence electrons in a triplet ground state and is not known as a free molecule. The triple-decker sandwich complex [(CpCr)(2)(µ,η(5)-As(5))] requires 53.1 kcal mol(-1) to undergo cleavage (as calculated by DFT methods) and therefore this reaction is clearly endothermic. All new products have been characterized by single-crystal X-ray crystallography. A favoured orientation of the guest molecules inside the host cages has been identified, which shows π⋅⋅⋅π stacking of the five-membered rings (Cp and cyclo-As(5)) of the guests and the cyclo-P(5) rings of the nanoballs of the hosts.