Size‐Determining Dependencies in Supramolecular Organometallic Host–Guest Chemistry

Abstract

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.

Anionic Hosts for the Incorporation of Cationic Guests

“…Considering that ferrocene is known as an appropriate guest molecule for fullerene‐like hosts,4a,4d the ferrocenium cation [FeCp 2 ] + is the natural choice. When a solution of 1 a in CH 2 Cl 2 is layered with a solution of [FeCp 2 ][PF 6 ] and CuBr in acetonitrile, the formation of brown plates of the 2D polymer [( 1 a )CuBr] n 13a ( 2 a ) and big dark blocks of [FeCp 2 ]@[{Cp*Fe(η 5 ‐P 5 )} 12 (CuBr) 17.3 ] ( 3 ) at the phase boundary is observed already after one day.…”

“…Furthermore, the known Cl‐derivative of this sphere is capable of the trapping of several templates such as o ‐carborane,4g [CpCr(η 5 ‐As 5 )]4d and [FeCp 2 ],4d although crystallizing in the cubic crystal system. Also in 3 , one molecule of the sandwich complex is enclosed within the cavity of the host.…”

“…Comparing the template properties, we not only succeeded in incorporating stable molecules as for instance ferrocene,4d o ‐carborane4g (Figure 1 a) and C 60 ,4h but were also able to stabilize otherwise very reactive and labile species such as white phosphorus and yellow arsenic by enclosure in a supramolecular host (Figure 1 c) 4c. So far, all incorporated guests are neutral compounds, which fit in the neutral host environment.…”

Cyclo‐P4‐Bausteine – Verwirklichung nichtklassischer Fulleren‐Analogie und weiterer Topologien

“…Diese beispiellosen Kohlenstoff-freien Analoga mit I h -C 80 -(Abbildung 1) und I-C 140 -Gerüsten repräsen-tieren weniger stabile Fulleren-artige Verwandte. [2] Voreiniger Zeit haben wir untersucht, ob nichtklassische Fullerene mit variablen Ringgrçßen [3] auch über einen metallosupramolekularen Zugang erhältlich sind. Der cyclo-P 4 -Komplex [Cp''Ta(CO) 2 (h 4 -P 4 )] [4] (1a;C p '' = 1,3-C 5 H 3 tBu 2 ) scheint prädestiniert zu sein fürd ie Bildung von Bällen mit einem viergliedrigen Ringmotiv.E rste Untersuchungen der Reaktivitätv on 1a mit CuCl zeigten die Bildung des sphäri-schen Supramoleküls [{Cp''Ta(CO) 2 (h 4 -P 4 )} 6 {CuCl} 8 ]( 2a), das ausschließlich vier-u nd sechsgliedrige Ringe enthält.…”

“…[6] Dieses einzelne Ergebnis führte zu der Frage,o bd as Konzept der strukturellen Anordnung von vier-u nd sechsgliedrigen Ringen in Supramolekülen auch auf sphärische Strukturmotive ausgedehnt werden kann, so wie es fürd en fünfgliedrigen Ring des Pentaphosphaferrocens mçglich war. [2,7] Auch sind weitere Informationen über den Bil- (2) ). Der innere Hohlraum von 2b hat einen Durchmesser [8] von 0.6 nm und eine kuboide Form;die Cu-Atomen besetzen die Ecken, und die P 4 -Ringe bilden die Flächen.…”