Toroidal Main Group Macrocycles: New Opportunities for Cation and Anion Coordination

Abstract

Inorganic macrocycles, possessing molecular frameworks composed entirely of elements other than carbon, are rare. Even rarer are species analogous to classical organic macrocycles (like crown ethers) that possess the potential ability to coordinate metal ions within their cavities. Recent studies reveal an emerging structural class of valence‐isoelectronic main‐group ligands of general formula [{E(µ‐E′R)}2Y]nx−, which possess fascinating coordination characteristics. Such species can coordinate metal ions within their cavities (using the donor centres Y and E′), their peripheral donor centres (E′) (in an exo fashion) and are also capable of coordinating anions (where Y = N−H). This short review highlights the recent synthetic and structural studies of these unusual ligand systems and pinpoints potential future areas of development. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Syntheses, Structure, and Reactivity of Amino(azido)stibanes

“…with respect to Me 3 Si-OTf elimination even at ambient temperatures and form in situ the highly reactive iminostibane Mes*N=SbX, which rapidly decomposes. Diazide Mes*N(SiMe 3 )Sb(N 3 ) 2 slowly decomposes when a Lewis acid such as B(C 6 F 5 ) 3 is present, thus leading to the formation of a salt that bears a heterocyclic Sb-N dication and an [N 3 -B(C 6 F 5 ) 3 ]…”

“…These ring systems are good starting materials for polycyclic inorganic and organometallic compounds. [1][2][3] The cyclo-distiba(III)-diazane [Cl-Sb(μ-NtBu)] 2 was first generated by the treatment of SbCl 3 with LiN(SiMe 3 )(tBu). [4] Stahl introduced a simple one-pot synthesis of [Cl-Sb(μ-NtBu)] 2 by using SbCl 3 and tBuNH 2 .…”

“…[1][2][3] The cyclo-distiba(III)-diazane [Cl-Sb(μ-NtBu)] 2 was first generated by the treatment of SbCl 3 with LiN(SiMe 3 )(tBu). [4] Stahl introduced a simple one-pot synthesis of [Cl-Sb(μ-NtBu)] 2 by using SbCl 3 and tBuNH 2 . The structure was determined by Chivers et al [5,6] Recently, a series of four-membered rings of the type [XSb(μ-NR)] 2 , which contain alternating antimony(III) and nitrogen centers, were synthesized and fully characterized (X = halogen, R = supermesityl = 2,4,6-tri-tert-butylphenyl = Mes*), and represent rare examples of cyclo-distibadiazanes.…”

The Selenium‐Based Hexameric Macrocycle [(Se)P(μ‐NtBu)2P(μ‐Se)]6

“…[1,2] The tetrameric, nitrogen-bridged macrocycle [{P(m-NtBu)} 2 (m-NH)] 4 (Scheme 1 a) is obtained by the condensation of the dimers [ClP(m-NtBu)] 2 and [(NH 2 )P-(m-NtBu)] 2 in the presence of Et 3 N.[3] However, the pentameric homologue is produced exclusively if this reaction is undertaken in the presence of I À ions, resulting in the hostguest complex [{P(m-NtBu)} 2 (m-NH)] 5 I À (Scheme 1 b).[4] The toroidal structures of the tetramer and pentamer and the presence of endo NÀH functionalities combine the appearance and host-guest characteristics of organic macrocycles such as calixarenes and porphyrins.Less progress has been made in attempts to extend this class of new ligands to macrocycles containing other bridging elements, owing largely to the inability to generalize the synthetic methods used for N-bridged species. Indeed, the only representative of this type reported to date is the oxygenbridged dimer [{P(m-N(2-py)} 2 (m-O)] 2 (2-py = 2-pyridyl), obtained by hydrolysis of [ClP{m-N(2-py)}] 2 in the presence of CuCl and pyridine.…”

Ein Dichlorcyclodibismadiazan

“…[8][9][10] Die einfachsten Cyclodipnikta(III)-diazane sind die Dichlorderivate [ClE(m-NR)] 2 (A, Schema 1), die nur für E = P, As und Sb bekannt sind, während die Bis(organoamino)derivate B und Bis(dimethylamino)derivate C für die ganze Reihe E = P-Bi beobachtet wurden. [1] Der langsame Fortschritt besonders in der Chemie des Bi 2 N 2 -Ringsystems im Vergleich zur Vielfalt in der Chemie der analogen P 2 N 2 -Ringe kann der Schwäche der Bi-N-Bindung zugeschrieben werden.…”