Formation and selection of the macrocycle [{(^tBuN)P(μ-N^tBu)}₂(μ-Se)₂{P(μ-N^tBu)}₂]₃

Abstract

Main group inorganic macrocycles, based on p-block element backbones other than carbon, are a challenging synthetic target that has been largely overlooked. In this study, we show that a simple strategy based on the combination of electrophilic and nucleophilic phosphazane building blocks can be extended to readily accessible [E(tBuN)P(μ-NtBu)]22- nucleophilic components, as exemplified by the Se-bridge PIII/PV phosphazane macrocycle [{(tBuN[double bond, length as m-dash])PV(μ-NtBu)}2(μ-Se)2{PIII(μ-NtBu)}2]3.

Guest Binding via N−H⋅⋅⋅π Bonding and Kinetic Entrapment by an Inorganic Macrocycle

“…[20][21][22][23][24][25][26][27][28][29] Of particular interest is the pentameric host macrocycle 1 (Figure 1), toroidal shape,l arge void volume, endo-cyclic N-H functionalities,a nd exo-cyclic t Bu groups of which make it ahighly unusual, sterically hindered H-bonding host. [20][21][22][23][24][25][26][27][28][29] Of particular interest is the pentameric host macrocycle 1 (Figure 1), toroidal shape,l arge void volume, endo-cyclic N-H functionalities,a nd exo-cyclic t Bu groups of which make it ahighly unusual, sterically hindered H-bonding host.…”

“…[17][18][19] Key advantages of inorganic anion receptors over organic counterparts are their inherently more polar nature and the ease by which their proton acidities can be modulated.Thehigh bond energy of PÀNs ingle bonds and their low polarity underpin the stability of adiverse range of previously reported phosphazane compounds,and provide agood foundation for the development of anew range of robust inorganic macrocycles. [20][21][22][23][24][25][26][27][28][29] Of particular interest is the pentameric host macrocycle 1 (Figure 1), toroidal shape,l arge void volume, endo-cyclic N-H functionalities,a nd exo-cyclic t Bu groups of which make it ahighly unusual, sterically hindered H-bonding host. Thehost properties of 1 should differ significantly from organic counterparts,e specially given the greater polarity of these P À N-bonded frameworks.Herein, we show that the highly polar nature of the binding site and the sterically congested periphery of 1 leads to unique types of host-guest binding involving NÀH···p-CX (X = CH, N, P) hydrogen bonding to organic and inorganic guests.W ea lso show that oxidation of the phosphorus periphery of 1 can be used to kinetically entrap anions within the macrocycle.T his produces chemically irreversible binding of Cl À and I À anions using acombination of hydrogen bonding and steric encasement, which results in better effective binding of these halides than in any organic or metal-organic architecture.Direct access to 1,w hich was previously prepared by ac omplicated two-step procedure involving the use of gaseous NH 3 ,i sp rovided here by an ew method wherein the cyclodiphosphazane [ClP(m-N t Bu)] 2 (A)iscombined with LiNH 2 in the presence of excess anhydrous LiI, followed by removal of the encapsulated iodide anion (Figure 2a and Section S2 in the Supporting Information).…”

“…Thehigh bond energy of PÀNs ingle bonds and their low polarity underpin the stability of adiverse range of previously reported phosphazane compounds,and provide agood foundation for the development of anew range of robust inorganic macrocycles. [20][21][22][23][24][25][26][27][28][29] Of particular interest is the pentameric host macrocycle 1 (Figure 1), toroidal shape,l arge void volume, endo-cyclic N-H functionalities,a nd exo-cyclic t Bu groups of which make it ahighly unusual, sterically hindered H-bonding host. Thehost properties of 1 should differ significantly from organic counterparts,e specially given the greater polarity of these P À N-bonded frameworks.…”

Guest Binding via N−H⋅⋅⋅π Bonding and Kinetic Entrapment by an Inorganic Macrocycle

“…The high bond energy of P−N single bonds and their low polarity underpin the stability of a diverse range of previously reported phosphazane compounds, and provide a good foundation for the development of a new range of robust inorganic macrocycles . Of particular interest is the pentameric host macrocycle 1 (Figure ), toroidal shape, large void volume, endo ‐cyclic N‐H functionalities, and exo ‐cyclic t Bu groups of which make it a highly unusual, sterically hindered H‐bonding host.…”

The Coordination Chemistry of the N‐Donor‐Substituted Phosphazanes

“…However, the vast majority of these phosphines are based on organic backbones and main group counterparts based on inorganic backbones have received far less attention. In the past decade, phosphazanes, based on thermodynamically stable P‐N single bonds, have emerged as excellent candidates for the construction of a range of new Lewis base donor ligand systems [5–17] . In particular, cyclo‐diphosph(III)azane ligands of the type [XP(μ‐NR)] 2 (X=RO, R 2 N, C≡CPh) (A, Figure 1) have been employed in the assembly of a broad range of MOF‐like coordination networks and discrete macrocyclic arrangements, utilizing the P donor atoms of their P 2 N 2 ring units [18, 19] .…”