Pre-arranged building block approach for the orthogonal synthesis of an unfolded tetrameric organic-inorganic phosphazane macrocycle

Inorganic macrocycles remain challenging synthetic targets due to the limited number of strategies reported for their syntheses. Among these species, large fully inorganic cyclodiphosphazane macrocycles have been experimentally and theoretically highlighted as promising candidates for supramolecular chemistry. In contrast, their hybrid organic-inorganic counterparts are lagging behind due to the lack of synthetic routes capable of controlling the size and topological arrangement (i.e., folded vs unfolded) of the target macrocycle, rendering the synthesis of differently sized macrocycles a tedious screening process. Herein, we report-as a proof-of-concept-the combination of pre-arranged building blocks and a two-step synthetic route to rationally enable access a large unfolded tetrameric macrocycle, which is not accessible via conventional synthetic strategies. The obtained macrocycle hybrid cyclodiphosphazane macrocycle, cis-[μ-P(μ-NtBu)]2(μ-p-OC6H4C(O)O)]4[μ-P(μ-NtBu)]2 (4), displays an unfolded open-face cavity area of 110.1 Å2. Preliminary theoretical host-guest studies with the dication [MeNC5H4]22+ suggest compound 4 as a viable candidate for the synthesis of hybrid proto-rotaxanes species based on phosphazane building blocks.

Construction of Inorganic Crown Ethers by s-Block-Metal-Templated Si-O Bond Activation

We herein report the synthesis, structures, coordination ability, and mechanism of formation of silicon analogs of crown ethers. An oligomerization of 2 D2 (I) (2 Dn ,=(Me4 Si2 O)n ) was achieved by the reaction with GaI3 and MIx (M=Li, Na, Mg, Ca, Sr). In these reactions the metal cations serve as template and the anions (I- /[GaI4 ]- ) are required as nucleophiles. In case of MIx =LiI, [Li(2 D3 )GaI4 ] (1) is formed. In case of MIx =NaI, MgI2 , CaI2 , and SrI2 the compounds [M(2 D4 )(GaI4 )x ] (M=Mg2+ (3), Ca2+ (4), Sr2+ (5) are obtained. Furthermore the proton complex [H(2 D3 )][Ga2 I7 ] (6) was isolated and structurally characterized. All complexes were characterized by means of multinuclear NMR spectroscopy, DOSY experiments and, except for compound 3, also by single crystal X-ray diffraction. Quantum chemical calculations were carried out to compare the affinity of M+ to 2 Dn and other ligands and to shed light on the formation of larger rings from smaller ones.

Recent advances in organophosphorus-chalcogen and organophosphorus-pincer based macrocyclic compounds and their metal complexes

The design and development of phosphorus based macrocycles containing one or more other heteroatoms is of crucial importance for the enhancement of modern synthetic chemistry. In recent years focus on phosphorus based macromolecules has led to intriguing and innovative structures with a variety of applications, including photophysical and host-guest properties, and in organic synthesis. This article summarizes the recent advancements in the synthesis of macrocycles that consist of organophosphorus-chalcogen (P-E, P[double bond, length as m-dash]E; E = O, S, Se) and organophosphorus-pincer based macrocyclic ligands and their transition metal complexes with emphasis given to synthetic methodologies. The reactions involve the modification of simple macrocycles with phosphorus sources or phosphorus-based chalcogenating reagents. Transition metal complexes of phosphine-based macrocyclic pincer ligands and their reactivity are also included.

Size-control in the synthesis of oxo-bridged phosphazane macrocycles via a modular addition approach

Inorganic macrocycles remain largely underdeveloped compared with their organic counterparts due to the challenges involved in their synthesis. Among them, cyclodiphosphazane macrocycles have shown to be promising candidates for supramolecular chemistry applications due to their ability to encapsulate small molecules or ions within their cavities. However, further developments have been handicapped by the lack of synthetic routes to high-order cyclodiphosphazane macrocycles. Moreover, current approaches allow little control over the size of the macrocycles formed. Here we report the synthesis of high-order oxygen-bridged phosphazane macrocycles via a "3 + n cyclisation" (n = 1 and 3). Using this method, an all-P^III high-order hexameric cyclodiphosphazane macrocycle was isolated, displaying a larger macrocyclic cavity than comparable organic crown-ethers. Our approach demonstrates that increasing building block complexity enables precise control over macrocycle size, which will not only generate future developments in both the phosphazane and main group chemistry but also in the fields of supramolecular chemistry.

N-Bridged Acyclic Trimeric Poly-Cyclodiphosphazanes: Highly Tuneable Cyclodiphosphazane Building Blocks

We have synthesized a completely new family of acyclic trimeric cyclodiphosphazane compounds comprising NH, Nⁱ Pr, N^t Bu and NPh bridging groups. In addition, the first NH-bridged acyclic dimeric cyclophosphazane has been produced. The trimeric species display highly tuneable characteristics so that the distance between the terminal N(H)R moieties can be readily modulated by the steric bulk present in the bridging groups (ranging from ≈6 to ≈10 Å). Moreover, these species exhibit pronounced topological changes when a weak non-bonding NH⋅⋅⋅π aryl interaction is introduced. Finally, the NH-bridged chloride binding affinities have been calculated and benchmarked along with the existing experimental data available for monomeric cyclodiphosphazanes. Our results underscore these species as promising hydrogen bond donors for supramolecular host-guest applications.

Covalent and ionic bonding in bi- and tricyclic Group 15 amides: equidistant P-I and As-I bonds and fluxional cations

A series of trivalent Group 15 bis(tert-butylamido)cyclodiphosph(iii)azane element bi- and tricycles of the formulae {[(tBuNP)2(tBuN)2]ElX}, El = P, As, Sb, Bi, where X = Ph, OPh, OtBu, N3, hexamethyldisilylamide (HMDS), OTf, was synthesized from the corresponding chlorides via salt elimination. The ensuing compounds were studied spectroscopically and X-ray crystallographically with a particular focus on the length of the El-X bond. While the Group 15 element to phenyl and HMDS were of normal lengths and completely covalent, those to azide appeared to be partly ionic. The {[(tBuNP)2(tBuN)2]ElI} showed El-I bonds that were substantially longer than the typical element iodide bonds, suggesting a very high degree of polarity and bordering on ionic bonding. Finally, the triflate [(tBuNP)2(tBuN)2]P] + [SO3CF3]- proved to be an ion pair in the solid state. The antimony analog, however, showed a long covalent Sb-O bond in the solid state, although it appears to dissociate into ions in solution. The phosphonium triflate salt is fluxional and exhibits a previously unseen highly symmetrical structure in solution. The bonding trends from completely covalent to completely ionic are discussed in terms steric restrictions and the delocalization of charge in either the cation or the anion.

Catechol and 1,2,4,5-tetrahydroxybenzene functionalized cyclodiphosphazane ligands: synthesis, structural studies, and transition metal complexes

This paper describes the syntheses of two novel cyclodiphosphazane derivatives and their coordination chemistry with Cu^I, Ru^II, Rh^I, Pd^II and Au^I is also described.

Orthogonality in main group compounds: a direct one-step synthesis of air- and moisture-stable cyclophosphazanes by mechanochemistry

Mechanochemistry has been established to be an environmentally-friendly way of conducting reactions in a solvent-free manner.

The chameleonic reactivity of dilithio bis(alkylamido)cyclodiphosph(iii)azanes with chlorophosphines

Analogous reactions do not necessarily give analogous products.

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

The Se-bridged P^III/P^V phosphazane macrocycle [{(^tBuN)P^V(μ-N^tBu)}₂(μ-Se)₂{P^III(μ-N^tBu)}₂]₃ is obtained selectively using [Se(^tBuN)P(μ-N^tBu)]₂²⁻ as a nucleophilic component.

Isomerisation, reactivity and coordination chemistry of a new hybrid, multi-functional phosphazane

The unsymmetrical P^III/P^V cyclodiphosphazane [(S)(H)P(μ-N^tBu)₂PNH^tBu] provides entry into the mixed chalgogenide dianion [(S)P(μ-N^tBu)₂P(Se)N^tBu]²⁻, and unique insight into the mechanisms of cis/trans isomerism in phosph(iii)- and phosph(v)-azanes.

Insights into the formation of inorganic heterocycles via cyclocondensation of primary amines with group 15 and 16 halides

The cyclocondensation reaction of primary amines with pnictogen and chalcogen halides is a major preparative route for the generation of inorganic heterocycles involving a Group 15 or 16 element linked to nitrogen.

Synthesis and structure of the extended phosphazane ligand [(1,4-C6H4){N(μ-PNtBu)2NtBu}2]4−

Reaction of (1,4-C₆H₄)[N(PCl₂)₂]₂ with ^tBuNH₂ in the presence of Et₃N gives the bridged phosph(iii)azane (1,4-C₆H₄)[N(μ-PNH^tBu)₂N^tBu]₂ (1H₄), which can be deprotonated to give the tetraanion (1,4-C₆H₄)[N(μ-PN^tBu)₂N^tBu]₂⁴⁻ (1⁴⁻). The latter represents a new type of phosphazane ligand.

Cyclodiphosphazanes: options are endless

This short review describes the transition metal chemistry of cyclodiphosphazanes.

A versatile hard–soft N/S-ligand for metal coordination and cluster formation

The new ligand [S-P(μ-N^tBu)]₂²⁻ has adaptable hard–soft character with respect to the coordinated metal centre and can be used to construct large cage architectures.

Synthesis and structures of [S(H)P(μ-NR)]2, potential building blocks for inorganic phosphorus–sulfur macrocycles

Steric factors are the principle influence on the favourability of the cis and trans isomers of the novel dimers [S(H)P(μ-NR)]₂.

Spirocyclic, macrocyclic and ladder complexes of coinage metals and mercury with dichalcogeno P2N2-supported anions

Reactions of the dianions [^tBuN(E)P(μ-N^tBu)]₂²⁻ (E = Se,S) with M(i) reagents (M = Ag, Au) or HgCl₂ produce complexes of [^tBu(H)N(E)P(μ-N^tBu)₂P(E)N^tBu]⁻ with spirocyclic, macrocyclic or ladder structures.

Novel zeotype frameworks with soft cyclodiphosphazane linkers and soft Cu4X4 clusters as nodes

Two novel zeolitic phosphane cluster frameworks have been synthesized by using ferrocenyl cyclodiphosphazanes [Fe(η⁵-C₅H₄)₂{P(μ-N^tBu)}₂] as ditopic linkers and [Cu₄X₄] clusters as tetrahedral nodes.

Confinement of halide ions within homologous inverse coordination hosts; modification of halide-ion selectivity

The structures of a series of spherical host-guest complexes [{MeE(PPh)(3)Li(4)·3thf}(4)(μ(4)-X)](-) (E = Al, [1X](-); E = Ga, [2X](-); E = In, [3X](-)) reveal that changing the halide ions (X = Cl, Br, or I) within their central tetrahedral Li(4) sites has negligible effect on the structural parameters.