The formation of dimeric phosph(iii)azane macrocycles [{P(µ-NtBu)}2·LL]2[LL = organic spacer]

Abstract

The dimeric macrocycles [[P(mu-NtBu)]2.LL]2 [LL = OCH2C(Me)2CH2O (1), 2,6-(NH)2C5H3N (2), 1,2-(NH)2C6H4(3)] have been obtained by the reactions of the appropriate diols and diamines (LLH2) with the dimeric phosph(III)azane [ClP(mu-NtBu)]2. Under different conditions the reaction of 1,2-(NH2)2C6H4 with [ClP(mu-NtBu)]2 gives the monomer [[P(mu-NtBu)]2.[1,2-(NH)2C6H4]] (4) (instead of the dimer 3). Contrary to the literature, the results illustrate that the formation of dimeric macrocycles is common in these reactions and dependent among other factors on the steric demands and length of the organic spacer (LL) as well as the reaction conditions.

Chiral Ditopic Cyclophosphazane (CycloP) Ligands: Synthesis, Coordination Chemistry, and Application in Asymmetric Catalysis

“…The corresponding free energy of activation (Δ G ≠ ) for this process of 31 kJ mol −1 was found to be similar to that previously reported for oxygen‐bridged phosphazane macrocycles 25b…”

“…Coordination of chiral cyclophosphazanes to metals : In the next step of the study we investigated the complexation behavior of the two phosphorus lone pairs of the CycloP ligands to several late transition metals, in particular to assess the rigidity of the chiral ligands upon metal coordination. This was an important issue because previous studies suggested that ansa cyclophosphazanes of this type could potentially oligomerize giving dimeric macrocyclic species,25b and the presence of Lewis acidic metal centers could also result in ring‐expansion 27…”

Mechanochemical Synthesis of Phosphazane‐Based Frameworks

“…[40] Because compound 1 is soluble in the most non-protic organic solvents, it is the nature of the nucleophile that dictates the choice of the solvent. For instance, the reaction of compound 1 with o-phenylenediamine at room temperature in toluene/Et 3 Ns tirred for sixteen hours produces the dimeric macrocycle [{P(m-NtBu)} 2 {1,2-(NH) 2 C 6 H 4 }] 2 ;w hereas the heating compound 1 in THF/Et 3 Nt or eflux overnight results in the formation of the monomeric cyclic compound [{P(m-NtBu)} 2 {1,2-(NH) 2 C 6 H 4 }].…”

“…In the traditional syntheses of these species, the choice of the reaction conditions and solvents plays a crucial role in influencing the formation(s) of the reaction product(s). For instance, the reaction of compound 1 with o ‐phenylenediamine at room temperature in toluene/Et 3 N stirred for sixteen hours produces the dimeric macrocycle [{P(μ‐N t Bu)} 2 {1,2‐(NH) 2 C 6 H 4 }] 2 ; whereas the heating compound 1 in THF/Et 3 N to reflux overnight results in the formation of the monomeric cyclic compound [{P(μ‐N t Bu)} 2 {1,2‐(NH) 2 C 6 H 4 }] . Because compound 1 is soluble in the most non‐protic organic solvents, it is the nature of the nucleophile that dictates the choice of the solvent.…”

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

“…[28,29] Thevast majority of structures comprising P III atoms and/ or their applications have been based on disubstituted cyclodiphosphazane monomeric species (Figure 1, type m III ). [18,23,30] However,s everal acyclic( a)a nd cyclic (c)i norganic cyclodiphosphazane oligomeric species have been successfully synthesised and described in the literature (monomers,dimers,trimers,tetramers and pentamers,types m, d, t, tt and p,respectively,F igure 1). [14,31] Them ajority of the efforts made in cyclodiphosphazane chemistry have been focused on the synthesis of both hybrid and fully inorganic cyclic cyclodiphosphazane species due to their potential applications in host-guest chemistry.…”