Steric control in the oligomerisation of phosphazane dimers; towards new phosphorus–nitrogen macrocycles

Abstract

The reaction of [ClP(mu-NtBu)]2 (1) with H2O (1 : 2 equivalents) in the presence of excess Et3N gives the new chain compound [(mu-O)[P(mu-NtBu)2P(H)=O]2] (3), consisting of two P2N2 rings linked by a mu-O atom and terminating in P(V)(H)=O groups. A similar chain species is obtained from the reaction of the lithiate of [(tBuNH)P(mu-NtBu)2P(H)=O] (5) with [ClP(mu-NtBu)2P(NHtBu)] (2), the product being [(mu-O)[P(mu-NtBu)2P(NHtBu)]2] (6). Compounds 3 and 6 are the first examples of O-bridged chain phosphazanes and potential precursors to new phosphorus-nitrogen macrocycles. The syntheses and X-ray structures of 3, 5 and 6 are reported.

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

“…[6] This reaction can be rationalized by a change from a Pcentered to an O-centered nucleophile. In this sense, the reaction can be seen to involve an intermediate possessing "masked" functionality.…”

“…Sulfur and selenium macrocycles have been the focus of considerable attention in the past two decades owing to their unusual redox properties and their ability to stabilize lowoxidation-state metals. [14] Most attention has been paid to 6 (R = 2-MeO-C 6 H 4 , [17] Ph [18] ). However, in both of these cases the dimer-bridging m-NR groups adopt trans conformations with respect to the Sb 2 N 2 ring constituents, so as to place all of the associated R groups exo to the cavity.…”

A mixed-valent cyclodiphosphazane: Transition metal chemistry and cis/trans isomerisation

“…The exocyclic and endocyclic P-N bond distances in 7 are shorter than that found in 2, but follow the same trend. 32 In general, the exocyclic P-N distances are shorter and comparable with typical P-N distances observed in both cyclic and acyclic diphosphazanes 49 and P-N bond distances associated with P V centers are shorter than that of P III centers in cyclodiphosphazanes.…”

“…[26][27][28][29] Recently we explored the coordination chemistry of acyclic dimers of cyclodiphosphazanes derived from cis-{ClP(μ-N t Bu) 2 P(NH t Bu)}. 14,30,31 Hydrolysis of the P-Cl bond in cis-{ClP(μ-N t Bu) 2 P(NH t Bu)} to produce cis-{( t BuNH)P(μ-N t Bu) 2 P(O)H} was reported by Wright and co-workers, 32 while a similar compound was accidentally isolated by Kumaraswamy and co-workers. 33 Herein we report transition metal chemistry and cis/trans isomerisation of cis-{( t BuNH)P(μ-N t Bu) 2 P(O)H}.…”

“…44 The P2-O1 bond distance in 5 [1.474(2) Å] is similar to that of 2 [1.468(2) Å], whereas the P2-H2 bond distance in 5 [1.26(2) Å] is shorter than that of the free ligand 2 [1.35(2) Å]. 32 The steric and electronic aspects of the coordinating ligands dictate the conformations of d 8 square planar complexes. The bulky ligands generally confer trans configuration, whereas the strong σ -donor ligands impose cis conformation around the metal center due to the trans influence.…”