2,6-(Diphenylmethyl)-Aryl-Substituted Neutral and Anionic Phosphates: Approaches to H-Bonded Dimeric Molecular Structures

Abstract

2,6‐(Diphenylmethyl)‐4‐alkyl‐phenyl substituted phosphates, ArOP(O)(OH)2 (Ar=2,6‐CHPh2‐4‐R‐C6H2; R=Me (9), Et (10), iPr (11), and tBu (12)), were synthesized from the corresponding phenols. The single crystals of these compounds were obtained from their solutions of CH3CN or CH3COCH3. The molecular structures of these compounds, in the solid state, determined by single crystal X‐ray analysis reveal that they possess a hitherto unknown structural motif among monoorganophosphate esters viz., a dimeric hydrogen bonded structure involving a P−OH donor and a P=O acceptor group affording an eight‐membered ring. This structural motif is similar to what is commonly found in the solid state structures of carboxylic acids. In all of these compounds the solid state structure is restricted to the dimeric motif except in 9 where a 1D hydrogen‐bonded polymer formation is observed when it crystallized from acetonitrile. Deprotonation of these monoorganophosphates with triethylamine afforded the anionic phosphates, [ArOP(O)(OH)(O)]− containing Et3NH+ as the counter cation (Ar=2,6‐CHPh2‐4‐R‐C6H2; R=Me (13), Et (14), iPr (15), and tBu (16)). The solid state molecular structures of 13–16 again reveal hydrogen‐bonded dimeric structures in the solid state. In order to demonstrate the proof‐of‐principle with regard to the reactivity of the monoorganophosphates, we explored the reaction of 9 with ZnCl2 in the presence of pyrazole (PzH) and Et3N affording a dinuclear Zn(II) complex, [Et3NH]2[{ArOP(O)3}2{Zn(Cl)(PzH)}2] (Ar=2,6‐CHPh2‐4‐Me–C6H2) (17). The two Zn(II) centers are linked to each other by two dianionic [ArOP(O)3]2− ligands. Two additional triethylammonium cations and a terminal Zn−Cl moiety compensate the charge and complete the composition of 17.

Reactivity enhancement of a diphosphene by reversible N-heterocyclic carbene coordination

“…The P–O bond length found in 4 is 1.478(2) Å, which is shorter compared with that of 5 (1.492(2) Å) presumably because of a H-bonding interaction with an imidazolium cation. 25 The P–P distance in 4 (2.1946(8) Å) is slightly longer than that observed in the metal carbonyl (Lewis acid) free phospha-Wittig–Horner reagent, (Mes*PH–P(O)(OEt) 2 ) (2.1854 Å). 26 …”

Solvent-assisted monomeric molecular structure of the phosphate diester and the synthesis of menthol-based phosphate diesters

“…6 Aggregation behaviour of para-substituted monoarylphosphates have been very well studied and the formation of H-bonded non-porous and porous 3-D framework structures was reported. [29][30][31][32] Recently Murugavel et al, 33 and we 34 have shown that phosphate monoesters, 2,6-(CHPh) 2 -4-R-C 6 H 2 O-P(O)(OH) 2 form solvent assisted dimeric molecular structures in the solidstate. The corresponding anionic phosphate monoesters derived from these bulky phosphate monoesters exhibit structural diversity in supramolecular organization based on counter cations 35 as well as modulation of the nuclearity of molecular Mg(II)phosphates.…”

Structural Diversity in Supramolecular Organization of Anionic Phosphate Monoesters: Role of Cations

“…The hydrogen bonding between the two phosphate motifs leads to the formation of an eight-membered P 2 O 4 H 2 ring similar to what had been observed in the ion pair with the triethylammonium cation. 26 The solution- and solid-state CP-MAS 31 P{ 1 H} NMR spectra of 10 shows single singlet resonances at δ = −4.6 and −3.9 ppm, respectively, suggesting the presence of only one type of phosphorus center in the molecule.…”

“…Although molecular phosphate monoesters mostly form polymeric structures in the solid state, 17−25 we have recently reported the syntheses of several bulky aryl-substituted neutral and anionic phosphate monoesters ( 1 – 8 in Scheme 1), which exhibit H-bonded dimeric molecular structures analogous to those in carboxylic acids. 26 Through partial blockage of the H-bonding potential of the ArOP(O)(OH) 2 unit by using either a hydrogen-bonding acceptor solvent (such as acetone or acetonitrile) or a hydrogen-bonding donor as counter cation (such as triethylammonium), we were able to realize dimeric supramolecular structures (Scheme 1). Murugavel et al independently also reported the synthesis and molecular structures of 1 and 4 .…”