Terminal Titanyl Complexes of Tri- and Tetrametaphosphate: Synthesis, Structures, and Reactivity with Hydrogen Peroxide

Abstract

The synthesis and characterization of tri- and tetrametaphosphate titanium(IV) oxo and peroxo complexes is described. Addition of 0.5 equiv of [OTi(acac)] to dihydrogen tetrametaphosphate ([POH]) and monohydrogen trimetaphosphate ([POH]) provided a bis(μ,κ,κ) tetrametaphosphate titanyl dimer, [OTiPO] (1; 70% yield), and a trimetaphosphate titanyl acetylacetonate complex, [OTiPO(acac)] (2; 59% yield). Both 1 and 2 have been structurally characterized, crystallizing in the triclinic P1̅ and monoclinic P2 space groups, respectively. These complexes contain Ti≡O units with distances of 1.624(7) and 1.644(2) Å, respectively, and represent rare examples of structurally characterized terminal titanyls within an all-oxygen coordination environment. Complexes 1 and 2 react with hydrogen peroxide to produce the corresponding peroxotitanium(IV) metaphosphate complexes [OTiPO](3; 61% yield) and [OTiPO(acac)] (4; 65% yield), respectively. Both 3 and 4 have been characterized by single-crystal X-ray diffraction studies, and their solid-state structures are presented. Complex 3 functions as an oxygen atom transfer (OAT) reagent capable of oxidizing phosphorus(III) compounds (P(OMe), PPh) and SMe at ambient temperature to result in the corresponding organic oxide with regeneration of dimer 1.

Functionalization of Intact Trimetaphosphate: A Triphosphorylating Reagent for C, N, and O Nucleophiles

“…These reactions generate an acidic proton, which is scavenged by excess amine to produce an alkyl ammonium counterion that engages in hydrogen bonding with an anionic phosphate ring oxygen, as revealed in a crystallographic study of the salt of 2a (Figure S78). The acidic proton generated in such reactions should be a useful synthetic handle for introducing functionalized trimetaphosphate molecules into the coordination sphere of transition metals, along the lines of our previous work with monoprotonated TriMP. ,, As in the case of anion 1 , it is observed for 2a that the P–O bond lengths of the functionalized phosphorus atom are shortened to 1.585(1) Å with elongation of the opposing P–O bond to 1.651(1) Å. This structural effect is somewhat less pronounced than that observed for 1 , as the more electron releasing −NEt 2 substituent induces less buildup of positive charge on the phosphorus atom.…”

“…The bis­(triphenylphosphine)­iminium (PPN) salt of TriMP has been investigated in organic solvents as a ligand for transition metals. ,,− It has properties favorable for functionalization studies including a lack of acidic protons, solubility in polar organic solvents, and crystallinity of reaction products. TriMP is also the obvious choice for synthesizing triphosphorylated biomolecules; notable recent advances in this area using MstCl as activator are due to Mohamady and Taylor. ,, Phosphonium based condensing reagents have also been used as activators for phosphates and phosphonates for coupling with alcohols (Scheme ).…”

Cobalt and Vanadium Trimetaphosphate Polyanions: Synthesis, Characterization, and Electrochemical Evaluation for Non-aqueous Redox-Flow Battery Applications

“…This 31 P NMR resonance is shifted downfield from the region expected for a low-spin, S = 0 Co(III) d 6 complex based on the 31 P NMR signatures observed for diamagnetic trimetaphosphate species. 21,23 The downfield shift suggested that the high-spin S = 2 state may be populated to some extent at 25 • C. Solution magnetic susceptibility data of [PPN] 3 [3]·MeCN at 25 • C (Evans method, µ eff = 3.32 µ B , CD 3 CN) further substantiated contribution from the S = 2 high-spin state. These data in combination with the classification of trimetaphosphate as a weak-field ligand suggest that complex 3 exhibits a low-spin high-spin transition described by the 1 A 1 (O h ) 5 T 2 (O h ) states.…”

“…The cation, however, is a variable component of the current system. The PPN + cation was chosen for the present study on the basis of our previous work, [21][22][23] but other cations could be selected to optimize properties including solubility and cost. of acid for protonation of all three acac ligands of V(acac) 3 .…”

Cleavage of Catechol Monoalkyl Ethers by Aluminum Triiodide–Dimethyl Sulfoxide

“…Thus DMSO was transformed into dimethyl sulfide when treated with equimolar quantity of AlI 3 for 0.5 hour at 80 °C, as indicated by the NMR spectra recorded in CD 3 CN ( Figure 1). The Me 2 S proton appeared at 2.02 ppm 33 in the 1 H NMR spectrum (A), and the methyl carbon appeared at 17.02 ppm in the 13 C NMR spectrum (B) without noticeable residual DMSO, suggesting that a clean conversion had occurred. The in situ generated Me 2 S and iodine (Scheme 2, eq 1) existed probably as Me 2 S•I 2 complex, or in the form of ion pair (1, Scheme 2, eq 2).…”