Nonclassical Oxygen Atom Transfer as a Synthetic Strategy: Preparation of an Oxorhenium(V) Complex of the Bis(3,5-di-tert-butyl-2-phenoxo)amide Ligand

Abstract

Oxo(triphenylphosphine)[bis(3,5-di-tert-butyl-2-phenoxo)amido]rhenium(V) [(ONO(Cat))ReO(PPh3)] is prepared by the reaction of iododioxobis(triphenylphosphine)rhenium(V) [ReO2(PPh3)2I] with lead bis(3,5-di-tert-butyl-1,2-quinone-1-(2-oxy-3,5-di-tert-butylphenyl)imine) [Pb(ONO(Q))2]. In this reaction, the ONO ligand undergoes a two-electron reduction, with concomitant oxidation of PPh3 to OPPh3 and transformation of the dioxorhenium(V) fragment into a monooxorhenium(V) fragment, constituting a net nonclassical oxygen atom transfer. (ONO(Cat))ReO(PPh3) adopts a square pyramidal geometry with an apical oxo group [d(ReO) = 1.6873(14) Å] and a highly folded ONO ligand [O-Re-O = 129.55(6)°]. The fully reduced, trianionic oxidation state of the ONO ligand is confirmed by spectroscopic and metrical data.

New avenues for ligand-mediated processes – expanding metal reactivity by the use of redox-active catechol, o-aminophenol and o-phenylenediamine ligands

“…The group also reported an example of a nonclassical oxygen atom transfer in the synthesis of oxorhenium complex 32 (Scheme 16). 39 Reaction of the previously reported transmetalation agent 31, 40 containing two redox-active ONO ligands in the q oxidation state, with ReO 2 (PPh 3 ) 2 leads to the formation of PbI 2 , OPPh 3 and complex 32. Interestingly, the redox-active ligand is reduced by two electrons to the red 2À oxidation state in the reaction.…”

Octahedral to trigonal prismatic distortion driven by subjacent orbital π antibonding interactions and modulated by ligand redox noninnocence

“…The ONO ligands are markedly folded, with intraligand O-Os-O angles of 124(3)1 avg. Out of over 50 reported structurally characterized ONO compounds, only Pb(ONO) 2 13 and (ONO)ReO(PPh 3 ) 14 show similar degrees of ligand nonplanarity. The geometry at the metal center in Os(ONO) 2 is far from octahedral, with N1-Os-N2 = 128.54 (19), 133.33(19)1 and O2-Os-O4 = 146.57 (16), 140.68(16)1 for the two inequivalent molecules in the crystal.…”

Trianionic pincer and pincer-type metal complexes and catalysts

“…Further expansion across the periodic table employing an ONO 3À ligand comes from the laboratories of Brown. 164 Employing an intriguing metalation technique, the authors treat ReO 2 (PPh 3 ) 2 I 165,166 with the transmetalating agent 167, 167 which is an homoleptic bis-ONO lead(II) complex with the ONO ligand in the oxidized quinonate state. The reaction produces the Re(V) complex [ONO]Re(O)PPh 3 (168) featuring the ONO ligand in its reduced trianionic oxidation state (Scheme 81).…”