Oxidative Degradation of Ethers Promoted by Strontium and Barium Tetraphenylimidodiphosphinates

Abstract

The novel M[(OPPh2)2N]2.nTHF (M = Sr (2), Ba (3)) complexes were prepared and characterized. Upon exposure to atmospheric oxygen, 2 and 3 were transformed to the dinuclear species Sr2-[(OPPh2)2N]4.2C3H6O3 (4) and Ba(2)[(OPPh2)2N]4.2C4H8O3 (5), respectively. Compounds 4 and 5 contain coordinated carboxylic acids obtained from the oxidative degradation of DME and THF, respectively, which were used as solvents for crystallization.

Synthesis and Oligonuclear Structures of Strontium and Barium Complexes with Protonated and Deprotonated N-Mesityl-P,P-diphenylphosphinic Amide Ligands

“…The storage of [Ba 3 L 6 ] ( 3 ) in THF led to ether degradation but small amounts of rather pure [(thf) 2 Ba 3 L 6 ] ( 4 ) were isolated, as depicted in Scheme 4 . In agreement with earlier reports, 12 slow THF cleavage occurred in this ethereal solvent with Sr complex 1 , a significantly faster ether degradation was observed for barium complexes 3 and 4 .…”

“…There are no reports on complexes with the heavier alkaline-earth metals strontium and barium of type [R 2 P(O)–NR’] 2 Ae(L) n , most probably due to poor solubility in common organic solvents and the enormous reactivity initiating ether degradation reactions. 12 However, substitution of the hard oxygen base by a soft selenium atom allows the synthesis and isolation of selenophosphinic amides of type [{Ph 2 P(Se)N–R} 2 Ae(thf) 2 ] (Ae = Ca, Sr, and Ba) with bidentate ligands in mononuclear complexes with distorted octahedrally coordinated alkaline-earth metal atoms. 13 Lack of information on [R 2 P(O)–NR′] 2 Ae(L) n congeners initiated our investigation choosing N -mesityl- P , P -diphenylphosphinic amide ( I ) as an easily available substrate, 14 allowing the synthesis of oligonuclear strontium and barium complexes containing the rather bulky (diphenylphosphoryl)-(mesityl)amide anions.…”

Synthesis and Reactivity of Oxo-Peroxo-Vanadium(V) Bipyridine Compounds

“…In the absence of a reducing solvent, in CH 2 Cl 2 or MeCN, V IV O(OH) is unreactive with O 2 . The formation of oxidized THF products upon reaction of a vanadium(IV) complex with O 2 has previously been reported,6 as have stoichiometric and catalytic aerobic oxidations of THF mediated by a variety of transition metal and main group complexes 22…”

Reactions in “sacrificial” solvents

“…[51][52][53][54] The transformation with molecular oxygen is catalyzed by numerous salts or complexes of Fe, 50,55 Co, 52,56,57 Cu, 58,59 Ni, 59 Ag, 59 Pt, 60 Ru, 61,62 Pd, 63 Ir and Rh, 64 and Sr and Ba. 65 The heterogeneous catalysts Pd/C, 64 Rh/C, 64 and Pt 53,60,62 have also been used to oxidize THF. In the specific case of THF, further transformation of the hydroperoxide (A, Scheme 3) usually gives tetrahydrofuran-2-ol (B), g-butyrolactone (C), and 4-hydroxybutanal (D, the tautomer of tetrahydrofuran-2-ol), but products of more complex transformations (E, 52 F, 61 G, 61 and H 66 ) have also been described.…”