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.

Ca[(Ph 2 PO) 2 N] 2 ×nTHF (2) was obtained by direct synthesis from tetraphenylimidodiphosphinic acid and Ca8 in THF. X-ray quality single crystals of Ca 2 [(Ph 2 PO) 2 N] 4 ×H 2 O (3) and Ca[(Ph 2 PO) 2 N] 2 ×2C 4 H 8 O 3 (4) were obtained upon crystallization of 2 under different conditions. The solid-state structure of 3 reveals a Ca 2 O 3 core in which the two hexacoordinated calcium metals are linked together by three m-oxygen atoms from three independent tetraphenylimidodiphosphinate ligands. Compound 4 is a monomeric octahedral complex bearing two tetraphenylimidodiphosphinate ligands in the equatorial plane and two ahydroperoxidated THF molecules, formed in situ, in the axial positions. Compound 4 represents the first example of a metal center exhibiting this type of hydroperoxidation behavior.

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