Lanthanide Complexes Supported by Tripodal Chalcogenophosphinic Amide Ligands.

While transition metal complexes containing tripodal phosphinic amide ligands such as [N{CH2CH2NP(O)Ph2}3]3- ([poat]3-) are well documented, analogous complexes with lanthanide elements have not been explored. Herein, we report on the synthesis, structure, and reactivity of lanthanide complexes supported by the tripodal chalcogenophosphinic amide ligands [N{CH2CH2NP(E)R2}3]3- (R = Ph, E = O; R = iPr, E = S or Se). Treatment of LaCl3 and CeBr3 in tetrahydrofuran with K3poat afforded dinuclear [M2(poat)2] that reacted with trimethylphosphine oxide to yield the adducts [M2(OPMe3)2(poat)2] (M = La, Ce). Treatment of LaCl3 and CeBr3 with K3[N{CH2CH2NP(E)iPr2}3] (E = S, Se) gave mononuclear [M(N{CH2CH2NP(E)iPr2}3)] (M = La, Ce). The cyclic voltammograms of [CeIII(N{CH2CH2NP(E)iPr2}3)] exhibited reversible Ce(IV/III) redox couples at ca. -0.35 V vs Fc+/0 (Fc = ferrocene), showing the ability of the chalcogenophosphinic amide ligands to stabilize Ce(IV). Oxidation of [Ce(N{CH2CH2NP(E)iPr2}3)] with [Ce(LOEt)2Cl2] (LOEt- = [CpCo{P(O)(OEt)2}3]-) led to isolation of the Ce(IV) thiolate and selenolate complexes [CeIV(N{CH2CH2NP(E)iPr2}3)][CeIII(LOEt)Cl3] (E = S, Se).