UC Santa Barbara

Treatment of the U(III) trisamide, [U(NR2)3] (R = SiMe3) with 1 equiv of KSCPh3 in the presence of 1 equiv of 18-crown-6 affords the U(IV) terminal sulfide complex, [K(18-crown-6)][U(S)(NR2)3] in moderate yield. The reaction of [U(NR2)3] with 1 equiv of KOCPh3 generates a complex mixture of products from which, the U(IV) terminal oxo complex, [K(18-crown-6)][U(O)(NR2)3], the U(IV) alkoxide complex, [U(OCPh3)(NR2)3], and the triphenylmethyl anion salt, [K(18-crown-6)(THF)2][CPh3] can be isolated. Addition of 2 equiv of KC8 and 18-crown-6 to [U(OCPh3)(NR2)3] affords both [K(18-crown-6)][U(O)(NR2)3] and [K(18-crown-6)(THF)2][CPh3] via reductive deprotection of the triphenylmethyl group.

Treatment of [Th(I)(NR2)3] with 1 equiv of KOCPh3 or KSCPh3 affords [Th(OCPh3)(NR2)3] and [Th(SCPh3)(NR2)3] in moderate yields. Reductive deprotection of these with 2 equiv KC8 and 18-crown-6 generates the Th(IV) terminal chalcogenide complexes, [K(18-crown-6)][Th(O)(NR2)3] and [K(18-crown-6)][Th(S)(NR2)3], respectively. Both feature short Th=E distances indicative of multiple bond character.

Treatment of [U(NR2)3] or [U(I)(NR2)3] with 0.5 or 1 equiv, respectively, of [K(L)][Te2] (L =18-crown-6, 2,2,2-cryptand) affords the U(IV) terminal tellurides, [K(L)][U(Te)(NR2)3], [K(L)][U(η2-Te2)(NR2)3] in moderate yields. Addition of 0.5 equiv of [K(18-crown-6)][Se4] to [U(NR2)3] generates [K(18-crown-6)][U(η2-Se2)(NR2)3], which can be converted to [K(18-crown-6)][U(Se)(NR2)3] via addition of 1 equiv of Ph3P.

Treatment of [Th(I)(NR2)3] with 1 equiv of [K(18-crown-6)][Se4] or [K(18-crown-6)][Te2] affords the dichalcogenide complexes, [K(18-crown-6)][Th(η2-Se2)(NR2)3] and [K(18-crown-6)][Th(η2-Te2)(NR2)3], respectively. These can be converted to the monochalcogenides, [K(18-crown-6)][Th(Se)(NR2)3] and [K(18-crown-6)][Th(Te)(NR2)3], via addition of Et3P or Et3P and Hg, respectively.

Addition of 0.125 equiv of S8 or 1 equiv of Se to [K(18-crown-6)][U(S)(NR2)3] generates the dichalcogenide complexes, [K(18-crown-6)][U(η2-S2)(NR2)3] and [K(18-crown-6)][U(η2-SSe)(NR2)3], respectively. These reactions are reversible and addition of 1 equiv of R3P (R = Et, or Ph) regenerates [K(18-crown-6)][U(S)(NR2)3] and the corresponding phosphine-chalcogenide, R3P=E (E = S, Se). [K(18-crown-6)][U(η2-S2)(NR2)3] is reversibly converted to the U(IV) trisulfide, [K(18-crown-6)][U(η3-S3)(NR2)3] via addition or removal of S, with 0.125 equiv of S8 or R3P, respectively.