Heterobimetallic cerium(iv) oxo clusters supported by a tripodal oxygen ligand.

Heterometallic Ce(IV)/M (M = Mo(VI), Re(VII), V(V)) oxo clusters supported by the Kläui tripodal oxygen ligand [(η(5)-C5H5)Co{P(O)(OEt)2}3](-) (LOEt(-)) have been synthesized and structurally characterized, and the catalytic activity of the Ce(IV)/V(V) oxo cluster in the oxidation of thioanisoles has been studied. Treatment of [Ce(LOEt)Cl3] (1) with [Ag2MoO4] afforded the reported Ce(IV)/Mo(VI) cluster [H4(CeLOEt)6Mo9O38] (2), whereas that with [AgReO4] yielded the Ce(IV)/Re(VII) cluster [{LOEtCe(ReO4)2(H2O)(µ-ReO4)}2] (3) that contains an 8-membered Ce2Re2O4 ring. Treatment of 1 with [Ag3VO4] afforded the Ce(IV)/V(V) cluster [H2(CeLOEt)4(V[double bond, length as m-dash]O)4(µ4-O)(µ3-O)12] (4) containing a {Ce4V4O13} oxo-metallic core. The solid-state structure of 4 consists of four {VO4}(3-) units bridged by four {LOEtCe(3+)} moieties and a µ4-oxo ligand. Each Ce atom in 4 is 9-coordinated, whereas the geometry around each V atom is pseudo square pyramidal with a terminal oxo at the apical position. Cluster 4 is an active catalyst for the oxidation of substituted thioanisoles with tert-butyl hydroperoxide. For example, the oxidation of thioanisole with tert-butyl hydroperoxide in the presence of 0.01 mol% of 4 gave a ca. 30 : 1 mixture of the sulfoxide and sulfone products in 96% yield.

Probing the Reactivity of the Ce═O Multiple Bond in a Cerium(IV) Oxo Complex.

The reactivity of the cerium(IV) oxo complex [(LOEt)2CeIV(═O)(H2O)]·MeC(O)NH2 (1; LOEt- = [CoCp{P(O)(OEt)2}3]-, where Cp = η5-C5H5) toward electrophiles and Brønsted acids has been investigated. The treatment of 1 with acetic anhydride afforded the diacetate complex [CeIV(LOEt)2(O2CMe)2] (2). The reaction of 1 with B(C6F5)3 yielded [CeIV(LOEt)2(Me2CONH2)2][B(C6F5)3(OH)]2 (3), in which the [B(C6F5)3(OH)]- anions are H-bonded to the O-bound acetamide ligands. The treatment of 1 with HCl and HNO3 afforded [CeIV(LOEt)2Cl2] and [CeIV(LOEt)2(NO3)2], respectively. Protonation of 1 with triflic acid (HOTf) gave the diaqua complex [CeIV(LOEt)2(H2O)2](OTf)2 (4), in which the triflate anions are H-bonded to the two aqua ligands. The treatment of 1 with phenol afforded the phenoxide complex [CeIV(LOEt)2(OPh)2] (5). The oxo-bridged bimetallic complex [(LOEt)2(Me2CONH2)CeIV(O)NaLOEt] (6) with the Ce-Ooxo and Na-Ooxo distances of 1.953(4) and 2.341(4) Å, respectively, was obtained from the reaction of 1 with [NaLOEt]. Density functional theory calculations showed that the model complex [(LOMe)2CeIV(Me2CONH2)(O)NaLOMe] (6A; LOMe- = [CoCp{P(O)(OMe)2}3]-) contains a polarized Ce═O multiple bond. The energy for dissociation of the {NaLOMe} fragment from 6A in acetonitrile was calculated to be +33.7 kcal/mol, which is higher than that for dissociation of the H-bonded acetamide from [(LOMe)2CeIV(═O)(H2O)]·MeC(O)NH2 (1A) (calculated to be +17.4 kcal/mol). In hexanes containing trace water, complex 1 decomposed readily to a mixture of a tetranuclear cerium(IV) oxo cluster, [CeIV4(LOEt)4(µ4-O)(µ2-O)4(µ2-OH)2] (7), and a cerium(III) complex, [CeIII(LOEt)2(H2O)2][LOEt] [8(LOEt)], whereas the cerium/sodium oxo complex 6 is stable under the same conditions. The crystal structures of 3, 4·H2O, 6, and 8(LOEt) have been determined.

Ruthenium chalcogenonitrosyl and bridged nitrido complexes containing chelating sulfur and oxygen ligands.

Ruthenium thio- and seleno-nitrosyl complexes containing chelating sulfur and oxygen ligands have been synthesised and their de-chalcogenation reactions have been studied. The reaction of mer-[Ru(N)Cl3(AsPh3)2] with elemental sulfur and selenium in tetrahydrofuran at reflux afforded the chalcogenonitrosyl complexes mer-[Ru(NX)Cl3(AsPh3)2] [X = S (1), Se (2)]. Treatment of 1 with KN(R2PS)2 afforded trans-[Ru(NS)Cl{N(R2PS)2}2] [R = Ph (3), Pr(i) (4), Bu(t) (5)]. Alternatively, the thionitrosyl complex 5 was obtained from [Bu(n)4N][Ru(N)Cl4] and KN(Bu(t)2PS)2, presumably via sulfur atom transfer from [N(Bu(t)2PS)2](-) to the nitride. Reactions of 1 and 2 with NaLOEt (LOEt(-) = [Co(η(5)-C5H5){P(O)(LOEt)2}3](-)) gave [Ru(NX)LOEtCl2] (X = S (8), Se (9)). Treatment of [Bu(n)4N][Ru(N)Cl4] with KN(R2PS)2 produced Ru(IV)-Ru(IV)µ-nitrido complexes [Ru2(µ-N){N(R2PS)2}4Cl] [R = Ph (6), Pr(i) (7)]. Reactions of 3 and 9 with PPh3 afforded 6 and [Ru(NPPh3)LOEtCl2], respectively. The desulfurisation of 5 with [Ni(cod)2] (cod = 1,5-cyclooctadiene) gave the mixed valance Ru(III)-Ru(IV)µ-nitrido complex [Ru2(µ-N){N(Bu(t)2PS)2}4] (10) that was oxidised by [Cp2Fe](PF6) to give the Ru(IV)-Ru(IV) complex [Ru2(µ-N){N(Bu(t)2PS)2}4](PF6) ([10]PF6). The crystal structures of 1, 2, 3, 7, 9 and 10 have been determined.

Synthesis, Structure, and Reactivity of a Tetranuclear Cerium(IV) Oxo Cluster Supported by the Kläui Tripodal Ligand [Co(η(5) -C5 H5 ){P(O)(OEt)2 }3 ](.).

A tetranuclear Ce(IV) oxo cluster compound containing the Kläui tripodal ligand [Co(η(5) -C5 H5 ){P(O)(OEt)2 }3 ](-) (LOEt (-) ) has been synthesized and its reactions with H2 O2 , CO2 , NO, and Brønsted acids have been studied. The treatment of [Ce(LOEt )(NO3 )3 ] with Et4 NOH in acetonitrile afforded the tetranuclear Ce(IV) oxo cluster [Ce4 (LOEt )4 O7 H2 ] (1) containing an adamantane-like {Ce4 (µ2 -O)6 } core with a µ4 -oxo ligand at the center. The reaction of 1 with H2 O2 resulted in the formation of the peroxo cluster [Ce4 (LOEt )4 (µ4 -O)(µ2 -O2 )4 (µ2 -OH)2 ] (2). The treatment of 1 with CO2 and NO led to isolation of [Ce(LOEt )2 (CO3 )] and [Ce(LOEt )(NO3 )3 ], respectively. The protonation of 1 with HCl, ROH (R=2,4,6-trichlorophenyl), and Ph3 SiOH yielded [Ce(LOEt )Cl3 ] (3), [Ce(LOEt )(OR)3 ] (4), and [Ce(LOEt )(OSiPh3 )3 ] (5), respectively. The chloride ligands in 3 are labile and can be abstracted by silver(I) salts. The treatment of 3 with AgOTs (OTs(-) =tosylate) and Ag2 O afforded [Ce(LOEt )(OTs)3 ] (6) and 1, respectively. The electrochemistry of the Ce-LOEt complexes has been studied by using cyclic voltammetry. The crystal structures of complexes 1-5 have been determined.