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In an attempt to synthesize heterometallic cerium nitrido complexes, we studied the reactions of cerium complexes supported by the Klaui tripodal ligand [Co(η5-C5H5){PO(OEt)2}3]- (LOEt-) with transition-metal nitrides. Whereas no reactions were found between Ce-LOEt complexes and [RuVI(LOEt)(N)Cl2] (2), treatment of the Ce(iv) oxo complex [CeIV(LOEt)2(O)(H2O)]·MeCONH2 (1) with 2 resulted in reduction of both the Ce(iv) and Ru(vi) complexes, and formation of a heterometallic Ce(iii)/Ru(iii) complex with a bridging deprotonated acetamide ligand, [(LOEt)2(H2O)CeIII{μ-O,N-MeC(O)NH}RuIII(LOEt)Cl2] (4), along with a minor product, [CeIII(LOEt)2(NO3)]. Ce(iv)-LOEt complexes such as [CeIV(LOEt)2Cl2] (3) can oxidize [ReV(LOEt)(N)(PPh3)Cl] to give the Re(vi) nitride [ReVI(LOEt)(N)(PPh3)Cl]+. Chloride abstraction of 3 by TlPF6 followed by reaction with [PPh4]2[MnV(N)(CN)4] afforded a diamagnetic red solid that is tentatively formulated as a heterometallic Ce(iv)/Mn(v) complex, [Ce(LOEt)2(H2O){Mn(N)(CN)4}] (5). Reactions of 3 with [nBu4N][MVI(N)(cat)2] (cat2- = catecholate(2-)) afforded the Ce(iii)/M(vi) complexes [(LOEt)2CeIII{(μ-cat)2MVI(N)}] [M = Ru (6), Os (7)], in which the Ce(iii) and M(vi) centers are bridged by two oxygen atoms of the two catecholate ligands. Similarly, the catecholate-bridged Ce(iii)/Re(v) complex [(LOEt)2CeIII{(μ-cat)2ReV(O)}] (8) was prepared from 3 and [Me4N][ReV(O)(cat)2]. In CH2Cl2, 8 was air-oxidized to the Ce(iii)/Re(vii) complex [CeIII(LOEt)2(H2O)2][cis-{ReVII(O)2(cat)2}] (9) with a cis-dioxo-Re(vii) counter-anion. The crystal structures of 4, 6, and 9 have been determined.

Iridium porphyrin complexes containing μ-nitrido, hydroxo, hydrosulfido, and alkynyl ligands have been synthesized and structurally characterized, and their oxidation has been studied. The alkyl-IrIII porphyrin complex [Ir(tpp)R] (tpp2- = 5,10,15,20-tetraphenylporphyrin dianion; R = C8H13; 1) was synthesized by reaction of [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) with H2tpp in refluxing monoethylene glycol. Treatment of 1 with PPh3 and [(LOEt)Ru(N)Cl2] (LOEt- = [(η5-C5H5)Co{P(O)(OEt)2}3]-) gave [Ir(tpp)(R)(PPh3)] (2) and the μ-nitrido complex [R(tpp)Ir(μ-N)RuCl2(LOEt)] (3), respectively. The cyclic voltammogram of 3 exhibited a reversible oxidation couple at 0.44 V versus Fc+/0 (Fc = ferrocene). The oxidation of 3 with [(4-BrC6H4)3N](SbCl6) resulted in Ir-C bond homolysis and formation of the chloride complex [Cl(tpp)Ir(μ-N)RuCl2(LOEt)] (4). The short Ir-N(nitrido) bond distances in 3 [1.944(3) A] and 4 [1.831(4) A] are indicative of multiple bond character and thus these two μ-nitrido complexes can be described by the two resonance forms: IrIII-N[triple bond, length as m-dash]RuVI and IrV[double bond, length as m-dash]N[double bond, length as m-dash]RuIV. Similarly, the oxidation of 2 with [(4-BrC6H4)3N](SbCl6) yielded [Ir(tpp)Cl(PPh3)] (5). Chloride abstraction of 5 with TlPF6 in tetrahydrofuran (thf) afforded [Ir(tpp)(PPh3)(thf)](PF6) (6) that reacted with CsOH·H2O and Li2S to give the hydroxo [Ir(tpp)(OH)(PPh3)] (7) and hydrosulfido [Ir(tpp)(PPh3)(SH)] (8) complexes, respectively. Treatment of 6 with phenylacetylene in the presence of CuI and Et3N yielded the bimetallic complex [Ir(tpp)(PPh3)(μ-η1:η2-C[triple bond, length as m-dash]CPh)(CuI)] (9), whereas the transmetallation of 6 with LiC[triple bond, length as m-dash]CPh afforded the mononuclear alkynyl complex [Ir(tpp)(PPh3)(C[triple bond, length as m-dash]CPh)] (10). The electrochemistry of the Ir porphyrin complexes has been studied using cyclic voltammetry. On the basis of the measured redox potentials of [Ir(tpp)(PPh3)X], the ability of X- to stabilize the IrIV state is ranked in the order: R- > PhC[triple bond, length as m-dash]C- > Cl- ∼ OH-. Oxidation of 8 and 9 with [(4-BrC6H4)3N](SbCl6) led to isolation of 5 and [Ir(tpp)(PPh3)(H2O)]+, respectively. The crystal structures of complexes 3, 4, and 7-10 have been determined.

The 4-coordinated RuII chalcogenolate complexes [Ru(STipp)2(PPh3)2] (Tipp = 2,4,6-triisopropylphenyl, 1) and [Ru(SeMes)2(PPh3)2] (Mes = 2,4,6-trimethylphenyl, 2) have been synthesized, and their reactions with PhICl2 and organic azides have been studied. Complex 2 synthesized from [RuII(PPh3)3Cl2] and NaSeMes displays a seesaw structure with P–Ru–P and Se–Ru–Se bond angles of 103.43(13) and 145.26(6)°, respectively. Natural bond order analyses revealed that in each of 1 and 2, there are two n → σ* (donor–acceptor) π interactions between the chalcogen lone pairs and the Ru–P antibonding molecular orbitals. The calculated second-order perturbation interaction energies of the two interactions for 1 (20.5 and 18.3 kcal mol−1) are stronger than those of 2 (13.6 and 11.0 kcal mol−1), suggesting the thiolate ligand (TippS−) is a stronger π-donor than the selenolate ligand (MesSe−) with respect to RuII. Chlorination of 1 with PhICl2 afforded the dichloride complex [Ru(STipp)2Cl2(PPh3)] (3), which was hydrolyzed to the hydroxo complex [Ru(STipp)2(OH)Cl(PPh3)] (4) after column chromatography on silica in air. Treatment of 4 with HCl and methyl triflate gave 3 and [Ru(STipp)2(OH)(OTf)(PPh3)] (OTf = triflate, 5), respectively. Reactions of 1 and 2 with p-tolyl azide (p-tolN3) afforded the tetrazene complexes [Ru{N4(p-tol)2}(ER)2(PPh3)] (ER = STipp (6), SeMes (7)), whereas that with tosyl azide (TsN3) gave the imido complexes [Ru(κ2-NTs)(STipp)2(PPh3)] (ER = STipp (8), SeMes (10)). The short Ru–Nimido distances in 8 [1.883(3) A] and 10 [1.892(2) A] are indicative of multiple bond character. Treatment of 8 with TsN3 afforded the tetrazene complex [Ru(N4Ts2)(STipp)2(PPh3)] (9), but no cycloaddition was found between 10 and TsN3. Nucleophilic attack of the imido ligand in 10 with methyl triflate yielded the amido complex [Ru(κ2-NMeTs)(SeMes)2(PPh3)](OTf) (11). The crystal structures of 2, 4, 6, and 8–11 have been determined.

Cerium(IV) pseudohalide complexes supported by the Klaui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]− (LOEt−) have been synthesized and structurally characterized. The treatment of [CeIV(LOEt)2Cl2] (1) with 2 equivalents of [AgX] in acetonitrile afforded [CeIV(LOEt)2X2] [X− = NCS− (2), N3− (3), F− (4)]. The reaction of 1 with [AgCN] in dichloromethane at −40 °C led to formation of a bimetallic CeIV/AgI cyanide complex that decomposed in solution at room temperature. In the presence of BPh3, 1 reacted with [AgCN] to yield the cyanoborate complex [CeIV(LOEt)2(NCBPh3)2] (6) that is stable in solution. The chlorination of [CeIII(LOEt)2(NO3)] with PhICl2 afforded [CeIV(LOEt)2(NO3)Cl] (7) that reacted with [AgCN] to yield the heterometallic CeIV/AgI cyanide complex [{Ce(LOEt)2(NO3)}2{μ-Ag(CN)2}][AgCl2] (8). The reaction of [CeIV(LOEt)Cl3] with [AgN3] afforded the tetranuclear CeIV oxo azido cluster [Ce4(LOEt)4(μ4-O)(μ2-O)2(μ2-N3)6] (9). The structures of complexes 2, 3, 6 and 9 have been established by X-ray crystallography.

Reactions of [Ce(IV)(LOEt)2Cl2] (LOEt(-) = [Co(η(5)-C5H5){P(O)(OEt)2}3](-)) and [Ce(μ-O){N(Pr(i)2PO)2}4Cl2] with PhIO afford the λ3-iodane complexes [Ce(IV)(LOEt)2{OI(Cl)Ph}2] and [Ce{N(Pr(i)2PO)2}3{OI(Cl)Ph}], respectively, whereas that between [Ce(IV)(LOEt)2Cl2] and PhIO2 or excess PhIO yields the λ5-iodane adduct [Ce(IV)(LOEt)2{OI(O)ClPh}2]. The crystal structures of the Ce(IV)λ3- and λ5-iodane complexes have been determined and their oxo transfer reactivities have been investigated.

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.

Rhenium nitrido complexes containing the Kläui tripodal ligand [Co(η(5)-C5H5){P(O)(OEt)2}3](-) (LOEt(-)) have been synthesised and their reactions with [Ir(I)(cod)Cl]2 (cod = 1,5-cyclooctadiene) and [Rh(II)2(OAc)4] (OAc(-) = acetate) have been studied. The treatment of [Bu(n)4N][Re(VI)(N)Cl4] with NaLOEt in methanol afforded the Re(VI) nitride [Re(VI)(LOEt)(N)Cl(OMe)] (1). Reactions of 1 with [Ir(I)(cod)Cl]2 and [Rh(II)2(OAc)4] gave the μ-nitrido complexes [(LOEt)(OMe)ClRe(VI)(μ-N)Ir(I)(cod)Cl] (2) and [Rh(II)2(OAc)4{(μ-N)Re(VI)(LOEt)(OMe)Cl}2] (4), respectively. [(LOEt)Cl(PPh3)Re(V)(μ-N)Ir(I)(cod)Cl] (3) and [(LOEt)Cl(PPh3)Re(VI)(μ-N)Ir(I)(cod)Cl][PF6] (3·PF6) have been synthesised from the reactions of [Ir(I)(cod)Cl]2 with [Re(V)LOEt(N)Cl(PPh3)] and [Re(VI)LOEt(N)Cl(PPh3)](PF6), respectively. Similarly, the redox pair [Rh(II)2(OAc)4{(μ-N)Re(V)(LOEt)(PPh3)Cl}2] (5) and [Rh(II)2(OAc)4{(μ-N)Re(VI)(LOEt)(PPh3)Cl}2](PF6)2 (·(PF6)2) have been synthesised from the reactions of [Rh2(OAc)4] with [Re(V)LOEt(N)Cl(PPh3)] and [Re(VI)LOEt(N)Cl(PPh3)](PF6), respectively. While [(LOEt)Cl2Ru(VI)(μ-N)Ir(I)(cod)] (6) was obtained from [Ru(VI)(LOEt)(N)Cl2] and [Ir(I)(cod)Cl]2, the interaction between [Ru(VI)(LOEt)(N)Cl2] and [Rh(II)2(OAc)4] in CH2Cl2 is reversible. The crystal structures of complexes 2, 3, 3·PF6, 5, 5·(PF6)2 and 6 have been determined. X-ray crystallography indicates that the nitrido bridges in 2, 3, 3·PF6 and 6 can be described as MN-Ir (M = Re, Ru) showing Ir-N multiple bond character, whereas the interaction between Re≡N and Rh in 5 and 5·(PF6)2 is mostly of the donor-acceptor type. The electrochemistry of the Re nitrido complexes has been investigated by cyclic voltammetry.

Treatment of [(L(OEt))(2)Ti(2)(mu-O)(2)(mu-SO(4))] (L(OEt)(-) = [(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)}(3)](-)) with [Ru(H)(Cl)(CO)(PPh(3))(3)] and Ag(OTf) (OTf(-) = triflate) in the presence of Na(2)CO(3) gave the Ti(IV)-Ru(II) complex [(L(OEt))(2)Ti(2)(mu-O)(3)(mu(3)-SO(4))Ru(CO)(PPh(3))(2)] (2) whereas that with [Re(CO)(5)(OTf)] afforded the Ti(IV)-Re(I) complex [H(L(OEt))(2)Ti(2)(mu-O)(3)(mu-SO(4))Re(CO)(3)(H(2)O)] (3). The crystal structures of complexes 2.HOTf and [3.2/3(Et(3)NHOTf).5/12(H(2)O)](3) have been determined. Complex 2 consists of an adamantane-like Ti(2)RuSO(6) core, in which the {Ru(II)(PPh(3))(2)(CO)} moiety is facially coordinated to a tridentate-O,O',O''(sulfate) [(L(OEt))(2)Ti(2)(mu-O)(3)(mu(3)-SO(4))](2-) metalloligand. The anion [(L(OEt))(2)Ti(2)(mu-O)(3)(mu-SO(4))Re(CO)(3)(H(2)O)](-) in 3 can be viewed as consisting of a fac-{Re(I)(CO)(3)} fragment coordinated with one aqua ligand and a bidentate-O,O'-[(L(OEt))(2)Ti(2)(mu-O)(3)(mu-SO(4))](2-) metalloligand.