Diversification of the Carbodicarbene Class by Embedding an Anionic Component in its Scaffold.

Carbodicarbene (CDC) has become an emerging ligand in many fields due to its strong σ-donating ability.

Carbodicarbene: geminal-Bimetallic Coordination in Selective Manner.

The reaction of Pd(OAc)2 with free carbodicarbene (CDC) generates a Pd acetate trinuclear complex 1 via intramolecular C(sp3 )-H bond activation at one of the CDC methyl side arms. The solid structure of 1 reveals the capability of CDC to facilitate a double dative bond with two palladium centers in geminal fashion. This is attributed to the chelating mode of CDC, which can frustrate π-conjugation within the CDC framework. Such effect maybe also amplified by ligand-ligand interaction. The formation of other gem-bimetallic Pd-Pd, Pd-Au, and Ni-Au provides further structural evidence for this proof-of-concept in selective installation. Structural analysis is supported by computational calculations based on state-of-the-art energy decomposition analysis (EDA) in conjunction with natural orbitals for chemical valence (NOCV) method.

Reactions of cerium complexes with transition metal nitrides: synthesis and structure of heterometallic cerium complexes containing bridging catecholate ligands.

In an attempt to synthesize heterometallic cerium nitrido complexes, we studied the reactions of cerium complexes supported by the Kläui 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.

A Combined Experimental and Theoretical Study of the Versatile Reactivity of an Oxocerium(IV) Complex: Concerted Versus Reductive Addition.

A combined experimental and theoretical investigation on the cerium(IV) oxo complex [(LOEt )2 Ce(=O)(H2 O)]⋅MeC(O)NH2 (1; LOEt - =[Co(η5 -C5 H5 ){P(O)(OEt)2 }3 ]- ) demonstrates that the intermediate spin-state nature of the ground state of the cerium complex is responsible for the versatility of its reactivity towards small molecules such as CO, CO2 , SO2 , and NO. CASSCF calculations together with magnetic susceptibility measurements indicate that the ground state of the cerium complex is of multiconfigurational character and comprised of 74 % of CeIV and 26 % of CeIII . The latter is found to be responsible for its reductive addition behavior towards CO, SO2 , and NO. This is the first report to date on the influence of the multiconfigurational ground state on the reactivity of a metal-oxo complex.

One-Pot Tandem Photoredox and Cross-Coupling Catalysis with a Single Palladium Carbodicarbene Complex.

The combination of conventional transition-metal-catalyzed coupling (2 e- process) and photoredox catalysis (1 e- process) has emerged as a powerful approach to catalyze difficult cross-coupling reactions under mild reaction conditions. Reported is a palladium carbodicarbene (CDC) complex that mediates both a Suzuki-Miyaura coupling and photoredox catalysis for C-N bond formation upon visible-light irradiation. These two catalytic pathways can be combined to promote both conventional transition-metal-catalyzed coupling and photoredox catalysis to mediate C-H arylation under ambient conditions with a single catalyst in an efficient one-pot process.

Tetravalent cerium pseudohalide complexes supported by the Kläui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3].

Cerium(iv) pseudohalide complexes supported by the Kläui 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.

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.

Iodosylbenzene and iodylbenzene adducts of cerium(IV) complexes bearing chelating oxygen ligands.

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.

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.