Heterodinuclear Metal Complexes Research Articles

Model, Mixed and Non-mixed Oxide Catalysts for the Fischer–Trøpsch Reaction Derived from [M1M2(dba)2]: M1 = Co, Ni; M2 = Co, Ni and [M1M2(daaen)]: M1 = Cu; M2 = Co. Part 1: Supported on Non-porous Powder (Cab-O-Sil™)

Homo and hetero-dinuclear metal complexes were used as precursors to model, supported, mixed and non-mixed metal oxide catalysts. These metal complexes contained either Co(II) pairs, Ni(II) pairs, or the mixed pair: Co(II)–Ni(II) having the (dba) ligands. Another mixed pair, Cu(II)–Co(II) was prepared having the (daaen) ligand. Calcination and reduction of precursor supported on silica (Cab-O-Sil™) yielded catalysts that were active for the Fischer–Tropsch reaction. In a batch reactor, both Ni2(dba)2/SiO2 and NiCo(dba)2/SiO2 catalyst gave CH4 as the major product; whereas, the CuCo(daaen)/SiO2 catalyst produced carbon nanotubes as the major product. The Co2(dba)2/SiO2 catalyst was the most stable and active one towards the production of hydrocarbons in a batch reactor. Subsequent testing in a flow reactor revealed that the cobalt catalysts showed 99% CO conversion and 67% liquid hydrocarbon selectivity.

Synthesis of homo- and heterodinuclear metal complexes with dimethylsilylene bridged unsymmetrical bis(cyclopentadienyl) ligand

The reaction of the dilithium salt Li 2[Me 2Si(C 5H 4)(C 5Me 4)] ( 2) of Me 2Si(C 5H 5)(C 5HMe 4) ( 1) with [MCl(C 8H 12)] 2 (M=Rh, Ir) and [RhCl(CO) 2] 2 afforded homodinuclear metal complexes [{Me 2Si(η 5-C 5H 4)(η 5-C 5Me 4)}{M(C 8H 12)} 2] (M=Rh: 3; M=Ir: 4) and [{Me 2Si(η 5-C 5H 4)(η 5-C 5Me 4)}Rh 2(CO) 2(μ-CO)] ( 5), respectively. The reaction of 2 with RhCl(CO)(PPh 3) 2 afforded a mononuclear metal complex [{Me 2Si(C 5HMe 4)(η 5-C 5H 4)}Rh(CO)PPh 3] ( 6) leaving the C 5HMe 4 moiety intact. Taking advantage of the difference in reactivity of the two cyclopentadienyl moieties of 2, heterodinuclear complexes were prepared in one pot. Thus, the reaction of 2 with RhCl(CO)(PPh 3) 2, followed by the treatment with [MCl(C 8H 12)] 2 (M=Rh, Ir) afforded a homodinuclear metal complex [Rh(CO)PPh 3{(η 5-C 5H 4)SiMe 2(η 5-C 5Me 4)}Rh(C 8H 12)] ( 7) consisting of two rhodium centers with different ligands and a heterodinuclear metal complex [Rh(CO)(PPh 3){(η 5-C 5H 4)SiMe 2(η 5-C 5Me 4)}Ir(C 8H 12)] ( 8). The successive treatment of 2 with [IrCl(C 8H 12)] 2 and [RhCl(C 8H 12)] 2 provided heterodinuclear metal complex [Ir(C 8H 12){(η 5-C 5H 4)SiMe 2(η 5-C 5Me 4)}Rh(C 8H 12)] ( 9). The reaction of 2 with CoCl(PPh 3) 3 and then with PhCCPh gave a mononuclear cobaltacyclopentadiene complex [{Me 2Si(C 5Me 4H)(η 5-C 5H 4)}Co(CPhCPhCPhCPh)(PPh 3)] ( 10). However, successive treatment of 2 with CoCl(PPh 3) 3, PhCCPh and [MCl(C 8H 12)] 2 in this order afforded heterodinuclear metal complexes [M(C 8H 12){(η 5-C 5H 4)SiMe 2(η 5-C 5Me 4)}Co(η 4-C 4Ph 4)] (M=Rh: 11; M=Ir: 12) in which the cobalt center was connected to the C 5Me 4 moiety. Although the heating of 10 afforded a tetraphenylcyclobutadiene complex [{Me 2Si(C 5Me 4H)(η 5-C 5H 4)}Co(η 4-C 4Ph 4)] ( 13), in which the cobalt center was connected to the C 5H 4 moiety, simple heating of the reaction mixture of 2, CoCl(PPh 3) 3 and PhCCPh resulted in the formation of a tetraphenylcyclobutadiene complex [{Me 2Si(C 5H 5)(η 5-C 5Me 4)}Co(η 4-C 4Ph 4)] ( 14), in which the cobalt center was connected to the C 5Me 4 moiety. The mechanism of the cobalt transfer was suggested based on the electrophilicity of the formal trivalent cobaltacyclopentadiene moiety. In the presence of 1,5-cyclooctadiene, the reaction of 2 with CoCl(PPh 3) 3 provided a mononuclear cobalt cyclooctadiene complex [{Me 2Si(C 5Me 4H)(η 5-C 5H 4)}Co(C 8H 12)] ( 15). The reaction of 15 with n-BuLi followed by the treatment with [MCl(C 8H 12)] 2 (M=Rh, Ir) afforded the heterodinuclear metal complexes of [Co(C 8H 12){(η 5-C 5H 4)SiMe 2(η 5-C 5Me 4)}M(C 8H 12)] (M=Rh: 16; M=Ir: 17). Treatment of 6 with Fe 2(CO) 9 at room temperature afforded a heterodinuclear metal complex [{Me 2Si(C 5HMe 4)(η 5-C 5H 4)}{Rh(PPh 3)(μ-CO) 2Fe(CO) 3}] ( 18) in which the C 5HMe 4 moiety was kept intact. Treatment of dinuclear metal complex 5 with Fe 2(CO) 9 afforded a heterotrinuclear metal complex [{(η 5-C 5H 4)SiMe 2(η 5-C 5Me 4)}{Rh(CO)Rh(μ-CO) 2Fe(CO) 3}] ( 19) having a triangular metal framework. The crystal and molecular structures of 3, 11, 12, 18 and 19 have been determined by single-crystal X-ray diffraction analysis.

Heterodinuclear metal complexes of phenol-based compartmental macrocycles

This article concerns recent progress in the derivation of heterodinuclear metal complexes from phenol-based compartmental macrocycles. Focus is placed on the design of unsymmetrical macrocycles whose two metal-binding sites, sharing two phenolic oxygens, are dissimilar with respect to the cavity size, coordination number, or the nature of donor atom. The stereochemistry, physicochemical properties and reactivities of the heterodinuclear complexes derived from these compartmental macrocycles are reviewed.

Homo- and hetero-dinuclear metal complexes of bridging ligands containing phenol and azole moieties. Structure, spectroscopy, electrochemistry and magnetochemistry

A series of phenoxo-bridged homo- and hetero-dinuclear complexes of 4-methyl-2,6-bis(5-methylpyrazol-3-yl)-phenol (H3L1) have been synthesized and characterized. Variable-temperature magnetic susceptibility measurements carried out for the homo-dinuclear complexes [Cu2(H2L1)2][ClO4]21, [Cu2(H2L1)(acac)2][ClO4]2, [Cu2(H2L1)(µ-OH)Cl2]3, [Ni2(H2L1)2(H2O)4][ClO4]24 and [Fe2(H2L1)4(µ-OH)2]·4H2O 7 have shown that in all the cases the dinuclear metal centres are antiferromagnetically coupled with the following values of the exchange coupling constant J: –242 (1), –55 (2), –170 (3), –24 (4) and –11 cm–1(7). The ESR spectra of the heterodinuclear complexes [ZnCu(H2L1)2][ClO4]2·2H2O 5 and [ZnMn(H2L1)2Cl2]6 have been examined. The 1H NMR spectra of the dicopper(II) complexes 1 and 2 are reasonably sharp and the isotropic shifts of 1 are relatively less compared to those of 2. The crystal structures of 7 and 2·CHCl3 have been determined. That of 7 comprises two edge-shared sterically non-equivalent FeO4N2 distorted octahedra. The structure of 2·CHCl3 consists of two nearly square-planar copper(II) centres supported by a phenoxide bridge. The cryomagnetic behaviour of two phenoxo-bridged dimeric iron(III) complexes derived from a bis(iminomethyl)triphenol and a bis(aminomethyl)triphenol have also been studied.