Methylene-Bridged Heterobinuclear Complexes of Iridium and Ruthenium:  Models for Bimetallic Fischer−Tropsch Catalysts

Abstract

The heterobinuclear complexes [IrRu(CO)3(μ-H)(dppm)2] (1) and [IrRuH(CO)3(μ-CO)(dppm)2] (2) are prepared from the reactions of [PPN][HRu(CO)4] with [IrCl(dppm)2] and [Ir(CO)(dppm)2][Cl], respectively (PPN = (Ph3P)2N; dppm = Ph2PCH2PPh2). Protonation of both monohydride species yields the dihydride [IrRu(CO)3(μ-H)2(dppm)2][BF4] (3), which under an atmosphere of carbon monoxide gives [IrRu(CO)4(dppm)2][BF4] (4). The methylene-bridged complex [IrRu(CO)3(μ-CH2)(μ-CO)(dppm)2][BF4] (5) is obtained by the reaction of compound 4 with diazomethane at ambient temperature. Although 5 does not react further with diazomethane under these conditions, carbonyl abstraction using trimethylamine oxide in the presence of CH2N2 yields the methylene-bridged ethylene adduct [IrRu(C2H4)(CO)3(μ-CH2)(dppm)2][BF4] (6). Labeling studies indicate that the majority of the 13C-labeled methylene group of 5 remains in the bridging site, with approximately 10% of the label incorporated into the ethylene formed. Compound 6 can also be prepared from 5 and ethylene in the presence of Me3NO. The compounds [IrRuL(CO)3(μ-CH2)(dppm)2][BF4] (L = NCMe, PMe3, CH2CHCN) can also be prepared from 5 in the presence of Me3NO or by ethylene displacement from 6. Although the PMe3 adduct has this group bound to Ir, as for the ethylene ligand in 6, the acrylonitrile and acetonitrile groups are bound to Ru. Furthermore, the acrylonitrile ligand is N-bound through the cyano group, analogous to the acetonitrile ligand. The structures of [IrRuH(CO)3(μ-CO)(dppm)2] (2), [IrRu(CO)3(μ-CH2)(μ-CO)(dppm)2][BF4] (5), and [IrRu(PMe3)(CO)3(μ-CH2)(dppm)2][BF4] (7) have been determined by X-ray methods. Compounds 2 and 7 have comparable edge-shared bioctahedral structures in which the geometries at the different metals in each structure are similar. The bridging carbonyl in 2 is replaced by a methylene group in 7, and the Ir-bound hydride is replaced by PMe3. Compound 5 has bridging CO and CH2 groups on opposite faces of the IrRuP4 framework with two terminal carbonyls on Ru and one on Ir.

Geminal Carbon–Hydrogen Bond Activation in Cumulenes Promoted by Adjacent Iridium/Ruthenium Centers

“…Although identification of these resonances is somewhat equivocal, with neither metal displaying coupling to the 31 P nuclei, we assign them on the basis that the Ir-bound diphosphine ends are observed at higher field than those bound to Ru, as is often the case. 12,13 Furthermore, this assignment is consistent with the 13 C{ 1 H} NMR spectra, with accompanying selective 31 P decoupling, which establishes that the pair of 13 to terminal carbonyls that couple to the Ru-bound 31 P nuclei, while the carbonyl at ca. δ 182 is coupled to the Ir-bound 31 P nuclei.…”

The rational synthesis of tetranuclear heterometallic butterfly clusters: reactions of [M2(CO)6(μ-pyS)2] (M = Re, Mn) with group VIII metal carbonyls

“…calc. for C 22 H 8 Fe 4 N 2 O 12 S: C,35.33;H,1.08;N,3.74. Found: C,35.59;H,1.17 Reaction of [ReOs 3 (CO) 13 (l 3 -pyS)] (3) with PPh 3 A CH 2 Cl 2 solution (10 mL) of Me 3 NO (10 mg, 0.133 mmol) was added drop-wise to a CH 2 Cl 2 solution (20 mL) of 3 (75 mg, 0.061 mmol) and PPh 3 (32 mg, 0.122 mmol) and the mixture was stirred at 25 1C for 2 h. The solvent was then removed under reduced pressure, and the residue chromatographed by TLC on silica gel.…”

21 Organometallic chemistry of bi- and poly-nuclear complexes

“…The formation of ethylene from diazomethane-generated methylene groups was detected when the complex was activated by CO abstraction. 208 209 Extended structures with M-M' bonded frameworks are attracting increasing interest not only as potential catalytically active species, but also as part of the search for nano-scale materials with useful chemical, electronic, magnetic and optical properties. [210][211][212][213] Mixed-metal clusters of moderate to high nuclearity have attracted increasing levels of interest, both from the wide variety of structural types they illustrate, catalytic and luminescent properties and also as a consequence of their use in the preparation of supported bimetallic nano-particles.…”