75503-67-2Relevant academic research and scientific papers
Probing metal-metal bond reactivity in a series of acetylene-bridged binuclear complexes and the structure of a methyl isocyanide adduct, [Rh2Cl(CNMe)2(μ-CF3C2CF 3)(Ph2PCH2PPh2)2][BF 4]
Cowie, Martin,Dickson, Raymond S.,Hames, Barry W.
, p. 1879 - 1890 (2008/10/08)
The reactions of [Rh2Cl2(μ-HFB)(DPM)2] (1), [Rh2I2(μ-HFB)(DPM)2] (2), and [Rh2Cl2(μ-DMA)(DPM)2] (3) (HFB = hexafluoro-2-butyne, DMA = dimethyl acetylenedicarboxylate) with CO, SO2, and CNMe have been investigated. With CO and SO2 the complexes [Rh2X2(μ-L)(μ-acetylene)(DPM)2] (X = Cl, I; L = CO, SO2) are obtained in which these ligands have inserted into the metal-metal bonds. The carbonyl group is more tightly bound than SO2, and the iodo complex binds these groups stronger than the analogous chloro complex. These ligands are also more tightly bound when the accompanying bridging group is DMA instead of HFB. Reactions of compounds 1, 2, and 3 with CNMe proceed first by terminal attack to give the 1:1 adducts [Rh2X2(CNMe)(μ-acetylene)(DPM)2]. Subsequent reaction with additional CNMe yields either [Rh2X(CNMe)2(μ-acetylene)(DPM)2][X] or [Rh2X2(CNMe)2(μ-acetylene)(DPM) 2], and further reaction yields [Rh2(CNMe)4(μ-acetylene)(DPM)2][X] 2. The 1:1 and 2:1 adducts are each present in two isomeric forms whose relative abundance depends on the halide and the bridging acetylene groups present. No briding isocyanide groups are observed. The structure of one of the 2:1 adducts, as the BF4- salt [Rh2Cl(CNMe)2(μ-HFB)(DPM)2][BF4] has been structurally characterized by X-ray techniques. This compound crystallizes in the space group P21/n with a = 16.366 (3) A?, b = 18.685 (3) A?, c = 20.425 (4) A?, β = 104.35 (1)°, V = 6051.1 A?3, and Z = 4. On the basis of 6800 unique observations and 367 parameters varied, the structure refined to R = 0.059 and Rw = 0.097. The complex has a bridging hexafluoro-2-butyne group, accompanying Rh-Rh bond, and a terminal Cl on one Rh center with two terminal CNMe groups on the other. This geometry is very similar to those proposed for the other isocyanide products.
Acetylene activation in binuclear rhodium complexes and the structure of [Rh2Cl2(μ-CO)(μ-CH3O2CC 2CO2CH3)(Ph2PCH2PPh 2)2]: A complex containing a bridging acetylene and a ketonic carbonyl ligand
Cowie, Martin,Southern, Timothy G.
, p. 246 - 253 (2008/10/08)
trans-[RhCl(CO)(DPM)]2 and [Rh2Cl2(μ-CO)(DPM)2] react with DMA and HFB (DMA = CH3O2CC2CO2CH3; HFB = CF3C2CF3; DPM = Ph2PCH2PPh2), yielding the complexes [Rh2Cl2(μ-CO)(μ-acetylene)(DPM)2]. The bromo and iodo derivatives have also been prepared from [Rh2Br(CO)(μ-CO)(DPM)2][Br], [Rh2Br2(μ-CO)(DPM)2], [Rh2I(CO)(μ-CO)(DPM)2][I], and [Rh2I2(μ-CO)(DPM)2]. One member of this series, [Rh2Cl2(μ-CO)(μ-DMA)(DPM)2], has been structurally characterized by X-ray crystallography. This complex crystallizes in the space group P41212 with a = 15.021 (2) A?, c = 25.738 (5) A?, and Z = 4. On the basis of 4566 unique observed reflections, the structure has been refined to R = 0.049 and Rw = 0.066. The molecule contains an acetylene ligand bound to both metals as a cis-dimetalated olefin, a bridging ketonic carbonyl ligand, and no metal-metal bond. All parameters about the acetylenic carbon atoms suggest sp2 hybridization of these atoms. Similarly, the Rh-CO-Rh angle (116.0 (4)°) and the large metal-metal separation (3.3542 (9) A?) suggest that the carbonyl carbon atom is also sp2 hybridized and bound to the metals by two localized electron-pair bonds. The 13C NMR chemical shifts for these carbonyl carbons are at unusually high field compared to those for conventional carbonyl ligands, being more comparable to the values observed for organic carbonyl groups. The complex [Rh2Cl2(μ-CO)(DPM)2] catalyzes the cyclotrimerization of DMA but not its hydrogenation. In contrast, [Rh2Cl2(μ-CO)(DPM)2] catalyzes the hydrogenation of phenylacetylene to styrene but does not bring about its cyclotrimerization.
