Author : Raymond Stanley Dickson
Release : 1984
Genre : Chemistry
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Structural and Reactivity Studies on Binuclear Metal Complexes - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Structural and Reactivity Studies on Binuclear Metal Complexes write by Raymond Stanley Dickson. This book was released on 1984. Structural and Reactivity Studies on Binuclear Metal Complexes available in PDF, EPUB and Kindle. This thesis describes the synthesis and characterization of some diphosphine-bridged, binuclear rhodium complexes which contain bridging acetylene ligands, and some chemistry of these complexes with selected small molecules. The X-ray crystal structure of an unusual ironpalladium-bonded heterobinuclear complex is also reported. The complexes [Rh2x2([Mu]-RCCR)(DPM)2] (I: X = Cl, R = CF3; 2: X = I, R = CF3; 3: X = Cl, R = C02CH3; DPM = bis(diphenylphosphino)methane) were synthesized by the reaction of [RhCl(C8H12)]2 and two equivalents of DPM with the appropriate activated acetylene, CF3C2CF3(hexa-fluoro2-butyne, HFB) or CH3O(O)CC2C(O)OCH3(dimethylacetylenedicarboxylate, DMA), followed by halide metathesis of 1 with KI to obtain 2. The crystal structure of [Rh2Cl2([Mu]-HFB)(DPM)2] (1) was determined to establish the mode of acetylene binding in this complex (space group P43, a = 21.283(1) A, c = 14.255(1) A, z = 4; 5243 unique reflections; R = 0.040, Rw = 0.055). The complex was shown to be a distorted "A-frame" complex, having a metal-metal bond (Rh(1)-Rh(2) = 2.7447(9) A), two terminal chloride ligands and a bridging acetylene moiety coordinated parallel to the metal-metal axis, as a so-called cisdimetallated olefin. Most parameters of this group suggested sp2 hybridization of the central two carbon atoms. The reactions of compouns 1, 2 and 3 with CO and SO2 were reversible and gave products in which these small molecules had inserted into the Rh-Rh bonds. Protonation by the strong acids CF3SO3H and HBF4•(C2H5)2o also occurred reversibly at the metal-metal bonds and was most probably accompanied by anion coordination at one metal centre. However, methyl isocyanide (CNMe) reacted quite differently, yielding complexes in which the isocyanide ligands are bound terminally. Although all of compounds 1 - 3 reacted with CNMe in a rather analogous manner there were some subtle differences observed. Stepwise addition of CNMe to compound 1 yielded two unsymmetrical, isomeric 1:1 adducts, [Rh2Cl2 (CNMe) (Mu-HFB ) (DPM)2], followed by a 2:1 adduct, [Rh2Cl(CNMe)2(Mu-HFB)(DPM)2] [Cl] , and finally by a 4:1 adduct [Rh(CNMe)4(Mu-HFB)(DPM)2][Cl]2. The iodo analogue species 2 gave analogous products except that the isomer ratio of the 1:1 adduct differed and a second symmetric 2:1 adduct, [Rh2I2(CNMe)2(Mu-HFB)(DPM)2], was also observed. With the DMA-bridged species 3 only one 1:1 adduct was observed and all other products were analogous to the reactions of compound 1. The unsymmetrical 2:1 adduct of compound 1 was isolated as the BF4- salt, [Rh2Cl(CNMe)2(Mu-HFB)-(DPM)2][BF4]. Its X-ray crystal structure determination (space group P21/n, a = 16.366(3) A, b = 18.685(3) A, c = 20.425(4) A, [Beta] = 104.35(1)°, Z = 4; 6800 unique observations; R = 0.059, Rw = 0.097) showed that the metalmetal bonded complex retained the cis-dimetallated olefinic binding mode of the acetylene group; one metal had a terminal chloro ligand whereas the other had two terminal CNMe groups. [(PPh3)PdFe(SC5H4)2] was prepared and crystallized as the hemitoluene solvate by Mr. T.G. Rucker, Dr. B.W. Hames and Dr. Dietmar Seyferth at M.I.T., via the reaction of Pd(PPh3)4 with Fe(C5H4)2S3. The X-ray crystal structure (space group C2/c, a = 39.258(5) A, b = 10.548(2) A, c = 13.612(4) A, [Beta] = 101.69(2)°, Z = 8; 3255 unique observed reflections; R = 0.040, Rw = 0.046) showed that the compound had an unusual iron-palladium dative-bonded structure (Fe[right arrow]Pd = 2.878(1) A) with the palladium chelated at trans positions by the two cyclopentadienethiolato sulfurs. The triphenylphosphine ligand is attached to the palladium trans to the metal-metal bond. The tilt angle found between the two cyclopentadienthiolate rings was only 19.6°, about half of those observed for other Cp2MLn compounds.