Dinuclear and Tetranuclear Gold-Nitrogen Complexes. Solvent Influences on Oxidation and Nuclearity of Gold Guanidinate Derivatives

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• 作者：Ahmed A. Mohamed ; Andrew P. Mayer ; Hanan E. Abdou ; Michael D. Irwin ; Lisa M. Pé ; rez ; John P. Fackler ; Jr.
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：December 24, 2007
• 年：2007
• 卷：46
• 期：26
• 页码：11165 - 11172
• 全文大小：385K
• 年卷期：v.46,no.26(December 24, 2007)
• ISSN：1520-510X

文摘

The sodium salt of the Hhpp ligand, Hhpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, a 6,6 bicyclic,guanidine system, reacts with (THT)AuCl (THT = tetrahydrothiophene) in THF or CH₂Cl₂ to form the Au(II) complex,[Au₂(hpp)₂Cl₂]. The Au(II) complex forms either by oxidation with solvents such as CH₂Cl₂ or disproportionation ofAu(I) with concomitant Au(0) formation. The reaction in ethanol gives the colorless tetranuclear Au(I) complex,[Au₄(hpp)₄]. The tbo ligand, Htbo = 1,4,6-triazabicyclo[3.3.0]oct-4-ene a bicyclic 5,5 guanidine system, behaveddifferently from the hpp ligand, and only the colorless tetranuclear gold complex, [Au₄(tbo)₄], formed in THF,CH₂Cl₂, or ethanol. The X-ray structure of the oxidized species, [Au₂(hpp)₂Cl₂], shows a Au(II)-Au(II) distance of2.4752(9) Å, the shortest gold-gold bond reported prior to the characterization here of the [(PhCOO)₆Au₄(hpp)₂Ag₂], Au(II)-Au(II) = 2.4473(19) Å. A preliminary description of the formation of this material, obtained by reacting[Au₂(hpp)₂Cl₂] with Ag(OOCPh), is included in this paper. The four Au(I) atoms in the tetranuclear complexes arearranged in a parallelogram with Au-Au distances ranging from 2.8975(5)-2.9392(6) Å in [Au₄(hpp)₄] and 3.1139(12)-3.2220(13) Å in [Au₄(tbo)₄]. density functional theory (DFT) and MP2 calculations on [Au₂(hpp)₂Cl₂] find thatthe highest occupied molecular orbital (HOMO) is predominately hpp and chlorine-based with some Au-Au *character. The lowest unoccupied molecular orbital (LUMO) has metal-to-ligand (M-L) and metal-to-metal (M-M)* character (approximately 50% hpp/chlorine, and 50% gold). DFT calculations on [Au₄(hpp)₄] show that theHOMO and HOMO-1 are each a mixture of metal-metal antibonding character and metal-ligand antibonding characterand that the LUMO is predominately metal based s character (85% Au and 15% hpp).