蟽- vs 蟺-Bonding in Manganese(II) Allyl Complexes

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• 作者：Laura K. Engerer ; Christin N. Carlson ; Timothy P. Hanusa ; William W. Brennessel ; Victor G. Young ; Jr.
• 刊名：Organometallics
• 出版年：2012
• 出版时间：September 10, 2012
• 年：2012
• 卷：31
• 期：17
• 页码：6131-6138
• 全文大小：445K
• 年卷期：v.31,no.17(September 10, 2012)
• ISSN：1520-6041

文摘

Reaction of two equivalents of K[1,3-(SiMe₃)₂C₃H₃] (= K[A鈥瞉) with MnCl₂ in THF produces the allyl complex A鈥?sub>2Mn(thf)₂; if the reaction is conducted in ether, the solvent-free heterometallic manganate species K₂MnA鈥?sub>4 is isolated instead. With the related allyl K[1,1鈥?3-(SiMe₃)₃C₃H₂] (= K[A鈥砞), reaction with MnCl₂ in THF/TMEDA produces the corresponding adduct A鈥?sub>2Mn(tmeda). In the solid state, both A鈥?sub>2Mn(thf)₂ and A鈥?sub>2Mn(tmeda) are monomeric complexes with 蟽-bonded allyl ligands (Mn鈥揅 = 2.174(2) and 2.189(2) 脜, respectively). In contrast, K₂MnA鈥?sub>4 is a two-dimensional coordination polymer, in which two of the allyl ligands on the Mn cation are 蟽-bonded (Mn鈥揅 = 2.197(6), 2.232(7) 脜) and the third is 蟺-bonded (Mn鈥揅 = 2.342(7)鈥?.477(7) 脜). Both 蟽-allyls are 蟺-coordinated to potassium cations, promoting the polymer in two directions; the 蟺-allyl ligand is terminal. Density functional theory (DFT) calculations indicate that isolated high-spin (C₃R₂H₃)₂Mn (R = H, SiMe₃) complexes would possess 蟺-bound ligands. A mixed hapticity (蟺-allyl)(蟽-allyl)MnE structure would result with the addition of either a neutral ligand (e.g., THF, MeCN) or one that is charged (Cl, H). Both allyl ligands in a bis(allyl)manganese complex are expected to adopt a 蟽-bonded mode if two THF ligands are added, as is experimentally observed in A鈥?sub>2Mn(thf)₂. The geometry of allyl鈥揗n(II) bonding is readily modified; DFT results predict that [(C₃H₅)Mn]⁺ and (C₃H₅)MnCl should be 蟽-bonded, but the allyl in (C₃H₅)MnH is found to exhibit a symmetrical 蟺-bonded arrangement. Some of this behavior is reminiscent of that found in bis(allyl)magnesium chemistry.