Hohloch Stephan, Garner Mary E, Parker Bernard F, Arnold John
Department of Chemistry, University of California, Berkeley, CA 94720, USA.
Dalton Trans. 2017 Oct 17;46(40):13768-13782. doi: 10.1039/c7dt02682j.
We report the synthesis, characterization, and preliminary reactivity of new heteroleptic thorium and uranium complexes supported by the macrocyclic TMTAA ligand (TMTAA = Tetramethyl-tetra-aza-annulene). The dihalide complexes Th(TMTAA)Cl(THF) (1), [UCl(TMTAA)] (2) and U(TMTAA)I (3) are further functionalized to the Cp* derivatives ThCp*(TMTAA)Cl (4), UCp*(TMTAA)Cl (5) and UCp*(TMTAA)I (6) (Cp* = pentamethylcyclopentadienide). Compounds 4-6 are also obtained through a one-pot reaction from standard thorium(iv) and uranium(iv) starting materials, Li2TMTAA and KCp*. Complexes 1-6 function as valuable starting materials for salt metathesis chemistry. Treatment of precursors 4 or 5 with trimethylsilylmethyllithium (LiCHTMS) results in the new actinide TMTAA alkyl complexes ThCp*(TMTAA)(CHTMS) (7) and UCp*(TMTAA)(CHTMTS) (8), respectively. The TMTAA-derived alkyl complexes (7 and 8) show unexpected stability and are stable for several weeks at room temperature in solution and in the solid-state. Additionally, double substitution of the halide ligands in 1-3 shows a strong dependence on the nucleophile used. While weaker nucleophiles, such as amides, and more sterically demanding nucleophiles, such as Cp (Cp = cyclopenadienide), favour the formation of bis-TMTAA "sandwich" complexes [An(TMTAA)] (An = Th (9) and An = U (10)), the use of oxygen-functionalized ligands like the ODipp anion (Dipp = diisopropylphenyl) results in the formation of the doubly substituted species Th(ODipp)TMTAA (11) and U(ODipp)TMTAA (12). We also describe the divergent reactivity of the TMTAA ligand towards uranium(iii). Unlike the syntheses of actinide(iv) TMTAA complexes, the synthesis of a uranium(iii) TMTAA was not successful and only uranium(iv) species could be obtained.
我们报道了由大环TMTAA配体（TMTAA = 四甲基 - 四氮杂环壬四烯）支撑的新型杂配钍和铀配合物的合成、表征及初步反应活性。二卤化物配合物Th(TMTAA)Cl(THF)（1）、[UCl(TMTAA)]（2）和U(TMTAA)I（3）进一步官能团化为Cp衍生物ThCp(TMTAA)Cl（4）、UCp*(TMTAA)Cl（5）和UCp*(TMTAA)I（6）（Cp* = 五甲基环戊二烯基）。化合物4 - 6也可通过由标准钍(IV)和铀(IV)起始原料Li2TMTAA和KCp进行的一锅法反应制得。配合物1 - 6作为盐复分解化学中有价值的起始原料。用三甲基硅基甲基锂（LiCHTMS）处理前体4或5分别得到新的锕系TMTAA烷基配合物ThCp(TMTAA)(CHTMS)（7）和UCp*(TMTAA)(CHTMTS)（8）。源自TMTAA的烷基配合物（7和8）表现出意想不到的稳定性，在室温下于溶液和固态中可稳定存在数周。此外，1 - 3中卤化物配体的双取代显示出对所用亲核试剂的强烈依赖性。较弱亲核试剂如酰胺，以及空间位阻较大的亲核试剂如Cp（Cp = 环戊二烯基），有利于形成双 - TMTAA“夹心”配合物[An(TMTAA)]（An = Th（9）且An = U（10）），而使用像ODipp阴离子（Dipp = 二异丙基苯基）这样的氧官能化配体则导致形成双取代物种Th(ODipp)TMTAA（11）和U(ODipp)TMTAA（12）。我们还描述了TMTAA配体对铀(III)的不同反应活性。与锕系(IV) TMTAA配合物的合成不同，铀(III) TMTAA的合成未成功，只能得到铀(IV)物种。
