Early-late, mixed-metal compounds supported by amidophosphine ligands.
Early-late, mixed-metal compounds supported by amidophosphine ligands.
复制标题
由酰胺基膦配体支持的早期-晚期混合金属化合物。
作者：
Q. F. Mokuolu;Paul A. Duckmanton;P. Hitchcock;Claire Wilson;A. Blake;Lena Shukla;J. Love
描述了由独特的酰胺基膦配体 m-(But2CH)N(C6H4)PPh2L1 支持的一系列离散的早期-晚期混合金属配合物的顺序合成、结构表征和反应性研究。该配体使用席夫碱/ButLi方案合成，所得锂盐LiL1采用固态四聚结构，其中存在双配位N-Li-N和eta6:eta6-芳基Li茂金属键合基序。 HL1 与不稳定的 Pt(II) 和 Pd(II) 氯化物之间的反应形成 MCl2(HL1)2 配合物 4 (M = Pt) 和 5 (M = Pd)，其中在 4 的固态结构中发现了弱的 N-H...pi(芳基) 氢键相互作用。这些化合物被发现对与 Ti 酰胺和烷基的转氨基和质子解反应呈惰性；相反，观察到从Ti到Pt的逐步烷基转移，产生Pt(CH2SiMe3)2(HL1)2 6。使用早期金属优先的方法获得了混合金属配合物。金属配体 TiCl2(L1)2 与不稳定的第 10 族和第 9 族化合物之间的反应导致形成 TiCl2(mu-L1)2PtCl2 8、TiCl2(mu-L1)2PtMe2 9、TiCl2(mu-L1)2PdCl2 10、TiCl2(mu-L1)2NiBr2 11 和[TiCl2(mu-L1)2RhCl(CO)]2 12. 在固态下，第 4/10 族化合物 8、9 和 10 采用相似的结构，同时表现出分子内 But2C-H...Cl-Ti 氢键和芳基 NP π 堆积相互作用；这种氢键相互作用在溶液中是保守的。与上述4/10族配合物不同，Ti-Rh配合物12采用固态四核结构，通过类似的氢键和π堆积相互作用稳定。 4/10族配合物被评估为烯烃聚合和交叉偶联反应的催化剂。与MAO结合，混合金属配合物8和10是较差的乙烯聚合催化剂，并产生高分子量和多分散性的聚合物。 Ti-Ni配合物11仅形成低聚材料，而单核Ti金属配体TiCl2(L1)2给出了最好的结果，显示出低活性(6.14 kg mol(-1) bar(-1) h(-1))和中等多分散性(12)。 Ti-Pd 络合物 10 在芳基化和 Suzuki-Miyaura 反应中进行了评估。虽然在芳基化反应中观察到很少或没有催化活性，但发现 10 在 80 摄氏度下可以影响活化的芳基溴和苯基硼酸之间的 Suzuki 偶联。与 TiCl2(L1)2 不同，8 和还原剂 C8K 或 Mg 之间的反应会产生难以处理的混合物。然而，两种化合物的循环伏安法表明，在相似的电位（约-0.7 V）下发生可逆的单电子还原过程，并被认为是形成一卤化物TiCl(L1)2和TiCl(mu-L1)2PtCl2。还研究了金属定位 TiCl(mu-L3)3Pt 的反应性。虽然还原反应不成功，但金属笼与 CO 反应形成 Ti-Pt 羰基，TiCl(mu-L3)3Pt(CO) 13。 13 的 X 射线晶体结构表明，CO 在 Pt 中心的容纳导致了笼的膨胀和失控芳基-H...Pt 相互作用的丧失。此外，TiCl(mu-L3)3Pt 与过量 MeI 的反应导致形成 Ti(IV)-Pt(II) 络合物反式 TiCl2(mu-L3)2(kappa1-L3MeI)Pt(Me)I。
The sequential syntheses, structural characterisation and reactivity studies of a series of discrete early-late mixed-metal complexes supported by the unique amidophosphine ligand m-(But2CH)N(C6H4)PPh2L1 are described. This ligand was synthesised using a Schiff-base/ButLi protocol and the resultant lithium salt LiL1 found to adopt a tetrameric structure in the solid state in which both two-coordinate N-Li-N and eta6:eta6-arylLi metallocene bonding motifs are present. Reaction between HL1 and labile Pt(II) and Pd(II) chlorides formed MCl2(HL1)2 complexes 4 (M = Pt) and 5 (M = Pd) in which a weak N-H...pi(aryl) hydrogen bonding interaction was identified in the solid-state structure of 4. These compounds were found to be inert to transamination and protonolysis reactions with Ti amides and alkyls; instead, stepwise alkyl transfer from Ti to Pt, resulting in Pt(CH2SiMe3)2(HL1)2 6 was observed. Access to mixed-metal complexes was achieved using an early-metal-first approach. Reaction between the metalloligand TiCl2(L1)2 and labile Group 10 and group 9 compounds resulted in the formation of TiCl2(mu-L1)2PtCl2 8, TiCl2(mu-L1)2PtMe2 9, TiCl2(mu-L1)2PdCl2 10, TiCl2(mu-L1)2NiBr2 11, and [TiCl2(mu-L1)2RhCl(CO)]2 12. In the solid state, the Group 4/10 compounds 8, 9 and 10 adopt similar structures that exhibit both intramolecular But2C-H...Cl-Ti hydrogen bonding and arylNP pi-stacking interactions; this hydrogen-bonding interaction is conserved in solution. Unlike the above Group 4/10 complexes, the Ti-Rh complex 12 adopts a tetranuclear structure in the solid state that is stabilised by similar hydrogen-bonding and pi-stacking interactions. The Group 4/10 complexes were assessed as catalysts for olefin polymerisation and cross-coupling reactions. In combination with MAO, the mixed-metal complexes 8 and 10 were poor ethylene polymerisation catalysts and resulted in polymers of both high molecular weight and polydispersity. The Ti-Ni complex 11 formed oligomeric material only, while the mononuclear Ti metalloligand TiCl2(L1)2 gave the best results, showing low activity (6.14 kg mol(-1) bar(-1) h(-1)) and moderate polydispersity (12). The Ti-Pd complex 10 was assessed in arylamination and Suzuki-Miyaura reactions. While little or no catalytic activity was observed in arylamination reactions, 10 was found to effect Suzuki coupling between activated aryl bromides and phenylboronic acid at 80 degrees C. Unlike with TiCl2(L1)2, reactions between 8 and the reducing agents C8K or Mg led to intractable mixtures. However, the cyclic voltammetry of both compounds indicated that a reversible one-electron reduction process occurs at a similar potential (ca. -0.7 V) and was assigned to the formation of the monohalides TiCl(L1)2 and TiCl(mu-L1)2PtCl2. The reactivity of the metallocage TiCl(mu-L3)3Pt was also investigated. While reduction reactions were unsuccessful, the metallocage reacted with CO to form the Ti-Pt carbonyl, TiCl(mu-L3)3Pt(CO) 13. The X-ray crystal structure of 13 revealed that accommodation of CO at the Pt centre has caused the cage expansion and loss of agostic aryl-H...Pt interactions. Furthermore, reaction of TiCl(mu-L3)3Pt with excess MeI resulted in the formation of the Ti(IV)-Pt(II) complex trans-TiCl2(mu-L3)2(kappa1-L3MeI)Pt(Me)I.