Sietzen Malte, Batke Sonja, Antoni Patrick W, Wadepohl Hubert, Ballmann Joachim
Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 276, 69120 Heidelberg, Germany.
Dalton Trans. 2017 May 9;46(18):5816-5834. doi: 10.1039/c7dt00413c.
The benzylene-linked [PNP] scaffolds HN(CH-o-CHPPh) ([A]H) and HN(CH-o-CHPPh) ([B]H) have been used for the synthesis of zirconium and hafnium complexes. For both ligands, the dimethylamides [A]M(NMe) ([A]1-M) and [B]M(NMe) ([B]1-M) were prepared and converted to the iodides [A]MI ([A]2-M) and [B]MI ([B]2-M) (M = Zr, Hf). Starting from these iodides, the corresponding benzyl derivatives [A]MBn ([A]3-M) and [B]MBn ([B]3-M) (M = Zr, Hf) were obtained via reaction with BnMg(OEt). For zirconium, the benzylic ligand positions in [A]3-Zr and [B]3-Zr were found to cyclometalate readily, which led to the corresponding κ-[PCNP]ZrBn complexes [A]4-Zr and [B]4-Zr. As these complexes failed to hydrogenate cleanly, cyclometalated derivatives with only one alkyl substituent were targeted and the mixed benzyl chlorides κ-[PCNP]MBnCl ([B]5-M, M = Zr, Hf) were obtained in the case of ligand [B]. Upon hydrogenation of [B]5-Zr, the η-tolyl complex [B]Zr(η-CH)Cl ([B]6-Zr) was generated cleanly, but the corresponding hafnium complex [B]5-Hf was found to decompose unselectively in the presence of H. Using a closely related carbazole-based [PNP] ligand, Gade and co-workers have shown recently that zirconium η-arene complexes similar to [B]6-Zr may serve as zirconium(ii) synthons, namely when reacted with 2,6-Dipp-NC (L) or pyridine (py). Both these substrates were shown to react cleanly with [B]6-Zr, which led to the formation of the bis-isocyanide complex [B]ZrCl(L) ([B]7-Zr) and the 2,2'-bipyridine derivative [B]ZrCl(bipy) ([B]8-Zr), respectively. Upon reaction of [B]Zr(η-CH)Cl ([B]6-Zr) with NaBEtH, the cyclometalated derivative κ-[PCNP]Zr(η-CH) ([B]9-Zr) was isolated. In an attempt to synthesise terminal hydrides, complexes [A]MI ([A]2-M) were treated with KBEtH, which led to the isolation of the cyclometalated hydrido complexes κ-[PCNP]M(H)(κ-EtBH) ([A]10-M; M = Zr, Hf) featuring a κ-bound triethyl borohydride moiety.
与亚苄基相连的[PNP]支架HN(CH-o-CHPPh) ([A]H)和HN(CH-o-CHPPh) ([B]H)已被用于合成锆和铪配合物。对于这两种配体，制备了二甲基酰胺[A]M(NMe) ([A]1-M)和[B]M(NMe) ([B]1-M)，并将其转化为碘化物[A]MI ([A]2-M)和[B]MI ([B]2-M)（M = Zr，Hf）。从这些碘化物出发，通过与BnMg(OEt)反应得到了相应的苄基衍生物[A]MBn ([A]3-M)和[B]MBn ([B]3-M)（M = Zr，Hf）。对于锆，发现[A]3-Zr和[B]3-Zr中的苄基配体位置很容易发生环金属化，这导致了相应的κ-[PCNP]ZrBn配合物[A]4-Zr和[B]4-Zr的形成。由于这些配合物不能顺利进行氢化反应，因此目标是合成只有一个烷基取代基的环金属化衍生物，在配体[B]的情况下得到了混合苄基氯化物κ-[PCNP]MBnCl（[B]5-M，M = Zr，Hf）。对[B]5-Zr进行氢化反应时，干净地生成了η-甲苯基配合物[B]Zr(η-CH)Cl（[B]6-Zr），但发现相应的铪配合物[B]5-Hf在氢气存在下会无选择性地分解。使用一种密切相关的咔唑基[PNP]配体，Gade及其同事最近表明，类似于[B]6-Zr的锆η-芳烃配合物可以作为锆(ii)合成子使用，即在与2,6-Dipp-NC（L）或吡啶（py）反应时。结果表明，这两种底物都能与[B]6-Zr顺利反应，分别生成双异氰化物配合物[B]ZrCl(L)（[B]7-Zr）和2,2'-联吡啶衍生物[B]ZrCl(bipy)（[B]8-Zr）。[B]Zr(η-CH)Cl（[B]6-Zr）与NaBEtH反应后，分离得到了环金属化衍生物κ-[PCNP]Zr(η-CH)（[B]9-Zr）。为了尝试合成末端氢化物，用KBEtH处理配合物[A]MI（[A]2-M），这导致分离得到了环金属化氢化物配合物κ-[PCNP]M(H)(κ-EtBH)（[A]10-M；M = Zr，Hf），其具有一个κ-键合的三乙基硼氢化物部分。
