Jump to main content
Jump to site search

Issue 18, 2017
Previous Article Next Article

Benzylene-linked [PNP] scaffolds and their cyclometalated zirconium and hafnium complexes

Author affiliations

Abstract

The benzylene-linked [PNP] scaffolds HN(CH2-o-C6H4PPh2)2 ([A]H) and HN(C6H4-o-CH2PPh2)2 ([B]H) have been used for the synthesis of zirconium and hafnium complexes. For both ligands, the dimethylamides [A]M(NMe2)3 ([A]1-M) and [B]M(NMe2)3 ([B]1-M) were prepared and converted to the iodides [A]MI3 ([A]2-M) and [B]MI3 ([B]2-M) (M = Zr, Hf). Starting from these iodides, the corresponding benzyl derivatives [A]MBn3 ([A]3-M) and [B]MBn3 ([B]3-M) (M = Zr, Hf) were obtained via reaction with Bn2Mg(OEt2)2. For zirconium, the benzylic ligand positions in [A]3-Zr and [B]3-Zr were found to cyclometalate readily, which led to the corresponding κ4-[PCNP]ZrBn2 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 κ4-[PCNP]MBnCl ([B]5-M, M = Zr, Hf) were obtained in the case of ligand [B]. Upon hydrogenation of [B]5-Zr, the η6-tolyl complex [B]Zr(η6-C7H8)Cl ([B]6-Zr) was generated cleanly, but the corresponding hafnium complex [B]5-Hf was found to decompose unselectively in the presence of H2. Using a closely related carbazole-based [PNP] ligand, Gade and co-workers have shown recently that zirconium η6-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)2 ([B]7-Zr) and the 2,2′-bipyridine derivative [B]ZrCl(bipy) ([B]8-Zr), respectively. Upon reaction of [B]Zr(η6-C7H8)Cl ([B]6-Zr) with NaBEt3H, the cyclometalated derivative κ4-[PCNP]Zr(η6-C7H8) ([B]9-Zr) was isolated. In an attempt to synthesise terminal hydrides, complexes [A]MI3 ([A]2-M) were treated with KBEt3H, which led to the isolation of the cyclometalated hydrido complexes κ4-[PCNP]M(H)(κ3-Et3BH) ([A]10-M; M = Zr, Hf) featuring a κ3-bound triethyl borohydride moiety.

Graphical abstract: Benzylene-linked [PNP] scaffolds and their cyclometalated zirconium and hafnium complexes

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 02 Feb 2017, accepted on 05 Apr 2017 and first published on 12 Apr 2017


Article type: Paper
DOI: 10.1039/C7DT00413C
Citation: Dalton Trans., 2017,46, 5816-5834
  •   Request permissions

    Benzylene-linked [PNP] scaffolds and their cyclometalated zirconium and hafnium complexes

    M. Sietzen, S. Batke, P. W. Antoni, H. Wadepohl and J. Ballmann, Dalton Trans., 2017, 46, 5816
    DOI: 10.1039/C7DT00413C

Search articles by author