Hydride Transfer to Gold: Yes or No? Exploring the Unexpected Versatility of Au···H‐M Bonding in Heterobimetallic Dihydrides

Luca Rocchigiani, Wim Klooster, Simon J. Coles, David Hughes, Peter Hrobarik, Manfred Bochmann

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Abstract

The potential for coordination and H-transfer from Cp2MH2 (M = Zr, W) to gold(I) and gold(III) complexes was explored in a combined experimental and computational study. [(L)Au]+ cations react with Cp2WH2 giving [(L)Au(κ2-H2WCp2)]+ (L = IPr (1), cyclic (alkyl)(amino)carbene (2), or phosphines PPh3 (3) and Dalphos-Me (4) [IPr = 1,3-bis(diisopropylphenyl)imidazolylidene; Dalphos-Me = di(1-adamantyl)-2-(dimethylamino)phenyl-phosphine], while [Au(DMAP)2]+ (DMAP = p-dimethylaminopyridine) affords the C2-symmetric [Au(κ-H2WCp2)2]+ (5). The Dalphos complex 4 can be protonated to give the bicationic adduct 4H, showing Au(I)…H+-N hydrogen bonding. The gold(III) Lewis acid [(C^N-CH)Au(C6F5)(OEt2)]+ binds Cp2WH2 to give an Au-H-W σ-complex. By contrast, the pincer species [(C^N^C)Au]+ adds Cp2WH2 by a purely dative W→Au bond, without Au···H interaction. The biphenyl-based chelate [(C^C)Au]+ forms [(C^C)Au(µH)2WCp2]+, with two 2-electron-3-centre W-H…Au interactions and practically no Au-W donor acceptor contribution. In all these complexes strong but polarised W-H bonds are maintained, without H-transfer to gold. On the other hand, the reactions of Cp2ZrH2 with gold complexes led in all cases to rapid H-transfer and formation of gold hydrides. Relativistic DFT calculations were used to rationalize the striking reactivity and bonding differences in these heterobimetallic hydride complexes along with an analysis of their characteristic NMR parameters and UV-Vis absorption properties.
Original languageEnglish
Pages (from-to)8267-8280
Number of pages14
JournalChemistry - A European Journal
Volume26
Issue number37
Early online date26 Feb 2020
DOIs
Publication statusPublished - 2 Jul 2020

Keywords

  • bridging ligands
  • density functional calculations
  • gold
  • hydrides
  • tungsten

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