Synthesis of Hybrid Ligands with Nitrile and Cage Phosphane Donor Groups and their Applications in Gold-Mediated Reactions

Filip Horký; Maren Neubrand; Ivana Císařová; Jiří Schulz; Petr Štěpnička

doi:10.1002/cplu.202300196

Synthesis of Hybrid Ligands with Nitrile and Cage Phosphane Donor Groups and their Applications in Gold-Mediated Reactions

Chempluschem. 2023 Aug;88(8):e202300196. doi: 10.1002/cplu.202300196. Epub 2023 Jun 20.

Authors

Filip Horký¹, Maren Neubrand^{1

2}, Ivana Císařová¹, Jiří Schulz¹, Petr Štěpnička¹

Affiliations

¹ Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40, Prague, Czech Republic.
² Visiting Erasmus student from, Institute of Inorganic Chemistry, University of Stuttgart (Germany).

PMID: 37283065
DOI: 10.1002/cplu.202300196

Abstract

Altering the donor properties of phosphane ligands through substituent variation is an established tool in coordination chemistry and catalysis. This contribution describes the synthesis of two new hybrid donors (L) combining 1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphaadamantane-8-yl (PCg) and nitrile donor groups at different molecular scaffolds, viz. ferrocene-1,1'-diyl (fc) and 1,2-phenylene. These ligands were used to prepare dimeric Au(I) complexes [Au₂ (μ(P,N)-L)₂ ][SbF₆ ]₂ , which were evaluated as silver-free, preformed catalysts in Au-mediated cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol to 2,3-dimethylfuran. The catalyst featuring the ferrocene-based ligand, viz., [Au₂ (μ(P,N)-CgPfcCN)₂ ][SbF₆ ]₂ , showed the best catalytic performance at low catalyst loading (0.5 or 0.15 mol.%), which exceeded that of its diphenylphosphanyl analog [Au₂ (μ(P,N)-Ph₂ PfcCN)₂ ][SbF₆ ]₂ studied earlier and the prototypical Au(I) precatalyst [Au(PPh₃ )(MeCN)][SbF₆ ].

Keywords: P,N ligands; cyclization reactions; gold complexes; homogeneous catalysis; metallocenes.