E4 Butterfly Complexes (E=P, As) as Chelating Ligands

• Published in: Angewandte Chemie International Edition Vol. 54; no. 44; pp. 13116 - 13121
• Main Authors: Schwarzmaier, Christoph, Heinl, Sebastian, Balázs, Gábor, Scheer, Manfred
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 26.10.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: arsenic; butterfly complexes; Carbon monoxide; chelate ligands; Chelation; Copper; Infrared spectroscopy; Ligands; Magnetic resonance spectroscopy; NMR; NMR spectroscopy; Nuclear magnetic resonance; Phosphorus; Protonation; Spectrometry; Spiro compounds; Stoichiometry; Wing tips; butterfly complexes; protonation; arsenic; chelate ligands; phosphorus
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201506784

The coordination properties of new types of bidentate phosphane and arsane ligands with a narrow bite angle are reported. The reactions of [{Cp′′′Fe(CO)2}2(μ,η1:1‐P4)] (1 a) with the copper salt [Cu(CH3CN)4][BF4] leads, depending on the stoichiometry, to the formation of the spiro compound [{{Cp′′′Fe(CO)2}2(μ3,η1:1:1:1‐P4)}2Cu]+[BF4]− (2) or the monoadduct [{Cp′′′Fe(CO)2}2(μ3,η1:1:2‐P4){Cu(MeCN)}]+[BF4]− (3). Similarly, the arsane ligand [{Cp′′′Fe(CO)2}2(μ,η1:1‐As4)] (1 b) reacts with [Cu(CH3CN)4][BF4] to give [{{Cp′′′Fe(CO)2}2(μ3,η1:1:1:1‐As4)}2Cu]+[BF4]− (5). Protonation of 1 a occurs at the “wing tip” phosphorus atoms, which is in line with the results of DFT calculations. The compounds are characterized by spectroscopic methods (heteronuclear NMR spectroscopy and IR spectrometry) and by single‐crystal X‐ray diffraction studies. The butterfly has landed: The first examples of the coordination of E4 butterfly complexes (E=P, As) are presented. It is shown that the “wing‐tip” E atoms are capable of acting as ligands towards Cu+ cations. The E4 moieties act as bidentate ligands with a very narrow bite‐angle, which is comparable to that of dppm (bis(diphenylphosphino)methane).