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Halide‐Substituted Phosphacyclohexadienyl Iron Complexes: Covalent Structures vs. Ion Pairs
Author(s) -
Hoidn Christian M.,
Leitl Julia,
Ziegler Christoph G. P.,
Shenderovich Ilya G.,
Wolf Robert
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201801135
Subject(s) - chemistry , ionic bonding , covalent bond , halogen , halide , crystallography , metal , electrophile , nuclear magnetic resonance spectroscopy , coordination complex , inorganic chemistry , oxidation state , ion , stereochemistry , organic chemistry , alkyl , catalysis
The coordination chemistry of phosphinines (phosphabenzenes) has been intensively investigated over the last decades, but metal complexes of halophosphinines and related halide‐substituted phosphacyclohexadienyls have remained scarce. Here, we describe the synthesis of a series of complexes [Cp*Fe(1‐F‐PC 5 Ph 3 H 2 )] ( 2‐F , Cp* = C 5 Me 5 ), [Cp*Fe(1‐Cl‐PC 5 Ph 3 H 2 )] ( 2‐Cl ), [Cp*Fe(PC 5 Ph 3 H 2 )]Br ( 2‐Br ) and [Cp*Fe(PC 5 Ph 3 H 2 )]I ( 2‐I ), which were obtained by reacting the previously reported 2,4,6‐triphenylphosphinine iron complex [K([18]crown‐6)(thf) 2 ] [Cp*Fe(PC 5 Ph 3 H 2 )] ( 1 ) with electrophilic halogenating agents. To the best of our knowledge, 2‐F and 2‐Cl are the first π‐coordinated λ 3 ‐halophosphacyclohexadienyl complexes with covalent P–X bonds (X = halogen). In the solid state 2‐Br and 2‐I show ionic structures with [Cp*Fe(PC 5 Ph 3 H 2 )] + cations and separated X – anions. Anion exchange of I – in 2‐I for [BAr F 4 ] – {Ar F = 3,5‐(CF 3 ) 2 C 6 H 3 } affords [Cp*Fe(PC 5 Ph 3 H 2 )][BAr F 4 ] ( 2‐[BAr F 4 ] ), which also displays an ionic structure. These new complexes were further characterized by solid‐state and solution 31 P NMR spectroscopy, UV/Vis spectroscopy, elemental analyses, electrical conductivity measurements in solution, and DFT calculations. The resulting data indicate that 2‐F retains its covalent P–F bond in THF, fluorobenzene, and acetonitrile solution, while the remaining 2‐X complexes containing heavier halogen atoms (X = Cl, Br, and I) apparently form ion pairs in such solvents.