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σ‐Donor versus η 6 ‐π‐Arene Interactions in Monomeric Europium(II) and Ytterbium(II) Thiolates − An Experimental and Computational Study
Author(s) -
Niemeyer Mark
Publication year - 2001
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 - 10.1002/1099-0682(200108)2001:8<1969::aid-ejic1969>3.0.co;2-0
Subject(s) - chemistry , methylcyclohexane , adduct , crystallography , monomer , dimer , toluene , nuclear magnetic resonance spectroscopy , europium , stereochemistry , organic chemistry , ion , polymer
Abstract The base‐free, hydrocarbon‐soluble complexes M(SAr*) 2 ( 4a : M = Eu, orange; 4b : M = Yb, purple; Ar* = 2,6‐Trip 2 C 6 H 3 ; Trip = 2,4,6‐ i Pr 3 C 6 H 2 ) have been prepared by a protolysis reaction of the Grignard‐analogous compound RLnI (R = 2‐F 3 CC 6 H 4 ) with HSAr*. Compound 4b has been characterized by melting point, elemental analysis, 1 H, 13 C, and 171 Yb NMR, IR spectroscopy, UV/Vis spectrophotometry, mass spectrometry, and X‐ray crystallography. Additionally, the purple Yb III complex YbI 2 (SAr*)(THF) 3 ( 3 ) and the yellow DME adduct Yb(SAr*) 2 (dme) 2 ( 5 ) have been synthesized and characterized by X‐ray crystallography. The solid‐state structures of 4a and 4b (as THF or benzene hemisolvates) show monomeric units with the metal atom bonded to two terminal thiolate ligands [av. M−S: 281.7 pm ( 4a )/269.1 pm ( 4b )]. Additional η 6 ‐π‐arene interactions are observed to two C 6 H 2 rings of the Trip substituents [av. M···C: 306.5 pm ( 4a )/297.3 pm ( 4b )]. The binding energy for these interactions has been determined by variable‐temperature 1 H NMR spectroscopy to be 54.3 kJ mol −1 (in methylcyclohexane) and 57.1 kJ mol −1 (in toluene). The nature and strength of the η 6 ‐π‐arene bonding has been studied by ab initio calculations on the model systems [M(arene)] 2+ (arene = C 6 H 6 , C 6 F 6 , 1,3,5‐Me 3 C 6 H 3 , 1,3,5‐ i Pr 3 C 6 H 3 ) and Yb(SH) 2 (C 6 H 6 ) n ( n = 1, 2). The results are compared with the binding energies in the σ‐donor adducts [M(THF)] 2+ , [M(dme)] 2+ , and [M(imidazol‐2‐ylidene)] 2+ .