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Understanding Structure Formation in Organolithium Compounds: An Experimental and Quantum‐Chemical Approach
Author(s) -
Götz Kathrin,
Gessner Viktoria H.,
Unkelbach Christian,
Kaupp Martin,
Strohmann Carsten
Publication year - 2013
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201200495
Subject(s) - chemistry , methyllithium , adduct , lithium (medication) , tetramer , dimer , reactivity (psychology) , agostic interaction , organolithium compounds , crystal structure , ether , hydrogen bond , monomer , polarity (international relations) , ligand (biochemistry) , stereochemistry , computational chemistry , crystallography , molecule , organic chemistry , ion , metal , medicine , biochemistry , deprotonation , alternative medicine , receptor , pathology , cell , enzyme , endocrinology , polymer
As the reactivity of organolithium compounds is strongly connected with the structure of the involved species, the structural knowledge is a prerequisite for the understanding of reaction mechanisms. Using the example of methyllithium, we address particularly the issues of stabilizing non‐classical interactions in organolithium aggregates and the relations between disaggregation and polarity, using a combination of X‐ray structure analysis and quantum‐chemical methods. The structure analyses of a series of MeLi adducts, among them the diethyl ether adduct (MeLi · Et 2 O) 4 , exhibit varying arrangements of the α‐hydrogen atoms relative to lithium. α ‐Hydrogen orientations differ even when changing the stereochemistry of the ligand in dimeric adducts. Computations confirm only weak stabilizing effects of agostic Li–H interactions, which compete with other aspects of the spatial situation in the formed aggregates. NPA and QTAIM analyses on different aggregates (e.g. monomer, dimer, tetramer, extended crystal environment) with different co‐ligands reveal a complicated relation between the degree of aggregation and Li–C bond polarity but a more clearcut dependence on the lithium coordination number.