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“Isomerism” of Coordination Modes and Numbers in Pentanuclear Organozinc Hydroxylamides: An Exercise in Subtle Substituent Size Effects
Author(s) -
Ullrich Matthias,
Berger Raphael J. F.,
Lustig Christian,
Fröhlich Roland,
Mitzel Norbert W.
Publication year - 2006
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.200600625
Subject(s) - chemistry , heteroatom , substituent , stereochemistry , ligand (biochemistry) , cluster chemistry , organometallic chemistry , group 2 organometallic chemistry , crystallography , coordination complex , cluster (spacecraft) , zinc , coordination number , metal , molecule , medicinal chemistry , ring (chemistry) , crystal structure , organic chemistry , ion , biochemistry , receptor , programming language , computer science
Abstract The first organometallic zinc hydroxylamides [Zn(RZn) 4 (ONMe 2 ) 6 ] ( 1 : R = Me; 2 : R = i Pr) and [Zn(EtZn) 4 (ONEt 2 ) 6 ] ( 3 ) have been prepared by alkane elimination from dialkylzinc solutions upon treatment with N , N ‐dialkylhydroxylamines. The molecular structures of 1 and 2 reveal that a subtle change in the constitution of the aggregates can make a striking difference. By the simple exchange of the MeZn + groups with i PrZn + groups, the coordination number of the central Zn 2+ nucleus increases from four ( 1 ) to six ( 2 ). The two cluster types are unprecedented in both hydroxylamine and organometallic chemistry. Compounds 1 and 3 adopt a doubly bridged fenestrane‐like Zn 5 N 6 O 6 core with two dangling NR 2 moieties, whereas i PrZn species 2 comprises an octahedroid backbone with all donor atoms attached to the five Zn nuclei with the maintenance of the same heteroatom composition as 1 and 3 . Variable‐temperature 13 C NMR experiments of all‐ethyl cluster 3 reveal that the R 2 NO – ligands rapidly exchange between the RZn + and Zn 2+ cations. This process is rationalised by a plausible model which also points out that the core structure of 3 could be an intermediate motif in the observed heteroatom connectivity exchange. In line with this, computational investigations reveal that both skeletons are very similar in energy. In sum, the coordination flexibility of the hydroxylamide ligand makes this group of organometallic zinc complexes a highly dynamic family of cluster compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)