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A Systematic Exploration of Nickel–Pyrazolinato Chemistry with Alkali Metals: New Cages From Serendipitous Assembly
Author(s) -
Aromí Guillem,
Bell Aidan R.,
Helliwell Madeleine,
Raftery James,
Teat Simon J.,
Timco Grigore A.,
Roubeau Olivier,
Winpenny Richard E. P.
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200304939
Subject(s) - nickel , alkali metal , chemistry , crystallography , intramolecular force , paramagnetism , antiferromagnetism , crystal structure , molecule , hydroxide , stereochemistry , inorganic chemistry , physics , organic chemistry , condensed matter physics , quantum mechanics
The preparation and properties of fourteen novel paramagnetic [Ni II x ] aggregates bridged by pivalate, pyrazolinolate and in most cases hydroxide are reported. A rich structural diversity has been achieved by changing the nature of the alkali of the base used during the synthesis, leading to the nuclearities [Ni II 4 Na I 4 ] ( 2, 3, 4 ), [Ni II 5 Na I 4 ] ( 5, 6, 7 ), [Ni II 5 Li I 6 ] ( 8 ), [Ni II 8 M I 2 ] (M=K ( 9, 10 ), Rb ( 11, 12 ), Cs ( 13, 14 ) and [Ni II 8 ] ( 15 ). All compounds have been characterised by single‐crystal Xray diffraction; however, full crystallographic details are given only for the representative molecules [Ni 4 Na 4 (fpo) 4 (piv) 8 (Hpiv) 8 ] ( 2 ), [Ni 5 Na 4 (OH) 2 (mpo) 4 (piv) 8 (Hpiv) 2 (MeCN) 2 ] ( 5 ), [Ni 5 Li 6 (OH) 2 (fpo) 2 (piv) 12 (Hpiv) 4 ] ( 8 ), [Ni 8 K 2 (OH) 4 (ppo) 4 (piv) 10 (Hppo) 2 (Hpiv) 2 (MeCN) 2 ] ( 9 ), [Ni 8 Rb 2 (OH) 4 (ppo) 4 (piv) 10 (Hppo) 2 (Hpiv) 2 (MeCN) 2 ] ( 11 ), [Ni 8 Cs 2 (OH) 4 (ppo) 4 (piv) 10 (Hppo) 2 (Hpiv) 2 (MeCN) 2 ] ( 13 ) and [Ni 8 (OH) 4 (mpo) 2 (PhCH 2 CO 2 ) 10 (Hmpo) 8 ] ( 15 ). Variable‐temperature bulk magnetisation measurements have been performed for each type of complex. The [Ni II 4 Na I 4 ] clusters show intramolecular antiferromagnetic coupling and a spin ground state of S =0. Complexes of the type [Ni II 5 Na I 4 ] also display antiferromagnetic superexchange, leading to an S =1 spin ground state. The molecule with nuclearity [Ni II 5 Li I 6 ], in contrast, exhibits ferromagnetic interactions, resulting in the presence of low energy states with high multiplicity, and a spin ground state S >1. The [Ni II 8 M I 2 ] and [Ni II 8 ] clusters have the same topology of spin carriers, which display predominantly antiferromagnetic interactions to yield a diamagnetic ground state. The coupling within these octanuclear Ni II clusters is rationalised in terms of the nature of the Ni‐O‐Ni angles within the core.