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Highly Substituted Tris(pyrazolyl)methane Ligands and Some Zinc Complexes Thereof
Author(s) -
Titze Christoph,
Hermann Jörg,
Vahrenkamp Heinrich
Publication year - 1995
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19951281107
Subject(s) - chemistry , perchlorate , zinc , denticity , inorganic chemistry , medicinal chemistry , bromide , zinc bromide , hydrate , pyrazole , crystal structure , organic chemistry , ion
Tris(pyrazolyl)methane ligands in which two or three of the pyrazole carbon atoms bear organic substituents ( L 1 ‐L 7 ) were synthesized from chloroform and the corresponding pyrazole under phase transfer conditions. Their behavior towards zinc salts was found to span the range from no reaction at all to hydrolytic destruction. One hydrolysis product isolated and structurally characterized was the perchlorate complex [(HPz 5 ) 3 Zn‐OClO 3 ]ClO 4 ( 1 ), other ones were the 2:1 complexes (HPz 3 ) 2 ZnBr 2 ( 2 ) and (HPz 6 ) 2 Zn(NO 3 ) 2 ( 3 , HPz n = substituted pyrazole). Zinc perchlorate and tris(trimethylpy‐razolyl)methane ( L 2 ) formed the octahedral binary complex [ L 2 2 Zn](ClO 4 ) 2 ( 4 ) as evidenced by a structure determination. Zinc halides produced the 1:1 complexes L 1 · ZnBr 2 ( 5), L 4 · ZnCl 2 ( 6 ), and L 4 · ZnBr 2 ( 7 ), which according to the structure determinations of 6 and 7 contain tetrahedral ZnN 2 Hal 2 units with only bidentate tris(pyrazolyl)methane ligands. In contrast, the zinc nitrate complex L 4 · Zn(NO 3 ) 2 ( 8 ) was found to have an octahedral structure with mono‐ and bidentate nitrate and tridentate L 4 . The bromide complex 7 was converted by silver perchlorate hydrate into the labile compound [ L 4 · ZnBr]ClO 4 ( 9 ) and then into the unstable product [ L 4 · Zn‐OH 2 ](ClO 4 ) 2 ( 10 ), both presumed to contain zinc in a tetrahedral ZnN 3 Br or ZnN 3 O environment, respectively. The ease of hydrolytic self‐destruction prevented the exploitation of the reactivity of 9 and 10 in analogy to that of the corresponding tris(pyrazolyl)borate zinc complexes.