1 , 2 , 4 - triazolo [ 4 , 3 - a ] pyrimidines : a new kind of ligands . Structure of the silver ( I ) dimer with the 7 - oxo derivative

This paper describes the silver dinuclear complex [Ag2L2(NO3)2] Æ 2H2O, where L represents the bridging ligand 7,8-dihydro-7oxo-1,2,4-triazolo[4,3-a]pyrimidine, this being the first example of a coordination compound of a 1,2,4-triazolo[4,3-a]pyrimidine derivative. As a difference with the most studied 1,2,4-triazolo[1,5-a]pyrimidine derivatives, the coordination takes place through the contiguous nitrogen atoms of the triazole ring, closing a six member Ag2N4 core with a higher intermetallic distance, 3.4791(3) Å. Linear coordination of silver is not possible in this geometry, so flat trigonal coordination involving also the nitrate counteranion is found instead. 2004 Elsevier B.V. All rights reserved.