Molecular squares, coordination polymers and mononuclear complexes supported by 2,4-dipyrazolyl-6 H -1,3,5-triazine and 4,6-dipyrazolylpyrimidine ligands

• Published in: Dalton transactions : an international journal of inorganic chemistry 2019-11, Vol.48 (46), p.17310-17320
• Main Authors: Capel Berdiell, Izar, Farmiloe, Sarah E., Kulmaczewski, Rafal, Halcrow, Malcolm A.
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/C9DT04003J

The Fe[BF 4 ] 2 complex of 2,4-di(pyrazol-1-yl)-6 H -1,3,5-triazine (L 1 ) is a high-spin molecular square, [{Fe(L 1 )} 4 (μ-L 1 ) 4 ][BF 4 ] 8 , whose crystals also contain the unusual HPzBF 3 (HPz = pyrazole) adduct. Three other 2,4-di(pyrazol-1-yl)-6 H -1,3,5-triazine derivatives with different pyrazole substituents (L 2 –L 4 ) are unstable in the presence of first row transition ions, but form mononuclear, polymeric or molecular square complexes with silver( i ). Most of these compounds involve bis-bidentate di(pyrazolyl)triazine coordination, which is unusual for that class of ligand, and the molecular squares encapsulate one or two BF 4 − , ClO 4 − or SbF 6 − ions through combinations of anion⋯π, Ag⋯X and/or C–H⋯X (X = O or F) interactions. Treatment of Fe[NCS] 2 or Fe[NCSe] 2 with 4,6-di(pyrazol-1-yl)-2 H -pyrimidine (L 5 ) or its 2-methyl and 2-amino derivatives (L 6 and L 7 ) yields mononuclear [Fe(NCE) 2 L 2 ] and/or the 1D coordination polymers catena -[Fe(NCE) 2 (μ-L)] (E = S or Se, L = L 5 –L 7 ). Alcohol solvates of isomorphous [Fe(NCS) 2 L 2 ] and [Fe(NCSe) 2 L 2 ] compounds show different patterns of intermolecular hydrogen bonding, reflecting the acceptor properties of the anion ligands. These iron compounds are all high-spin, although annealing solvated crystals of [Fe(NCSe) 2 (L 5 ) 2 ] affords a new phase exhibiting an abrupt, low-temperature spin transition. Catena -[Fe(H 2 O) 2 (μ-L 5 )][ClO 4 ] 2 is a coordination polymer of alternating cis and trans iron centres.