Iron and ruthenium complexes having a pincer-type ligand with two protic amidepyrazole arms: Structures and catalytic application

This paper describes the iron and ruthenium complexes ligated by 2,6-di(5-pivalamido-IH-pyrazol-3-yl) pyridine (amide-LH2) bearing electron-withdrawing NHCOBut groups on the two protic pyrazole arms. Treatment of FeCl2 center dot 4H(2)O with an equimolar amount of amide-LH2 followed by addition of two trimethylphosphine and an excess of sodium triflate gave the pincer-type iron complex [Fe(MeCN) (amide-LH2)(PMe3)(2)](OTf)(2) (1b; OTf = OSO2CF3). Impact of the amido groups in 1b on the reactions with hydrazines was evaluated. Complex 1b catalyzed disproportionation of hydrazine into ammonia and dinitrogen, although the catalytic activity was lower than that of the Bu-t-LH2 analogue la. X-ray analysis of 1b as well as the ruthenium complex [{RuCl2(pph(3))(2)}(2)(mu(2)-amide-LH2)(2)] (2b) revealed that the pendant carboxamide groups along with the pyrazole NH units are engaged in hydrogen bonds in the second coordination sphere. (C) 2017 Elsevier Ltd. All rights reserved.