Iron(II) complexes containing poly(1-pyrazolyl)methane ligands

A number of iron(II) compounds containing the poly(1-pyrazolyl)methane ligands bis(1-pyrazoyl)methane (BPM, 3), bis(3,5-dimethyl-1-pyrazolyl)methane (dmBPM, 4), and tris(1-pyrazolyl)methane (TPM, 2), were synthesised and characterised: cis-[Fe(BPM)2Cl2] (5), trans-[Fe(BPM)2(NCS)2] (9), [Fe(BPM)2Cl]+(BPh4)− (7), [Fe(dmBPM)2Cl2] (6), [Fe(dmBPM)2Cl]+(BPh4)− (8), [Fe(TPM)2]2+(Cl−)2 (10), and [Fe(TPM)(NCS)2] (11). The solid-state structures of cis-[Fe(BPM)2Cl2] (5) and trans-[Fe(BPM)2(NCS)2] (9) were determined by single crystal X-ray diffraction analysis. The compound cis-[Fe(BPM)2Cl2] (5) crystallises as colourless prisms from ethanol and trans-[Fe(BPM)2(NCS)2] (9) crystallises as colourless plates from methanol. All complexes were characterised by 1H- and 13C-NMR spectroscopy, infrared and far infrared spectroscopy, and mass spectroscopy. All of the iron(II) poly(1-pyrazolyl)methane compounds display temperature-dependent paramagnetism.