The complex [FeL21](ClO 4 ) 2 ·H 2 O (1a) (L 1 =4-methyl-2,6-bis(1H-pyrazol-1-yl)pyrimidine) was synthesized by the reaction of Fe(ClO 4 ) 2 ·6H 2 O with new NNN-tridentate pyrazolylpyrimidine ligand L 1 in MeOH/EtOH mixture. It is the first example of iron(II) spin crossover complexes with 2,4(6)-di(1H-pyrazol-1-yl)pyrimidines and manifests gradual spin transition centered around 150K on the χ M T versus T curve without hysteresis. A broad heat capacity anomaly with the maximum at 150K was observed on the C p (T) dependence, Δ trs H=5.50kJ/mol and Δ trs S=42.0J/(molK). Surprisingly, the syntheses of iron(II) perchlorate compound with L 1 performed in EtOH and iPrOH afford another modification of the complex, [FeL21](ClO 4 ) 2 ·H 2 O (1b), being high spin in the 78–300K temperature range. The complexes with 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methylpyrimidine (L 2 ), [FeL22](ClO 4 ) 2 ·EtOH (2), [FeL22](CF 3 SO 3 ) 2 (3), [FeL 2 Cl 2 ] 0.5H 2 O (4) and [FeL 2 (NCS) 2 ] (5) were synthesized in EtOH solutions. They are in the high spin state within 78–300K temperature range.