Addition of aminomethylphosphane P{CH2N(CH2CH2)2O}3 (1), PPh2{CH2N(CH2CH2)2O} (2) or PPh2{CH2N(CH2CH2)2NCH2CH3} (3) to a methanolic solution of RuCl3 results in reduction of ruthenium(III) ions giving finally ttt-[RuCl2(1)2] (1A), ttt-[RuCl2(2)2] (2A) and ttt-[RuCl2(3)2] (3A). The synthesized complexes are the first examples of ruthenium(II) coordination compounds possessing aminomethylphosphanes chelating via phosphorus and nitrogen atoms. They were fully characterized (NMR, ESI-MS, IR, elemental analysis, X-ray crystallography). Preliminary studies of the in vitro cytotoxicity on the A549 cell line (human lung adenocarcinoma) and interactions with human serum proteins (albumin and apotransferrin) showed moderate activity of the complexes. Interestingly, the P,N-chelation leads to formation of strained 4-membered Ru–P–C–N–Ru rings, which in the case of 2A and 3A undergo opening in the presence of CH3CN, which results in rearrangement to ctc-[RuCl2(2)2(CH3CN)2] (2B) and ctc-[RuCl2(3)2(CH3CN)2] (3B).