Preparation and Structure of Tetraphenylphosphonium Aquotetrachlorothionitrosylosmium(II), [PPh₄][(H₂O)Os(NS)Cl₄]

Trithiazyltrichloride reacts with osmium trichloride to give a green product of composition Os(NS)Cl 3 (1). Addition of [PPh 4 ]Cl to 1 in aqueous solution yields [PPh 4 ] 2 [Os(NS)Cl 5 ] (2) which is converted to [PPh 4 ][(H 2 O)Os(NS)CI 4 ] (3) by recrystallisation from a 1:1 water/methanol mixture. Crystals of 3 are monoclinic, space group P2 1 /c, with a = 1103.3(2), b = 1959.8(3), c = 1254.3(2) pm, β = 96.51(3)° and Z = 4. The structure was solved by automated Patterson interpretation and refined to R = 0.029 for 3177 unique observed diffractometer data. The osmium atom is octahedrally co-ordinated with H 2 O trans to the NS group. The Os-N-S unit is almost linear [174.9(3)°] with Os-N 173.1(4) and N-S 151.4(5) pm. The anions form dimeric units in the crystal, each held together by four O-H···Cl hydrogen bonds