The Crystal Structure of Diammonium trans-Tetraammindisulfitonithenate(II)Tetrahydrate,trans-(NH4)2[Ru(SO3)2(NH3)4]·4H2O,and the Tuning of the trans-Influence of the Sulfite Ligand

Abstract

Abstract trans-(NH4)2[Ru(SO3)2(NH3)4]·4H2O(1) (monoclinic, P21/n; a = 629.8(3), b = 1000.6(2), c = 1345.7(5) pm, β = 112.25(4)°, Z = 2; R = 0.021; Rw = 0.017) is obtained as pale greenish-yellow crystals by reaction of trans-[Ru(SO3H)2(NH3)4] (2) with aqueous ammonia, and crystallization at +5 °C. The compound, when isolated, is stable at room temperature for only a few days even under inert gas, but persists under the mother liquor. In the centrosymmetric anion trans-[Ru(SO3)2(NH3)4]2- the bonds Ru-S = 230.5(1) pm are significantly longer than in the neutral complex 2 (227.6(1) pm), whereas the Ru-N bonds are the same in both com­plexes within experimental error (averages 214.1 and 214.0 pm). Hence, the mutual trans-influence of the sulfite ligands is weakened on protonation; the bonding of the co-ligands in cis-position is not affected. The internal structure of the sulfite ligand in 1 with long S-O bonds (average 151.2(5) pm) and small angles O-S-O (average 106.1(6)°) and the weakened Ru-S bond are a good match. The structure of 1 is held together by a complex network of hydrogen bonds, in which all potential hydrogen-bond donors (OH2, NH4 +, NH3) and acceptors (H2O ,SO3) are involved. The structural findings are reflected in the vibrational spectra.