Crystal structures of sulfamates MeLi(NH2SO3)(2) (Me : K, Rb and Cs) and physical properties of KLi(NH2SO3)(2) (refractive indices, thermal expansion, elastic properties)

New sulfamates KLi(NH2SO3)(2), RbLi . (NH2SO3)(2) and CsLi(NH2SO3)(2) were prepared from nonstoichiometric (ratio Li : Me = 3 : 1) aqueous solutions o f LiNH2SO3 and MeNH2SO3 (Me = K, Rb, Cs) at room temperature. Large single crystals of KLi(NH2SO3)(2) were grown from these solutions by controlled lo wering of the temperature between 293 K and 288 K. The crystal structures w ere investigated using single-crystal X-ray diffraction methods. KLi(NH2SO3 )(2): space group P2(1). Z = 2, a = 5.196(1) Angstrom, b = 8.475(1) Angstro m, c = 8.868(1) Angstrom, 105.05(1)degrees, T-meas. = 293 K, R1 = 0.026; Rb Li(NH2SO3)(2): space group P(1) over bar, Z = 4, a = 7.844(1) Angstrom, b = 9.804(1) Angstrom, c = 10.825(1) Angstrom, alpha = 108.77(1)degrees, beta = 93.29(1)degrees, gamma = 98.64(1)degrees, T-meas. = 293 K, R1 = 0.033; Cs Li(NH2SO3)(2): space group P(1) over bar, Z = 2, a = 5.535(1) Angstrom, b = 7.877(1) Angstrom, c = 9.857(1) Angstrom, alpha = 74.07(1)degrees, beta = 76.33(1)degrees, gamma = 87.07(1)degrees, T-meas. = 200 K; R1 = 0.023. The common feature of the three crystal structures are alternating layers of Me + and lithium cations together with anionic [NH2SO3](-) tetrahedra. Li+ coo rdination polyhedra and [NH2SO3](-) anions, linked via common corners, form one type of these sheets. Additionally, these layers are stabilized by hyd rogen bonds. Me+ coordination polyhedra are linked to each other and to the above mentioned layers by common corners and edges. RbLi(NH2SO3)(2) and Cs Li(NH2SO3)(2) possess similar structures. Generally, the observed interatom ic distances and angles agree with crystal chemical expectations. Differential scanning calorimetry measurements showed that KLi(NH2SO3)(2) u ndergoes a first-order structural phase transition at 401 K and melts at 42 3 K. Between 153 K and 423 K no indications of further phase transitions we re observed. In addition, the refractive indices and the tensor of thermal expansion wer e measured. Further, the elastic and thermoelastic constants of KLi(NH2SO3)(2) were det ermined from ultrasonic resonant frequencies of thick plane-parallel plates and their shift upon variation of temperature, respectively. The elastic b ehaviour of KLi(NH2SO3)(2) is similar to the average elastic properties of LiNH2SO3 and KNH2SO3.