Acta Crystallographica Section B

Structural Science

Volume 53, Part 2 (April 1997)

research papers

Acta Cryst. (1997). B53, 262-271 [ doi:10.1107/S010876819601292X ]

New Inclusion Compounds of Selenourea with Tetraethyl- and Tetra-n-propylammonium Halides

Q. Li and T. C. W. Mak

Abstract: Air-sensitive selenourea inclusion complexes tetraethylammonium chloride-selenourea (1/2), (C2H5)4N⁺.C1^-.2[(NH₂)₂CSe] (1), tetra-n-propyl-ammonium chloride-selenourea (1/3), (n-C₃H₇)₄N⁺.C1^-.3[(NH₂)₂CSe] (2), tetra-n-propylammonium bromide-selenourea (1/3), (n-C3H₇)₄N⁺.Br^-.3[(NH₂)₂CSe] (3), and tetra-n-propylammonium iodide-selenourea (1/1), (n-C₃H₇)₄N⁺.I^-.(NH₂)₂CSe (4), have been prepared and characterized by X-ray crystallography. Crystal data, Mo K [alpha] radiation: (1), space group P2₁/n, Z = 4, a = 8.768 (5), b = 11.036 (6), c = 19.79 (1) Å, [beta] = 96.92 (1)°, R_F = 0.055 for 1468 observed data; (2), space group Cc, Z = 4, a = 18.091 (4), b = 13.719 (3), c = 11.539 (2) Å, [beta] = 111.93 (3)°, R_F = 0.051 for 1187 observed data; (3), space group Cc, Z = 4, a = 18.309 (4), b = 13.807 (3), c = 11.577 (2) Å, [beta] = 112.45 (3)°, R_F = 0.049 for 1592 observed data; (4), space group P2₁/n, Z = 4, a = 8.976 (1), b = 14.455 (2), c = 15.377 (3) Å, [beta] = 94.16(1)°, R_F = 0.062 for 1984 observed data. In the crystal structure of (1) the parallel alternate arrangement of selenourea-chloride ribbons and selenourea chains generates a puckered layer and the cations are sandwiched between them. In the isomorphous complexes (2) and (3) wide selenourea-halide double ribbons are crosslinked by bridging selenourea molecules via N-HSe and N-HX hydrogen bonds [average NSe = 3.521 (8) and 3.527 (7), NCl = 3.354 (8) and NBr = 3.500 (7) Å in (2) and (3), respectively] to form a channel-like three-dimensional network and the cations are accommodated in a single column within each channel. In the crystal structure of (4) the selenourea molecules are joined in the shoulder-to-shoulder fashion via N-HSe hydrogen bonds [NSe = 3.529 (7) and 3.534 (7) Å] to generate a ribbon and each selenourea molecule also forms a pair of chelating N-HI hydrogen bonds [NI = 3.567 (7) and 3.652 (7) Å] to an adjacent iodide ion.