The crystal and molecular structures of A(S2COCH2CH2CMe3)3, A = As(III), Sb(III) and Bi(III)

The crystal and molecular structures of tris(3,3-dimethylbutyldithiocarbonato)-arsenic(III), -antimony(III) and -bismuth(III), A(S 2 COCH 2 CH 2 CMe 3 ) 3 , have been determined at room temperature. The colorless crystals of A = As(III) are triclinic, space group P1 with unit cell dimensions a=11.837(2) A, b=13.430(2) A, c = 10.284(1) A, α = 98.39(1)°, β = 102.472(9)°, γ = 101.73(1)°, Z = 2 and D x = 1.316 Mg m -3 . The colorless crystals of A = Sb(III) are monoclinic, space group P2 1 /c with unit cell dimensions a=16.110(3) A, b=6.077(4) A, c=31.101(3) A, β=97.65(1)°, Z=4 and D x = 1.439 Mg m -3 The yellow crystals of A = Bi(III) are also monoclinic, space group P2 1 /c with unit cell dimensions a=16.149(3) A, b=6.063(3) A, c = 31.052(7) A, β = 97.25(2)°, Z = 4 and D x = 1.632 Mg m -3 . The structures were solved by direct methods and each refined by a full-matrix least-squares procedure to final R=0.042 using 3118 reflections for A=As(III); to R=0.051 using 3357 reflections for A = Sb(III); and to final R = 0.056 for 2606 reflections for A = Bi(III). The A = As(III) structure comprises isolated molecules with the central atom existing in a distorted capped octahedral geometry. A disorted pentagonal bipyramidal geometry is found in the A = Sb(III) structure where loose association, via Sb... S interactions, are found between centrosymmetrically related pairs. An analogous structure is found for A = Bi(III), however, relatively stronger Bi... S interactions are in existence. A discussion of the different motifs found for A(S 2 COR) 3 structures indicates the importance of crystal packing effects, i.e. the desire to maximise A... S intermolecular contacts, in these structures.

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