Silver(I) complexes of the potentially chelating olefinic ligands 2,2-dimethylbut-3-enyl methyl sulphide and 2,2-dimethyl-2-silabut-3-enyl methyl sulphide. Crystal structure analysis of bis(2,2-dimethylbut-3-enyl methyl sulphide)silver(I) tetrafluoroborate, (2,2-dimethylbut-3-enyl methyl sulphide)silver(I) perchlorate, (2,2-dimethylbut-3-enyl methyl sulphide)nitratosilver(I), and (2,2-dimethylbut-3-enyl methyl sulphide)-trifluoroacetatosilver(I)

Abstract

The ligands 2,2-dimethylbut-3-enyl methyl sulphide (1a) and 2,2-dimethyl-2-2-silabut-3-enyl methyl sulphide (1b) form analogous sets of complexes with a series of silver salts. Thus, 1 : 1 complexes have been obtained from Ag[BF₄], Ag[ClO₄], Ag[NO₃], and Ag[O₂CCF₃], 1 : 2 (Ag : ligand) complexes from Ag[BF₄] and Ag[ClO₄], and 2 : 1 (Ag : ligand) complexes from Ag[NO₃]. In the solid state (i.r. and X-ray) the ligands are chelated, while in solution (¹H n.m.r.) both the Ag–sulphur and Ag–olefin bonds are labile even at low temperatures (–80 °C). Crystal-structure analyses have been completed on Ag[BF₄]·2(1a), Ag[ClO₄]·(1a), Ag[NO₃]·(1a), and Ag[O₂CCF₃]·(1a). The complex Ag[BF₄]·2(1a) contains discrete [Ag·2(1a)]⁺ cations (which have two-fold crystallographic symmetry) and disordered BF₄^– anions. Polymeric structures have been found for the remaining three complexes. In [Ag·(1a)][ClO₄] polymeric cation chains are present, while the perchlorate ions are not co-ordinated to silver. In Ag[NO₃]·(1a) the nitrato-group is bidentate (Ag–O 2.537 and 2.647 Å), whereas the carboxyl group in Ag[O₂CCF₃]·(1a) is predominantly unidentate (Ag–O 2.29 and 2.99 Å). In all four structures the five-membered –Ag–S–C(1)–C(2)–C(3)– ring adopts a C(2) envelope conformation. The olefin co-ordination is defined by the S–Ag–C(3)C(4) torsion angles 148.6 in Ag[BF₄]·2(1a), 140.9 in Ag[ClO₄]·(1a), 158.7 in Ag[NO₃]·(1a) and 140.2° in Ag[O₂CCF₃]·(1a). Crystals of Ag[BF₄]·2(1a) are monoclinic, space group C2/c, with four formula units in a cell of dimensions a= 10.838(2), b= 11.720(2), c= 16.355(2)Å, β= 105.02(1)°, R= 0.049 for 645 observed reflections. Crystals of Ag[ClO₄]·(1a) are orthorhombic, space group P2₁2₁2₁, with four formula units in a cell of dimensions a= 8.229(3), b= 10.645(3), c= 13.917(3)Å, R= 0.066 for 1 259 reflections. Crystals of Ag[NO₃]·(1a) are monoclinic, space group P2₁/c, with four molecules in a cell of dimensions a= 11.049(1), b= 7.823(1), c= 14.352(3)Å, β= 118.392(7)°, R= 0.049 for 1 653 reflections. Crystals of Ag[O₂CCF₃]·(1a) are monoclinic, space group P2₁/b, with four molecules in cell of dimensions a= 10.194(3), b= 15.784(5), c= 8.125(4)Å, γ= 95.49°, R= 0.099 for 846 reflections.