Steric control of aggregation in neutral silver(I) thiolates, [AgSR]n. Crystal and molecular structures of [AgSCH(SiMe3)2]8, a discrete molecular biscycle of weakly interacting [AgSCH(SiMe3)2]4 units, and of [AgSC(SiPhMe2)3]3 and [AgSC(SiMe3)3]4, discrete molecular monocycles containing linearly ... (original) (raw)

1987, Inorganic Chemistry

By the use of a novel series of sterically hindered thiolate ligands, (RR'R"Si),CH,-,SH, the colorless silver-thiolate complexes [AgSC(SiMe,Ph),], (5a) and [AgSC(SiMe3),14 (4a) and the yellow species [AgSCH(SiMe3),18 (3a) and [Ag,(SCH,-(SiMe3)]3(OCH3)], (2a) have been synthesized and structurally characterized. The structure of Sa consists of a discrete nonplanar six-membered cycle of alternating silver and sulfur atoms, Ag,S,, exhibiting no secondary A g S interactions between trinuclear units. In contrast, the structure of 4a consists of a planar eight-membered cycle, Ag&, and exhibits unstrained digonal Ag-S coordination, unperturbed by secondary A g S interactions. The results suggest that a degree of control of aggregation may be introduced by employing ligands possessing sufficient steric bulk. Furthermore, the reduction of ligand steric hindrance in-SCH(SiMe3)2 has profound structural consequences as illustrated by the structure of 3a, which consists of two weakly interacting [AgSCH(SiMe,),], cycles, facing each other and connected by secondary A g. S interactions, producing a T-shaped geometry about the Ag centers. Further reduction in the steric bulk of the ligand results in the polymeric structure of 2a. The complex three-dimensional polymer may be described in terms of kinked chains of fused octanuclear Ag4S4 cyclic links cross-linked through bridging Ag,S, monocycles. Crystal data: for 5a, triclinic Pi, a = 11.236 (2) A, b = 16.445 (3) A, c = 25.686 (4) A, CY = 92.79 (1)". /3 = 97.52 (l)", y = 108.77 (I)O, V = 4434.2 (9) A', Da,d = 1.34 g cm-, for Z = 2, R = 0.061 for 9537 reflections; for 4a, orthorhombic Pbca, a = 17.478 (3) A, b = 28.314 (4) A, c = 29.706 (4) A, V = 14700.6 (12) A3, DmId = 1.28 g cm-' for Z = 8, R = 0.069 for 2759 reflections; for 3a, monoclinic C2/c, a = 18.339 (4) A, b = 24.623 (4) A, c = 24.473 (4) A, @ = 96.74 (I)', V = 10974.6 (1 1) A', Dald = 1.45 g cm-, for 2 = 4, R = 0.063 for 3919 reflections; for 2b, monoclinic C2/c, a = 17.023 (3) A, b = 29.470 (5) A, c = 23.372 (4) A, /3 = 104.21 (l)", V = 11366.2 (14) A', Dald = 1.92 g cm-, for 2 = 16, R = 0.069 for 1366 reflections.