EXODENTATE VERSUS ENDODENTATE COORDINATION OF A CROWN THIOETHER LIGAND IN SILVER(I) COMPLEXES OF 2,5,8-TRITHIA[9]-ORTHO-BENZENOPHANE (TT[9]OB) - STRUCTURES OF [AG(TT[9]OB)2][X] (X = CLO4, BPH4, CF3SO3)

The crown thioether ligand 2,5,8-trithia [9]-o-benzenophane, TT[9]OB, is known to have an exodentate conformation in the uncomplexed form; the sulfur donor atoms are oriented away from the center of the macrocyclic ring. This ligand reacts with AgX (X = ClO4-, BF4-, BPh4-, CF3SO3-) in a 2:1, ligand to metal ratio to give complexes of the general formula [Ag(TT[9]-OB)2][X]. Although these complexes are simple mononuclear species, the solid-state structures vary dramatically with the counterion X. The complex [Ag(TT[9]OB)2][ClO4] crystallized in the space group P2(1)/n with a = 8.317 (2) angstrom, b = 26.178 (11) angstrom, c = 13.361 (5) angstrom, beta = 101.14 (2)-degrees, V = 2854 (3) angstrom3, and Z = 4. The structure refined to R = 7.06% and R(w) = 7.58% for 1577 reflections with F(o)2 > 3-sigma(F(o)2)). The Ag atom is in an octahedral environment defined by the six S atoms of two facially coordinated TT[9]OB ligands. The complex [Ag(TT[9]OB)2][BF4] is isostructural with [Ag(TT[9]OB)2][ClO4]. The complex [Ag(TT[9]OB)2][BPh4] crystallized in the space group C2/c with a = 16.257 (5) angstrom, b = 16.031 (6) angstrom, c = 16.962 (4) angstrom, beta = 93.25 (3)-degrees, V = 4413 (4) angstrom3, and Z = 4. The structure refined to R = 6.79% and R(w) = 6.90% for 1495 reflections with F(o)2 > 3-sigma(F(o)2). The Ag atom is in a distorted tetrahedral coordination environment defined by two S atoms from each TT[9]OB ligand. The complex [Ag(TT[9]OB)2][CF3SO3] crystallized in the space group P1BAR with a = 12.390 (2) angstrom, b = 14.158 (4) angstrom, c = 9.290 (3) angstrom, alpha = 91.04 (3)-degrees, beta = 109.64 (2)-degrees, gamma = 83.37 (2)-degrees, V = 1524.9 (9) angstrom3, and Z = 2. The structure refined to R = 6.76% and R(w) = 7.28% for 2815 reflections with F(o)2 > 3-sigma(F(o)2). The Ag atom is in a tetrahedral coordination environment defined by three S atoms from one facially coordinated TT[9]OB ligand and one S atom from the other TT[9]OB ligand which has an exodentate conformation. Variable-temperature H-1 NMR spectroscopy indicates that a rapid fluxional process interconverts the observed geometries in solution and that the most favorable solution structure is a symmetric one. Solution oxidation potentials are consistent with an octahedral S6 environment at Ag(I).