Synthesis and coordination chemistry of 1-phenyl-1-phospha-4,7-dithiacyclononane

Reaction of PhP(CH2CH2SH)(2) with 1,2-dichloroethane and Cs2CO3 under high dilution conditions affords 1-phenyl-1-phospha-4,7-dithiacyclononane (L) as an oil in 52% yield. The geometry of L has been probed by H-1 NMR spectroscopy, which indicates an equilibrium mixture containing gauche S-C-C-S and S-C-C-P segments, and molecular mechanics calculations which find a lowest energy endodentate conformation minimum and also energetically accessible exodentate minima. Endo- and exodentate conformations are observed in the crystal structure of [Cu(eta(1)-L)(eta(3)-L)][PF6] (1) formed by the reaction of L with [Cu(NCMe)(4)[PF6]. Reaction of Hg(ClO4)(2) with L affords [HgL2][ClO4](2) (2) whose structure has also been established by X-ray diffraction. The mercury ion is in a very distorted octahedral environment with two short Hg-P bonds (average 2.404 Angstrom) and four long Hg-S bonds (average 3.092 Angstrom). Reaction of L with AgBF4 or Ni(BF4)(2) or CoBr2 or Fe(BF4)(2) affords [AgL2][BF4] (3), [NiL2][BF4](2), (4), [CoL2]BL2 (5) and FeL2][BF4](2) (6), respectively, which were characterised by FAB mass spectroscopy and elemental analysis. Cyclic voltammetry studies were used to compare the redox properties of 4, 5 and 6 with their trithiacyclononane (9S3) analogues and in compound 4 the ligand L was found to stabilise Ni in the oxidation states 0, I, Il and III. UV-Vis spectroscopic measurements show that L is a stronger field ligand than 9S3. EXAFS studies were also performed on 4, 5 and 6, which established that all three complexes are six-coordinate. (C) 1999 Elsevier Science S.A. All rights reserved.