Synthetic approach to the transition metal complexes of crown thioethers

Abstract

Due to both the chelate and macrocyclic effects, the complexes of crown thioethers are considerably more stable than those of comparable acyclic thioethers. Generally, crown thioethres can stabilize the lower oxidation state of a metal ion and by virtue of the softness of their sulfur donor atoms, they have strong affinities to the late transition metal, especially to the heavy metals such as Hg. Unlike other crown thioethers, 1, 4, 7-trithiacyclononane (9S3) has a "endodenate" conformation and consequently is preorganized for binding facially to a metal ion. In addition, 9S3 is a electronic equivalent as a 6-electron donor to 9N3, Tp$^-$ or Cp$^-$. Originated from this fact, the coordination chemistry of 9S3 has been rapidly developing. In this dissertation, the new synthetic routes to a wide range of heteroleptic complexes of 9S3 were devised and the full characterizations including the molecular structure analyses and the physical properties measurements were carried out. In the reaction course of 9S3 with group 6 metal carbonyls whose reaction chemistry has been well established, M(CO)$_3$(9S3)(M=Cr, Mo, W) were synthesized and their oxidative decarbonylation recations were pursued. From the reactions with I$_2$ and NOBF$_4$, [Mo(CO)$_3$(9S3)I](I$_3$)(1), [W(CO)$_2$(9S3)I]. BPh$_4$(2) and [M(CO)$_2$(NO)(9S3)]BF$_4$ were isolated. The former two compounds were characterized by X-ray diffraction method to confirm the 7-coordination around M(II) with C$_s$ symmetry. On recrystallization of 1 for a long period, Mo(CO)$_2$I$_2$(9S3) was obtained and characterized by analysis and IR spectroscopy. In this recation scheme, 9S3 seems to stabilize the lower-valent state as the results of both electronic property to function as a $\pi$-acceptor and conformational rigidity on ligation. Also, it is inferred that the existence of a strong $\pi$-donor ligand such as oxo or nitrido can stabilize the 9S3 complexes on high-oxidation states. To understand the ligation propert...