Pyridinethiolate Titanocene Metalloligands and Their Self-Assembly Reactions To Yield Early–Late Metallamacrocycles

New
titanocene pyridinethiolate compounds [(RCp)2Ti­(4-Spy)2] (R = H (1), Me (2); Cp = cyclopentadienyl;
4-Spy = pyridine-4-thiolate) and [Cp2Ti­(2-Spy)2] (3; 2-Spy = pyridine-2-thiolate) have been prepared
by reaction of the corresponding Li­(Spy) salt with the appropriate
compound [(RCp)2TiCl2]. Compounds 1 and 2 have been used as metalloligands in self-assembly
reactions with the acceptor late-transition-metal compounds [M­(H2O)2(dppp)]­(OTf)2 (M = Pd (a) Pt (b); dppp = 1,3-bis­(diphenylphosphino)­propane),
and the series of early–late tetranuclear metallamacrocycles
[{(RCp)2Ti­(4-Spy)2}­{M­(dppp)}]2(OTf)4 (R = H, M = Pd (12a2); R = H, M = Pt (12b2);
R = Me, M = Pd (22a2); R = Me, M = Pt (22b2)) arising from
the anti isomer of the titanocene metalloligands have been obtained.
Only ligand transfer reactions from Ti to either Pd or Pt atoms have
been observed when the pyridine-2-thiolate derivative 3 has been assayed in self-assembly processes. The obtained species
have been characterized by NMR spectroscopy and ESI­(+) mass spectrometry.
The supramolecular assemblies have shown to be nonrigid in solution,
and their fluxional behavior has been studied by VT 1H
NMR spectroscopy. A DFT study including ab initio molecular dynamics
in order to elucidate the structures and the relative stability of
the isomers has been performed.