New Re(III) complexes with alkylthioureas as precursor to other Re(III) compounds. Crystal structures of [Re(N-ethylthiourea)6](PF6)3 and [Re(N-N’-dimethyl thiourea)6] (PF6)3

D. GAMBINO; J. BENITEZ; L. OTERO; E. KREMER; E. J. BARAN; O. E. PIRO

POLYHEDRON

Pergamon

Año: 1999 p. 2099 - 2107

0277-5387

Abstract. New Re(III) complexes with thiourea derivatives have been synthesized by reduction of perrhenate with tin(II) chloride in 2N hydrochloric acid in the presence of excess alkylthiourea. The obtained compounds were [Re (alkylthiourea-S) ]X .nH O, where X is Cl- or PF6- and alkylthiourea is N-methylthiourea (Metu), N, N9-dimethylthiourea (Me tu) or N-ethylthiourea (Ettu). Complexes were characterized by elemental and thermal analyses and by electronic and FTIR spectroscopy. Their kinetic stabilities in aqueous and III methanolic solutions were also studied. Results were compared with those previously reported for [Re (tu-S) ]Cl .4HO, where tu = thiourea. Molecular structures of [Re (Ettu) ](PF6) and [Re (Metu) ](PF6) were determined by single crystal X-ray diffraction  methods. The coordination polyhedra around the Re(III) ion are distorted octahedra. The six alkylthiourea ligands are sulfur bonded to the central atom [d(Re–S) ranges from 2.402(4) to 2.441(4) A° for the ethylthiourea complex and from 2.416(3) to 2.446(3) for the dimethylthiourea one]. Capability of working as starting materials via ligand substitution, in methanolic medium for these new Re(III) complexes and for previously reported [Re (tu) ]Cl .4HO is stated. Selected incoming ligands, 1,2-bis(diphenylphosphino) ethane (dppe) and 1,3-bis(diphenylphosphino) propane (dppp), lead to the already known [Re (dppe) Cl ]Cl.2MeOH and [Re (dppp) Cl ]Cl with good yields. Re(III) complexes with thiourea and alkylthioureas can be ordered according to their substitution rate as follows: [Re(tu) ] < [Re(Ettu) ] = [Re(Metu) ] < [Re(Me tu) ].