Synthesis and properties of polynuclear complexes containing {Mo(NO)[HB(dmpz)3]Cl} metal centres axially bound to a Ru(tpp) core (dmpz = 3,5-dimethylpyrazol-1-yl; tpp =meso-5,10,15,20-tetraphenylporphyrinate)

Abstract

A series of mononuclear complexes [Mo(NO){HB(dmpz)3}Cl(L)][dmpz = 3,5-dimethylpyrazol-1-yl; L = a potentially bridging ligand of which one terminus (pyridyl or phenolate) is attached to the Mo and the second terminus (pyridyl) is pendant] were attached to the axial positions of a Ru(tpp) core (tpp =meso-5,10,15,20-tetraphenylporphyrinate)via the pendant pyridyl groups. By using [Ru(tpp)(CO)(EtOH)], of which only the axial EtOH ligand is substitution labile, binuclear complexes [{(OC)(tpp)Ru}(µ-L){Mo(NO)[HB(dmpz)3]Cl}] were prepared. With [Ru(tpp)(thf)2](thf = tetrahydrofuran), in which both thf ligands are labile, the trinuclear complexes [{Cl[HB(dmpz)3](ON)Mo}(µ-L){Ru(tpp)}(µ-L){Mo(NO)[HB(dmpz)3]Cl}] were prepared. The new complexes have been thoroughly characterised by 1H NMR, fast atom bombardment mass spectrometry, IR, UV/VIS and EPR spectroscopy and electrochemistry as appropriate. Weak electrochemical interactions between the molybdenum groups and the Ru(tpp) core are apparent. In the trinuclear complexes with two axial paramagnetic molybdenum groups (17 valence-electron configuration) a weak spin-exchange interaction between the two remote molybdenum centres can be detected when the intermediate bridging ligands L are 4,4′-bipyridine but not when L is 3,3′-dimethyl-4,4′-bipyridine, possibly due to an increased dihedral twist of the two bridging ligands in the latter case.