Pt···Pt vs Pt···S Contacts Between Pt-Containing Heterobimetallic Lantern Complexes

A trio of Pt-based
heterobimetallic lantern complexes of the form
[(py)­PtM­(SAc)4(py)] (M = Co, 1; Ni, 2; Zn, 3) with unusual octahedral coordination
of Pt­(II) was prepared from a reaction of [PtM­(SAc)4] with
excess pyridine. These dipyridine lantern complexes could be converted
to monopyridine derivatives with gentle heat to give the series [PtM­(SAc)4(py)] (M = Co, 4; Ni, 5; Zn, 6). An additional family of the form [PtM­(SAc)4(pyNH2)] (M = Co, 7; Ni, 8;
Zn, 9) was synthesized from reaction of [PtM­(SAc)4(OH2)] or [PtM­(SAc)4] with 4-aminopyridine.
Dimethylsulfoxide and N,N-dimethylformamide
were also determined to react with [PtM­(SAc)4] (M = Co,
Ni), respectively, to give [PtCo­(SAc)4(DMSO)]­(DMSO), 10, and [PtNi­(SAc)4(DMF)]­(DMF), 11. Structural and magnetic data for these compounds and those for
two other previously published families, [PtM­(tba)4(OH2)] and [PtM­(SAc)4(L)], L = OH2, pyNO2, are used to divide the structures among three distinct categories
based on Pt···Pt and Pt···S distances.
In general, the weaker donors H2O and pyNO2 seem
to favor metallophilicity and antiferromagnetic coupling between 3d
metal centers. When Pt···S interactions are favored
over Pt···Pt ones, no coupling is observed and the
pKa of the pyridine donor correlates with
the interlantern S···S distance. UV–vis–NIR
electronic and 1H NMR spectra provide complementary characterization
as well.