Unique axial interaction of a quadruply-bonded Cr(II)-Cr(II) with two Pt(II) atoms in the linearly aligned Pt-Cr-Cr-Pt supported by four 6-diphenylphosphino-2-pyridonate ligands

Linearly aligned tetranuclear Pt(II)-Cr(II)-Cr(II)-Pt(II) complexes were pr epared using a tridentate pyphos ligand (pyphos = 6-diphenylphosphino-2-pyr idonate). The bonding between Cr(II) and Pt(II) was discussed on the basis of magnetic measurements. A dichromium complex, [Cr-2(pyphos)(4)] (1), was prepared by the reaction of [Cr-2(OAc)(4)] with the sodium salt of pyphos l igand. The complex 1 has four phosphorus atoms capable of holding transitio n metals at both of the axial positions of the Cr-2 moiety. Three tetranucl ear Pt(II)-Cr(II)-Cr(II)-Pt(II) complexes, i.e., [Cr2Pt2Me4(pyphos)(4)] (2) , [Cr2Pt2Cl4(pyphos)(4)] (3), and [Cr2Pt2Cl2Me2(pyphos)(4)] (4), have been prepared by the addition of the respective platinum species, (PtMe2)-Me-II, (PtCl2)-Cl-II, and (PtMeCl)-Me-II, to the axial positions of the Cr, moiety of 1. Magnetic measurements of 1-4 together with a crystallographic study for the complexes 1 and 2 revealed that the quadruply-bonded Cr-Cr distance was delicately altered by the nature of the Pt atoms, i.e., the kind of su bstituents (Cl and/or Me) on the Pt atoms.