2,6-Bis(diphenylphosphino)pyridine-bridged hetero-polynuclear complexes consolidated by Fe-->M (M = Ag, Hg) dative bonding.

The bridging phosphine ligand 2,6-bis(diphenylphosphino)pyridine (L) was used to synthesize a new, neutral organometallic ligand [Fe(CO)(4)](2)(micro-L) 1, which exhibits eclipsed and staggered conformations in two crystalline forms. This Fe,N,Fe-tridentate ligand reacts with silver perchlorate to form the hetero-trinuclear complex [[Fe(CO)(4)](2)Ag(micro-L)](ClO(4)) 2, in which the central silver(I) atom bridges a pair of iron(0) atoms at Fe-Ag distances of 2.627(3) and 2.652(3) A; the Fe-Ag-Fe angle is 170.98(9) degrees. The reaction of 1 with mercury(II) chloride gives [Fe(CO)(4)](2)Hg(2)Cl(4)(micro-L), 3. The ligand also reacts with mercury(II) acetate to form a hetero-octanuclear complex [[Fe(CO)(3)Hg](2)(micro-L)](2) 4 and a novel hetero-heptanuclear complex Fe(3)(CO)(8)Hg(4)(micro-L)(2)(MeCO(2))(2) 5. Complex 4 displays a square metallic core in which the iron and mercury atoms occupy the corners and the centers of the edges, respectively. The metal atoms in 5 are linked to form a kinky line with bends at the iron atoms.