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(μ-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}2Ag(μ-L)](ClO4) 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) Å; the Fe−Ag−Fe angle is 170.98(9)°. The reaction of 1 with mercury(II) chloride
gives {Fe(CO)4}2Hg2Cl4(μ-L), 3. The ligand also reacts with mercury(II) acetate to form a hetero-octanuclear
complex [{Fe(CO)3Hg}2(μ-L)]2 4 and a novel hetero-heptanuclear complex Fe3(CO)8Hg4(μ-L)2(MeCO2)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.