Reaction of [Pt{Fe(CO)3(NO)}2(PhCN)2] with diphenyl(2-pyridyl)phosphine selenide. Crystal structure of [(CO)3Fe(μ3-Se){Pt(CO)P(2-C5H4N)Ph2}2] and its theoretical study

The reaction between the linear trinuclear complex [Pt{Fe(CO)3(NO)}2(PhCN)2] and Ph2(2-C5H4N)PSe led to the isolation and characterization of the 46-electron cluster [(CO)3Fe(μ3-Se){Pt(CO)P(2-C5H4N)Ph2}2] (1), whose structure has been determined by X-ray diffraction methods. The cluster typology, which consists of an open triangle PtFePt capped by a μ3-Se atom, is rather rare. The chemical bonding in 1 and in similar systems has been analyzed through density functional theory (DFT) and qualitative MO approaches. A strict analogy with the well understood L2M(μ-acetylene)ML2 systems is invoked by considering 1 as formed by the (CO)3FeSe tetrahedral unit stabilized by sidewise interactions of the triple bond with two d10-L2M fragments. Otherwise, the 18-electron (CO)3FeSe monomer is unstable as an isolate molecule. This is confirmed by our DFT calculations that indicate how the well characterized dimer (CO)3Fe(μ-Se2)Fe(CO)3 lies as much as, approximately, 58 kcal mol−1 deeper in energy. Finally, by considering an analogy with [L2M(μ-dichalcogen)ML2]0, +2 redox systems (M=Pd, Pt), reduction of 1 to a dianion has been hypothesized and the structure of the latter has been tentatively explored by DFT calculations.