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

The reaction between the linear trinuclear complex [Pt{Fe(CO)(3)(NO)}(2)(PhCN)(2)] and Ph-2(2-C5H4N)PSe led to the isolation and characterization of the 46-electron cluster [(CO)(3)Fe(mu(3)-Se){Pt(CO)P(2-C5H4N)Ph-2}(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 mu(3)-Se atom, is rather rare. The chemical bonding in I and in similar systems has been analyzed through density functional theory (DFT) and qualitative MO approaches. A strict analogy with the well understood L2M(mu acetylene) ML2 systems is invoked by considering I as formed by the (CO)(3)FedropSe tetrahedral unit stabilized by sidewise interactions of the triple bond with two d(10)-L2M fragments. Otherwise, the 18-electron (CO)(3)FedropSe monomer is unstable as an isolate molecule. This is confirmed by our DFT calculations that indicate how the well characterized dimer (CO)(3)Fe(mu-Se-2)Fe(CO)(3) lies as much as, approximately, 58 kcal mol(-1) deeper in energy. Finally, by considering an analogy with [L2M(mu-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.