OXIDANT-INDUCED HYDRIDE ABSTRACTION FROM [PT(MU-PBU2T)(H)((PBU2H)-H-T)](2) YIELDING [PT-2(MU-PBU2T)(2)(H)((PBU2H)-H-T)(2)]C-3(CN)(5) - SPECTROSCOPIC, CRYSTALLOGRAPHIC, AND THEORETICAL COMPARISON OF THE STRUCTURES OF 2 TAUTOMERS

The platinum(II) phosphido-bridged dihydride [Pt(mu-PBu2t)(H)((PBu2H)- H-t)](2), 1, reacts with tetracyanoethylene (TCNE) in toluene to give the charge-transfer complex 1.TCNE, which is stable only in the solid state. By dissolving 1.TCNE in polar solvents, electron transfer occur s rapidly, followed by loss of one of the hydride ligands and formatio n of the unsaturated Pt(II)Pt(II) derivative [Pt-2(mu-PBu2t)(2)(H)((PB u2H)-H-t)(2)]+TCNE-, 2a. Recrystallization of 2a in the air gives crys tals of [Pt-2(mu-PBu2t)(2)(H)((PBu2H)-H-t)(2)](+) [C-3(CN)(5)](-), 2b, whose structure was solved by X-ray diffraction. The same type of rea ction was observed when 1 was reacted with tetracyanoquinodimethane (T CNQ), forming the analogous, structurally characterized, TCNQ(-) salt of cation 2(+). What happened to the hydride ligand displaced from 1 w as better seen when 1 was reacted with an equimolar amount of [Cp2Fe]P F6 as the oxidant (Cp = cyclopentadienyl). In this case we isolated a 1:1 mixture of (2)PF6, 2d, and [Pt-2(mu-PBu2t)(mu-H)((PBu2H)-H-t)(3)(H )PF6, 3d, the latter also known to form by the reaction of complex 1 w ith strong acids. According to this observation, the reaction of 1 wit h two equivalents of [Cp2Fe]PF6 and one of triethylamine (NEt3) gives quantitatively [NEt3H]PF6 and 2d. The electronic structure of cation 2 (+) was also investigated by means of ab initio and density functional calculations. Ignoring the different metals, cation 2(+) can be consi dered a ''tautomer'' of the known phosphine-bridged dipalladium cation d-2(mu-PBu2t)(mu-(PBu2H)-H-t)((PBU2H)-H-t)(2)](+), 4(+). Differences and analogies between the structures of the two cations were investiga ted by means of spectroscopic, crystallographic, and theoretical tab i nitio and density functional) analyses.