Transformations and Reactions of Re2(CO)8(μ-SbPh2)(μ-H) Induced by the Addition of a Platinum(tri-t-butylphosphine) Group

Abstract

Three products Re(2)[Pt(PBu(t)(3))](mu-SbPh(2))(CO)(8)(mu-H), 2, Re(2)[Pt(CO)(PBu(t)(3))]Ph(CO)(8)(mu(3)-SbPh)(mu-H), 3, and Re(2)[Pt(PBu(t)(3))](2)(CO)(8)(mu(4)-Sb(2)Ph(2))(mu-H)(2), 4, were obtained from the reaction of Re(2)(CO)(8)(mu-SbPh(2))(mu-H), 1, with Pt(PBu(t)(3))(2). Compound 3 was also obtained from 2 by further reaction with Pt(PBu(t)(3))(2). Compound 2 is a Pt(PBu(t)(3)) adduct of 1 formed by the insertion of the platinum atom into one of the Re-Sb bonds of 1 with formation of two Pt-Re bonds. Compound 3 contains an open Re(2)Pt cluster and was also obtained in a low yield by the addition of CO to 2. The addition of SbPh(3) to 2 yielded the compound Re(2)Pt(PBu(t)(3))(Ph)(CO)(8)(SbPh(3))(mu(3)-SbPh)(mu-H), 5, a SbPh(3) derivative of 3. Compound 4 can be viewed as a dimer of the fragment Re[Pt(PBu(t)(3))](CO)(4)(SbPh)(mu-H). The two halves of the molecule are held together by Pt-Sb bonds and a significant interaction directly between the Sb atoms, Sb-Sb distance, 2.9834(7) A. The Sb-Sb bonding in 4 was explained by density functional calculations. Compound 4 adds 2 equiv of CO at 1 atm/25 degrees C, one to each platinum atom, to yield the compound [Re(CO)(4)Pt(H)(CO)(PBu(t)(3))(mu(3)-SbPh)](2) which exists as a mixture of two noninterconverting isomers, cis-6 and trans-6. Both isomers of 6 were isolated and structurally characterized. Each isomer of 6 consists of a central planar Re(2)Sb(2) core composed of two Re(CO)(4) groups with two bridging SbPh ligands. There is a Pt(H)(CO)(PBu(t)(3)) group coordinated to each antimony atom of 6. In the cis-isomer both Pt(H)(CO)(PBu(t)(3)) groups lie on the same side of the Re(2)Sb(2) plane. In the trans-isomer the Pt(H)(CO)(PBu(t)(3)) groups lie on opposite sides of the Re(2)Sb(2) plane.