Addition of Palladium and Platinum Tri-<i>tert</i>-Butylphosphine Groups to Re−Sn and Re−Ge Bonds

The reaction of Re2(CO)8[μ-η2-C(H)C(H)Bun](μ-H) with Ph3SnH at 68 °C yielded the new compound Re2(CO)8(μ-SnPh2)2 (10) which contains two SnPh2 ligands bridging two Re(CO)4 groups, joined by an unusually long Re−Re bond. Fenske−Hall molecular orbital calculations indicate that the bonding in the Re2Sn2 cluster is dominated by strong Re−Sn interactions and that the Re−Re interactions are weak. The 119Sn Mössbauer spectrum of 10 exhibits a doublet with an isomer shift (IS) of 1.674(12) mm s-1 and a quadrupole splitting (QS) of 2.080(12) mm s-1 at 90 K,characteristic of Sn(IV) in a SnA2B2 environment. The IS is temperature dependent, −1.99(14) × 10-4 mm s-1 K-1; the QS is temperature independent. The temperature-dependent properties are consistent with the known Gol'danskii−Kariagin effect. The germanium compound Re2(CO)8(μ-GePh2)2 (11) was obtained from the reaction of Re2(CO)8[μ-η2-C(H)C(H)Bun](μ-H) with Ph3GeH. Compound 11 has a structure similar to that of 10. The reaction of 10 with Pd(PBut3)2 at 25 °C yielded the bis-Pd(PBut3) adduct, Re2(CO)8(μ-SnPh2)2[Pd(PBut3)]2 (12); it has two Pd(PBut3) groups bridging two of the four Re−Sn bonds in 10. Fenske−Hall molecular orbital calculations show that the Pd(PBut3) groups form three-center two-electron bonds with the neighboring rhenium and tin atoms. The mono- and bis-Pt(PBut3) adducts, Re2(CO)8(μ-SnPh2)2[Pt(PBut3)] (13) and Re2(CO)8(μ-SnPh2)2[Pt(PBut3)]2 (14), were formed when 10 was treated with Pt(PBut3)2. A mono adduct of 11, Re2(CO)8(μ-GePh2)2[Pt(PBut3)] (15), was obtained similarly from the reaction of 11 with Pt(PBut3)2.