New Rhenium−Tin Cluster Adds Palladium Phosphine Groups across Re−Sn Bonds

The new rhenium−tin complex Re2(CO)8(μ-SnPh2)2, 1 was obtained in 52% yield from the reaction of Re2(CO)8(μ-H)[μ-C(H)C(H)Bu] with Ph3SnH. Compound 1 contains two SnPh2 groups bridging a long Re−Re single bond, Re−Re = 3.1971(4) Å [3.1902(4) Å], Re−Sn = 2.7429(4) Å [2.7445(4) Å], and 2.7675(4) [2.7682(5) Å]. A bis-Pd(PBut3) adduct of 1, Pd2Re2(CO)8(μ-SnPh2)2(PBut3)2, 2 was obtained from the reaction of 1 with Pd(PBut3)2. Compound 2 contains Pd(PBut3) groups bridging two of its four Re−Sn bonds. The Re−Re bond and the unbridged Re−Sn bonds in 2 are significantly longer than those in 1, 3.245(1) Å and 2.8167(14) Å, respectively. Fenske−Hall molecular orbital calculations on 1 and 2 have been performed to explain the metal−metal bonding in these unusual mixed-metal polynuclear metal complexes.