Metal “Capture” by a Heterotrimetalloligand, Heterometallic d¹⁰−d¹⁰ Interactions, and Unexpected Iron-to-Platinum Silyl Ligand Migration: a Combined Experimental and Theoretical Study

The heterotrinuclear chain complex Hg[Fe{Si(OMe)3}(CO)3(dppm-P)]2 (dppm = Ph2PCH2PPh2) 1 which has a transoid arrangement of the phosphine donors was used as a versatile chelating metallodiphosphine ligand owing to the easy rotation of its metal core about the Fe−Hg σ-bonds. Its reaction with the labile Pt(0) olefin complex [Pt(C7H10)3] yielded [HgPt{Si(OMe)3}Fe2(CO)6{Si(OMe)3}(μ-dppm)2] 5 which resulted, after coordination of the dangling phosphine donors to Pt, from an unprecedented intramolecular rearrangement involving a very rare example of silyl ligand migration between two different metal centers, and the first one in metal cluster chemistry. The major structural differences observed between the heterometallic complexes obtained from 1 and d10 Cu(I), Pd(0), or Pt(0) precursors have been established by X-ray diffraction. The bonding situation in the silyl migrated Pt complex 5 was analyzed and compared to those in the isoelectronic, but structurally distinct complexes obtained from Cu(I) and Pd(0) precursors, [Hg{Fe[Si(OMe)3](CO)3(μ-dppm)}2Cu]+ (2) and [Hg{Fe[Si(OMe)3](CO)3(μ-dppm)}2Pd] (4), respectively, by means of extended Hückel interaction diagrams. DFT calculations then allowed the energy minima associated with the three structures to be compared for 2, 4, and 5. All three minima are in close competition for the Pd complex 4, but silyl migration is favored by ∼10 kcal mol-1 for 5, mainly due to the more electronegative character of Pt with respect to Pd.