Synthesis, structure and thermolysis of cis-dialkylplatinum(II) complexes – Experimental and theoretical perceptions

• Platinum(II)-dialkyl complexes were synthesized and structurally characterized.
• On heating, the shorter chain dialkyl complexes prefer to undergo only the β-hydride elimination pathway.
• On contrary, the longer chain dialkyl complexes undergo selectively reductive elimination.
• DFT calculations reveal the shorter Pt(1)-H(β) distances leading to β- hydride elimination in shorter chain dialkyl complexes.

The formation of new CC bonds by metal complexes always stimulates great interest because these fundamental reaction types possess numerous potential applications in organic synthesis. These reactions are well documented for a variety of transition metal complexes. Herein we report synthesis and characterization of a series of platinum-dialkyl complexes (1–10) of the type [Pt(L2)R2], (where L2 = dppp (1,3-bis(diphenylphosphino)propane or L = PPh3; R = n-butyl to n-nonyl) with a view to understand the organic product distribution patterns on thermolysis. The single crystal X-ray structures of the complexes [Pt(dppp){CH2(CH2)3CH3}2] (1) and [Pt(dppp){CH2(CH2)6CH3}2] (7) are reported. Thermal decomposition studies of these complexes show interesting behaviour; the longer chain dialkyls i.e. C7C9 complexes undergo reductive elimination whereas the shorter chain dialkyl complexes and C3C6 prefer only the β-hydride elimination reaction. Possible mechanistic aspects are discussed. Theoretical calculations reveal the strongest delocalizations in both complexes involve the interaction of PtC bond pair electron density with the trans positioned PtP antibonding orbital and vice-versa.

Reaction Pathways in Platinum-Dialkyl Complexes – Reductive elimination is more preferred than β-hydride elimination with longer chain lengths.Figure optionsDownload as PowerPoint slide