Synthesis, Reaction and Catalysis of Heterodinuclear Alkyl-and Hydridoplatinum(or palladium) Complexes

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Reaction of (dppe)HPd-MoCp(CO)_3 with ethyl Reaction of (dppe)HPd-MoCp(CO)_3 with ethyl acrylate caused immediate reductive elimination of the hydridomolybdenum complex MoHCp(CO)_3. In this reaction, further Markovnikov addition of the metal hydride to ethyl acrylate slowly took place to give an insertion product Mo[CH(CO_2Et)Me]Cp(CO)_3. In the presence of Pc1(η^2-CH_2=CHCO_2Et)(dppe) or Pd(PPh_3)_4, smooth catalytic insertion of olefin into Mo-H bond has been achieved. When hydridomolybdenum complex MoHCp(CO)_3 in benzene was treated with ethyl acrylate in the presence 5 mol% of Pd(η^2-CH_2=CHCO_2Et)(dppe) at room temperature, insertion product Mo[CH(CO_2Et)Me]Cp(CO)_3 was selectively formed quantitatively in 6 h. Acrylonitrile and ethylene also gave corresponding insertion products in 100 and 58% yields. No insertion took place for styrene, propylene, or 1-butene, though catalytic isomerization of 1-butene took place to give a mixture of cis- and trans-2-butene, suggesting reversible insertion of 1-butene into M-H bond. Insertion of 1,2-disubstituted olefins such as dimethyl fumarate and dimethyl maleate was relatively slow and it took a few hours to complete, giving 59 and 79% yields, respectively. A mechanism including cis-insertion of olefin into Pd-H bond through heterodinuclear hydridopalladium intermediate is proposed.