Synthesis and Reactions of Heterodinuclear Organoplatinum Complexes Having an Unsymmetrical PN Ligand

Synthesis and organic group transfer of organodiplatinum complex with a 1,2-bis(diphenylphosphino)ethane ligand

A series of homometallic alkyl- and phenyldinuclear complexes containing one platinum–platinum bond, (dppe)RPt–Pt(η5-Cp)(CO) (R = Me, Et, CH2CMe3, Ph), have been prepared by oxidative addition of the Pt–C bond of PtR(η5-Cp) to Pt(styrene)(dppe), and were characterized by spectroscopic methods and (or) X-ray structure analysis. The geometry at Pt with a dppe ligand is square planar, and the carbonyl and Cp ligand of the Pt(η5-Cp)(CO) moiety lie orthogonal to the coordination plane of former platinum. Competitive organic group transfer reactions along the Pt–Pt bond in these complexes took place to give PtR(η5-Cp)(CO) and PtR(η1-Cp)(dppe) on thermolysis. Alkyl or aryl transfer from Pt with a dppe ligand were enhanced by addition of olefin, whereas treatment with CO and tertiary phosphine ligands causes Cp transfer from Pt(η5-Cp)(CO).Key words: organoplatinum–platinum complex, organic group transfer.

Synthesis of heterobimetallic Ru-Mn complexes and the coupling reactions of epoxides with carbon dioxide catalyzed by these complexes

The heterobimetallic complexes [(eta5-C5H5)Ru(CO)(mu-dppm)Mn(CO)4] and [(eta5-C5Me5)Ru(mu-dppm)(mu-CO)2Mn(CO)3] (dppm = bis-diphenylphosphinomethane) have been prepared by reacting the hydridic complexes [(eta5-C5H5)Ru(dppm)H] and [(eta5-C5Me5)Ru(dppm)H], respectively, with the protonic [HMn(CO)5] complex. The bimetallic complexes can also be synthesized through metathetical reactions between [(eta5-C5R5)Ru(dppm)Cl] (R = H or Me) and Li+[Mn(CO)5]-. Although the complexes fail to catalyze the hydrogenation of CO2 to formic acid, they catalyze the coupling reactions of epoxides with carbon dioxide to yield cyclic carbonates. Two possible reaction pathways for the coupling reactions have been proposed. Both routes begin with heterolytic cleavage of the RuMn bond and coordination of an epoxide molecule to the Lewis acidic ruthenium center. In Route I, the Lewis basic manganese center activates the CO2 by forming the metallocarboxylate anion which then ring-opens the epoxide; subsequent ring-closure gives the cyclic carbonate. In Route II, the nucleophilic manganese center ring-opens the ruthenium-attached epoxide to afford an alkoxide intermediate; CO2 insertion into the RuO bond followed by ring-closure yields the product. Density functional calculations at the B3LYP level of theory were carried out to understand the structural and energetic aspects of the two possible reaction pathways. The results of the calculations indicate that Route II is favored over Route I.