Synchronous hydride transfer

Summary BusSnH is an effective reagent for partial conversion of Si-Cl into Si-H groups. The hydrogenation mechanism postulates the coordination of the catalyst or the solvent to silicon giving a hypervalent intermediate in the first step, followed by the attack of tributyltin hydride by a single electron transfer or a synchronous hydride transfer. This mechanism implies that the intermediate containing a hypervalent silicon atom reacts faster than the starting tetracoordinate silane. 

The hydride transfer and the ring-opening of hexamethylenetetramine may occur in a synchronized fashion ... 

Treatment of acetals with thiols in excess produces an equilibrium mixture from which the corresponding dithioacetal may be obtained a favourable case from this point of view is the conversion of formamide acetals R2NCH(OMe)2 into corresponding mercaptals. Vinyl sulphides CH2=CHSR give acetaldehyde dithioacetals CHs—CH(SR)2, in 40% yield, and acetylene, on being heated at 170—180 °C in the presence of KOH, through synchronous intramolecular transfer of hydride and thiolate. 

Although thiol and hydride/thiolate complexes are known, there are few studies which show that the hydrogen can move between metal and sulfur [35-38]. The transfer of a proton from sulfur to metal has been proposed before. For example, the so-called oxidative-addition of RSH to [IrCl(CO)(PPh3)2] has been suggested to involve a three-centre, Ir-H-SR transition state in which the lengthening of the S-H bond is synchronous with the binding of these two atoms to the iridium centre [39]. More recently [40] an agostic Os—H-S interaction has... 

TS32-37 is characterized by a synchronous transfer of a proton from the nitrogen and a hydride from the Ru. The presence of a NH or NH2 group in the ligand is... 

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