The equilibrium between disilenes (R 2 Si=SiR 2 )a nd their silylsilylene (R 3 SiÀSiR) isomers has previously been inferred but not directly observed, except in the case of the parent system H 2 Si = SiH 2 .H ere,w er eport an ew method to prepare base-coordinated disilenes with hydride substituents. By varying the bulk of the coordinating base and other silicon substituents,wehave been able to control the rearrangement of disilene adducts to their silylsilylene tautomers.R emarkably, 1,2 migration of at rimethylsilyl group is preferred over hydrogen migration. AD FT study of the reaction mechanism provides ar ationale for the observed reactivity and detailed information on the bonding situation in base-stabilized disilenes.

Hydroboration is an emerging methodf or mild and selectiver eduction of carbonyl compounds. Typically, transition-metal or reactive main-group hydride catalysts are used in conjunction with am ild reductant such as pinacolborane. The reactivity of the main-group catalysts is ac onsequence of the nucleophilicity of their hydride ligands. Silicon hydrides are significantly less reactive and are therefore not efficient hydroboration catalysts. Here, a readily prepared silyl anion is reportedt ob ea ne ffective initiator for the reduction of aldehydes and ketonesr equiring mild conditions,l ow catalyst loadings and with a good substrate scope. The silyl anion it is shown to activate HBpint og enerateareactive borohydride in situ which reacts with aldehydes and ketones to afford the hydroboration product. Scheme1.Previously reported main-group catalysts and mechanisms for the hydroboration of carbonyl compounds.

The equilibrium between disilenes (R2Si=SiR2) and their silylsilylene (R3Si−SiR) isomers has previously been inferred but not directly observed, except in the case of the parent system H2Si=SiH2. Here, we report a new method to prepare base‐coordinated disilenes with hydride substituents. By varying the bulk of the coordinating base and other silicon substituents, we have been able to control the rearrangement of disilene adducts to their silylsilylene tautomers. Remarkably, 1,2 migration of a trimethylsilyl group is preferred over hydrogen migration. A DFT study of the reaction mechanism provides a rationale for the observed reactivity and detailed information on the bonding situation in base‐stabilized disilenes.

The syntheses of five new phosphaamidines RNC(tBu)P(H)(R’’) of readily variable steric bulk are described. Crystallographic and multinuclear NMR studies indicate the geometry of the phosphaamidine is dependent on the steric bulk of the peripheral substituents. In one case, multiple isomers were observed in solution. Complexation of the phosphaamidines to magnesium by reaction of either 0.5 or 1 equivalents of nBu2Mg forms either hetero- (LMgnBu) or homoleptic (L2Mg) species respectively, culminating in the isolation of a monomeric, unsolvated three-coordinate magnesium phosphaamidinate.