Transition-metal hydrides amines

The well-established reducing properties of the Sn—H bond have led to a number of useful synthetic methods for forming a tin-metal bond. In particular, many early transition-metal hydrides, -amides and -silanes readily eliminate H2/amines/silanes upon treatment with the Sn—H bond. Some examples are illustrated in equations 79-83 for... 

The elimination of amines may also be accomplished by using the reactions of organotin amides and transition-metal hydrides, or transition-metal amides and tin hydrides4. Neither route has attracted much attention recently. 

The noncompatibility of transition metal hydrides with coexisting ketones result in alcohol by product formation. The starting (and product) amines are limited to those that only weakly complex with the transition metal species in the catalytic cycle. 

Finally, dienes may be converted into monoenes under transition metal hydride transfer conditions. Acidic organic alcohols, e.g., catechol, are effective in these reactions, and 1,5-cyclooctadiene is reduced to cyclooctene Hydrogen transfer from amines such as 1,3-propanediamine is also efficient. Thus, when 1,5-cyclooctadiene and 1,3-propanediamine are stirred at 140°C for 2 h in the presence of Pd black, cyclooctene is obtained in 85% yield together with 24 ° ... 

Acidic transition-metal hydrides have been used to prepare metal-silicon bonded compounds by an interesting condensation reaction that proceeds with amine elimination (equation 30)66. An attempt to carry out a similar reaction between Ph3SiH and the zirconium amide Cp2Zr(NMe2)2 failed67. 

The primary, secondary, and tertiary aliphatic amines do not form simple addition complex ions with bare transition metal ions. Only Ag+ reacts with MeNH2 to form a simple addition product [AgMeNH2]+ (107). The Pb+ ion also forms addition products, [PbMeNH2]+ and [Pb(MeNH2)2]+, with methylamine (143). Other bare transition metal ions (144) react with amines via removal of one hydrogen to form the metal hydride and the amine cation with one hydrogen removed [RR N]+. 

Most transition metal ions react with aliphatic amines by hydride abstraction and some second- and third-row metal ions react by dehydrogenation and de-methanation. This area has been adequately reviewed by Eller and Schwarz (9), but to highlight a specific example, the reaction of ammonia with bare Ti+ will be discussed. 

Hydride abstraction from alkylamines forms the corresponding imi-nium ions, whose coordination to transition metals gives either a ir-complex or cr-bonded three-membered ring (Scheme 15) (26). Ligation of the cationic dehydro amines to Rh is aided by substantial electron donation from the metal to the electron-deficient carbon atom to produce the Rh(IH) complex with a covalent C—Rh bond and an N—Rh dative bond, consistent with the long C—N bond (1.467 A) and the small H— C( 1)-—N—C(2) dihedral angle (124.6°) as well as the noncoplanarity of the CH2—CH bond and a possible CH—NH2 plane seen in the allylam-ine oxidative addition product (24). 

Asymmetric hydrometallation of ketones and imines with H-M (M = Si, B, Al) catalyzed by chiral transition-metal complexes followed by hydrolysis provides an effective route to optically active alcohols and amines, respectively. Asymmetric addition of metal hydrides to olefins provides an alternative and attractive route to optically active alcohols or halides via subsequent oxidation of the resulting metal-carbon bonds (Scheme 2.1). 

The hydroamination reactions which are assisted or catalyzed by transition metal species can be utilized in the cyclization of unsaturated amines. Palladium(II) is not recommended for such transformations, since low yields were obtained even using stoichiometric amounts of palladium chloride47. Since an enamide is formed by /J-hydride elimination, a reduction step must be performed to obtain the saturated nitrogen heterocycle. A catalytic cyclization reaction, analogous to the Wacker process, was performed from /V-alkenyl tosylamides, such as 1, using... 

Transition-metal-coordinated NjR complexes react with complex hydrides to form NHNR complexes or free NHj or amines in reactions whose stoichiometries are not established ... 

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