Borane complexes metal-nitrogen

Alanes and boranes are initially electrophilic rather than nucleophilic, and coordinate onto free electron pairs in the molecule prior to hydride delivery. The chemistry of metal hydrides has been extensively reviewed, as has the reduction of nitrogen heterocycles with complex metal hydrides. Generally, NBH reductions, carried out in alcohols, produce tetrahydropyridines, whilst LAH generates mainly di-hydropyridines. 

In 1998 Simpkins et al. reported that the metallation and alkylation of N-methylisoindoline-borane complex 122 with n-BuIi/5 provided products 123 in up to 94 6 er (Scheme 38) [88,89]. The mechanism of the reaction was established to involve an asynunetric deprotonation to give an organolithium which is configurationally stable at nitrogen but stereochemically labile with respect to the C-Li bond. 

Common reducing agents are hydrogen in the presence of metallic or complex catalysts (e.g. Ni, Pd, Pt, Ru, Rh), hydrides (e.g. alanes, boranes, LIAIH, NaBHJ, reducing metals (e.g. Li, Na, Mg, Ca, Zn), and low-valent compounds of nitrogen (e.g. NjHj, NjHJ, phosphorus (e.g. triethyl phosphite, triphenyiphosphine), and sulfur (e.g. HO-CHj-SOjNa = SFS, sodium dithionite = Na S O. ... 

Aminomethylphosphines are convenient objects for a comparison of phosphorus and nitrogen donor ability in complexation reactions. Coordination compounds of heterocyclic aminomethylphosphines with metals are discussed in Section VII. In this section we present reactions of aminomethylphosphines with boranes (BH3). 

Abstract. Two novel three-nitrogen cryptands with V-aryl substituents are prepared by cyclization of l,10-diaza-18-crown-6 with mixed anhydrides of 6-arylaza-3,9-dioxadecanedioic acid followed by borane reduction of the resultant bicyclic diamides. For the alkali metal cations, the V-phenyl [3.2.2] cryptand exhibits strongest complexation for Rb in picrate extractions. 

---