Borane complexes phosphorus-nitrogen

The chemistry of boron-phosphorus compounds has been reviewed. Numerous boron-phosphorus derivatives have been reported, but relatively few boron-arsenic or boron-antimony compounds have been described. Boron-phosphorus compounds are similar in many ways to boron - nitrogen derivatives, but the tendency to share bonding electrons in covalent tetrahedral compounds is much more evident with phosphorus than with nitrogen. In fact, most boron-phosphorus chemistry involves tetrahedral boron. They are typically either phosphine-borane complexes, such as RgP-BRj, or phosphinoboranes (R2PBR 2) , cyclic or polymeric derivatives of the hypothetical H3P BH3. The chemistry of these compounds and that of boron phosphate and thiophosphate is described below. Boron phosphides are discussed in Section 2.6. 

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). 

The stereochemistry of boron is simple in many of its compounds with the halogens (but note BgClg), oxygen, nitrogen, and phosphorus, three coplanar or four tetrahedral bonds being formed. The more complex stereochemistry of the element in electron-deficient systems (elementary B, some borides, and the boranes) is dealt with separately. The planar arrangement of three bonds from a B atom has been demonstrated in many molecules BX3 and BR3 (Table 24.1), in cyclic molecules of the types noted in the previous section, in many oxy-ions (see later section), and in crystals such as the graphite-like form of BN (p. 847) and AlBj (p. 842). 

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