P- and N-Coordination of the Ambidentate Ligand HN[P(i-Pr)2]2 with Group 13 Trihalides

Reaction of bis(dialkylphosphino)amines R2PNHPNR2 (R = i-Pr, t-Bu, Ph) with halogens X2 (X = Cl, Br, I): different solvents – different stories

The bis(dialkylphosphino)amines R2PNHPNR2 react with elemental halogens X2 in dichloromethane to produce cationic products of the general form [(R)2P(X)-N-(R)2P(X)]+ (R = i-Pr, Ph, t-Bu; X = Cl, Br, I). All of the nine possible products have been isolated and characterized using X-ray diffraction. The dichloro compounds crystallize as [HCl2]- salts, while the dibromo and diiodo products have been isolated as trihalides, [X3]-. A number of these compounds have been shown to react further with methanol to produce salts containing [(R)2P(OCH3)N(R)2P(OCH3)]+ cations, some of which have also been characterized using X-ray crystallography. Conversion of [(Ph)2P(I)-N-(Ph)2P(I)][I3] to [(Ph)2P(OCH3)-N-(Ph)2P(OCH3)] [I3] was monitored using 31P NMR spectroscopy which revealed a stepwise reaction of the former compound with methanol. The results are discussed within the context of coupled reactions; this is then used to rationalize a mechanism for the formation of a rare catenated bismuth compound we reported previously. We suggest that the formation of the weak Bi-Bi bonds is offset by a coupled or a connected reaction mechanism, involving an irreversible reaction forming strong P-OR bonds in another of the isolated products.

Heavy Metals Make a Chain: A Catenated Bismuth Compound

Catenation is common for the light main-group elements whereas it is rare for the heavy elements. Herein, we report the first example of a neutral molecule containing a Bi₄ chain. It is prepared in a one-step reaction between bismuth trichloride and bis(diisopropylphosphino)amine in methanol suspension. The same reaction carried out in dichloromethane gives quite different products. All products have been characterized spectroscopically and using single-crystal X-ray analysis.