THE PHOSPHINOPHOSPHINIDENE-PHOSPHORANES ( T)BU(2)P-P=P(R)(T)BU(2) FROM LI(THF)(2)[ETA(2)-((T)BU(2)P)(2)P] AND ALKYL-HALIDES

We report the formation of (t)Bu(2)P-P=P(R)(t)Bu(2) a and ((t)Bu(2))(2 )PR b (with R = Me, Et, Pr-n, Pr-i, (n)Bu, PhCH(2), H2C= CH-CH2 and CF 3) reactions of Li(THF)(2)[eta(2)-((t)Bu(2)P)(2)P] 2 with MeCl, Mel, E tCl, EtBr, (PrCl)-Pr-n, (PrBr)-Pr-n, (PrCl)-Pr-i, (n)BuBr, PhCH(2)Cl, H2C=CH-CH2Cl or CF3Br. In THF solutions the ylidic compounds a predomi nate, whereas in pentane the corresponding triphosphanes b are preferr ably formed. With ClCH2-CH=CH2 only b is produced; CF3Br however yield s both (t)Bu(2)P-P=P(Br)(t)Bu(2) and (t)Bu(2)P-P=P(CF3)(t)Bu(2), but n o b. The ratio of a:b is influenced by the reaction temperature, too. The compounds (t)Bu(2)P-P=P(Et)(t)Bu(2) 4a and ((t)Bu(2)P)(2)PEt 4 b, e. g., are produced in a ratio of 4: 3 at -70 degrees C in THF, and 1: 1 at 20 degrees C; whereas 1:1 is obtained at -70 degrees C in pentane , and 1 :2 at 20 degrees C. Neither (t)BuCl nor H2C=CHCl react with 2. The compounds a decompose thermally or under UV irradiation forming ( t)Bu(2)PR and the cyclophosphanes ((t)Bu(2)P)(n)P-n.