Tetrakis(dialkylamino)cyclotetraphosphines and Bis(dialkylamino)dihalobiphosphines

Article abstract of DOI:10.1021/jo00210a028

Dehalogenation of R2NPCl2 (R = isopropyl or cyclohexyl) with magnesium in tetrahydrofuran gives the corresponding cyclotetraphosphines (R2N)4P4; the corresponding biphosphines (i-Pr2N)2P2X2 (X = Cl and Br) can be isolated from reactions of i-Pr2NPX2 with more limited quantities of magnesium.Dehalogenations with magnesium of R2NPCl2 derivatives having R2N groups smaller than diisopropylamino lead to redistribution of the dialkylamino groups giving (R2N)2P-P(NR2)2 (R2N = piperidino) or (R2N)3P (R2N = diethylamino or dimethylamino).Such redistribution reactions can be suppressed but not eliminated by using the homogenous dehalogenating agent (Me3Si)2Hg in hydrocarbon solvents.The steric bulk of the diisopropylamino groups in (i-Pr2N)4P4 reduces its chemical reactivity relative to other cyclotetraphosphines; thus (i-Pr2N)4P4 is unreactive toward oxygen, carbon disulfide, potassium metal, and various metal carbonyls under conditions where other cyclotetraphosphines react with these reagents.However, the P4 ring in (i-Pr2N)4P4 is cleaved under mild conditions by hydrogen chloride as well as by bromine and iodine.