Formation and rearrangement of Sn~(II) phosphanediide cages

摘要

The room-temperature reactions of Sn(NMe_2)_2 with less sterically demanding primary phosphines (RPH_2) give the homoleptic phosphanediide compounds [SnPR], in high yields (R = tBu (1a), cyclohexyl (1b), 1-adamantyl (1c)). However, the room-temperature reaction of Mes~*PH _2 (Mes~* = 2,4,6-tBu_3C_6H_2) with Sn(NMe_2)_2 gives the model intermediate [{SnPMes~*}_2(μNMe_2)SnP(H)MeS~*] (3), together with the product of complete deprotonation [SnPMes~*]_3 (4). Phosphorus-phosphorus bonded products are produced in these reactions at elevated temperatures. If the reaction producing 1a is heated to reflux then [tBuP(H)P(H)tBu] is produced as the major product (together with tin metal). The novel octanuclear cage [(SnPtBu]_7Sn(PtBu)_3] (2) can also be isolated in low yield, resulting from formal addition of the heterocyclic stannylene [(/BuP)_3Sn] to a Sn-P single bond of the intact structure of la. Prolonged heating of the reaction producing 3 and 4 leads to the formation of the diphosphene [PMes~*]_2 (5) and tin metal. The X-ray structures of the heptamer 1a (n = 7), octanuclear 2 and trinuclear 3 are reported.