Formation and rearrangement of SnII phosphanediide cages

The room-temperature reactions of Sn(NMe2)2 with less sterically demanding primary phosphines (RPH2) give the homoleptic phosphanediide compounds [SnPR]n in high yields (R=tBu (1 a), cyclohexyl (1 b), 1-adamantyl (1 c)). However, the room-temperature reaction of Mes*PH2 (Mes*=2,4,6-tBu3C6H2) with Sn(NMe2)2 gives the model intermediate [{SnPMes*}2(μ-NMe2)SnP(H)Mes*] (3), together with the product of complete deprotonation [SnPMes*]3 (4). Phosphorusphosphorus bonded products are produced in these reactions at elevated temperatures. If the reaction producing 1 a 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 [(tBuP)3Sn] to a SnP single bond of the intact structure of 1 a. 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 1 a (n=7), octanuclear 2 and trinuclear 3 are reported