Formation and Rearrangement of Sn^II Phosphanediide Cages

Abstract

The room-temperature reactions of Sn(NMe(2))(2) with less sterically demanding primary phosphines (RPH(2)) give the homoleptic phosphanediide compounds [SnPR](n) 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(3)C(6)H(2)) with Sn(NMe(2))(2) gives the model intermediate [{SnPMes*}(2)(mu-NMe(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}(7)Sn(PtBu)(3)] (2) can also be isolated in low yield, resulting from formal addition of the heterocyclic stannylene [(tBuP)(3)Sn] to a Sn-P single bond of the intact structure of 1a. 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.

Diphosphastannylenes: Precursors for Phosphorus–Phosphorus Coupling?

“…The concept of steric protection was also applied by Wright et al and Power et al in the related tin(II) phosphinidenes/phosphanediide [SnPR] n [R = t Bu, cyclohexyl, 1‐adamantyl, 2,4,6‐ t Bu 3 C 6 H 2 , C 6 H 3 ‐2,6‐(C 6 H 3 ‐2,4,6‐ i Pr 2 ) 2 ] 7. These compounds, containing a P–Sn multiple bond or a highly polarized P–Sn single bond, are supposed to be efficient in the P–P dehydrocoupling reactions,7g,8 similarly to the transition‐metal relatives 9. This was further corroborated when tin(II) phosphanediides were heated producing phosphorus–phosphorus‐bonded products 8…”

Cage Compounds of Phosphorus and the Heavier Group 14 Elements

“…The tin–tin distances are between 2.8239(7) Å and 2.8867(8) Å and lie in the range of those found in [Sn 8 (PSi i Pr 3 ) 6 Cl 2 ]7 [2.834(1)–2.888(2) Å] or in grey tin (2.80 Å). Moreover, the Sn–P bond lengths in 2 [2.506(2)–2.689(2) Å] are similar to those in [Sn 8 (PSi i Pr 3 ) 6 Cl 2 ] [2.538(5)–2.728(5) Å]7 and [Sn 7 ( t BuP) 7 ]12 [2.573(5)–2.670(5) Å]. Interestingly, the P–Sn–P as well as the Sn–P–Sn angles in both Sn 2 P 2 four‐membered rings of 2 are relatively close to 90°, while the P–Sn–P and the Sn–P–Sn angles in the rest of the molecule show quite different values.…”

“…This heptameric structural motive is also observed in the aluminium‐phosphorus compound [MeAlPSiMe 2 Thex] 7 (Thex = thexyl, –CMe 2 i Pr)13 and in the tin compounds [Sn 7 (PSi i Pr 3 ) 7 ]7 and [Sn 7 (PR) 7 ] (R = t Bu, cyclohexyl, 1‐adamantyl) 12. The Pb–P distances in the upper six‐membered ring capped by lead are shorter [2.670(3)–2.682(3) Å] than the ones in the lower six‐membered ring capped by a phosphorus atom [2.701(2)–2.735(2) Å].…”

“…2.667 Å in Me 3 Sn–SnMe 3 ), but they are significantly shorter than the sum of their van der Waals radii (4.2 Å). The Sn–P bond lengths in 1 exhibit values between 2.557(6) Å and 2.592(6) Å and lie in the typical range of Sn II –P single bonds as well as in the range of the Sn–P distances found in [Sn 7 (PSi i Pr 3 ) 7 ]7 (2.645 Å) and [Sn 7 ( t BuP) 7 ]12 [2.573(5)–2.670(5) Å].…”

“…The compounds 3 and 4 are the first examples of Pb/P cage compounds of type B and C , whereas only recently the first type A compounds of lead have been published 11. The lead cage compound 4 completes the row of the known hexameric tin and germanium derivatives [Sn 6 (PSi i Pr 3 ) 6 ] and [Ge 6 (PSi i Pr 3 ) 6 ]of type B , while 3 represents the lead congener of the tin compounds [Sn 7 (PSi i Pr 3 ) 7 ]7 and [Sn 7 (PR) 7 ] ( R = t Bu, cyclohexyl, 1‐adamantyl)12 of type C .…”