Heterobimetallic (Imido)antimony/Lithium Cages Containing [Sb(NR)₃]^3- Trianions

Abstract

The reactions of [Sb(NMe(2))(3)] with the primary (amido)lithiums [PhCH(2)CH(2)N(H)Li](n)(), [CyN(H)Li](n)() (Cy = C(6)H(11)), [2,4-dmpN(H)Li](n)() [2,4-dmp = 2,4-(MeO)(2)C(6)H(3)], and [(t)()BuN(H)HLi](n)() give the heterobimetallic cage complexes [{Sb(NCH(2)CH(2)Ph)(3)}(2)Li(6).2THF] (1), [{Sb(NCy)(3)}(2)Li(6).2HNMe(2)].2C(6)H(5)CH(3) (2), [Sb{N(2,4-dmp)}(3)](2)Li(6).2THF.2C(6)H(5)CH(3) (3), and [{Sb(NBu(t)())(3)}(2)Li(6)] (4), respectively. The low-temperature X-ray structures of 1-4 show that they are composed of 14-membered polyhedral cages constructed from the association of two [Sb(NR)(3)](3)(-) trianions with six Li(+) cations. Crystal data; 2, triclinic, P&onemacr;, a = 12.775(6) Å, b = 13.191(9) Å, c = 11.015(5) Å, alpha = 111.55(4) degrees, beta = 95.39(4) degrees, gamma = 115.26(4) degrees; 3, triclinic P&onemacr;, a = 10.435(4) Å, b = 12.654(5) Å, c = 14.278(6) Å, alpha = 75.31(4) degrees, beta = 79.33(4) degrees, gamma = 84.33(4) degrees; 4, monoclinic P2(1)/c, a = 9.994(1) Å, b = 17.421(2) Å, c = 10.680(2) Å, beta = 111.33(1) degrees (the structure of 1 being reported previously). Lewis base solvation of the N(6)Li(6) substructures of 1-3 results in distortion and deformation of the Li frameworks. The structural variations in the cores of 1-4 indicate that the bonding in these species is dominated by the valence and bonding demands of the p block metal centers.

Syntheses and structures of [Me2Si{As(PtBu)3}2] and [(CyP)3SiMe2] (Cy=cyclohexyl, C6H11)

“…We therefore investigated the in situ generation of the anion 2 via the 3:1 reaction of CyPHLi with As(NMe 2 ) 3 in TMEDA/THF. An in situ 31 P{ 1 H} spectroscopic study of this reaction mixture does indeed show the presence of significant amounts of the [(CyP) 4 As] À anion, in addition to a number of other unidentified species. Reaction of this solution at À78°C with an excess of Me 2 SiCl 2 gave a precipitate of LiCl.…”

“…These reactions are difficult to control in the case of the Sb heterocycles [(RP) n Sb] À owing to the relative weakness of P-Sb bonds and the resulting thermal instability (Scheme 1, step 2). For example, the five-membered, heterocyclic anion [(CyP) 4 Sb] À (Cy = cyclohexyl) decomposes at temperatures above ca. 0°C into the Zintl ion [Sb 7 ] 3À and the cyclic phosphane [CyP] 4 [4].…”

“…For example, the five-membered, heterocyclic anion [(CyP) 4 Sb] À (Cy = cyclohexyl) decomposes at temperatures above ca. 0°C into the Zintl ion [Sb 7 ] 3À and the cyclic phosphane [CyP] 4 [4]. This type of main group dehydrocoupling reaction can be seen to be driven thermodynamically by the strength of the P-P single bond, which has the highest homoatomic bond energy between of any of the group 15 elements (ca.…”

“…201 kJ mol À1 ) [5]. The phosphorus counterparts [( t BuP) 4 P] À have been obtained by the in situ reactions of t BuPCl 2 and PCl 3 with Na metal in THF (Scheme 2) [6].…”

“…Given the reactivity patterns described above, there is an obvious potential for the development of a general approach to neutral heterocycles of the type [(RP) n ER 0 m ] using reactions of [(RP) n As] À anions like 1 with group 13 or 14 organohalide electrophiles [group 13 R 0 EX 2 (E = P-Bi); group 14 R 0 2 EX 2 ; E = C-Sn; X = halogen] (Scheme 4). In the current work we have explored this potential for the first time in a study of the reactions of the anions 1 and the related five-membered anion [(CyP) 4 As] À (2) with Me 2 SiCl 2 . We find, however, that the reaction of 1 with Me 2 SiCl 2 in 3:2 stoichiometric ratio (suggested by analogy with reaction d, Scheme 3) does not produce the heterocyclic product [( t BuP) 3 SiMe 2 ] (Scheme 4, top).…”