Vesal Naseri

Recent perspectives on main group-mediated dehydrocoupling of P–P bonds

Transition metal-mediated dehydrocoupling is a developing synthetic tool for the preparation of an extensive range of main group element-element bonded species, with broad applications to molecular and polymeric materials. Recent results have stressed the relationship between this class of transition metal reagents and their entirely main group counterparts. But what are the similarities and differences between transition metal and main group systems?

Stoichiometric and catalytic Sn-mediated dehydrocoupling of primary phosphines

The room-temperature reactions of stannocene, Cp*(2)Sn, with a range of primary phosphines, RPH(2), result in diphosphanes [RP(H)P(H)R]. The reactions involving Cp*(2)SnCl(2), however, result in catalytic dehydrocoupling; the first example of main group metal catalysed dehydrocoupling to be identified.

Formation of a new class of 7π radicals via sterically induced P–P bond cleavage of the dimers [(CH)2(NR)2P]2

The 2c-2e- P-P bonded dimers [(CH)2(NR)2P]2 dissociate in solution to give the persistent new 7pi radicals [(CH)2(NR)2P]*, which are isoelectronic with the well known S/N thiazolyl radicals.

Formation and Rearrangement of SnII Phosphanediide Cages

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.

A mechanistic study of the C–P bond cleavage reaction of 1,2-(PH2)2-C6H4 with nBuLi/Sb(NMe2)3

In situ 31P NMR spectroscopic studies of the reaction of the primary diphosphine 1,2-(PH2)2-C6H4 with the mixed-metal base system nBuLi/Sb(NMe2)3, combined with X-ray structural investigations, strongly support a mechanism involving a series of deprotonation steps followed by antimony-mediated reductive C-P bond cleavage. The central intermediate in this reaction is the tetraphosphide dianion [C6H4P2]2(2-) ([]) from which the final products, the 1,2,3-triphospholide anion [C6H4P3]- () and [PhPHLi] (.Li), are evolved. An EPR spectrocopic study suggests that homolytic C-P bond cleavage is likely to be involved in this final step.

Confinement of halide ions within homologous inverse coordination hosts; modification of halide-ion selectivity

The structures of a series of spherical host-guest complexes [{MeE(PPh)(3)Li(4)·3thf}(4)(μ(4)-X)](-) (E = Al, [1X](-); E = Ga, [2X](-); E = In, [3X](-)) reveal that changing the halide ions (X = Cl, Br, or I) within their central tetrahedral Li(4) sites has negligible effect on the structural parameters.