Tin and Lead Phosphanido Complexes: Reactivity with Chalcogens.

The reactivity of tin and lead phosphanido complexes with chalogens is reported. The addition of sulfur to [(BDI)MPCy2] (M = Sn, Pb; BDI = CH{(CH3)CN-2,6-iPr2C6H3}2) results in the formation of phosphinodithioates [(BDI)MSP(S)Cy2] regardless of the conditions; however, when selenium is added to [(BDI)MPCy2], a selenium insertion product, phosphinoselenoite [(BDI)MSePCy2], can be isolated. This compound readily reacts with additional selenium to form the phosphinodiselenoate complex [(BDI)MSeP(Se)Cy2]. In contrast, the addition of selenium to [(BDI)SnP(SiMe3)2] results in the formation of the heavy ether [(BDI)SnSeSiMe3]. Differences in the solution and solid-state molecular species of tin phosphinoselenoite and phosphinodiselenoate complexes were probed using multinuclear solution and solid-state NMR spectroscopy.

The Reactivity of Germanium Phosphanides with Chalcogens.

The reactivity of germanium phosphanido complexes with elemental chalcogens is reported. Addition of sulfur to [(BDI)GePCy2] (BDI = CH{(CH3)CN-2,6-iPr2C6H3}2) results in oxidation at germanium to form germanium(IV) sulfide [(BDI)Ge(S)PCy2] and oxidation at both germanium and phosphorus to form germanium(IV) sulfide dicylohexylphosphinodithioate complex [(BDI)Ge(S)SP(S)Cy2], whereas addition of tellurium to [(BDI)GePCy2] only gives the chalcogen inserted product, [(BDI)GeTePCy2]. This reactivity is different from that observed between [(BDI)GePCy2] and selenium. Addition of selenium to the diphenylphosphanido germanium complex, [(BDI)GePPh2], results in insertion of selenium into the Ge-P bond to form [(BDI)GeSePCy2] as well as the oxidation at phosphorus to give [(BDI)GeSeP(Se)Ph2]. In contrast, addition of selenium to the bis(trimethylsilyl)phosphanido germanium complex, [(BDI)GeP(SiMe3)2], yields the germanium(IV) selenide [(BDI)Ge(Se)P(SiMe3)2].

Lead and tin ß-diketiminato amido/anilido complexes: competitive nucleophilic reactivity at the ß-diketiminato γ-carbon.

The ß-diketiminatolead(II)-amido and -anilido complexes, [(BDI)Pb(NRR')] (BDI = [{N(2,6-iPr2C6H3)C(Me)}2CH]; NRR' = NH(2,6-iPr2C6H3), N(iPr)2), react at the amido/anilido nitrogen atom with simple saturated electrophiles such as methyltriflate. Addition of unsaturated electrophiles to these complexes either results in the formation of a complex mixture of products, or in the case of phenylisocyanate, reaction at the γ-carbon of the ß-diketiminato ligand to form a complex that is the net result of a nucleophilic attack by the γ-carbon atom of the ß-diketiminato ligand at the electrophilic carbon centre of phenylisocyanate. As this reactivity contrasts with that of ß-diketiminatolead(II) alkoxo complexes as well as ß-diketiminatotin(II) alkoxo complexes, we examined the reactivity between phenylisocyanate and the isostructural ß-diketiminatotin(II)-amido and -anilido complexes. Reactivity at the γ-carbon was also observed in these systems. Density functional calculations were performed to help understand the differences in reactivity.

Why compete when you can share? Competitive reactivity of germanium and phosphorus with selenium.

Addition of one equivalent of selenium to a germanium-phosphanide complex results in insertion of selenium into the Ge-P bond, not oxidation at germanium or phosphorus. Addition of excess selenium results in oxidation at phosphorus, although of germanium oxidation is still observed.

Group 14 metal terminal phosphides: correlating structure with |J(MP)|.

A series of heavier group 14 element, terminal phosphide complexes, M(BDI)(PR(2)) (M = Ge, Sn, Pb; BDI = CH{(CH(3))CN-2,6-iPr(2)C(6)H(3)}(2); R = Ph, Cy, SiMe(3)) have been synthesized. Two different conformations (endo and exo) are observed in the solid-state; the complexes with an endo conformation have a planar coordination geometry at phosphorus (M = Ge, Sn; R = SiMe(3)) whereas the complexes possessing an exo conformation have a pyramidal geometry at phosphorus. Solution-state NMR studies reveal through-space scalar coupling between the tin and the isopropyl groups on the N-aryl moiety of the BDI ligand, with endo and exo exhibiting different J(SnC) values. The magnitudes of the tin-phosphorus and lead-phosphorus coupling constants, |J(SnP)| and |J(PbP)|, differ significantly depending upon the hybridization of the phosphorus atom. For Sn(BDI)(P{SiMe(3)}(2)), |J(SnP)| is the largest reported in the literature, surpassing values attributed to compounds with tin-phosphorus multiple-bonds. Low temperature NMR studies of Pb(BDI)(P{SiMe(3)}(2)) show two species with vastly different |J(PbP)| values, interpreted as belonging to the endo and exo conformations, with sp(2)- and sp(3)-hybridized phosphorus, respectively.

Carbon dioxide activation by "non-nucleophilic" lead alkoxides.

A series of terminal lead alkoxides have been synthesized utilizing the bulky beta-diketiminate ligand [{N(2,6-(i)Pr(2)C(6)H(3))C(Me)}(2)CH](-) (BDI). The nucleophilicities of these alkoxides have been examined, and unexpected trends were observed. For instance, (BDI)PbOR reacts with methyl iodide only under forcing conditions yet reacts readily, but reversibly, with carbon dioxide. The degree of reversibility is strongly dependent upon minor changes in the R group. For instance, when R = isopropyl, the reversibility is only observed when the resulting alkyl carbonate is treated with other heterocumulenes; however, when R = tert-butyl, the reversibility is apparent upon any application of reduced pressure to the corresponding alkyl carbonate. The differences in the reversibility of carbon dioxide insertion are attributed to the ground-state energy differences of lead alkoxides. The mechanism of carbon dioxide insertion is discussed.

The synthesis of monomeric terminal lead aryloxides: dependence on reagents and conditions.

The successful synthesis of terminal lead aryloxides is shown to be dependent upon reaction conditions, including choice of solvent and alkali metal aryloxide precursor.