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.

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.

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

The β-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 β-diketiminato ligand to form a complex that is the net result of a nucleophilic attack by the γ-carbon atom of the β-diketiminato ligand at the electrophilic carbon centre of phenylisocyanate. As this reactivity contrasts with that of β-diketiminatolead(II) alkoxo complexes as well as β-diketiminatotin(II) alkoxo complexes, we examined the reactivity between phenylisocyanate and the isostructural β-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.

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