Tri(tert-butyl) plumbyl derivatives of group 14 elements: Multinuclear magnetic resonance studies: Determination of coupling signs

Article abstract of DOI:10.1016/S0022-328X(97)00090-9

A solution of tri(tert-butyl)plumbyl-lithium in THF (2) was prepared by the reaction of hexa(tert-butyl)diplumbane (1) with an excess of lithium. Treatment of this reagent with a variety of Group 14 electrophiles gave tetraorganolead compounds ^tBu₃Pb-R (3, R = Me (a), Et (b), ⁿPr (c), ⁿBu (d), CH₂Ph (e), CH₂SiMe₃ (f)), plumbylsilanes ^tBu₃Pb-SiR¹₂R² (4, R¹ = R² = Me (a), R¹ = Me, R² = ^tBu (b), R¹ = Me, R² = SiMe₃ (c), R¹ = Me, R² = Ph (d), R¹ = R² = Ph (e)), one plumbylgermane ^tBu₃Pb-GeMe₃ (5a), plumbylstannanes ^tBu₃Pb-SnR³₃ (6, R³ = Me (a), Et (b), ⁿBu (c), ^tBu (d), Ph (e), 1,1′-ferrocenediyl (f)), and hexaorganodiplumbanes ^tBu₃Pb-PbR⁴₃ (7, R⁴ = Me (a), Et (b), ⁱPr (c), ⁿHex (d), ^cHex (e)], ⁱPr₃Pb-PbEt₃ (10) and ^tBu₂(Me)Pb-Pb(Me)^tBu₂ (11) as a side product. The plumbylstannanes Et₃Pb-SnMe₃ (9a) and ⁱPr₃Pb-SnMe₃ (9b) were prepared for comparison of NMR data. All compounds were characterized by ¹H, ¹³C, ²⁹Si, ¹¹⁹Sn and ²⁰⁷Pb NMR data. Signs of coupling constants ⁿJ(²⁰⁷Pb, ¹³C) (n = 1, 2), ¹J(²⁰⁷Pb, ²⁹Si), ¹J(²⁰⁷Pb, ¹¹⁹Sn) and ¹J(²⁰⁷Pb, ²⁰⁷Pb) were determined by appropriate 1D heteronuclear double resonance experiments and 2D heteronuclear shift correlations. The influence of the ^tBu₃Pb group on the bonding situation is reflected by sign changes of several coupling constants when compared with analogous trimethyllead derivatives.