Tetryl-Tetrylene Addition to Phenylacetylene

Abstract

Phenylacetylene adds [Ar*GeH₂ -SnAr'], [Ar*GeH₂ -PbAr'] and [Ar'SnH₂ -PbAr*] at rt in a regioselective and stereoselective reaction. The highest reactivity was found for the stannylene, which reacts immediately upon addition of one equivalent of alkyne. However, the plumbylenes exhibit addition to the alkyne only in reaction with an excess of phenylacetylene. The product of the germylplumbylene addition reacts with a second equivalent of alkyne and the product of a CH-activation, a dimeric lead acetylide, were isolated. In the case of the stannylplumbylene the trans-addition product was characterized as the kinetically controlled product which isomerizes at rt to yield the cis-addition product, which is stabilized by an intramolecular Sn-H-Pb interaction. NMR chemical shifts of the olefins were investigated using two- and four-component relativistic DFT calculations, as spin-orbit effects can be large. Hydride abstraction was carried out by treating [Ar'SnPhC=CHGeH₂ Ar*] with the trityl salt [Ph₃ C][Al(OC{CF₃ })₄ ] to yield a four membered ring cation.

Keywords: NMR chemical shift calculations; germaniumhydrides; stannyl cations; tetrylenes; tinhydrides.

Scheme 1

Tetryl‐tetrylenes.

Scheme 2

Addition of germylstannylene 1 to phenylalkyne.

Figure 1

ORTEP of 4. Hydrogen atoms were placed in idealized positions. iPr groups are omitted for clarity. Ellipsoids at 50 % probability. Interatomic distances [Å] and angles [deg]: Sn‐C2 2.213(4), Sn‐C4 2.214(4), Ge‐C3 1.931(4), Ge‐C1 1.973(4), C3‐C4 1.344(5), Ge‐H1 1.48(5), Ge‐H2 1.45(5), C2‐Sn‐C4 99.34(13), C3‐Ge‐C1 113.80(16), C3‐C4‐Sn 124.0(3), C4‐C3‐Ge 126.1(3).

Scheme 3

Reaction of germylplumbylene 2 with an excess of phenylalkyne.

Figure 2

ORTEP of 5. Hydrogen atoms were placed in idealized positions. iPr groups are omitted for clarity. Ellipsoids at 50 % probability. Interatomic distances [Å] and angles [deg]: Pb‐C2 2.319(7), Pb‐C4 2.318(7), Ge‐C3 1.922(7), Ge‐C1 1.986(7), C3‐C4 1.352(10), Ge‐H1 1.41(3), Ge‐H2 1.41(3), C2‐Pb‐C4 98.4(2), C3‐Ge‐C1 115.1(3), C3‐C4‐Pb 122.3(6), C4‐C3‐Ge 126.5(6).

Figure 3

ORTEP of 7. Hydrogen atoms were placed in idealized positions. Ellipsoids at 50 % probability. Interatomic distances [Å] and angles [deg]: Pb‐C1 2.467(5), Pb‐C1’ 2.498(5), C1‐C2 1.100(7), C2‐C3 1.491(7), Pb‐C4 2.343(5), Pb‐C1‐Pb’ 92.2(2), C1‐Pb‐C1’ 87.8(2), C4‐Pb‐C1 92.6(2), C4‐Pb‐C1’ 104.4(2), C2‐C1‐Pb 130.7(4), C2‐C1‐Pb’ 136.5(4), C1‐C2‐C3 176.9(6).

Scheme 4

Addition of stannylplumbylene 3 to phenylacetylene.

Figure 4

ORTEP of Z‐8. Hydrogen atoms were placed in idealized positions. iPr groups and hydrogen atoms are omitted for the sake of clarity. Ellipsoids at 50 % probability. Interatomic distances [Å] and angles [deg]: C1‐Sn 2.161(7), C3‐Sn 2.146(8), C3‐C4 1.336(9), C2‐Pb 2.318(7), C4‐Pb 2.274(7), C1‐Sn‐C3 113.3(3), C4‐Pb‐C2 99.1(3).

Scheme 5

Formation of the kinetic and thermodynamic products.

Scheme 6

Isomerization of E‐8 into Z‐8.

Scheme 7

Hydride abstraction from alkyne addition product 4.

Figure 5

ORTEP of 9. Hydrogen atom connected to the germanium atom was found. Other hydrogen atoms, which are not shown were placed in idealized positions. iPr groups and anion [Al(OC{CF₃}₃)₄]⁻ are omitted for the sake of clarity. Ellipsoids at 50 % probability. Interatomic distances [Å] and angles [deg]: Ge‐Sn 2.669(1), C1‐Sn 2.145(2), C3‐Sn 2.138(2), C3‐C4 1.342(3), C2‐Ge 1.942(2), C4‐Ge 1.949(2), Sn‐C5 2.765(2), Sn‐C9 3.054(2), C1‐Sn‐C3 123.3(1), C4‐Ge‐C2 120.4(1), C4‐Ge‐Sn 70.6(1), C3‐Sn‐Ge 70.8(1), C1‐Sn‐Ge 157.9(1), C3‐C4‐Ge 116.6(2), C4‐C3‐Sn 100.9(2), Sn‐C1‐C6 106.5(2), Sn‐C1‐C8 131.3(2).