Stannenes stable

Stannene 1 was found to be an extremely air-sensitive compound, which was identified only by its trapping reactions.99 Replacement of the bis(tri-methylsilyl)methyl groups with the bulky aromatic group 2,4,6-triisopropylphenyl led to the isolation of the stable stannene 2 as its diethyl ether... 

A stannaketenimine has been synthesized by the low-temperature reaction of a diarylstannylene with mesityl isocyanide.87 The stannaketenimine is thermally stable, crystals being obtained by sublimation at 40°C/0.01 mmHg. In this case, the stannylene acts as the Lewis acid for formation of the adduct and, along with the stannenes described above, covers the full range of bonding modes available to the stannenes. 

Stannenes, R2Sn=CR2, are usually prepared either by coupling of a stable stannylene with a stable carbene, or by an elimination reaction (Equation (185)). 

In contrast to the extensively studied doubly bonded systems of silicon and germanium, the chemistry of the corresponding tin compounds, i.e. distannenes and stannenes, has not been fully disclosed yet probably due to the much higher reactivity and instability of such low-coordinated organotin compounds. In the following sections we briefly describe the synthesis and properties of stable distannenes and stannenes. 

The formation of n-complexes of silenes, as well as of germenes or stannenes is of central importance to the reactivity of the unsaturated systems. I will only offer one example out of many to illustrate the facts. As we found out, our stable silaneimine (Bu2Si=NSirBu3 takes up carbon monoxide under formation of supersilyl isocyanide as well as cyclosiloxanes (Scheme 7). 

Alkylation or arylation of stannous chloride gives stannylenes, RaSn , which normally self react to give linear or cyclic oligomers, but if the R groups are very bulky (t-butylphenyl, or 2,6-bis(2,4,6-tri-isopropylphenyl)phenyl), kinetically stable stannylenes can be obtained (see Chapter 2.8). In the solid state, the stannylenes usually dimerize to give the distannenes, R 2Sn=SnR 2, where R denotes a bulky group. Reaction of a stannylene with a carbene gives a stannene, R 2Sn=CR2. 

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