Compounds with Sn-N Bonds

K. Jones and M. F. Lappert, Organotin compounds with Sn—N bonds. 

The influence of various substituents on 5 Sn for series of tetra-coordinate tin(I V) compounds SnX4 n Yn (n = 0 ) can be graphically depicted as U-shaped curves. These substituent effects are not linear, but approximately pair-wise additive. Some representative Sn NMR data are given in Table 2.1.3 (tin hydrides). Table 2.1.4 (tetraorgano. tin). Table 2.1.5 (tin halides). Table 2.1.6 (tin chalcogenides), and Table 2.1.7 (compounds with Sn—N, Sn—P, Sn—As, Sn—Sb, and Sn—Bi bonds). 

Tin-tin bonds are usually best prepared by reducing an Sn-0 or Sn-N bonded compound with a tin hydride. For example, trimethyl (diethylamino)tin is reduced by alkyltin trihydrides to give decaorganotetratins (256). 

There has been little recent work on the stannaimines, R2Sn=NR. The compound [(Me3Si)2N]2SnNAr (Ar = 2,6-diisopropylphenyl) can be obtained as dark red crystals that are stable below —30 °C, and have an Sn=N bond length of 203.0(3) pm. Above —30 °C, cyclization slowly occurs by intramolecular addition of CH of an isopropyl group to the double bond. It reacts with 2,6-diethylphenyl azide to give the stannatetraazole (Equation (194)).592... 

Examples of compounds with a Sn-Sb bond" are (Me3Sn)2Sb-Sb(SnMe3)2 (46) and (Me3Sn)3Sb (47) photolysis of (46) provides (47). IR spectra of (Me3Sn)3E (E = P, As, or Sb) indicate planar [SnsE] cores. The Sn-P, Sn-As, and Sn-Sb bonds are thermally relatively stable, but are oxygen and water sensitive. Tin-phosphorus bonded compounds add to heterocumulenes (as do Sn-N bonded compounds), and to alkenes, allenes, and alkynes such as CH2=CHCH2C1, CH2=CHPh and PhC=CH (unlike Sn-N bonded species) (equation 90). 

Hyperconjugation by a C-Sn o bond (and indeed by most carbon-metal a bonds) is much more effective than C-H hyperconjugation, and it is an important factor in determining the structure and stability of not only radicals and cations, but also of compounds with filled n systems such as allyl-, benzyl-, and cyclopentadienyl-stannanes. The importance of vinyl-, allyl-, and aryl-stannanes in organic synthesis owes much to the stabilisation of radical and cation intermediates by a stannyl substituent, and under suitable conditions this can accelerate a reaction by a factor of more than 1014. 

The principal methods for forming the carbon-tin bond involve the reaction of organo-metallic reagents with tin compounds (equation 4-1), the reaction of stannylmetallic compounds with organic halides (equation 4-2), the reaction of tin or tin(II) compounds with alkyl halides (equation 4-3), the hydrostannation of alkenes or alkynes (equation 4-4), the reaction of acidic hydrocarbons with Sn-0 and Sn-N bonded compounds (equation 4-5), and carbonyl-forming eliminations (equation 4-6) the symbol sn represents 4Sn. 

The Reaction of Acidic Hydrocarbons with Sn-O and Sn-N Bonded Compounds... 

Substituted compounds Bu3SnCH2CH2OH, Bu3SnCH2C=N. The compounds containing the entity SnCC=0 are dealt with in part here, but also in the section dealing with Sn-0 bonded compounds, as they are in equilibrium with the enolates C=C-OSn. y-Substituted compounds Me3SnCH2CH2CH2Cl, Cl3SnCH2CHMeC(=0)0Me. 

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