Mercapto derivatives of triorganotin Y,C,Y-pincer complexes: Role of Y,C,Y-chelating ligands in a new coordination mode of organotin compounds

We report the use of triorganotin fragments R2L1-2Sn containing N,C,N and O,C,O-ligands L1-2(L1 = C6H3(Me2NCH2)2-2,6−, L2 = C6H3(tBuOCH2)2-2,6−) on stabilization of both thiol-form in R2L1-2Sn-2-SPy (2-SPy = pyridine-2-thiolate) and thione-form in R2L1-2Sn(mimt) (mimt = 1-methylimidazole-2-thiolate) of the polar groups. Treatment of ionic organotin compounds [Me2L1Sn]+[Cl]− (1) and [Ph2L2Sn]+[OTf]− (2) with appropriate sodium salts Na-2-SPy and Na(mimt) resulted in the isolation of Me2L1Sn-2-SPy (3), Ph2L2Sn-2-SPy (4), Me2L1Sn(mimt) (5), Ph2L2Sn(mimt) (6). While polar group 2-SPy exists in its thiol-tautomeric form in compounds 3 and 4, the second polar group (mimt) has been stabilized as the thione-tautomeric form by triorganotin fragments R2L1-2Sn in compounds 5 and 6. The products were characterized by 1H, 13C and 119Sn NMR and IR spectroscopy, ESI/MS, elemental analyses and structures of 3, 6 were determined by X-ray diffraction study. The reactivity of compound 4 containing non-coordinated nitrogen atom of 2-SPy polar group towards CuCl and AgNO3 is also reported. The reactions led to isolation of organotin compounds Ph2L2SnCl (7) and Ph2L2SnNO3 (8) as the result of polar group transfer. The mechanism of this reaction has been investigated and compounds Ph3Sn-2-SPy (9) and Ph2L2Sn-4-SPy (10) (4-SPy = pyridine-4-thiolate) have been prepared for this purpose.

Graphical abstractTreatment of ionic organotin compounds [Me2L1Sn]+[Cl]− (1) and [Ph2L2Sn]+[OTf]− (2) with appropriate sodium salts Na-2-SPy and Na(mimt) provided Me2L1Sn-2-SPy (3), Ph2L2Sn-2-SPy (4), Me2L1Sn(mimt) (5), Ph2L2Sn(mimt) (6). While polar group 2-SPy exists in its thiol-tautomeric form in compounds 3 and 4, the second polar group (mimt) has been stabilized as the thione-tautomeric form by triorganotin fragments R2L1-2Sn in compounds 5 and 6. The reactivity of 4 containing non-coordinated nitrogen atom of 2-SPy polar group towards CuCl and AgNO3 is also reported.Figure optionsDownload full-size imageDownload as PowerPoint slide