Intramolecular Donor-Assisted Cyclization of Organotin Compounds

Abstract

New intramolecularly coordinated organotin compounds containing the monoanionic O,C,O‐coordinating ligand {4‐tert‐Bu‐2,6‐[P(O)(OEt)2]2C6H2}− have been synthesized by substitution reactions starting from organotin halides. In view of the enhanced reactivity of the intramolecularly coordinated compounds {4‐tert‐Bu‐2,6‐[P(O)(OEt)2]2C6H2}SnR2R′ (2, R = Ph, R′ = CH2SiMe3; 3, R = R′ = Ph; 6, R = R′ = Cl), cationic tin species are suggested to occur as intermediates in the formation of the heterocyclic compounds [1(Sn),3(P)‐Ph2SnOP(O)(OEt)‐5‐tert‐Bu‐7‐P(O)(OEt)2]C6H2 (8), [1(Sn), 3(P)‐Ph(Me3SiCH2)SnOP(O)(OEt)‐5‐tert‐Bu‐7‐P(O)(OEt)2]C6H2 (15), and {[1(Sn),3(P)‐Cl2SnOP(O)(OEt)‐5‐tert‐Bu‐7‐P(O)(OEt)]C6H2}2 (16). The latter compounds are formed by intramolecular cyclizations of pentacoordinate cationic tin species under elimination of ethyl halide. Furthermore, the synthesis of [1(Sn),3(P)‐Ph2SnOP(O)(OH)‐5‐tert‐Bu‐7‐P(O)(OH)2]C6H2 (13) is described. Reaction of 8 with an excess of Me3SiBr leads to the unexpected formation of {2‐[P(O)(OEt)(OSiMe3)]‐4‐tert‐Bu‐6‐[P(O)(OEt)2]C6H2}SnPhBr2 (9) as a result of an O–Sn bond cleavage initiated by Me3SiBr and subsequent reaction of the intermediate with further Me3SiBr under Sn–C bond cleavage. The high donor capacity and the rigidity of the new ligand {4‐tert‐Bu‐2,6‐[P(O)(OEt)2]2C6H2}− are demonstrated by X‐ray diffraction analyses of the tetraorganotin compound 2 and the monoorganotin trichloride 6. Furthermore, the molecular structures of the 2,3,1‐oxaphosphastannoles 8 and 16 are discussed.

Potentiometric, 1H NMR and ESI-MS investigation on dimethyltin(iv) cation–mercaptocarboxylate interaction in aqueous solution

“…The use of ligands having multiple donor sites led to intramolecular stabilization of several highly reactive compounds 41 and organotin cations. 42,43 Moreover, it is known that carboxylic acids bearing donor groups in their a or b positions act as bidentate ligands, giving rise to cyclic structures. 44 Accordingly, the formation of [ML + H] + species suggests that MPA acts as bidentate ligand giving rise to structure 3 (Fig.…”

The Role of Monoanionic Aryl Pincer Ligands in the Stabilization of Group 14 Metallylenes

“…[34] By adding SnCl4 to chlorostannylene 33, a redox process took place to form trichlorotin derivative 103, where the tin atom is hexacoordinated. [61] The 119 Sn chemical shift at -528.8 ppm (see [61] Tin(II) containing cations of stannylene 35 were obtained being stabilized by intermolecular coordination of the Lewis bases of the type 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (NHC Dip ) or 4-dimethylaminopyridine (DMAP), as shown in Scheme 14. [62] The structural features of the products 98 and 99 exhibit some steric constraints and a high s character of the lone pair of electrons on the tin atoms.…”