The 1H, 13C, 15N and 117Sn NMR study of the intramolecular Sn–N interaction in tri- and tetraorganotin compounds containing the chiral 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand

Structural assignment of organotin hydrides containing the oxazoline ligand

“…Triorganotin hydrides 1-5 have already been reported [9][10][11]. The synthesis of the remaining triorganotin hydrides and diorganotin dihydrides involved treatment of R 3 SnX (Ph 2 SnMeI for 6 and 8, Me 2 Sn-n-BuI for 7, Me 3 SnCl for 10, Ph 3 SnCl for 9 and 11) with the o-lithiophenyl-oxazole prepared by metallation of 2-(4-bromophenyl)-4-isopropyl-4,5-dihydro-oxazole with n-butyl lithium in THF at À70°C (Scheme 1).…”

“…1) [9,10]. On the basis of the NMR results, especially the J( 15 N-117/119 Sn) coupling constants it appeared that the tin atom in the hydrides was weakly intramolecularly coordinated to the nitrogen atom from the oxazoline part.…”

New chiral tin compounds containing the 2-(4-isopropyl-2-oxazolinyl)-5-phenyl ligand

“…In the case of 7 tin bromide 11 or iodide 12 was formed according to the general rule. Such phenomena could be explained by intramolecular assistance at the tin [10,18]. In view of these results the reported triorganotin bromides and iodides 9-12 were prepared in a much simpler way via addition of stoichiometric amount of bromine or iodine to stannanes 5 and 8 (Scheme 1).…”

“…We have recently described that the tin atom in tetraorganotin compounds containing the chiral oxazoline was in fact pentacoordinated due to the weak Sn-N coordination [10,11]. Newly synthesized compounds 5-8, which are substrates in two-step reaction leading to hydrides 13 and 14 also share this feature.…”

“…We have recently described the synthesis and NMR study of tin hydrides 1-3 containing the chiral oxazoline moiety (Fig. 1) [10,11]. On the basis of the NMR results, especially the J( 15 N-117/119 Sn) coupling constants it appeared that the tin atom in the hydrides was indeed intramolecularly coordinated to the nitrogen from the ligand.…”