60528-56-5Relevant academic research and scientific papers
Crystal and Molecular Structure of SnMePhBr and Proton Nuclear Magnetic Resonance Study of the Puckering of the Chelate Ring in Five -co-ordinate Triorganotin Halides SnRR'-X and SnRR'X
Koten, Gerard van,Jastrzebski, Johann T.B.H.,Noltes, Jan G.,Verhoeckx, Godefridus J.,Spek, Anthony L.,Kroon, Jan
, p. 1352 - 1358 (1980)
8-Dimethylaminomethyl-5-methoxynaphthyl- and 2-dimethylaminomethylbenzyl-diorganotin halides have been prepared via the organolithium-diorganotin dihalide route in 50-55percent yield.The molecular srtucture of the title compound (3) has been determined by a single-crystal X-ray diffraction study using standard Patterson and Fourier techniques, and refined by block-diagonal least squares to R=0.024 for 3014 observed diffractometer data (Mo-Kα radiation).Crystals are triclinic, space group P1 with Z=2 in a unit cell of dimensions a=7.795(5), b=11.178(2), c=12.159(1) angstroem, α=106.20(2), β=91.75(3), and γ=100.83(3)o.The Sn co-ordination is pseudo-trigonal bipyramidal with N and Br in axial positions .Dynamic 1H n.m.r. spectroscopy shows that the trigonal-bipyramidal structure is retained in solution.In the slow-exchange limit (3) exists in two diastereoisomeric forms as a result of the puckering of the chelate ring and the chirality at the Sn centre.On raising the temperature two different processes occur, the first of which involves interconversion between the two ring conformations.The second process (either Berry pseudo-rotation processes in the five-co-ordinate conformer, or Sn-N bond dissociation followed by combined pyramidal inversion at the N centre and rotation about the C-N bond) is difficult to define because of the coincident CH2 and OMe resonances.Dynamic 1H n.m.r. spectra of SnMePh)Br (5) reveal that the six-membered chelate ring containing two sp3-C atoms is very flexibile compared with the five-membered ring in SnMePhBr.Accordingly stereoisomerization in the five-co-ordinate conformer of (5) could be detected.
