127332-13-2Relevant academic research and scientific papers
Dynamic behavior and rearrangements of group 14 organometallic substituted alkenylboranes
Wrackmeyer, Bernd,Horchler, Klaus
, p. 1881 - 1886 (2008/10/08)
Alkenylboranes 7 and 8 with a group 14 organometallic group (R23M; M = Sn, Pb, R2 = Me, Et, Ph) at the C=C double bond, in a cis position with respect to the boryl group, are obtained via organoboration of the corresponding alkynylstannanes (5) and -plumbanes (6) (R23M-C≡C-R1; R1 = H, Me, tBu, Ph) with trialkylboranes (R3B, R = Et (2a), iPr (2b)). Many of the lead compounds are thermally and photolytically unstable. The dialkylboryl group in 7 and 8 prefers the conformation 10, where the C2B plane is perpendicular to the C=C-B plane as shown by dynamic 1H and 13C NMR spectra. In the alkene derivatives 7 and 8 cleavage of the =C-R bond occurs readily, re-forming the alkynylmetal compound (5,6) and the trialkylboranes 2 (deorganoboration). Direct proof is given for this by two-dimensional 1H/1H exchange NMR spectra. The preferred structure 10 makes CB (σπ) interactions possible, weakening the =C-R bond, and together with a weak M-C= bond the organoboration becomes readily reversible. The structure 10 is also favorable for R2/R exchange, which has been found to take place between lead and boron in 8, leading to alkenes 13 and 13′. Only one example for 8 has been found for cis/trans isomerization into 15. All products are characterized by their 11B, 13C, 119Sn, and 207Pb NMR data.
