Question

For the 29Si NMR spectra of SiF5- and SiF62- what are the features for borh compounds at low and high temperatures?

Answer 1

Sol:

Following are the features of both the compounds i.e, ​​​​​​

1. At low temperature both will have two kind of fluorine i.e, axial and equatorial and two peaks observed for them.
2. As the temperature increases both will show fluxation or fluxionality i.e, molecule exhibit rapid intramolecular rearrangements among their component atoms. Thus, the axial and equatorial and axial fluorine become equivalent and one single peak is observed, which is also called coalesce (come together to form one mass or whole) as the two peaks combine to form one single peak.
3. In ²⁹Si NMR, Spin(I)= 1/2
4. Using Pascal triangle splitting can be determined.
   29 Si NMR @. sifs Finst find out it's hybridi scettion, geometry vend shippe. sit 4 valence electrons + 1 e i si spad . Geometry and shape ax Triagonal bipynahidal fan - Axial Fluorine atom Feq = Equatorial fluorine votom . ?
   
   sol: 29 Si NMR Splitting sifs Faxial K [29 si NMR Ispin ŽI (anit 1) =(2x3x} +1) : 3+1 fequitorial (a niti) - (KK 2X4+1) : 2+1 3 ... triplet O quartet 1 : 1 1 :2 : 1 :3 : 3 : لر 1 1 1:2:1 1: 3: 3:1 a Intensity natio pascal triangle .
   
   sifs 29 Si NMR when teryperature increase j.e. at high tecuperature Fax : feq (Fuxation) .: Now, both axial and equitorial proton became 1 - Singlet anal equivalent 1 1 - doublet (0:2) 1 2 1- triplet (0:3) splitting I 3 3 - quartet (n=4) I (anti) 1 4 6 4 1 -quintetfor:s) Rx sx 2 + 1) s. 10 10 s. 14 Sextreff :) 1:8:10:10:8:1 + intensity Pascal triangle .: Sextet matio Fax I
   
   Sol: High teryperature linit 29 Si NMR Coalesce @ sifs Temperature m Broadening of peaks Feo Low teaperature limit Fax • At low temperature two ty Puorine observed one is axial fluorine atorms (2) vand equitorial fluorine atoms (3) Thus, at low teryperature limit show two peals. . As temperature increase broadening of peak occurs intill the two peak coalesce. Then, m fwrther increasing temperature, se, at high temperature linis single narrow peak of seived.
   
   sol: 29 si NMR Thus, o n a high temp. @ sifs i.l. a sextet Temperature ICE & low temp. 1 quartet for fax triplet for fear
   
   sol: 29 si NMR Similarly fom Sifar- S: 2+ 4 valence electron +2 i si .- Fus -FAP •FAP - Fap r : Fred Fax FO in sp3d² hybridisation . Georyetry and sheepe = oh
   
   sol: 29 Si NMR Similarly fom fifa 2 . Two different kind of fluorine also found here, ie fox and fea at low teryperature in splitting Fax - fear Fax (an I +1) = (2x 4x + 2+1) : 4+1 : 5 .. wuintet le 4:6:4 (2nI+1) =(2x axt+1) • 2+1 - 3 . triplet intensity in Mario 1:2:1 where, = number of other kind of fluorine atom in the environ- Ment I spin – for 29 si NMR.
   
   Sol: 29 Si NMR Similarly fom filfe → At high temperature licit fax= few .. now Splitting = (anti) = (2x 6 x 1/2 +1) = 6ti = 7 . septet si - fear fax هلدر 6:15:30:18 6:1 s Intensity ratio
   
   sol: 29 si NMR It Mighuu temperature septet, which limit get narrow at I high tecuperature + coalesce que si si Temperature hea - & Broadening of peaks Fear le In F low te cuperature ellu fax انهن quintet for Fox triplet for fear