C4H6Si(H)N=C=O



 



















 






Nitrogen


Nuclear Quadrupole Coupling Constants


in 1-Isocyano-1-silacyclopent-3-ene


 








 








 

 





Calculation was made here of the nitrogen nqcc tensor in 1-isocyano-1-silacyclopent-3-ene on an ab initio structure given by MP2(full)/6-311+G(3df,3pd) optimization.  These nqcc's are compared in Table 1 with the experimental nqcc's of Guirgis et al. [2].  Structure parameters are given in Table 2, rotational constants in Table 3.

 








In Table 1,  subscripts a,b,c refer to the principal axes of the inertia tensor, subscripts x,y,z to the principal axes of the nqcc tensor.  RMS is the root mean square difference between calculated and experimental nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of nitrogen efg's/nqcc's.

 








 








   






Table 1.  Nitrogen nqcc's in 1-Isocyano-1-silacyclopent-3-ene (MHz).  Calculation was made on the MP2(full)/6-311+G(3df,3pd) ropt structure.
   









Calc
  Expt. [1] *
   






14N Xaa
1.192
1.1200(51)


Xbb -
 0.273              ?
-
 0.8616(52)


Xcc -
 0.919              ?
 -
 0.2584(52)


Xab -
 1.170



 







RMS
0.054 (7.2 %) **




RSD
0.030 (1.3 %)



 







Xxx -
 0.921




Xyy -
 0.919




Xzz
1.840












 







* Calculated here from expt 1.5Xaa = 1.6800(76) and 0.25(Xbb - Xcc) = -0.1508(23) MHz

** Calculated assuming Xbb and Xcc reversed, which clearly appears to be the case.  Why? See Table 3.




















 




Table 2.  1-Isocyano-1-silacyclopent-3-ene.  MP2(full)/6-311+G(3df,3pd) ropt (Å and degrees).
 


 Si
 C,1,B1
 C,2,B2,1,A1
 C,3,B3,2,A2,1,D1,0
 C,4,B4,3,A3,2,D2,0
 H,3,B5,2,A4,1,D3,0
 H,2,B6,1,A5,5,D4,0
 H,2,B7,1,A6,5,D5,0
 H,1,B8,2,A7,3,D6,0
 H,4,B9,3,A8,2,D7,0
 H,5,B10,4,A9,3,D8,0
 H,5,B11,4,A10,3,D9,0
 N,1,B12,2,A11,3,D10,0
 C,13,B13,5,A12,4,D11,0
 O,14,B14,13,A13,5,D12,0













 B1=1.8695957
 B2=1.50644659
 B3=1.34091713
 B4=1.50644659
 B5=1.08335079
 B6=1.09229052
 B7=1.08928247
 B8=1.46821794
 B9=1.08335079
 B10=1.09229052
 B11=1.08928247
 B12=1.71582809
 B13=1.19987027
 B14=1.17370723
 A1=100.89178012
 A2=118.74463401
 A3=118.74463401
 A4=120.39749672
 A5=112.04697043
 A6=113.43920644
  A7=116.38718445
 A8=120.85514002
 A9=111.11706497
 A10=112.33105111
 A11=110.38531329
 A12=131.64937155
 A13=178.05344203
 D1=13.56028138
 D2=0.
 D3=-167.03555512
 D4=100.29425819
 D5=-138.32547863
 D6=-141.7599018
 D7=179.40133919
 D8=105.39226006
 D9=-134.68844276
 D10=96.62414779
 D11=-71.50522255
 D12=-140.66592907



 








 













Table 3.  1-Isocyano-1-silacyclopent-3-ene.  Rotational constants (MHz), ropt = MP2/6-311+G(3df,3pd) optimization.
 





ropt   Expt [1]






A 3217. 3328.4182(23)

B 1038.
 1017.69404(53)

C 1032.
 1012.33297(58)

 



Note:  Calculated B and C differ little.  Small change in ropt structure could easily reverse these.  Also, could ground-state vibrations play a role?























[1] G.A.Guirgis, R.E.Sonstrom, A.J.Clark, B.H.Pate, and M.H.Palmer, J.Phys.Chem. A, 123(20),4389(2019).

 








 








Table of Contents




Molecules/Nitrogen




 








 













NCOSilacyclopentene.html






Last Modified 30 May 2019