CCL: Absolute shielding values of B2H6 or BF3:OEt2 at GIAO-Mp2/6-31+G*

 Sent to CCL by: Emilio =?ISO-8859-1?Q?Jos=E9_Ju=E1rez_P=E9rez?=
 [ejjuarez_._icmab.es]
 Hello Mr Shabbir,
 I hope help to you,
 > My question
 > 1-      On the basis of above lines, Can I take, 102.8 absolute
 > shielding value of BF3OEt2 at GIAO-MP2/6-31+G*or (96.7
 > +16.6)=113.3  .....?
 I followed this formulae in my paper: ( E. J. Juárez-Pérez, C.
 Viñas, A.
 González-Campo, F. Teixidor, R. Sillanpää, R. Kivekäs, R.
 Núñez, Chem.
 Eur. J. 2008, 14, 4924-4938. )
 A + B - C = D
 A: Computed Absolute shielding of the B2H6 at level X of theory.
 B: Experimental chemical shift of the B2H6 if the nmr reference is
 BF3·OEt2 == 16.6 ppm (as you quoted )
 C: Computed Absolute shielding of the case study borons at level X of
 theory.
 D: Computed Chemical shift at level X of theory of the case study borons
 with BF3·OEt2 as nmr reference .
  A few data (sorry I did not MP2)
   B   106.7      "B2H6 HF/6-31G(d) GIAO"
   B    83.6      "B2H6 B3LYP/6-311+G(2d,p) GIAO"
   B    93.5055   "B2H6 B3LYP/6-31G(d) GIAO"
   B    84.08645  "B2H6 B3LYP/6-311+G(d,p) GIAO"
   B   107.9845   "B2H6 B3LYP/sto-3G GIAO  d:acetone"
   B   89.1058    "B2H6 B3LYP/6-311G GIAO  d:acetone"
   B   93.0753    "B2H6 B3LYP/6-31+G(d) GIAO  d:acetone"
   B   98.3005    "B2H6 B3LYP/sto-3G SINGLE GAUGE ORIGIN d:acetone"
   B   62.6983    "B2H6 B3LYP/sto-3G IGAIM d:acetone"
   B   62.6976    "B2H6 B3LYP/sto-3G CGST  d:acetone"
   B   100.7578   "BF3OEt2 B3LYP/6-311+G(d,p) GIAO
   B    83.931    "B2H6 BP86/TZ2P GIAO"
 > > 3-	Is there any scaling factor that can we use for NMR calctions?
 I dont know. But it is very fast to calculate absolute shielding in boron atoms
 of the B2H6 at the same level that you optimized molecule.
 The calculation over BF3·OEt2 obviously is more complicated.
 My starting B2H6 structure (from Cambridge Database ) was it:
 1 B      -0.212824556797       0.815972688028       0.277083624792
 2 H      -1.178708708530       0.956389357742       0.961317434319
 3 H       0.475157611526       1.732217182820      -0.051321081303
 4 H       0.549202398820      -0.127486734845       0.801036573432
 5 H      -0.549201706108       0.127486656264      -0.801037123218
 6 B       0.212824556978      -0.815972733325      -0.277083646957
 7 H       1.178709056940      -0.956389500060      -0.961316770576
 8 H      -0.475158654622      -1.732216467110       0.051321209476
 > > 4-	Two signs are used in NMR shieldings, sigma or deta (lower cases of
 greek) difference b/w these two?
 I am not sure that means exactly sigma (or tau?) and I dont know the factor
 conversion between delta and sigma(tau?). You can see it in old papers (70th)
 and now I think
 that all people use delta (and BF3·OEt2 as reference)
 Regards,
 Emilio José Juárez Pérez
 PhD Student
 ICMAB-CSIC
 Campus UAB
 08193 Bellaterra (Barcelona). Spain
 ejjuarez _ icmab.es
 www.emiliojuarez.es
 Tel.    + 34 93 580 1853 (ext. 255)
 Fax    + 34 93 580 5729