CCL: Absolute shielding values of B2H6 or BF3:OEt2 at GIAO-Mp2/6-31+G*
- From: "Mr shabbir" <shabbir:_:nenu.edu.cn>
- Subject: CCL: Absolute shielding values of B2H6 or BF3:OEt2 at
- Date: Wed, 29 Oct 2008 00:08:42 -0400
Sent to CCL by: "Mr shabbir" [shabbir(-)nenu.edu.cn]
Hello CCL user,
I am in a bit little confusion. I have calculated the 11B NMR spectra of a
compound at GIAO-Mp2/6-31+G*. Now I want to correlate it with experimental.For
this purpose I have to take reference compound as B2H6 or BF3:OEt2. I have tried
my best to find their absolute shielding value and can get following important
references as under
The B NMR chemical shifts were first computed with B2H6 [calculated absolute
shift, (sigma B) = 96.7] as a reference. The 11B NMR chemical shifts were
finally referenced to BF3:OEt2 [deta (B2H6) 16.6 vs. BF3:OEt2].
The 11B and 13C chemical shifts (6 values) are reported relative to the
experimental standards, BF3OEt2 and tetramethylsilane (TMS), respectively.
For 11B, where it is inconvenient to compute the experimental NMR standard, B2H6
(which has delta 16.6 vs BF3eOEt2) is used instead. The sigma values for B2H6
are as follows:
GIAO-MP2/DZP =102.8 ppm and GIAO-MP2/TZP =100.7 ppm
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 .....?
2- Any one who knows any reference about the Absolute shielding values of B2H6
or BF3:OEt2 at GIAO-Mp2/6-31+G* or higher?
3- Is there any scaling factor that can we use for NMR calctions?
4- Two signs are used in NMR shieldings, sigma or deta (lower cases of greek)
difference b/w these two?
thanks in advance