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Organometalloidal derivatives of the transition metals
C65 Journal of Organometallic Chemisfry, 209 (1981) C55-%8 Elsevier Sequoia S-A., Lausanne - Printed in The Netherlands
preliminarycommunication ORGANOMETALLOIDAL
DERIVATIVES
OF THE TRANSITION
METALS
VI *. THE POTENTIAL OF *‘Si NMR SPECTROSCOPY IN ANALYSIS Z-ORGANOSILYL COMPLEXES OF THE TRANSITION METALS [I]
K.H.
PANNELL
Department A.R.
OF
of Chemistry,
University
of Texas
at El Paso,
The Open
University,
Walton
El Paso,
Texas
79968
(U.S.A.)
BASSINDALE
Department of Chemistry, (Great Britain)
Hall, Milton
Keynes,
MK7
6AA
and 3-W. FITCH Department (U.S.A.) (Received
of Chemistry, September
29th,
Southwest
Texas
State
University,
San Marcos,
Texas,
78666
1980)
The “Si FT NMR characteristics of a number of 7rorganosilyl-transition metal complexes have been determined and their usefulness for characterizing the complexes investigated.
The ability of silicon to stabilize various c and x complexes of the transition metals is.documented c.2,3] _ The kge variety of sllylmekbyl o cumplexes often result in in&~ I? bon& considerably more “s-taWe” than the nun silylated analogs, and the direct metak?+%con 0: bond often exhibits chemical properties illustrative of a Lessreactive h&age when compared to the metal carbon bond. In the area of s complexes, the isolation and characterization of such co,mplexes as Fe(CO),(Me,SKZC!SiMe,) [4 J and Fe(CO),(Me,Si(CH=CH,),) [5], and the enhanced oxidative and thermal stability of silylallyl complexes [S] illustrate the same idea. There have recently appeared a few reports on the utilization of *‘Si FT NMR for characterizing metal complexes containing o organosilyl ligands [ 7,8,9,10], and we have also made a study in this area [ 111. However, at the * ForpartVseeref.1. 0022-328X/81/0000-0000/$
02.50,
o 1981,
Elsevier
Sequoia
S.A.
AcacRh(CH,==CHSLMe,), -062 11.1 -632 -139 -0J8 -3.G4 1.06 2.46 1, ip-16.91 1.06 19.17
Complex
6(ppm)
(-7.6) (4.12) (-69.0) (0,391 (-7.6) (-19.26) (19.28) (-16,99) (-16.99) (-16.99) (-0.61)
(ligand) 6.98 6.98 b.84 -1,78 7.42 lo,71 20.31 18,34 --a.72 18.06 19.77
Lvi
2.3 2.4 2.0 1.9 2.2
J(MSU (Hz)
2,4
15 1.0
Complex
-v
om) (0-B) (0.6)
(llgund)
- --
--..
-..
__
a All spectrn were mcnsured in a BrulcerWP60 FT spectrometer using G-2016 CgDg solutions, with internal standnrds of TMS or hcxnmctllyldisUoxnnc. All 6 values are referenced to TMS. b Complcxca prcpnrcd using published procedures [4,18], c A second spectrum of this complex was run on a JEOL PX9OQ at Bedford Cob lege, University of London,
IX X
I II III IV V VI VII VIII
Complox
29si NMR PARAMETERS OF n ORGANOSIDYI,METAL COMJ'LEXES ah
TABLE 1
C67
present time there are no data in the literature concerning the “Si NMR characteristics of 7rorganosilyl complexes. It is the purpose of this communication to report for the first time such data. We have initially chosen a representative sample of complexes involving different metals (Fe, Rh, Co) with different ligands (vinyl, allyl, acetylenic and diacetylenic silanes), the data being presented in Table 1 along with the data from the appropriate ligand. Several points of information may be extracted from the data: 1. In each case where the Si atom is bonded directly to a coordinating C atom of the 7rligand (Si,), the 2gSi resonance exhibits a marked low field shift of 6-11 ppm. This shift appears to be additive such that in the examples where two metals are coordinated to the ligand C atom, e.g. complex VI vs. VII, the shift approximately doubles, from 10.7 to 20.3 ppm. 2. When the Si atom is insulated from the coordinating atom by C-atoms (SiB), a small high field shift is observed, 0.5-2.0 ppm. 3. Where the metal nucleus has a magnetic spin, M-Si coupling is observed for both Si, and Si,. The one single observation of coupling to Sip is unexpected, especially since the magnitude of the coupling is virtually the same as J(MSi,). We have obtained the 2gSi NMR spectrum of this complex .(IV) on two distinct instruments of 11.9 and 17.9 MHz, to confirm this coupling. 4. Nuclear Overhauser effects (NOE) have been studied on the -q values reported in Table 1 are derived from the relationship, Z’yD = 2.52 qbs/q [12]. Thus a value _rl = 2.52 signifies relaxation of the Si nucleus by a dipole--dipole relaxation while smaller values indicate progressive contributions by spin rotation relaxation. The -q values for the silicon nucleus are uniformly increased when the organosilicon ligand becomes coordinated to the transition metal. This suggests a decreased tumbling motion of the now larger assembly of atoms [12]. This decrease in mobility is attenuated as the Si atom is further removed from the site of complexation, as illustrated in complexes VII and IX. This aspect of the 2gSi NMR data of silyl metal complexes is dealt with in some detail elsewhere [ li]. Overall, the use of 2gSi NMR to characterize K organosilyl complexes has been illustrated. The progressive deshielding of Q Si atoms upon metal complexation could be explained in terms of simple electron density removal by the metal. However, as no comprehensive interpretation of 2gSi chemical shift data for simple organosilicon compounds is available, and since they often exhibit a well known “sagging pattern” of shifts with substituent electronegativity [14] attempts at such analysis must await the collection of further data *.
Acknowledgements Support of this research by the Robert A. Welch Foundation, Houston, Texas, and the North Atlantic Treaty Organization (NATO Grant 1804) is gratefully acknowledged. * A very recent article Cl51 records some similar data for (vinyl silane) Fe(COh present chemical shift information.
in keeping with the
C68
References 1 2 3 4 5 6 7 8 9 10 11 12
R.H. Pannell. J_ Organometal. Chem.. 198 (1980) 37. C.S. Cundy and M.F. Lappert. Advan. Organometal. Chem.. ll(l973) 253. 1. Haiduc and V. Popa. Advan_ Organometd. Chem.. 15 (1977) 113. K.H. PaxmelI and G.M. Crawford. J. Coord. Chem.. 2 (1973) 251. J-W_ Fitch and H.E. Herbold. Inolk Chem.. 9 (1970) 1926. K.H. Parme& M-F. Lappert and K. Stanley. J. Organometal. Chem.. 112 (1976) 37. S. Li. D.L. Johnson. J.A..Gladysz and K-L. Servis. J. 0rganometa.k Chem.. 166 (1979) 317. W. Malisch and W_ Ries. Chem. Ber.. 112 (1979) 1304. F.H. Kohler. H. HolIfelder and E.O. Fischer. J. Organometal. Chem., 168 (1979) 53. KM. Abraham and G. Urry. Inorg. Chem.. 12 (1973) 2850. K.H. PanneU and A.R. Bass&dale. Submitted for publication. R.K. Harris, J-D. Kennedy and W. McFarIane in R.K. Harris and B.E. Mann (Eds.). NMR and the Periodic Table. Academic Press. 1978. Chapter 10. 13 J-W. Fitch and W.T. Osterloh. J. Organometai. Chem.. In press. 14 R. Wolff and R_ Radeglia. 2. Phys. Chem. (Leipzig) 257 (1976) 181. 15 H. Sakurai. Y. Kamiyama. A. Mikoda. T. Kibayasbi. K. Sasaki and Y. Nakadaira. J. Organometal. Chem.. 201 (1980) C14.
preliminarycommunication ORGANOMETALLOIDAL
DERIVATIVES
OF THE TRANSITION
METALS
VI *. THE POTENTIAL OF *‘Si NMR SPECTROSCOPY IN ANALYSIS Z-ORGANOSILYL COMPLEXES OF THE TRANSITION METALS [I]
K.H.
PANNELL
Department A.R.
OF
of Chemistry,
University
of Texas
at El Paso,
The Open
University,
Walton
El Paso,
Texas
79968
(U.S.A.)
BASSINDALE
Department of Chemistry, (Great Britain)
Hall, Milton
Keynes,
MK7
6AA
and 3-W. FITCH Department (U.S.A.) (Received
of Chemistry, September
29th,
Southwest
Texas
State
University,
San Marcos,
Texas,
78666
1980)
The “Si FT NMR characteristics of a number of 7rorganosilyl-transition metal complexes have been determined and their usefulness for characterizing the complexes investigated.
The ability of silicon to stabilize various c and x complexes of the transition metals is.documented c.2,3] _ The kge variety of sllylmekbyl o cumplexes often result in in&~ I? bon& considerably more “s-taWe” than the nun silylated analogs, and the direct metak?+%con 0: bond often exhibits chemical properties illustrative of a Lessreactive h&age when compared to the metal carbon bond. In the area of s complexes, the isolation and characterization of such co,mplexes as Fe(CO),(Me,SKZC!SiMe,) [4 J and Fe(CO),(Me,Si(CH=CH,),) [5], and the enhanced oxidative and thermal stability of silylallyl complexes [S] illustrate the same idea. There have recently appeared a few reports on the utilization of *‘Si FT NMR for characterizing metal complexes containing o organosilyl ligands [ 7,8,9,10], and we have also made a study in this area [ 111. However, at the * ForpartVseeref.1. 0022-328X/81/0000-0000/$
02.50,
o 1981,
Elsevier
Sequoia
S.A.
AcacRh(CH,==CHSLMe,), -062 11.1 -632 -139 -0J8 -3.G4 1.06 2.46 1, ip-16.91 1.06 19.17
Complex
6(ppm)
(-7.6) (4.12) (-69.0) (0,391 (-7.6) (-19.26) (19.28) (-16,99) (-16.99) (-16.99) (-0.61)
(ligand) 6.98 6.98 b.84 -1,78 7.42 lo,71 20.31 18,34 --a.72 18.06 19.77
Lvi
2.3 2.4 2.0 1.9 2.2
J(MSU (Hz)
2,4
15 1.0
Complex
-v
om) (0-B) (0.6)
(llgund)
- --
--..
-..
__
a All spectrn were mcnsured in a BrulcerWP60 FT spectrometer using G-2016 CgDg solutions, with internal standnrds of TMS or hcxnmctllyldisUoxnnc. All 6 values are referenced to TMS. b Complcxca prcpnrcd using published procedures [4,18], c A second spectrum of this complex was run on a JEOL PX9OQ at Bedford Cob lege, University of London,
IX X
I II III IV V VI VII VIII
Complox
29si NMR PARAMETERS OF n ORGANOSIDYI,METAL COMJ'LEXES ah
TABLE 1
C67
present time there are no data in the literature concerning the “Si NMR characteristics of 7rorganosilyl complexes. It is the purpose of this communication to report for the first time such data. We have initially chosen a representative sample of complexes involving different metals (Fe, Rh, Co) with different ligands (vinyl, allyl, acetylenic and diacetylenic silanes), the data being presented in Table 1 along with the data from the appropriate ligand. Several points of information may be extracted from the data: 1. In each case where the Si atom is bonded directly to a coordinating C atom of the 7rligand (Si,), the 2gSi resonance exhibits a marked low field shift of 6-11 ppm. This shift appears to be additive such that in the examples where two metals are coordinated to the ligand C atom, e.g. complex VI vs. VII, the shift approximately doubles, from 10.7 to 20.3 ppm. 2. When the Si atom is insulated from the coordinating atom by C-atoms (SiB), a small high field shift is observed, 0.5-2.0 ppm. 3. Where the metal nucleus has a magnetic spin, M-Si coupling is observed for both Si, and Si,. The one single observation of coupling to Sip is unexpected, especially since the magnitude of the coupling is virtually the same as J(MSi,). We have obtained the 2gSi NMR spectrum of this complex .(IV) on two distinct instruments of 11.9 and 17.9 MHz, to confirm this coupling. 4. Nuclear Overhauser effects (NOE) have been studied on the -q values reported in Table 1 are derived from the relationship, Z’yD = 2.52 qbs/q [12]. Thus a value _rl = 2.52 signifies relaxation of the Si nucleus by a dipole--dipole relaxation while smaller values indicate progressive contributions by spin rotation relaxation. The -q values for the silicon nucleus are uniformly increased when the organosilicon ligand becomes coordinated to the transition metal. This suggests a decreased tumbling motion of the now larger assembly of atoms [12]. This decrease in mobility is attenuated as the Si atom is further removed from the site of complexation, as illustrated in complexes VII and IX. This aspect of the 2gSi NMR data of silyl metal complexes is dealt with in some detail elsewhere [ li]. Overall, the use of 2gSi NMR to characterize K organosilyl complexes has been illustrated. The progressive deshielding of Q Si atoms upon metal complexation could be explained in terms of simple electron density removal by the metal. However, as no comprehensive interpretation of 2gSi chemical shift data for simple organosilicon compounds is available, and since they often exhibit a well known “sagging pattern” of shifts with substituent electronegativity [14] attempts at such analysis must await the collection of further data *.
Acknowledgements Support of this research by the Robert A. Welch Foundation, Houston, Texas, and the North Atlantic Treaty Organization (NATO Grant 1804) is gratefully acknowledged. * A very recent article Cl51 records some similar data for (vinyl silane) Fe(COh present chemical shift information.
in keeping with the
C68
References 1 2 3 4 5 6 7 8 9 10 11 12
R.H. Pannell. J_ Organometal. Chem.. 198 (1980) 37. C.S. Cundy and M.F. Lappert. Advan. Organometal. Chem.. ll(l973) 253. 1. Haiduc and V. Popa. Advan_ Organometd. Chem.. 15 (1977) 113. K.H. PaxmelI and G.M. Crawford. J. Coord. Chem.. 2 (1973) 251. J-W_ Fitch and H.E. Herbold. Inolk Chem.. 9 (1970) 1926. K.H. Parme& M-F. Lappert and K. Stanley. J. Organometal. Chem.. 112 (1976) 37. S. Li. D.L. Johnson. J.A..Gladysz and K-L. Servis. J. 0rganometa.k Chem.. 166 (1979) 317. W. Malisch and W_ Ries. Chem. Ber.. 112 (1979) 1304. F.H. Kohler. H. HolIfelder and E.O. Fischer. J. Organometal. Chem., 168 (1979) 53. KM. Abraham and G. Urry. Inorg. Chem.. 12 (1973) 2850. K.H. PanneU and A.R. Bass&dale. Submitted for publication. R.K. Harris, J-D. Kennedy and W. McFarIane in R.K. Harris and B.E. Mann (Eds.). NMR and the Periodic Table. Academic Press. 1978. Chapter 10. 13 J-W. Fitch and W.T. Osterloh. J. Organometai. Chem.. In press. 14 R. Wolff and R_ Radeglia. 2. Phys. Chem. (Leipzig) 257 (1976) 181. 15 H. Sakurai. Y. Kamiyama. A. Mikoda. T. Kibayasbi. K. Sasaki and Y. Nakadaira. J. Organometal. Chem.. 201 (1980) C14.