Well defined correlations between the ligand properties and
catalytic parameters were limited and are attributed to the
multi-step nature of the process not fully accounting for variations
that may occur in selected steps. It was found that the linearity of
the hydroformylation products (aldehydes and alcohols) in general
decreased for the less electron donating ligands. No clear trend was
evident between the product linearity and the cone angles of the
ligands evaluated in this study. A general decrease was observed
for the % hydrogenation as a function of cone angle with the
6 E. Drent, D. H. L. Pello, J. C. L. J. Suykerbuyk and J. Van Gogh (Shell
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H. Luo and D. Li, Appl. Organomet. Chem., 2000, 14, 389.
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9
W. Braun, A. Salzer, F. Spindler and E. Alberico, Appl. Catal., A, 2004,
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74, 191.
1
0 D. Konya, K. Q. A. Lenero and E. Drent, Organometallics, 2006, 25,
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1
1
1 P. N. Bungu and S. Otto, Dalton Trans., 2007, 2876.
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3 J. P. Steynberg, K. Govender and P. J. Steynberg, Production of
oxygenated products, WO 2002014248, 2002.
exception of three ligands (PCy
3
, PCyp
3
and PA–C ), with cone
5
◦
angles > 169 , with values ranging from 22.5–40.2%. The Phoban
and Lim ligands gave the least hydrogenation of < 10%. No clear
relationship was found between the reaction rates and either the
ligand steric or electronic properties. The Phoban and two Lim
derived ligands resulted in systems about twice as active as most
of the other ligands investigated; all three of these ligands can be
considered as good electron donors, are sterically bulky and have
an unsymmetrical geometry.
1
1
4 C. Crause, L. Bennie, L. Damoense, C. L. Dwyer, C. Grove, N.
Grimmer, W. Janse van Rensburg, M. M. Kirk, K. M. Mokheseng,
S. Otto and P. J. Steynberg, Dalton Trans., 2003, 2036.
15 P. J. Steynberg, H. Van Rensburg, J. J. C. Grove, S. Otto and C. Crause,
Production of oxygenated products, WO 2003068719 A2, 2003.
6 C. Dwyer, A. Assumption, J. Coetzee, C. Crause, L. Damoense and M.
Kirk, Coord. Chem. Rev., 2004, 248, 653.
1
1
7 A. Polas, J. D. E. T. Wilton-Ely, A. M. Z. Slawin, D. F. Foster, P. J.
Steynberg, M. J. Green and D. J. Cole-Hamilton, Dalton Trans., 2003,
A general decrease was observed for the % hydrogenation as
a function of reaction rate with the Lim and Phoban systems,
giving both the most active systems as well as the least amount
4
669.
1
1
8 P. N. Bungu and S. Otto, J. Organomet. Chem., 2007, 692, 3370.
9 W. L. F. Armarego and C. L. L. Chai, Purification of Laboratory
Chemicals, Elsevier Science, USA, 5th edn, 2003.
of hydrogenation. In addition, the same ligands (PCy
3
, PCyp
3
and PA–C ) deviating from the hydrogenation vs. cone angle
5
20 S. Otto, A. Ionescu and A. Roodt, J. Organomet. Chem., 2005, 690,
337.
4
relationship also deviated significantly from the hydrogenation
vs. reaction rate comparison. This observation provides evidence
that the rate limiting step for these bulky symmetrical ligands may
have moved within the catalytic cycle and may be situated at the
carbonylation step where the chemoselectivity is also determined.
The favourable catalytic properties of the Phoban and Lim ligands
may be attributed to their unsymmetrical nature giving them the
ability to take on geometries beneficial to several steps in the
catalytic cycle.
2
1 Bruker, SAINT-Plus. Version 7.12 (including XPREP). Bruker AXS
Inc., Madison, Wisconsin, USA, 2004.
22 G. M. Sheldrick, SHELXL97, Program for refinement of crystal
structures, University of G o¨ ttingen, Germany, 1997.
2
3 K. Brandenburg and M. Berndt, DIAMOND, Version 2.1e, 2001,
Crystal Impact GbR, Bonn, Germany, 1999.
2
4 C. A. Tolman, Chem. Rev., 1977, 77, 313.
25 S. Otto, Acta. Cryst., 2001, C57, 793.
2
6 R. A. Baber, M. L. Clark, K. M. Heslop, A. C. Marr, A. G. Orpen,
P. G. Pringle, A. Ward and D. E. Zambrano-Williams, Dalton Trans.,
2
005, 1079.
2
2
2
3
3
7 R. Meijboom, M. Haumann, A. Roodt and L. Damoense, Helv. Chim.
Acta, 2005, 88, 676.
8 H. van Rensburg, R. P. Tooze, D. F. Foster and A. M. Z. Slawin, Inorg.
Chem., 2004, 43, 2468.
Acknowledgements
9 M. Haumann, R. Meijboom, J. R. Moss and A. Roodt, Dalton Trans.,
Financial support from Sasol Technology Research & Develop-
ment and from the research fund of the University of the Free State
is gratefully acknowledged. Part of this material is based on work
supported by the South African National Research Foundation
2
004, 1679.
0 R. A. Jones, M. H. Seeberger, A. J. Stuart, B. R. Whiylesey and T. C.
Wright, Acta Cryst., 1986, C42, 399.
1 P. Braunstein, D. G. Kelly, Y. Dusausoy, D. Bayeul, M. Lanfranchi and
A. Tiripicchio, Inorg. Chem., 1994, 33, 233.
2 J. A. Ibers, J. Organomet. Chem., 1968, 14, 423.
(
NRF) under Grant Number (GUN 2053397). Any opinion,
3
3
finding and conclusions or recommendations in this material are
those of the authors and do not necessarily reflect the views of
the NRF. Cytec is thanked for a generous supply of phosphine
ligands.
3 R. Weber, U. Englert, B. Ganter, W. Keim and M. M o¨ thrath, Chem.
Commun., 2000, 1419.
3
4 D. H. Farrar, A. J. Lough and A. J. Po e¨ , Acta Cryst., 1995, C51,
2
008.
3
5 P. Macchi, L. G. Gariaschelli, S. Martinengo and S. Sironi, Inorg.
Chem., 1998, 37, 6263.
3
3
6 P. N. Bungu and S. Otto, Acta Cryst., 2009, E65, o560.i
7 Estimated by using the VCH component from VCH- Bu and the C5
component from Lim-C .
5
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248 | Dalton Trans., 2011, 40, 9238–9249
This journal is © The Royal Society of Chemistry 2011