Doctorat de l'Université de Lyon, délivré par l'École Normale Supérieure de Lyon, en cotutelle avec l'Université d'Amsterdam (UvA). Complexes sulfonamido-phosphore-nickel pour l'oligomérisation sélective d'oléfines, étude de ligands dissymétriques et stratégies supramoléculaires.
1 Nickel oligomerisation
History and general considerations about nickel in organometallic chemistry [1–3]
- Electronic and atomic properties
Indeed, both the secalkylsalicylaldiminato derivatives and the [NiBr2(PEtPh2)2] complex exhibit an equilibrium between square planar and tetrahedral geometries in non-coordinating solvents. Two solvent molecules can be coordinated into square planar complexes by increasing the coordination number up to 6 and leading to octahedral complexes.
Production of olefins by oligomerisation reactions
- General market considerations
- Propylene oligomerisation processes
The catalyst is a chromium alkanoate complexed by a pyrrolyl ligand and activated by triethylaluminum.[24] The first plant using this technology was set up in Qatar in 2003. 2,3-DMB-2 is used for the synthesis of Danitol (or Rody)TM, a high-performance pyrethroid insecticide invented by Sumitomo in 1976, and to produce other intermediates (Pinacolone, Scheme 3).[32–35 ].
Activation of nickel complexes for olefin oligomerisation
- General considerations
- Aryl nickel complexes
- Allyl and cyclopentadienyl nickel complexes
- Alkyl nickel complexes
- Nickel hydrides and related complexes .1 Oxidative addition on zerovalent nickel
- Di-halide nickel complexes
Activation of the allyl complex (a) takes place at 40°C, while the complex with the cyclopentadienyl group (b) is activated at 130°C (both under 70 bar ethylene pressure).[66] The structure of the side product (leaving group) provides insight into the formation of the active species, presumably nickel hydride according to Keim et al.
Mechanistic considerations
- Nickel hydrides and the degenerated polymerisation mechanism
- Towards other mechanisms
- The potential of Ni(I)
This capability lies in the possibility of a concerted coupling mechanism (Figure 11).[101] In this approach, two ethylene molecules are coordinated to the metal in a coplanar fashion. These observations lead to the important question of whether this concerted coupling mechanism applies to nickel oligomerization.
2 Major families of catalysts
Monodentate ligands
Bidentate ligands
Modification of the steric bulk attached to the phosphine or the nitrogen affects the coordination chemistry and the catalysis. The properties of these catalysts strongly depend on the donor properties of the P and O atoms, which are controlled by the C1 and C2 substitution (complex 45).
Tridentate ligands
3 Supramolecular catalysis
- From Nature to supramolecular catalysis
- Ligand metal interaction
- Hydrogen bond interaction
- Ionic interaction
- Pi stacking interaction
The weak interaction takes place between the Zn atom (of the porphyrin) and the pyridine group. The selective formation of this assembly lies in a stronger affinity of the Zn porphyrins for N atoms than for phosphorus. The power of this approach has been demonstrated by the preparation of a library of 20 building blocks based on the porphyrins and 20 building blocks with a pyridyl, leading to a library of 400 supramolecular bidentate ligands.
4 Aim and outline of the thesis
Heinicke et al.[123] reported that increasing the basicity of the labile PR3 phosphine (and consequently its ability to coordinate to the metal) leads to shorter α-olefins and a decrease in activity. As mentioned above, the distribution in LAO is related to the coordination ability of the phosphine.
5 References
In Chapter 5 we identified that the electron density on the aminophosphine is the determining factor leading to the formation of stable nickel-zwitterionic cationic heterocomplexes. In Chapter 6, the catalytic performance of zwitterionic cationic nickel complexes and nickel hydride complexes was evaluated in the ethylene oligomerization reaction.
Synthesis of Sulphonamido-Based Phosphorus Ligands and their
Coordination to Nickel
1 Introduction
The first reaction involves the bis-addition of chlorophosphine to the mono-substituted product, in line with increased nucleophilicity of the mono-addition product (Table 2). In this chapter we describe the re-examination of the synthesis of METAMORPhos ligands through a comprehensive study of the reaction between sulfonamides and chlorophosphines.
2 Synthesis and characterisation of tautomeric ligands
However, increasing the steric bulk from phenyl to o-tolyl led to selective formation of the mono-addition product 8. This suggests that regardless of the substituents on the phosphorus, the formation of the bis-addition product is promoted.
3 Coordination chemistry of sulphonamido-based phosphorus ligands with nickel precursors
Next, we investigated whether the presence of a base during complexation would activate ligand 11 by inducing a shift in the tautomeric ratio. Similar experiments performed in the presence of PCy3 led to the formation of several compounds as indicated by 31P NMR that exhibited several peaks whereas only one doublet was expected.
4 Conclusion
In addition to this electronic effect, the presence of a base (or hydrogen bond acceptor moiety) can also induce a shift in the tautomeric equilibrium. However, the same reaction in the presence of triethylamine as a base resulted in complexation with METAMORPhos acting as an anionic PO ligand.
5 Experimental part
- General
- Synthesis of sulphonyl-iminophosphoranes Sulphonyl iminophosphorane 27
- Synthesis of complexes Complex 25
- Procedure for unlocked NMR
- Procedure for ligand titration
- Procedure for catalytic experiment
The suspension is then filtered under an argon atmosphere and the resulting clear solution is evaporated to a white solid (87% METAMORPhos and 13% iminobisphosphine). The suspension is then filtered under an argon atmosphere and the resulting clear solution is evaporated to a white solid.
6 References
Then part of the reaction mixture was transferred to the NMR tube via a cannula (or with a glass pipette) under argon circulation; the tube was then sealed and analyzed by NMR. Both 31 P and 1 H NMR were recorded and the contents of the tube were placed back into the Schlenk.
Iminobisphosphines to (non-) Symmetrical Di(phosphino)amine
Oligomerisation Reactions
These nickel precatalysts can be activated using MAO, providing fast catalysts for ethylene and propylene oligomerization reactions. Preliminary results considering this rearrangement strategy for chromium in the oligomerization of ethylene and propylene are also reported.
2 Results and Discussion
- Synthesis of iminobisphosphines
- Properties of iminobisphosphines
- Reaction of iminobisphosphines with nickel (II)
- Nickel-induced rearrangement of iminobisphosphines
- Nickel complexes evaluation in ethylene oligomerisation
- Nickel catalyst evaluation in propylene oligomerisation
- Ligand evaluation in chromium-catalysed ethylene oligomerisation Di(phosphino)amine ligands R 2 PN(R)PR 2 (Figure 7) associated with chromium have
All three nickel complexes adopt a square-planar geometry with a restricted cis coordination of the ligand, similar to the published di(phosphino)amine nickel complexes. The bond lengths and angles of the various complexes in the solid state are very similar. We were interested in the mechanism of the metal-induced rearrangement of these ligands and therefore performed some additional experiments.
3 Conclusion
The systems formed by the different ligands 1-3 and chromium precursors showed very low reactivity within one hour of reaction time and the ethylene uptake did not exceed 2 g. These preliminary tests suggested that either the complexation with the different ligands was not efficient or that these ligands have a detrimental effect on chromium-catalyzed ethylene oligomerization.
4 Experimental Section
- General
- Ligand synthesis
- Complex synthesis
- DPPE)
- DPiPrE)
- DPCyE)
- Catalytic reactions procedures
The suspension was then filtered under a nitrogen atmosphere and the resulting clear solution was evaporated to a white solid. The solvents are evaporated under reduced pressure and the powder was washed with pentane (3 x 20 ml) and dried in vacuo to yield a dark red solid (isolate yield: 444 mg, 54%).
Self-Assembled Organometallic Nickel Complexes as Catalysts for Selective
Oligomerisation of Ethylene
As the additional PPh3 ligand coordinated to the SHOP catalyst shown in Figure 1 is known to have a major impact on catalyst stability and product distribution, [5-7] we predicted that METAMORPhos-based nickel complexes and aminophosphine ligands would formed supramolecular pincer ligands that, due to the dynamic nature of supramolecular complexes, would favor the stability of the catalyst, but at the same time would preserve the vacancy required for adequate catalytic activity. We report here such a supramolecular ligand approach for the formation of stable nickel complexes based on hydrogen bonding, by the self-assembly of a METAMORPhos and an aminophosphine ligand.
2 Discussion
This latter geometry results in a rotation of the sulfonamido fragment, increasing the distance to the hydrogen bond donor. This geometry difference in the two complexes is further supported by the switch of the dihedral angle P-Ni-P-NMETMAMORPhos from 28.5° for 4 to 79.3° for 3.
4 Experimental part
- Synthesis of N-isopropyl-1,1-diphenylphosphinamine
- Synthesis of ligand 1
- Synthesis and characterisation of complex 3
- Synthesis and characterisation of complex 4
- High pressure ethylene NMR experiments
- Procedure for the oligomerisation of ethylene (semi-batch)
When the temperature inside the reactor stabilized, the mixing was stopped and the catalyst solution (10 or 50 µmol in toluene: 5 mL) was injected. Then the reactor was pressurized to 30 bar ethylene and the pressure was maintained by connecting to an ethylene supply cylinder (80 bar) positioned in a balance (half stack).
Zwitterionic and Nickel Hydride Complexes based on METAMORPhos
Ligand: a Parameter Study on their Formation
One of the prominent examples is the neutral (PO)-coordinated nickel aryl phosphine complex 1 that yields linear alpha-olefins (LAO) and enabled the development of the SHOP process in the late 1970s.[1-5] This one system was extensively expanded. We identified key structural factors, such as phosphorus substituents, ligands and chelate backbone, and linked them to performance in the oligomerization reaction.[6-8] In Chapter 4 we unveiled a new class of single-component nickel catalysts based on structure 2. studied the combination of METAMORPhos ligands (Figure 1) with aminophosphines and non-functionalized phosphines on the complex formation and stability.
2 Synthesis of the complexes
Reactivity of the system METAMORPhos / aminophosphine with Ni(COD) 2
- Access to zwitterionic bis(METAMORPhos) nickel complexes
- Diversification of the aminophosphines of the zwitterionic nickel complexes
Other products observed by 31P NMR probably correspond to degradation products of the homocomplex (37 and 61 ppm). Similarly, reduction of the steric bulk on the phosphine METAMORPhos (P(o-tolyl)2 in PPh2) led to the formation of the Ni(4,B) complex in good yields (> 95%).
Reactivity of the system METAMORPhos / phosphine (or phosphite) with Ni(COD) 2
- Trimethylphosphine (PMe 3 ) as co-ligand
- Tricyclohexylphosphine (PCy 3 ) as co-ligand
- Extension to other phosphines and phosphites
Crystals of complex 16 suitable for X-ray diffraction were grown by slow diffusion of pentane in a toluene solution of the complex. Crystals of complex 17 were grown by slow vapor diffusion of pentane in a toluene solution of the complex.
3 Mechanism of complex formation
Are zwitterionic and nickel hydride complexes interconvertible?
Influence of the Tolman cone angle for PR3 on the complex geometry based on METAMORPhos 3. This experiment proved that the zwitterionic and hydride complexes are two closely related structures and that the steric bulk of the phosphine co-ligand determines which of the two classes of compounds are being formed.
Role of the co-ligand in the mechanism
Alternatively, migratory hydride insertion into the coordinated double bond of 1,5-COD produces (IV). The distinction between zwitterionic and hydride complexes definitely occurs in the second step and is directed by the steric bulk of the co-ligand.
Ligand synthesis
Then, the chlorophosphine solution was added dropwise to the aniline solution with vigorous stirring, leading to the formation of a white solid. To this solution, chlorodicyclohexylphosphine (1 ml, 1.05 g, 4.5 mmol, 1 eq.) was added dropwise with vigorous stirring, resulting in a thick precipitate.
In situ approach for complex synthesis
12.7 (2JPP=39 Hz) The reaction of METAMORPhos ligands 9 and 10, which have a chiral center with Ni(COD)2 and PMe3, led to the formation of the corresponding zwitterionic complexes with a. The position of COD in complexes that can be located above or below P1,Ni,P2.
Synthesis and characterisation of supramolecular complexes 11-15
The resulting oil was co-evaporated several times with pentane to remove traces of cyclooctadiene. At the same time, the signals of the allylic fragment disappeared from the 1H NMR and new signals appeared at 5.6-6.2 ppm (see Figure 20), corresponding to free 1,3-COD according to the simulated 1H NMR pattern.
Synthesis and characterisation of phosphine-based zwitterionic complexes
Least-squares matrix: full Hydrogen site location: difference Fourier map R[F2 > 2σ(F H atoms treated by a mixture of independent and. This solid was triturated in 20 ml of pentane resulting in a powder and a solvent phase which is colored in purple which has been sprayed out.
Synthesis and characterisation of hydride complexes 23, 26 Complex 23
Zwitterionic and Nickel Hydride Complexes: Reactivity for Ethylene
Oligomerisation
A simple change in phosphorus substituents on the ligands of these complexes leads to a dramatic shift in selectivity from a broad LAO distribution (similar to SHOP) to selective 1-butene formation. Such a change in selectivity is unusual given that a change in the chelate phosphine of the SHOP system has only a minor impact on product distribution, leading in all cases to a broad (non-selective) LAO distribution.[1] We wondered whether the different zwitterionic nickel catalysts operate via one unique mechanism or via two different mechanisms that explain the difference in product distribution.
2 Catalytic experiments with isolated complexes
Complexes 8 and 9 were almost inactive at 40 °C (0.3 kgoligo/(gNi.h) and 1.1 kgoligo/(gNi.h), but increasing the temperature to 80 °C triggered their activation. At 80 °C C, complexes 8 and 9 show a similar consumption profile to 6 (around 8 kgoligo/(gNi.h)), which is representative of this class of PMe3 complexes and also corresponds to the activity of complex Ref.
3 Mechanistic aspects of the oligomerisation reaction
Reactivity of the complexes under an ethylene atmosphere
- Reactivity of nickel hydride complexes
- Reactivity of zwitterionic nickel complexes .1 Zwitterionic supramolecular complexes
Series of nickel complexes (isolated and in situ) based on the METAMORPHos scaffold and the corresponding 31P NMR signal of the METAMORPHos ligand phosphines. Interestingly, the 31P NMR signal of complex 1' at 89.8 ppm fits relatively well to the signal of the trans-(PO,P)Ni-ethyl complex 11 (δ(C6D6): 89.6 ppm, see Table 2 ), suggesting that 1' also adopts the structure of a trans-(PO,P)-chelated Niethyl complex.
Mechanistic and parameter study, influence of groups
