No abstract

No abstract

Contents 1. Abbreviations 747 2. Introduction 747 3. Stoichiometric Reactions with Carbon-Carbon 747 Bond Formation 4-Catalytic Reactions with Carbon-Carbon Bond 751 Formation 4.1. Reactions with Alkynes 751 4.2. Reactions with Alkenes 754 4.3. Reactions with Conjugated Dienes 755 4.4. Reactions with Methylenecyclopropanes 758 4.5. Reactions with Allene 759 4.6. Reactions with Aromatic Compounds 759 4.7. Electrochemical Reactions 759 5. The Relevance of C02 Complexes 760 6. Concluding Remarks 761 7. References 762

For over 30 years complexes with the general formula [NiPh(P,O)L] (L = tertiary phosphine; P,O = chelating phosphanylenolato ligand) have been used as highly efficient oligomerisation catalysts suitable for the production of linear alpha-olefins. The same complexes, which are usually referred to as SHOP-type catalysts (SHOP = Shell Higher Olefin Process) can also be used as ethylene polymerisation catalysts, provided they are treated with a phosphine scavenger that selectively removes the tertiary phosphine ligand (L). This Perspective examines the impact of various parameters (influence of the substituents, backbone size, solvent, use of co-catalysts, etc.) on the catalytic outcome of the complexes. Overall, this review shows that the selectivity and activity of the catalyst may be tuned efficiently through directed modification of the P,O chelator.

No abstract

The coordination properties of Ph2PCH2CN (L1) and Ph2PCH2COOC2H5 (L2) have been investigated. Complexes

Several aspects of the catalytic telomerization of 1,3-butadiene and C02 have been examined with the aims of studying the catalytic properties of reversible C02-carrier complexes and of selectively producing the 5-lactone 2-ethylidene-6-hepten-5-olide (3). When using Pd(II) complexes containing a cyclometalated ligand and a functional phosphine, only the specific C02 carriers [(o-C6H4CH2NMe2)Pd{R2PC(C02Et)=C(0)OH}] (2a, R = Ph; 2b, R = Cy) showed catalytic activity. They represent the first examples of C02 carriers having a catalytic activity in C02 chemistry. The complex isolated at the end of the reaction was identified as the cyclometalated phosphine carboxylate complex [(o-C6H4CH2NMe2)Pd|R2PCH2C(0)0|] (8). Another new catalytic system consisting of [Pd(MeCN)4] [BF4]2 associated to a phosphine ligand, p-hydroquinone, and triethylamine was tested under various conditions. Yield and selectivity of the six-membered ring lactone 3 are functions of the basicity and the bulk of the phosphine ligand. The yield of C02 telomers can be increased up to 76% (based on butadiene) by addition of acetophenone to the latter catalytic system containing PPh3. Furthermore, isomeric telomers of formula C9HI2Ó2 formed during catalysis can be converted into the 5-lactone 3, leading to an overall selectivity of 96%.

Three SHOP-type catalysts, in which the C=C(O) double bond was substituted by electron-withdrawing substituents, [Ni{Ph2PC(R1)=C(R2)O}Ph(PPh3)] (2: R1,R2 = -C(Me)=NN(Ph)-; 3: R1 = CO2Et, R2 = Ph; 4: R1 = CO2Et, R2 = CF3), were assessed as ethylene-oligomerisation and -polymerisation catalysts and compared to Keim's complex, [Ni{Ph2PCH=C(Ph)O}Ph(PPh3)] (1). A rationale for the influence of the double-bond substituents of the P,O-chelate unit on the catalytic properties is proposed, on the basis of X-ray diffraction studies, spectroscopic data and DFT-B3 LYP calculations. Whatever their relative electron-withdrawing strength, the R1 and R2 substituents induce an increase in activity with respect to catalyst 1. For those systems in which the basicity of the oxygen atom is decreased relative to that of the phosphorus atom, the chain-propagation rate increases with respect to that for catalyst 1. Reduction of the basicity of the P relative to that of the O, however, induces higher chain-termination rates.