Phosphines transition metal complexes

This chapter is concerned with the effects of nonbonded interactions in tertiary phosphine-transition-metal complexes on (a) cyclometallation and C-H activation and (b) the stability and conformations of large chelate rings. It also deals with how nonbonded interactions might be used in other areas of chemistry. 

The possibility of using I3C-NMR spectroscopy to assist in assigning the geometry of bis-phosphine transition metal complexes has attracted the attention of several groups (80, 86-90). The examination of the PMR spectra of such complexes and analysis of the resulting AA XnXJ, spectra has proved valuable (91) but has the disadvantage that it is limited to systems in which the phosphorus atom is attached to methyl, methoxy, or methylene or to related groups in which the protons couple to phosphorus but not to other protons. The condition for the observation of a 1 2 1 triplet (usually associated with trans phosphine molecules) in the proton resonance spectrum is... 

An alternative strategy to a phosphine macrocycle involves template-assisted reaction of two coordinated bidentate secondary phosphines with two equivalents of a dielectrophile, to form tetradentate phosphine transition metal complexes, 60 (Scheme 23).44... 

Other chiral phosphine/transition metal complexes catalyze the hydrogenation of a-pyridyl ketones (to biologicaly active amino alcohols like (/ ,S)-Mefloquine, an antimalarial agent (Hoffmann-La Roche [30]) or of a-benzamide ketones to... 

The absolute magnitude of /pp is 10-150 c./sec. smaller in fluoro-phosphine-transition-metal complexes (e.g., [Ni(CO) ,p4 [Mo(CO)3P3], [HCoPJ ), although in complexes of the chelating bisdifluorophosphine RN(Pp2)2, is larger than in the free... 

An additional interesting physical property associated with perfluorinated phosphine transition metal complexes is fluorocarbon solubility. In contrast to the generally poor solubility of complexes with hydrocarbon ligand substituents in fluorocarbon media, (dfepe)Cr(CO)4 (68) and ((CF3)3P)xFe(CO)5 x (46) are moderately soluble in perfiuoroalkane solvents. While cw-(dfepe)2RuH2 (81) is only sparingly soluble in most polar and nonpolar solvents, it is substantially more... 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

Although trialkyl- and triarylbismuthines are much weaker donors than the corresponding phosphoms, arsenic, and antimony compounds, they have nevertheless been employed to a considerable extent as ligands in transition metal complexes. The metals coordinated to the bismuth in these complexes include chromium (72—77), cobalt (78,79), iridium (80), iron (77,81,82), manganese (83,84), molybdenum (72,75—77,85—89), nickel (75,79,90,91), niobium (92), rhodium (93,94), silver (95—97), tungsten (72,75—77,87,89), uranium (98), and vanadium (99). The coordination compounds formed from tertiary bismuthines are less stable than those formed from tertiary phosphines, arsines, or stibines. 

C. A. McAuliffe and W. Levason, Phosphine, Arsine and Stibine Complexes of the Transition Elements, Elsevier, Amsterdam, 1979, 546 pp. A review with over 2700 references. See also C. A. McAuliffe (ed,), Transition-Metal Complexes of Phosphorus, Arsenic and Antimony Donor Ligands, Macmillan, London, 1972,... 

Transition metal complexes containing bidentate phosphine ligands. W. Levason and C. A. McAuliffe, Adv. Inorg. Chem. Radiochem., 1972,14,172-253 (315). 

Transition metal complexes of cyclic phosphines and their derivatives. D. G. Holah, A. N. Hughes and K. Wright, Coord. Chem. Rev., 1975,15, 239-278 (91). 

An investigation of the chelate effect the binding of bidentate phosphine and arsine chelates in square-planar transition metal complexes. D. M. A. Minahan, W. E. Hill and C. A. McAuliffe, Coord. Chem. Rev., 1984, 55, 31-54 (153). 

Coordination-catalyzed ethylene oligomerization into n-a-olefins. The synthesis of homologous, even-numbered, linear a-olefins can also be performed by oligomerization of ethylene with the aid of homogeneous transition metal complex catalysts [26]. Such a soluble complex catalyst is formed by reaction of, say, a zero-valent nickel compound with a tertiary phosphine ligand. A typical Ni catalyst for the ethylene oligomerization is manufactured from cyclo-octadienyl nickel(O) and diphenylphosphinoacetic ester ... 

Liicke et al. have prepared other phosphinated POSS compounds Tg[(CH2)2-PMe2]8 and Tg[(CH2)3-PMe2]8 by treating T8[CH = CH2]8 or T8[CH2-CH = CH2]8 with H-PMe2 under UV irradiation. The former compound has shown to have good coordination properties to carbonyl transition metal complexes such as CpMn(CO)3 (Table 15). 

Transition Metal Complexes Containing Bidentate Phosphine Ligands W. Levason and C. A. McAuliffe... 

Chiral phosphine based transition metal complexes are nsed as a powerful tool for asymmetric synthesis (3). A fundamental mechanistic nnderstanding is required for rhodium and mthenium catalyzed reactions. The starting point of those investigations was the clear and detailed stractnral description of the isolated pre catalyst system. 

The concept makes use of the complimentary strengths and weaknesses of the two unconventional media. While ionic liquids are known to be excellent solvents for many transition metal catalysts, the solubility of most transition metal complexes in scC02 is poor (if not modified with e. g. phosphine ligands with fluorous "ponytails" [64]). However, product isolation from scC02 is always very simple, while from an ionic catalyst solution it may become more and more complicated depending on the solubility of the product in the ionic liquid and on the product s boiling point. 

Among transition metal complexes used as catalysts for reactions of the above-mentioned types b and c, the most versatile are nickel complexes. The characteristic reactions of butadiene catalyzed by nickel complexes are cyclizations. Formations of 1,5-cyclooctadiene (COD) (1) and 1,5,9-cyclododecatriene (CDT) (2) are typical reactions (2-9). In addition, other cyclic compounds (3-6) shown below are formed by nickel catalysts. Considerable selectivity to form one of these cyclic oligomers as a main product by modification of the catalytic species with different phosphine or phosphite as ligands has been observed (3, 4). 

Some general reviews on hydrogenation using transition metal complexes that have appeared within the last five years are listed (4-7), as well as general reviews on asymmetric hydrogenation (8-10) and some dealing specifically with chiral rhodium-phosphine catalysts (11-13). The topic of catalysis by supported transition metal complexes has also been well reviewed (6, 14-29), and reviews on molecular metal cluster systems, that include aspects of catalytic hydrogenations, have appeared (30-34). 

Asymmetric hydrogenations catalyzed by supported transition metal complexes have included use of both chiral support materials (poly-imines, polysaccharides, and polyalcohols), and bonded chiral phosphines, although there have been only a few reports in this area. 

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