Ligands with transition metals

One of the chief defects of the phosphorus based pyrazolyl (PZ) ligands appears to be the hydrolytic sensitivity of the P—N bond particularly after interaction of the ligand with transition metal ions. The interactions of PhP(0)(3,5-Me2pz)2 and Ph2P(0)(3,5-Me2pz)2 with Pd11 salts accelerates the P—N bond hydrolysis.177... 

Phosphinoalkylsilanes as chelate ligands with transition metals have been studied, principally to provide a better understanding of metal-catalyzed industrial reactions such as hydrosilylation.51 Although many examples of bis-chelate metal complexes possessing a cA-arrangement of the phosphinoalkylsilyl ligands in a typical square-planar M(II)(M = Pd, Pt) environment have been synthesized,52... 

Spectroscopists also saw the potential of reacting ligands with transition metal under matrix isolation conditions. Photolysis of metal carbonyls in organic (383 or inert gas matrices (39) had already been done, but atoms offered the possibility of step-wise addition of ligands. DeKock (40), Turner (41 ), and Moskovits and Ozin (42) made early contributions, but the work of the last two became dominant (32). By 1972, there were the two distinct branches in transition metal atom chemistry, the preparative and matrix spectroscopic studies. 

Complexes of tetradentate macroheterocyclic ligands with transition metals, structure and spectra of 80UK2032. 

The main interest with porphyrins, however, lies not in the effects of variations in the conjugated n system but in the influence of various metal ions in the porphyrin cavity on the redox activity of the porphyrin ligands. With transition-metal ions both conjugative and inductive effects can be expected, and regularities in the oxidation and reduction potentials, as well as the differences between them, should yield direct information on the nature of the metal-porphyrin interactions. 

Thus, Cp 2(Cl)An[CHP(Me)R2] is eliminated even as an intermediate in the nmr exchange process. We must deduce from these data that the ylide ligand is more prone to serve as a monodentate [CHER3] ligand with transition metal Cp2(X)M than with Cp 2(X)An fragments. 

The 18-crown-6-ether (Scheme 19e) is six-coordinated only in highly ionic complexes of alkaline and alkaline-earth metals, in which it furnishes the metal ion with a hexagonal planar coordination sphere. Only the small lithium ion can fit in an octahedral conformation of the crown ether, even if significantly distorted. In a similar vein, complexes of this ligand with transition metals are found only for Cd(II) and Hg(II) ions in eight-coordinate complexes in which the crown ether occupies six equatorial sites of a hexagonal bipyranfid. 

Fujita et al. developed self-assembly of predesigned organic ligands with transition metals having 90° coordination angles. They incorporated cw-protected square planar metals, [(L)M], into metal-organic frameworks such as cages, cones, capsules, and boxes (Fig. 9.19) [9]. 

Q7 Which species can act as ligands with transition metals ... 

Pitcher, Buckingham, and Stone 285) have discussed the anomalous chemical shift of fluorine atoms bonded to the a-carbon atom of perfluoro-alkyl-transition metal derivatives in terms of mixing of nonbonding electrons of the halogen with orbitals of the metal. Bennett, Pratt, and Wilkinson (27) have discussed the shielding of protons of olefins in the complexes of these ligands with transition metals. 

Stephenson A, Ward MD (2011) Molecular squares, cubes and chains from self-assembly of bis-bidentate bridging ligands with transition metal dications. Dalton Trans 40 10360-10369... 

Examples of olefins which act as 4-electron ligands with transition metals are given in Table 7. It can be seen that these ligands form complexes with a wide variety of transition metals. A comparison of Tables 1 and 7 shows... 

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