Aliphatic ligands

The grafting of aromatic groups onto the skeletons of aliphatic ligands such as cyclam and/or the addition of other substituents to the ring is generally reflected by loss of ligand flexibility. For example, the restricted... 

To illustrate an example of substituents on aliphatic ligands, let us consider the case of a few triferric-metallacycle clusters of general formula [Fe3(CO)8(RC2R)2], Scheme 1. 

Finally, a further refinement of the Lever equation40 allows one, in applying the treatment of ligand electrochemical parameters EL, to account for the presence of eventual aromatic or aliphatic ligands bearing different substituents, i.e. to take into account the Hammett, or Taft, substituent parameters a (above discussed) for a certain ligand. The expression is ... 

Simple trialkylphosphines, R3P, can be prepared relatively easily by using excess Grignard or alkyllithium reagents.1,2 However, the synthesis of mixed R2 R P monophosphines or chelating aliphatic ligands of the type of R2 P(CH2 )n A (where A = a donor group and n - 2,3,4) have been almost prohibitively difficult, owing to the toxicity, chemical reactivity, oxidation sensitivity, and commercial unavailability of likely precursors. 

In the case of the purely aliphatic ligand 2,2,6,6-tetrakis(amino-methyl)-4-azaheptane (12), complex formation with copper appears to proceed in two steps, as elucidated by titration experiments with the fully protonated ligand (12 5 HC1). Three and two protons from (Hr,12) + are sequentially abstracted, and the predominant species after full deprotonation appears to be a dinuclear complex in which two copper(II) ions are coordinated, each in square planar fashion, by the l,3-diaminoprop-2-yl units of two molecules of pentaamine ligand, thus forming a macrocyclic complex of composition [Cu2(12)2]4+ (23). The UV/vis spectral data show an interesting solvent dependence, suggesting an equilibrium between [Cu2(12)2]4 + and two equivalents of mononuclear complex [Cu(12)]2+ under suitable conditions. ESR spectroscopic data are also compatible with the formulation of a dinuclear species. Further addition of base to an aqueous solution of [Cu2(12)2]4+ gives the mononuclear hydroxo complex [(12)Cu(OH)]+, as inferred from the UV/vis spectroscopic data. 

Dial compounds are known, both of the neutral aliphatic ligands and in their deprotonated (alkoxide) form,212 but generally have been studied for their reaction with 02 and other oxidizing... 

From Metallated Phosphines. The preparations of a number of flexible aliphatic ligands, e.g. (6), containing the dimethylphosphino-group have been described, in which the sodium dimethylphosphide used was prepared from tetramethyldiphosphine, ... 

Linear and cyclic polyamine complexes of mthenium(III) have been little studied relative to those of first-row transition elements such as cobalt(III) and nickel(II), presumably due to a lack of general routes of syntheses. A convenient and reproducible method for the syntheses of trans-[RuLCl2], where L is any multidentate aliphatic ligand with a four-amine donor combination, has been developed. Procedures for the preparation of trans-[RuLCl2] [L = (en)2,J 2,3,2,-tet,f and cyclamj] are described here. The literature method is closely followed except that the much safer hexafluorophosphate(l — ) anion is employed in place of perchlorate. 

An aliphatic ligand hydroxylation also proceeds upon decomposition of the (ji-rfirf -peToxo) dicopper(II) complex supported by Mechanistic studies indicated that the real active... 

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