Ligands elimination

For elimination of intramolecular energy losses, we have synthesized ligands with high hydrophobisity - perfluoro-P-diketones R -CO-CH -CO-R, (R = CgF j or CgF R = phenyl or a-thienyl), that without second ligand eliminate completely water molecules from the inner coordination sphere. These ligands we have used in analysis at determination of Sm, Eu, Nd, Yb microamounts in high-purity lanthanide and yttrium oxides. 

The pretreatment of the support and the treatment carried out for the CO ligand elimination define the characteristics of the metallic entities on the support. 

The supported Ru complex was activated by elimination of the p-cymene hgand, an elimination that did not occur by gentle heating under an N2 atmosphere. Both O2 and IBA were needed and a nearly stoichiometric amount of p-cymene was then detected by GC in the reaction solution. Based on the present DFT calculations [21], Scheme 10.1 for active catalyst preparation is proposed, where the ligand elimination proceeds by taking advantage of the exothermic reaction of IBA-1-O2 in the coordination sphere [17]. 

Because simple ligand elimination from a metal center is expected to via... 

Routes to prepare SH- complexes have, in principle, to overcome two major problems the formation of thermodynamically preferred metal sulfides and, via partial ligand elimination, the formation of polymeric species. This requires both a rigid stereochemistry brought about by bulky ligands and sufficient electron density on the metal centers. 

The key step in a cluster expansion reaction is the attachment of the incoming metal unit. Once this has taken place, a sequence of metal-metal bond formations accompanied by ligand eliminations can occur which is the reversal of the cluster unfolding reactions described in Section III,C. In uncontrolled cluster expansions, the first step is the combination of coor-dinatively unsaturated cluster and monometallic units, and the reaction is unlikely to stop at this stage. Under mild conditions the attachment may result from a nucleophile/electrophile combination, the products of which have been isolable in a few cases (see below). More insight into possible... 

In both the examples given above, there is concomitant loss of one or more neutral ligands. Elimination of CO is the rule in reactions of mononuclear metal carbonyls (e.g., entry 12) and cyclopentadienyl metal carbonyls (e.g., entry 4), but not those of polynuclear carbonyls (e.g., entry 16) or carbonyl halides (e.g., entry 33). Elimination of tertiary phosphines often occurs, especially when more than two molecules are present in the initial complex however, this is not always the case (see entry 24). Clearly, steric requirements and the dictates of the 18-electron rule determine the composition of the product, and normally act in concert when they conflict, as in the case of R3SiRuH3(PR3) (n = 2 or 3 entry 22), variable stoichiometry may result. Chelating diphosphines, with somewhat reduced steric requirements, are usually retained (e.g., entry 19), while complexed olefins are invariably lost the bulky ligand P(cyclohexyl)3 is associated with unusual products (entries 47 and 48). Particular mention may be made of the 17-electron species Cl3SiVH(Cp)2 and (Cl3Si)2V(Cp)2 shown... 

Reactant Volatile Hydrocarbon Product Observed Adsorbed Hydrocarbon Product Observed Proposed Ligand Eliminated Proposed Bond Activation Sequence (Greek letters designate C-H bonds at that position)... 

For Red) dimers with a Re—Re bond, photoexcitation induces homolysis of the Re—Re bond. The two rhenium(O) metal centers in Re2(CO)io each donate one electron from their d 2 orbitals to make a a M—M bond. Upon photoirradiation, the bonding a-orbital (ob) electron is excited into the antibonding a-orbital (qz ), which leads to metal-metal bond cleavage. It has been also reported that a CO ligand elimination proceeds competitively with the metal-metal bond homolysis reaction. When a cyclohexane solution of Re2(CO)io was irradiated by the 355-nm laser light, the ratio of the reaction quantum 5nelds of Re—Re bond... 

As stated above, CO2 reduction proceeds by the OER species of the rhenium complex serving two roles. That is, (1) serving as a single-electron donor and (2) ligand elimination to generate a... 

Ligand Elimination from the Tetrahedral XY4 Species Bond Length and Valence Angle Correlations... 

For metal-metal bonded complexes that contain multiple bonds, addition of ligands can reduce the bond order but does not have to destroy the metal - metal interaction entirely. The reactions shown below are written in the forward direction, which highlights addition reactions leading to a loss in multiple-bond character. It should be kept in mind that these are often in equilibria, and ligand elimination in the reverse direction can be a source of the multiply bonded species. 

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