Group III metal complexes

It should be noted that, in the case of [(R)(Me)SiCp2YR], the TOF of the hydrogenation of 1-hexene decreases dramatically, from 11 100 h 1 (R=Me) to 200 h 1 when an ether functional group is bound on the ansa bridge (R=(CH2)5OMe), which shows the sensitivity of Group III metal complexes towards polar functionalities [121]. 

Group 4 metal complexes of the dianion [ BuNP( -N Bu)2PN Bu] polymerize ethylene in the presence of a co-catalyst, but they are readily deactivated [10,14]. This behaviour is attributed to coordination of the lone-pair electrons on the phosphorus(III) centers to Lewis acid sites, which initiates ring opening of the ligand [15]. 

Hydrogenation of Alkenes with Group III Metal and Lanthanide Complexes 126... 

Tridentate diarylazo compounds containing o-hydroxy and o -sulfonamido groups form metal complexes which are insufficiently stable to be of value as dyestuffs. Analogous tetradentate azo compounds are, however, reported108 to give stable chromium(III) complexes, e.g. (158), although no dyestuff application of complexes of this type is known. 

Fraas, R. E. Ionic Fragmentation Processes of Beta-Diketonate Complexes of the Group III Metals, Doctoral Dissertation, University of Kentucky, Lexington, Kentucky, 1972. 221 pp. (Order no. 73- 7,343, University Microfilms, Ann Arbor, Mich.)... 

Group 9 metal complexes can catalyze important homogeneous reactions such as hydrogenation and hydroformylalion of alkenes. Some of them are employed in industry. The mechanisms of the catalytic reactions involve M(I) and M(III) intermediates having 16 and 18 electrons. In some cases, the catalytic intermediates have been isolated, and a mechanistic study of the cataK tic reactions has greatly contributed to the progress of organometallic chemistr. ... 

In 2000, the catalytic properties of (acac-<9,<9)2Ir(III)(R)(L) were discovered as a part of a program on developing thermally stable, group VIII metal complexes containing O-donor ligands. For example, [Ir( J,-acac-<9,<9,C3)(acac-<9,<9)(acac-C3)]2 catalyzes the anti-Markovnikov hydroarylation of benzene with propylene to yield ra-propylbenzene via a well-defined CH activation reaction.6... 

The only main Group III metal, other than boron, that has been utilized in the aldol reaction is aluminum, the enolates of which behave rather capriciously in terms of stereochemistry. The A1—C bond is relatively weak. However, aldol reactions with aluminum enolates derived from chiral acyl-iron complexes proceed with high asymmetric induction. 

A review on organometallic complexes containing a bond between a Group III metal (Al, Ga, In, or Tl) and a transition metal has been published. ... 

IrCl(COT)2]2 (COT = cyclooctene) reacts at 25°C with both P(t-Bu)2CH2 OCH3 and P(t-Bu)2CH(CH3)OCHj to form, in the presence of CO, Ir(III)-metallated complexes by oxidative addition of a C—H bond of the methoxy groups. ... 

Previously reported work demonstrated that substituents can be used to tune the energies of excited states responsible for the emission spectra of certain group VIII metal complexes (1) and to modify significantly the absorption spectra of complexes displaying metal-to-ligand charge transfer (MLCT) bands (2). In this presentation, we summarize some recent attempts to use ligand substituents in our studies of transition metal complex photochemical reaction mechanisms. The particular subjects of interest are the metal ammine complexes M(NH3)5L where M is Rh(III) or Ru(II) and L is a meta- or para-substituted pyridine. 

In this review discussion is restricted to those systems that involve a group III metal bound to various organic ligands and deals principally with simple exchange processes, but also includes some discussion of the more complex rearrangements, especially those in which multiple bonds are involved. 

A variety of Group 4 metal complexes, in combination with common olefin polymerization activators, have been evaluated as potential catalysts for syn-diospecific polymerization of styrene (for reviews, see Refs. 114, 115, 123, and 426). Monocyclopentadienyl and monoindenyl titanocenes generally exhibit the highest activities (eq. 5) (112-127). Curiously, half-sandwich titanium-trifluoride-based catalysts are more active than their trichloride analogues (124,427,428). The polymerization mechanism for sPS formation is under debate. Kinetic studies and spectroscopic investigations of the catalytic systems suggest a cationic Ti(III) complex as the active species (123). 

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