Diolate ligand

Recently, dithio-diolate ligands have been employed for construction of group 4 metal catalysts for the ROP of lactide. These metal dithiolate complexes form mononuclear species of the type [(OSSO)M(OR)2] with an octahedrally coordinated metal center. These fluxional compounds acted as highly active catalysts in the ROP of L- and rac-lactide. Hafnium complexes were also introduced as initiators for the ROP of L-lactide and rac-lactide (vide infra) in very limited cases. To our knowledge, the hafnium derivative 146 displayed the highest activity among the group 4 catalysts reported to date (complete conversion of 300 equiv. of... 

Figure 3 Examples of chiral diolate ligands employed within Schrock-class initiators.

CX = O or NCgH3-Me2-2,6 cocatalyst Et2AlCl. The cis content of the polymer varies from 41 to 100% depending on the nature of the chelating diolate ligand. Norborn-2-ene-5-spiro-3/-eA o-succinic anhydride, and norborn-2-ene-5-spiro-3/-exu-N-phenylsuccinimide and derivatives. 

This unique reactivity was subsequently utilized in the functionalization of unsaturated hydrocarbon substrates with CO (Scheme 39) [285, 286]. In the course of these studies the stereospecific synthesis of a diolato unit was observed via a samarium-mediated CO and CH (alkene) activation. A bridging trans-5,10-dihydroindeno[2,l-a]-5,10-diolate ligand forms terminal Sm-O bonds in [Cp Sm]2(O2C16H10) and its THF adduct. Two molecules of CO are formally inserted into the carbon carbon double bond of l,2-di-2-pyridylethene to form a terminal bisenolate moiety [286] (Table 18). 

The binuclear titanium complex shown in Scheme 364, supported by chiral diolate ligands, has been prepared as yellow crystals by the reaction of Cp TiCl3 with the corresponding diol in the presence of NEt3 in toluene at room temperature and its molecular structure determined by X-ray diffraction.888... 

Bis(2,5-dimethylpyrrolide) imido alkylidene complexes are monomeric, flux-ional 18-electron species [13]. They were first employed as precursors to Mo(NR)(CHCMe2Ph)(diolate) complexes that contain the relatively electron-withdrawing binaphtholate (3,3-bis-(9-anthracenyl), 3,3 -bispentafluorophenyl, 3,3 -bis(3,5-bis(trifluoromethyl)phenyl), or biphenolate (3,3 -di-fBrt-butyl-5,5 -bistrifluoromethyl-6,6 -dimethyl-l,l -biphenyl-2,2 -diolate) ligands. In... 

FIGURE 20.25 Mo alkylidene complexes with chelating diolate ligands (dme = dimethoxyethane). 

Numerous structures of alkoxo copper(ii) complexes have been determined. The tridentate diolate ligands [0(CH2)4N=C(Me)CH2C(CF3)20] and [0(CH2)3N=C(Me)CH2C(CF3)20] gave binuclear complexes [Cu2 m-0(CH2) N=C(Me)CH2C(CF3)20 2] (n = 4, 3). Each molecule has square planar Cu(ii) atoms with an essentially near planar 0NCu(/r-0)2CuN0 framework." " ... 

The routinely used imido and diolate ligands are indicated below the scheme. 

Total Synthesis of Natural Products with Enantiomerically Pure Chiral Olefin Metathesis Catalysts Bearing a C2-symmetric Diolate Ligand... 

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