Functionalized amidinate ligands

In a related study the synthesis of half-sandwich cyclopentadienyl titanium f-butylimido complexes containing pendant-arm-functionalized amidinate ligands... 

Very recently, yet another interesting approach to novel-functionalized amidinate ligands has been reported. It involves the combination of amidinate... 

Lanthanide(III) Complexes Containing Functionalized Amidinate Ligands... 

In addition to the substituents listed in Scheme 1, chiral groups may be introduced and unsymmetrically substituted amidinate anions are also possible. The amidinate anions may also contain additional functional groups, or two such anions can be linked with or without a suitable spacer unit. Yet another variety comprises the amidinate ligands being part of an organic ring system. All these aspects will be covered in the present review. 

Other amidinate anions normally form dinuclear copper(I) complexes with bridging amidinate ligands, although tetracopper(l) complexes have also been reported Silver(1) forms dimeric complexes with functionalized N,N -... 

The coordination chemistry of ancillary amidinate ligands with a pyridine functionality has been described. Magnesium, aluminum, zirconium, and lanthanum complexes have been prepared in which the amidinate anions act as tridentate, six-electron-donor ligands Amidinate ligands containing quinolyl substituents were constructed in the coordination sphere of lanthanide... 

Tetranudear gold(I) amidinate complexes are synthesized by the reaction of Au(THT)Cl with the potassium or sodium salt of the amidinate ligand in THF, Figure 1.4. Syntheses involving various substituted amidinates resulted in tetra-nuclear gold(I) clusters, [Au4(ArNC(H)NAr)4]. The C-functionalized substituted amidine ligands, ArNC(Ph)NHAr and ArNC(Me)NHAr, Ar=-QH5, were synthesized and reacted with Au(THT)Cl after deprotonation. Only tetranudear clusters were isolated. 

In the case of the monosubstituted amidinate complexes, a crystallographic study of 2c (Fig. I) confirms a monodentate coordination of the amidinate ligand to the silicon center. The C-N bonds are nearly equal. The Si-N bond (1.625(3) A) is remarkably short and indicates some double bond character [6]. The analogous germanium structure (Fig. 2), apart Irom the longer Ge-N bond (1.776(2) A), is quite similar. Though the N-H hydrogen atom has not been located in either case, it seems plausible that an N(2)-H functionality is present. 

Unsymmetrical amidinate ligands with an N-H functionality have likewise been shown to be suitable ligands for silicon coordination centers [4, 7]. In the case of germanium(ii), a tetrameric compound 4 has been obtained according to Eq. 3 [4]. 

The protocols for the utilization of ketone-derived silyl enol ethers in Tsuji-Trost reactions were preceded by a report of Morimoto and coworkers on the enantioselective allylation of sUyl ketene acetals 88. Without external activation, they reacted with the allylic substrate 19d in the presence of the palladium complex derived from the amidine ligand 89 to give y,5-unsaturated esters 90 in moderate chemical yield but high enantiomeric excess (Scheme 5.29) [46]. Presumably, the pivalate anion hberated during the oxidative addition functions as an activator of the silyl ketene acetal. The protocol is remarkable in view of the fact that asymmetric allylic alkylations of carboxylic esters are rare. Interestingly, the asymmetric induction originates from a ligand with an uncomplicated structure. The protocol seems however rather restricted with respect to the substitution pattern of allylic component and sUyl ketene acetal. 

The imidoyl chloride functionality of 44 enabled synthesis of a novel 5-HT ligand 46 with a pseudo-amidine structure via palladium-catalyzed cross-coupling (Equation 4) <1999TL8109>. 

A large number of bridge N-donor structures exist (Sec. 2.2A.2), for example 157,160,162,163,164,191,197, and 200 203. In this respect, it is necessary to note Ref. 78, where it is shown that amidines form (3.66), additionally to chelate structures of the type 625, the bimetallic complexes 626 with a bridge function of the ligand ... 

Non-functionalized Mono-Cp Complexes Containing Multidentate Ligands 4.08.7.2.1 Complexes containing bidentate amidinate and guanidinate [N2 ] ligands... 

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