Imide complexes

The formation of a bis(guanidinate)-supported titanium imido complex has been achieved in different ways, two of which are illustrated in Scheme 90. The product is an effective catalyst for the hydroamination of alkynes (cf. Section V.B). It also undergoes clean exchange reactions with other aromatic amines to afford new imide complexes such as [Me2NC(NPr )2]2Ti = NC6F5. ... 

Besides, iron(IV) imides have also been implicated as reaction intermediates in nitrogen atom/group transfer reactions [36]. The first structurally characterized iron-imide complex was reported by Lee and coworkers [37] through the reaction of FeCls with 2 equiv. of LiNH Bu in THF, giving one of the products as a stable site-differentiated cubane having three Fe(lll) and one Fe(IV) centers and the Fe(IV) center has a terminally bonded imido ligand (Scheme 4). 

Power and coworkers prepared the iron(V) bis-imide complex 3,5-Pr2 Ar Fe[N (1-Ad)]2l [42]. This complex has been characterized by X-ray crystallography with the iron in planar three-coordinate geometry. The Fe-N bond distances are 1.642(2) and 1.619(2)A. Magnetic studies of 3,5-Pr2 Ar Fe[N(l-Ad)]2 reveals that this complex has a low-spin cP configuration with S = jl ground state. This compound is notable as it is a stable Fe(V) imide being well characterized. 

A few stable gold(III) imidate complexes have been authenticated by X-ray structure determinations. Most of the claimed gold(III) imidate complexes including those containing succinimide, phthalimide, saccharin or N-methylidantoin derivatives [40] were subsequently reformulated as gold(I) species [41[. 

Optimized structures of these species are shown in Fig. 4.31 and geometrical and NBO descriptors are summarized in Table 4.21. As shown by comparisons with Table 4.19, the geometrical features of the nitride and imide complexes exhibit... 

Based on the established mechanism for titanium-catalyzed hydroamination, the authors propose a reversible reaction between a titanium imide complex and the alkyne to form metalloazacyclobutene 86, which in turn undergoes 1,1-insertion of the isonitrile into the Ti-C bond. The generated five-membered ring iminoacyl-amido complex 87 with the new C-C bond is protonated by the primary amine to afford the desired three-component coupling product, with regeneration of the catalytic imidotitanium species. Very recently, titanium-catalyzed carbon-carbon bond-forming reactions have been reviewed.122... 

Figure 6.20 IR and H NMR spectroscopic data suggesting intramolecular hydrogen-bonding responsible for increased reactivity of 2-methoxybenzimides (A) and proposed hydrogen-bonding pattern of the catalyst-imide complex supported by NMR titration (B) the chemical shift values in parentheses refer to the imide in the absence of 12.

Imidate complexes, synthesis, 211-212 Iminio(alkyl)carbene complexes, synthesis, 200-201... 

The Ti—N bond in this type of complex is short, ca. 1.7 A. The reduction of TiCl4(NH3)2 with NaH in the presence of L = Ph3PO gives the imide complex Ti(=NH)Cl2L2.42... 

Group 4 imido chemistry see Imide Complexes) is less well studied than that of the group 5-7 metals. An important reason for this is the change in reactivity of the imido ligand upon coordination to the more electropositive metals. The increased polarity of the M=NR unit in compounds... 

Imido zirconocenes see Imide Complexes) are synthesized from thermolysis of Cp2Zr(Me)NHR. They react with a wide variety of organic substrates (alkynes, imines, azides, carbodiimides, ketones) to yield [2 + 2] cycloaddition products (Scheme 4) see Metallacycle) ... 

TripNs to yield, along with N2 formation, the first monomeric A1 and Ga imide complexes HC(CMeNAr)2 M N(Trip) with M = A1 and Ga, respectively. In the case of the Ga imide complex (9), experimental data and theoretical calcnlations snpport a mnltiple bond character for the exocychc Ga N bond. 

Several of the above studies point to the conformational flexibility of NTf2 anions, which can adopt both cis and trans conformations see also the above-mentioned examples of the Li-NTf2 systems [126,131,154-156,239], Binnemans has suggested that the conformational flexibility of the NTf2 anion is the main culprit for the often poor quality of bis(trifluoromethylsulfonyl)imide complex crystals [71]. 

---