Metal amidinato complexes

Titanium imido complexes supported by amidinate ligands form an interesting and well-investigated class of early transition metal amidinato complexes. Metathetical reactions between the readily accessible titanium imide precursors Ti( = NR)Cl2(py)3 with lithium amidinates according to Scheme 84 afforded either terminal or bridging imido complexes depending on the steiic bulk of the amidinate anion. In solution, the mononuclear bis(pyridine) adducts exist in temperature-dependent, dynamic equilibrium with their mono(pyiidine) homologs and free pyridine. 

Metal amidinato complexes are principally accessible through several synthetic routes. The most prevalent of them include ... 

Several patents dealing with the use of volatile metal amidinate complexes in MOCVD or ALD processes have appeared in the literature.The use of volatile amidinato complexes of Al, Ga, and In in the chemical vapor deposition of the respective nitrides has been reported. For example, [PhC(NPh)2]2GaMe was prepared in 68% yield from GaMes and N,N -diphenylbenzamidine in toluene. Various samples of this and related complexes could be heated to 600 °C in N2 to give GaN. A series of homoleptic metal amidinates of the general type [MIRCfNROilnl (R = Me, Bu R = Pr, BuO has been prepared for the transition metals Ti, V, Mn, Fe, Co, Ni, Cu, Ag, and La. The types of products are summarized in Scheme 226. The new compounds were found to have properties well-suited for use as precursors for atomic layer deposition (ALD) of thin films. 

Fenske, D., Baum, G., Zinn, A. and Dehnicke, K. (1990) Ag2[Ph-C(NsiMe3)2]2 and Au2[Ph-C(NsiMe3)2]2 - amidinato complexes with short metal-metal distances. Zeitschrifi fur Natuiforschung B, 45, 1273-1278. 

Figure 4.42. Molecular structures of commonly used CVD precursor classes. Shown are (a) metal p-diketonate (acetylacetonate, acac) complex to grow a metal oxide film (H2 as the coreactant gas yields a metal film) (b) a heteroleptic (more than one type of ligand bound to the metal) p-diketonate complex to yield a Cu film the ancillary ligand helps prevent oligomerization, enhancing volatility (c) various types of complexes to deposit metallic, oxide, nitride, or oxynitride films (depending on coreactant gas(es) used - respective ligands are p-ketoiminato, p-diketiminato, amidinato, and guanidinato (d) a metal azolato complex commonly used to deposit lanthanide metal thin films.

The synthesis and characterization of the monomeric amidinato-indium(I) and thallium(I) complexes [Bu C(NAr)2]M[But(NAr(NHAr)] (M = In, Tl Ar = 2,6-Pr2CgH3) have been reported. Both compounds were isolated as pale yellow crystals in 72-74% yield. These complexes, in which the metal center is chelated by the amidinate ligand in an N, j -arene-fashion (Scheme 33), can be considered as isomers of four-membered Group 13 metal(I) carbene analogs. Theoretical studies have compared the relative energies of both isomeric forms of a model compound, In[HC(NPh)2]. ... 

Recently the first examples of complexes between the four-membered amidinato-Group 13 metal(l) heterocycles and transition metal fragments were reported. Complexes of the type CpFe(CO)2[M(X) But(NR)2 ] (M = Al, Ga, In X = Cl, Br R = Pri, Gy) were formed in salt-elimination reactions between Na[CpFe(CO)2] and [But(NR)2]MX2. A series of complexes between the four-membered amidinato-Group 13 metal(l) heterocycles and Group 10 metal(O) fragments have been prepared according to Scheme 35. ... 

In a systematic study, it was demonstrated that, using a specially designed bulky benzamidinate ligand, it is possible to isolate mono(amidinato) dialkyl complexes over the full size range of the Group 3 and lanthanide metals, i.e., from scandium to lanthanum. The synthetic methods leading to the neutral and cationic bis(alkyls) are summarized in Scheme 56. Figure 18 displays the molecular structures of the cations obtained with Sc, Gd, and La. ... 

Following the well-recognized role of carboxylato anions as bridging ligands in binuclear complexes with metal-metal bonds, Cotton and coworkers94"97 have explored the use of the isostructural and isoelectronic amidinato (NR )RC(NR") anions (31). 

The use of amidinato catalyst systems for the polymerization of olefins has first been reported in a patent application by us in cooperation with BASF company [6,7,46]. Since then various other patents dealing with the use of amidinato metal complexes as catalysts for olefin polymerizations have appeared. However, the main focus of these studies was on the use of group 4 metal amidinates as these have been found... 

A new class of titanium hydrazinediido half-sandwich complexes [Cp Ti(Nxy]N) (=NNR2)(L)] (A) was found to display remarkable activities in catalytic hydro-hydrazinations of alkynes at ambient temperatures (Scheme 13.6). A key feature has been the use of 2-aminopyrrolinato spectator ligands in which the amidinato binding unit is exocyclic with respect to the heterocycle [18]. The possibility of amidinates to convert from to coordination and thus to temporarily liberate a coordination site at the metal may be crucial in the development of active molecular catalysts. 

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