Transition metals homoleptic structures

Prior to 1980, well-characterized, homoleptic and heteroleptic diorganoamido derivatives of almost all the earlier (i.e. groups 3-6) transition metals had been reported. These continue to attract much attention and new examples are a constant feature of the literature. Tables and provide a listing of the structurally characterized (X-ray or... 

There are roughly 421 reports of homoleptic bis(dithiolene) units based on transition metal elements. The approximate tally of the structures as a function of central metal atom is outlined in Fig. 2. The examples predominantly contain late transition metals. The majority of complexes are Ni based, partially because of interest in these complexes for materials applications. Other common central elements are Cu, Pd, Pt, Au, and Zn. There are also a few Fe and Co complexes and a small number of structures based on Cr, Mn, Ag, Cd, and Hg. 

There are roughly 50 homoleptic tris (dithiolene) complexes reported in the CSDC (5). The elemental distribution of these structures is outlined in Fig. 15. As opposed to bis(dithiolene) complexes, tris(dithiolene) complexes are based predominantly on early transition metal elements. Many of the tris(dithiolene) complexes are centered on V, Mo, and W. There are also complexes of Ti, Zr, Nb, Ta, Cr, Tc, Re, Ru, and Os. In addition, there are tris(dithiolene) complexes of Fe and Co, elements that also form homoleptic complexes with two dithiolene ligands. A detailed listing of the structural units along with references and geometrical parameters (to be discussed) is given in Table IV. 

A great amount of research has focused on the electronic structure, spectroscopy, redox properties, and conductivity of homoleptic bis(l,2-dithiolene) complexes of c transition metal ions (51). The compounds are often highly... 

M. M. Olmstead, P. Power, and S. C. Shoner, Isolation and X-Ray Crystal Structures of Homoleptic, Transition-Metal Aryl Complexes [(LiEt20)4VPh5] and [(LiEt20)3CrPh5], Organomeiallics 1, 1380-1385 (1988). 

Average bond length and angle parameters for the homoleptic tris(dithiolene) complexes are less sensitive to the identity of the transition metal or dithiolene ligand than those of bis(dithiolene) structures. Ranges of values are summarized in Fig. 22. Average M—S bond lengths cluster between 2.263 and 2.543 A, with values for two [Fe(mnt)3]2 units (2.263 and 2.269 A) (18), Co CAlCO),, 3... 

R. B. King (2000). Coord. Chem. Rev., 200, 813-829. Structure and bonding in homoleptic transition metal hydride anions. 

TJ ecently there has been much interest in the synthesis, structure, char-acterization, and thermal decomposition of unusual stable homoleptic metal alkyls MR (I). (The term homoleptic is used to describe a metal complex in which all the ligands are identical (2), i.e. TiR4 and Sn(NR 2)2 are examples of homoleptic metal alkyls and dialkylamides whereas Ti(Cl)R3 and Sn(NR 2)R are heteroleptic compounds. ) There are three classes (2) of these complexes (a) transition metal compounds, (b) diamagnetic lower valent main group element derivatives such as the... 

Structural (X-ray) properties of homoleptic, mononuclear transition metal complexes of 1,2-dioxolenes 06CCR(250)2000. 

Another source of interest came from biochemistry. Research on the blue copper proteins revealed unusual electronic properties (redox potential and kinetics, EPR and optical behavior) that were suspected of arising from interaction of the copper ion with a thioether group from methionine [7]. While crystallographic studies established a weak interaction (Cu -- - S 2.9 A) [8,9,10], its influence on the electronic properties of the Cu site is now considered questionable. Nevertheless, the controversy regarding the blue eopper proteins, like the analogy to phosphines, served to focus attention on the broad issue of how thioether coordination affects the electronic structure of transition metal ions. Homoleptic thioether complexes provide the best way of assessing these consequences, since no other groups obscure the effect of thioether coordination. 

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