Hydrotris borate, ligand structure

A tris(imidazolyl)borate (138) complex of thallium(I) has been synthesized.The solid-state structure of hydrotris(imidazolyl)boratothallium(I) consists of one-dimensional, twisted, ladderlike strands, and three-coordinate thallium centers. Due to the position of the nitrogen donors, the tris(imidazolyl)borate ligand is not capable of forming metal chelates as are observed in tris(pyrazolyl)borates. Poly(benzotriazolyl)borate ligands have some features of both tris(pyrazo-lyl)borate and tris(imidazolyl)borate systems. Thallium(I) complexes of bis-, tris-, and tetrakis (benzotriazolyl)borates are reported. These adducts have been synthesized by treating the corresponding potassium derivative with an equimolar quantity of thallium(I) formate. ... 

The pursuit of simple homoleptic cobalt complexes has become a ubiquitous means of structurally characterising each novel derivative of the basic tetrakis-, hydrotris- or dihydrobis-(pyrazolyl)borate ligand motifs. Complexes of this type are inaccessible only for the most sterically demanding Tp ligands, in which case reports of the isolation of LCoX (X = halide, OR, SR...) complexes have instead proliferated. Examples of these are now known for essentially every... 

Hddchi S, Yoshizawa M, Sasakura Y, AMta M, Moro-oka Y (1998) First synthesis and structural characterization of dinuclear M(lll) Bis(i-oxo) complexes of nickel and cobalt with hydrotris(pyrazolyl)borate ligand. J Am Chem Soc 120 10567... 

Organonickel derivatives also offer cases of the -coordination of the substituted hydrotris(pyrazol-l-yl)borate ligand. For the palladium and platinum complexes, the M(II) M(IV) (M = Pd, Pt) transformation is facile. Organopalla-dium chemistry offers a new type of agostic interactions, C—H Pd, where the C—H bond belongs to one of the pyrazolate rings. Cyclopalladation of various pyrazol-l-ylborates and -methanes does not modify their structure. 

Synthesis of functional models of carbonic anhydrase has been attempted with the isolation of an initial mononuclear zinc hydroxide complex with the ligand hydrotris(3-t-butyl-5-methyl-pyrazolyl)borate. Vahrenkamp and co-workers demonstrate the functional as well as the structural analogy to the enzyme carbonic anhydrase. A reversible uptake of carbon dioxide was observed, although the unstable bicarbonate complex rapidly forms a dinuclear bridged complex. In addition, coordinated carbonate esters have been formed and hydrolyzed, and inhibition by small ions noted.462 A number of related complexes are discussed in the earlier Section 6.8.4. 

The hydrotris(triazolyl)borate (httazb, (133)) ligand gives a bis-ligand iron(II) complex [Fe-(httazb)2] 6H20, whose structure consists of layers of complex molecules separated by layers of water molecules. ... 

The whole series of pyrrol-l-ylborates, M[BH (NC4H4)4 ], has been synthesized (Tables 9 and 12). The mechanism of their formation and their hydrolysis kinetics have been studied in detail.100 The hydropyrazol-l-ylborates are very stable compounds and can be prepared in acid form.101 The di- and tri-pyrazol-l-ylborates are extensively used as complexing ligands (see Chapter 13.6). The photoelectron spectra of the sodium and thalliumfl) hydrotris(pyrazol-l-yl)borates and the electronic structure of the anion itself are reported.11 ... 

In a related approach by Zuo and Zhou the same type of donor corner, [TpFe(CN)3], where Tp is a scorpionate ligand with a three-fold axis of symmetry (hydrotris(pyrazolyl)borate), is combined with a higher connectivity acceptor linker, [Cu]2+. As the Cu center adopts a square pyramidal (CN)4Cu(H20) local coordination, the cluster structure observed is one with eight donor corners and... 

While indeed a clean photoreduction of COa to CO in the complex (prophos)Cu (C03)Cu (prophos) was observed the concomitant oxidation did not yield oxygen or hydrogen peroxide but phosphine oxide (30). In order to prevent this dead end, phosphines have to be replaced by ligands that do not act as oxygen atom acceptors. For this purpose we selected the tridentate ligand hydrotris (3,5-dimethyl-l-pyrazolyl)borate (Tp ) as a suitable ligand (40). Various Cu(I) and Cu(II) complexes of Tp or other Tp derivatives have been prepared and characterized (41-45). Unfortunately, we were not able to obtain simple carbonate complexes of the Cu Tp moiety (Structure 1). In the presence of COs, Cu Tp underwent a decomposition. 

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