Pseudotetrahedral

There is Httie known chemistry of tetrakis-Cp thorium complexes. Pseudotetrahedral molecules, (rj-ring) Tb (15), where ring = Cp [1298-75-5] or Ind [11133-17-6], have a measurable dipole, resulting from deviation of symmetry (88). Difference of coordination environments, eg, v] in the indenyl system and in the Cp system, appears to indicate great steric crowding about the thorium center, which probably limits the reactivity and synthetic derivatization of these complexes. 

Tetrakis-Cp uranium complexes are readily prepared via metathesis of UCl and KCp in refluxing benzene. These complexes are a relatively rare example of a pseudotetrahedral complex with four Tj -Cp rings, (rj-ring) (25). The Cp derivative has been shown to react with CO and CO2 to give acyl and carboxylato complexes. This complex also reacts with alkyl haUdes to afford the U(IV) complex, Cp UX (X = halide). 

Most of the phosphoryl and thiophosphoryl compounds are colourless gases or volatile liquids though PSBt3 forms yellow crystals, mp 37.8°, POI3 is dark violet, mp 53°, and PSI3 is red-brown, mp 48°. All are monomeric tetrahedral (C y) or pseudotetrahedral. Some physical properties are in Table 12.4. The P-O interatomic... 

Further interesting redox modified polypyrrole films were prepared e.g. a polymeric copper phenanthroline complex that can be reversibly de- and re-metallated because it retains the pseudotetrahedral environment after decomple-xation, A very diversified electrochemistry is displayed by polypyrrole films containing electron donor as well as electron acceptor redox centers in the same film... 

Studies of phosphine substitution have thus far focused almost exclusively on ti i- or tetranuelear clusters, with almost all trimetallic examples pseudotetrahedral... 

The P-N chelate (91) (dapdmp) exhibits a variety of coordination geometries in complexes with divalent Co. Pseudotetrahedral Co(dapdmp)X2 (X = C1, Br, I, NCS), low-spin five-coordinate [Co(dapdmp)2X]+ (X = C1, Br, I), planar [Co(dapdmp)2]2+ and pseudo-octahedral Co(dapdmp) (N03)2 were all identified.390 The tetradentate P2N2 Schiff base complex (92) is formed by reacting the free ligand with CoI2. The iodo complex is low spin and square pyramidal.391... 

A combination of matrix isolation IR and DFT studies have shown that condensation of monomeric NiX2 (X = C1, Br) in solid N2 matrices initially gives species NiX2- -(N2) with a physisorbed type of interaction. These can be converted by photolysis into pseudotetrahedral NiX2(r/l-N2)2 (115) moieties with end-on bound N2 in a chemisorbed type of interaction below 10 K. On warming to ca. 20 K the chemisorbed species revert to the physisorbed state.457... 

A detailed study involving racemization kinetics and spin states of a series of nine related complexes (507) has been undertaken.1357 In an X-ray crystallographic study of a series of complexes (R Pr1, R2 = Me, R3 = H, R4 = Me, Ph, Bu ) all complexes were found to possess pseudotetrahedral geometry.1358... 

Using a new tripodal ligand, Sorrell and co-workers synthesized compound (61).83 The dioxygen reactivity of the pseudotetrahedral complex of this ligand of composition [(L)Cu(MeCN)][BF4] (not structurally characterized) was examined. In MeOH at —78 °C, the thermal decomposition of the side-on peroxodicopper(II) adduct in the presence of water yields a bis(hydroxide)-bridged... 

The copper(I) analogue [Cu(L)][C104] (744) (distorted tetrahedral) of copper(II) complex (201) was also synthesized and its redox property investigated.193 Structuresof complex (745) (distorted tetrahedral)557 and complex (746) (pseudotetrahedral Cu-Cu 4.764 A)558 were also reported. 

The copper-alkoxo unit, which is usually synthesized in situ, plays a significant role in metal-promoted transformations of organic substrates by copper(I). To determine the reaction form of the Cu-OPh unit, Floriani and co-workers structurally characterized four complexes (772) (pseudotetrahedral Cu-Cu 3.223 AT (773) (pseudotetrahedral), (774) ( anion linear coordination) and (775) (planar trigonal).57 Using 3,3,6,6-tetramethyl-l-thia-4-cycloheptyne as terminal ligand the structural characterization of a copper(I)-alkyne complex (776) (Cu-Cu 2.940 A) was reported.573... 

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