Tripodal tetradentate ligands

The structures of the bis-ligand iron(II) complexes of the tripodal ligands tiis(pyiidin-2-yl)methane and tris(pyridin-2-yl)phosphine oxide have been determined." " The tetradentate tripodal ligand... 

Hydroxide is rarely found coordinated to Fe " in a mononuclear octahedral complex, but has been demonstrated in the purple salt [Fe(tnpa)(0H)(00CPh)]C104, where tnpa is the tetradentate tripodal ligand tris(6-neopentylamino-2-pyridylmethyl)amine, (203) the hydroxide is cis to the benzoate ligand." ... 

By reducing hydrated nickel(II) nitrate with NaBHt, in the presence of the tetradentate tripodal ligand np3 (equation 80), the complex [Ni(np3)j (66) has been obtained.263 Complex (66) undergoes oxidative reaction with HC104 or HBF4 to afford the nickel(II) hydrido complex [NiH ps)]-1".264 It also reacts with CO to give the carbonyl derivative263 and with white... 

Most of the nickel(l) complexes are four-coordinate, either tetrahedral (phosphine and arsine complexes) or square planar (macrocyclic and dithiolene complexes), but five-coordinate complexes are also easily formed in the presence of tetradentate tripodal ligands. 

Table 72 Selected Complexes with Tetradentate Tripodal Ligands...

A problem with the formation of the ternary ES—02 adduct is that it entails an attack of triplet 02 on the singlet substrate, which is a forbidden reaction. However, the presence of iron(III) may provide a mechanism for relaxing this barrier, as suggested by biomimetic studies showing that oxidative cleavage of catechols can be catalyzed by iron(III) centers [145,146], Building on this important early work, Que and coworkers synthesized a series of [Fe(L)(dbc)] complexes where L is a tetradentate tripodal ligand based on trimethylamine with... 

Sacconi and his school have prepared a large number of five-coordinate complexes containing a tetradentate tripod ligand with various donor sets. They have found... 

Few organo-Co(I) species are prepared this way. Exceptions are those with tetradentate tripod ligands CoR[E(CH2CH2PPh2)3](R = Me, Ph E = N, P) from bromocobalt analogs and organolithium . ... 

TETRADENTATE TRIPOD LIGANDS CONTAINING NITROGEN, SULFUR, PHOSPHORUS, AND ARSENIC AS DONOR ATOMS... 

Other tetradentate, tripodal ligands have been employed successfully to stabilise substrates of VNase and intermediates along the reduction pathway of N2. Examples with NSj, and PSj, ligands are provided in Figure 4.30. The complexes 47 contain vanadium in the oxidation states +III (neutral ligands such as hydrazine and isonitrile), -flV [monoanionic ligands such as methyldiazenido(l-) and cyanide(l—)] and... 

Ligand Design in Metal Chemistry 10.1.3.6 Tetradentate tripodal ligands... 

Increasing steric bulk at tetradentate tripodal ligands prevented dimer formation and stabilized end-on Cu-02 complexes, one of which was crystallographically and spectroscopically characterized (cavity around the copper center was shaped by the ligand (TMG TREN) (Figure 4.13).42 This dramatic result provided additional support for earlier end-on superoxide formulations for the 1 1 copper-dioxygen complexes supported by tripodal ligands (such as TPA or TREN derivatives)... 

Trigonal bipyramidal Cr complexes containing tetradentate tripod ligands are in Section 35.3.4.3. 

Figure 5 Tetradentate tripodal ligands for modeling intradiol-cleaving dioxygenases.

Figure 20 Coordination geometries found with tetradentate tripod ligands (a) trigonal bip3Tamidal in Cu(II), (b) trigonal pyramidal in Cu(I), (c) square pyramidal in Ru(II), (d) octahedral in Co(III), and (e) bridging in a tetranuclear Cr(0) complex. Only the relevant metal and donor atoms are represented as spheres, and substituents at the ligands are omitted for clarity.

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