Ligand TRIPHOS

The borohydride reduction of nickel(II) compounds in protic solvents may result either in the formation of nickel(O) complexes66,71 or in the formation of hydrido complexes of nickel(II). Two easily interconvertible isomers, Ni(triphos)2, have been obtained in the reduction of Ni(N03)2 in the presence of the ligand triphos, but their structures are not known with certainty. 

The ligands triphos or/ and np in presence of compounds of iron, cobalt, nickel, rhodium, iridium and palladium, by reaction with THF solutions of white phosphorus, P, or yellow arsenic, As, form mononuclear or dinuclear sandwich complexes containing the cyclo-triphosphorus or cyclo-triarsenic units which behave as 3n-electrons rings. 

The trinuclear gold(I) complexes [(AuX)3( j,-triphos)] (triphos = bis(2-diphenylphos-phinoethyl)phenylphosphine X = Cl, Br, I, CgFs ), where X = Br and I , were reported to emit at room temperature with emission energies significantly red-shifted from that ofthe free phosphine ligand (2477 cm for Br with Agx 350 nm 4482 cm for I with Aex 385 nm) [41]. The chloro, pentafluorophenyl, and l,3,5-tris(trifluor-omethyl)phenyl derivatives do not emit, even at Aex <300 nm. The emission properties... 

The X-ray structure of 4rCl(CO)(triphos)] confirms the trigonal-bipyramidal geometry of the Ir center, with the three phosphorus atoms occupying one axial and two equatorial positions and the Cl ligand in the remaining axial position.608... 

Triphos-derived tridentate ligands with mixed donor sets have been developed and subsequently used in Ni coordination chemistry. Nickel(II) complexes include dinuclear compounds (254) and (255) with P2S and P2O ligands, respectively.6... 

As to most chiral atropisomeric ligand, resolution or asymmetric synthesis is requisite. Mikami developed a novel ligand-accelerated catalyst. The chirality of atropos, but achiral triphos ligand-Ru complex, can be controlled by chiral diamines. Using ( -dm-dabn as controller, the single diastereomeric triphos-Ru complex was achieved through isomerization of (i )-triphos-Ru complex in dichloroethane at 80 °G (Scheme l).44... 

Kinetic evidence obtained for intramolecular proton transfer between nickel and coordinated thiolate, in a tetrahedral complex containing the bulky triphos ligand (Pl PCE CE PPh to prevent interference from binuclear p-thiolate species, is important with respect to the mechanisms of action of a number of metalloenzymes, of nickel (cf. urease, Section VII. B.4) and of other metals (289). 

As illustrated in Figure 19, which refers to [Co(triphos)(DBcat)]+, these complexes display both two sequential reduction processes centred on the metal ion and two sequential oxidation processes centred on the catechol ligand. 

Structure type Illb with an rj -S2 ligand that is coplanar with the two metal atoms has been detected in [(triphos)Ni(/i-S2)-Ni(triphos)] C104[triphos = bis(2-diphenylphosphinoethyl)phenylphos-phine] (99). 

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