Detection donor ligands

The ZwKKER reaction involving Co salts is frequently used for the detection of barbituric acid derivatives [31-35], but some purine, pyridine and piperidine derivatives and heterocyclic sulfonamides also yield colored derivatives. The Zwkker reaction is particularly sensitive when it is possible to form a tetrahedral complex [Co(Barb)2 Xj] (X = donor ligand, e.g. amine) [4]. 

A series of diastereomeric platinum(II) complexes of the type c -[PtL2Y2]2+ (L - 3-bromopyr-idine, quinoline, isoquinoline Y = PEt3, Y2 = dppp, (/ )-(I )-2,2 -bis(diphenylphosphino)-l, l -binaphthyl (R-( I )-binap)) have been prepared by the reaction of c -[PtY2(OTf)2] (OTf=tri-trifluoromethanesulfonate) with two equivalents of the N-donor ligand.207 Related complexes have also been studied, for example when L = pyridine.208 Restricted rotation about the Pt—N bonds in many of the complexes is usually detected by NMR spectroscopy, with only [Pt(dppp)(isoquinoline)2]2+ (65) exhibiting dynamic behavior at ambient temperatures. The PEt3... 

Monomeric dialkylaluminum hydrazides with terminal hydrazido groups (A, Scheme 2) were observed only in those cases in which donor ligands such as ether molecules (28 to 30) or hydride ions (26) saturate the aluminum atoms to yield coordination numbers of four. In the absence of Lewis bases dimers are formed of the monoaluminum and monogallium monohydrazido derivatives, a trimer has never been detected by crystal structure determinations. Three different types of structures were reported ... 

Dias and co-workers 48, 48a) investigated the photochemistry of the complexes MoCp2(CH3)2 48) and [MCp2(CH3)2]PF6 (M = Mo or W) 48, 48a) and found that only the cationic complexes were photosensitive. Irradiation of MoCp2(CH3)2 with pyrex-filtered light (A > 310 nm) led to no detectable reaction. However, irradiation of the complexes [MCp2(CH3)2] in the presence of added donor ligands led to photopro-... 

These results arc compared with those obtained for [Cr (salcn)CI] eatalyzed asymmetric oxidations of olefins by PhlO. The active intermediate of these systems was detected and identified as (Cr O(salcn)LJ (where L= Cl- or a solvent molecule). A reservoir of the active species in this system was also found to exist as a mixed-valence binuclcar species (L(salen)Cr "OCr (salen)L ] (L. L = Cl or solvent molecules). The high-valence ( r complexes arc in equilibrium and their ratio can be afTected by addition of donor ligands (DMSO, DMF, H3O). 

---