DMF complexes

In addition to the perfluoroalkylzinc compounds, the zinc reagent formed from 1,1,1-trifluorotrichloroethane has received considerable attention. This zinc compound was first reported as a stable ether complex [56]. Later, the DMF complex was isolated and the structure was determined by X-ray diffraction and shown to be monomeric [57] (equation 50). This zinc reagent undergoes a variety of functionalization reactions, and some typical examples are illustrated in Table 2 [47, 58, 59, 60, 61] The alcohol products (Table 2) can be converted to AiCF=CXCF3 (X = Cl, F) by further reaction with diethylaminosulfur trifluoride (DAST) and l,8-diazabicyclo[5 4.0]undec-7-ene (DBU) [60]... 

Oxidative addition of molecular hydrogen was considered to be involved in the alkyne hydrogenations catalyzed by [Pd(Ar-bian)(dmf)] complexes (4 in Scheme 4.4) [41, 42]. Although the mechanism was not completely addressed, 4 was considered to be the pre-catalyst, the real catalyst most likely being the [Pd(Ar-bian)(alkyne)] complex 18 in Scheme 4.11. Alkyne complex 18 was then invoked to undergo oxidative addition of H2 followed by insertion/elimination or pairwise transfer of hydrogen atoms, giving rise to the alkene-complex 19. 

Scheme 4.11 Proposed catalytic cycle for the hydrogenation of alkynes promoted by Pd(Ar-bian)(dmf) complexes.

The molarity of the reagent is then determined by titration against standard base. An aliquot (1 or 5 ml) is first diluted with water (20 or 100 ml) to convert the sulfur trioxide-DMF complex into sulfuric acid. The resulting solution is titrated to phenolphtalein end-point with standard 0.1 or 0.01 N aqueous alkali (NaOH or KOH) to determine the molarity f/2 of the Normality). It should be in the range of 0.9 to 1.2 depending on the amounts of S03 and DMF used. 

More stable than corresponding DMSO and DMF complexes. 

The formal reduction potential of silver ion in DMF was found to be +0.579 0.004 V vs. SCE. The values of the stability constants of the DMF complexes of silver(I) in various solvents are given in Table 38. It was observed that the complexes were most stable in nitroethane.274... 

Table 38 Stability Constants of DMF Complexes of Silver(I) in Various Solvents274...

M. M. Andrade and M. T. Barros, Facile conversion of O-silyl protected sugars into their corresponding formates using POCl3/DMF complex, Tetrahedron, 60 (2004) 9235-9243. 

If allowed to cool to 25°C, the dark layer may solidify, hampering the separation. This very acidic layer is the excess thionyl chloride/DMF complex. It should be handled with proper protection in a ventilated area To facilitate visual identification of the layers, the checkers added about 25 ml of hexane. 

Ni(0A0H)2H20 DMF complexes, show that the [Ni(OAOH)2] islands of these complexes are isostructural. While in the dihydrate complex these islands are planar and centrosymmetrical (Fig. 26) and connected to water molecules via hydrogen bonds (Fig. 27), the monohydrate complex contains two types of crystallographically independent centrosymmetrical islands their packing with DMF and H2O is shown in Fig. 28. As... 

In contrast to BINAP, DM-BIPHEP (3, R = 3,5-(CH3)2QH3 R = H) is conforma-tionally flexible and exists as an R and S equilibrium mixture [108]. Mixing of the RuCl2(dm-biphep)(dmf) , complex with (S,S)-DPEN produces a 3 1 diastereomeric mixture of (S)-DM-BIPHEP/(S,S)-DPEN-Ru(II) and the R/S,S complex. As the major S/S,S species is more reactive and enantioselective, T-acetonaphthone is quantitatively reduced to the R alcohol in 92% e.e., even with the mixed Ru complex. 

Reduction of Met(O) residues may also be performed prior to the acid deprotection step by use of the SO3/DMF complex in pyridine in the presence of a thiol.The reduction proceeds with the initial formation of a sulfonium ion and subsequent nucleophilic attack of the thiol (Scheme 2). The reaction is performed at room temperature and is generally completed within one hour. 

Base hydrolysis of 0-coordinated JV,JV-dimethylformamide in the complex [Co([15]aneN5)DMF] (40) is accelerated some 327-fold compared with the free ligand. The effect is considerably less marked in the macrocyclic complex when comparisons are made with the [Co(NH3)5(DMF)] " complex (rate acceleration ca. 10 ). The Lewis acidity of Co " is presumably reduced by the stronger cr-donors of the macrocyclic ligand. 

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