Hexamethylphosphoramide complexes

A well dried sample of this complex exploded violently when pushed through a funnel with a steel spatula. The pyridine adduct, which was being prepared, is claimed to be a useful, safe, oxidant, replacing the hexamethylphosphoramide complex of M0O5 (ibid.). 

This suggestion was supported by experiments. First, the polymerization catalyzed by the hexamethylphosphoramide complex, which has a monomeric structure, gave a high yield of isotactic polymer even... 

A striking difference was observed between the trimethylamine oxide complex and the hexamethylphosphoramide complex, although both complexes are monomeric. Polymerization did not occur by the former complex, whereas it proceeded smoothly with the latter one (Table 5). This difference can be explained by the difference in the electron donating power of the electron donor which occupies the fourth coordination site of the aluminum atom. Hexamethylphosphoramide can be replaced by an aliphatic aldehyde, while trimethylamine oxide cannot. 

Structures of an interesting pair of hexamethylphosphoramide complexes where the coordinated anion is nitrosodicyanomethanide [X, O—N=C(CN)2] have been obtained. Thus [NdX3 OP(NMe2)3 4] is a seven-coordinated distorted capped octahedron, where X is monodentate via oxygen, while [YbX2 OP(NMe2)3 4] is nearly irons octahedral with Yb—O (hmpa) = 2.197 A average. 

The metal atom in the hexamethylphosphoramide complex, Pr(HMPA)3Cl3, is octahedrally co-ordinated ", the amide being bonded via one O atom. 

Heterocyclic nitrogen donors and their adducts with zinc chloride have been studied.623,624 A large number of other ligand systems have also been characterized, for example, zinc halide adducts of 2,2-dimethylpropane-1,3-diamine and hexamethylphosphoramide have been studied.625,626 The formation of mixed ligand complexes with chloride and substituted pyridines has been studied.627 The zinc tris(pyridyl) chloride anion has also been structurally characterized.628 Manganese(II) ions have been used to probe the stereochemistry in reactions of zinc halides with pyrazine.629... 

Two isomeric l,l-bis(zirconium) complexes, 143a and 143b, were obtained in a 3 1 ratio by transmetallation of gem-aluminiozirconium complexes 3 (Schemes 7.1 and 7.43) [15]. Indeed, when gem-aluminiozirconium complex 3 [24] was treated with 1 equivalent of hexamethylphosphoramide, red-brown crystals (31 % yield) were isolated. 

This order is always found for M = Mg, but not necessarily for M = Al, Cu, and Zn. In order to ensure that the required order is achieved, a complexing agent such as hexamethylphosphoramide (HMPA) or tris(3,6-dioxaheptyl)-amine (TDA-1) is added to render the metal reduction potential more negative. 

Cardillo et al. (1976) have used dicyclohexyl-18-crown-6 ([20] + [21]) and dibenzo-18-crown-6 [11] to solubilize K2Cr04 in hexamethylphosphoramide. The complex reacts with activated halides to produce aldehydes, according to (39). 

In the presence of the dioxomolybdenum complex M0O2 (dipic) (HMPA) (dipic = pyridine-2,6-dicarboxylate, HMPA = hexamethylphosphoramide), 2-methylhex-2-ene and phenylhydroxylamine produce the amine 194 in 52% yield other alkenes react analogously199. 

DMF, and Nbl jSDMF have been shown to involve O-bonded DMF molecules by i.r. studies. The latter compound may be constituted as [Nb-(DMF)g]l4 since no bands attributable to Nb—I were observed, and this formulation is supported by preliminary conductance data in DMF solution. E.s.r. studies of NbCl4,2L complexes (L = DMF, DMA, THA, dioxan, dimethoxyethane, hexamethylphosphoramide, or AA -diethylformamide) indicate that they adopt a trans-octahedral geometry. 

Ni[R-dtp]2 complexes form paramagnetic five-co-ordinate adducts with hexamethylphosphoramide Xo date no phosphate esters have been found to form adducts. However, the NMR spectra of solutions of Ni(R-dtp>2 complexes after long standing or gentle heating clearly show that scrambling reactions of the type ... 

Reaction of Z-a./j-unsaturated iron-acyl complexes with bases under conditions similar to those above results in exclusive 1,4-addition, rather than deprotonation, to form the extended enolate species. However, it has been demonstrated that in the presence of the highly donating solvent hexamethylphosphoramide, y-deprotonation of the -complex 6 occurs. Subsequent reaction with electrophiles provides a-alkylated products such as 736 this procedure, demonstrated only in this case, in principle allows access to the a-alkylatcd products from both Z- and it-isomers of a,/j-unsaturated iron-acyl complexes. The hexamethylphosphoramide presumably coordinates to the base and thus prevents precoordination of the base to the acyl carbonyl oxygen, which has been suggested to direct the regioselective 1,4-addition of nucleophiles to -complexes as shown (see Section 1.1.1.3.4.1.2.). These results are also consistent with preference for the cisoid conformations depicted. 

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