Tris phosphane oxide

In the group of Izod, the tris(phosphane oxide) 19 was 1,2-dilithiated by the reaction with two equivalents of w-butyllithium in THF at room temperature (Scheme 7). The similarity of the structural formula of compound 20 (Lewis formula) to 1,2-dilithium compounds found by Sekiguchi and coworkers (see Section n. E), where two lithium centres are bridging a C2 unit, is not maintained in the solid state. The X-ray structural analysis reveals a centrosymmetric dimer containing no carbon-lithium contacts (Figure 8). 

In fact, tris(pyrrolidino)phosphane oxide has a donor number of 1.22. 

Starting from acylated 2-azidomethylbenzimidazoles (145), an additional imidazole ring can be condensed by transformation of the azido group with tri-n-butylphosphane into the appropriate iminophosphorane intermediate 146. After extrusion of phosphane oxide, cyclization occurs to the 1-substituted 4//-imidazo[l,5-a]benzimidazole 147 (Scheme 58) (89T1823 94S1197). 

It is important to use dry air and dry equipment because difluorotris(perfluoroalkyl)-25-phos-phanes react very rapidly with water to form tris(perfluoroalkyl)phosphane oxides. Under these conditions, the electrochemical perfiuorination of triethyl-, tripropyl-, and tributylphosphanc oxides yields 15-50% of the corresponding difluorotris(perfluoroalkyl)-A5-phosphanes. A decrease in yield is observed with a longer carbon chain (chain with 2C atoms 42%, with 6C atoms 24 %).63 Byproducts are perfluorinated alkanes. Addition of bromine makes it possible to electrochemically fluorinate trialkylphosphane oxides with a carbon chain length of C5 to... 

Similarly, the reaction between sulfur tetrafluoride and tris(dimethylamino)phosphane proceeds with oxidation of the phosphane in addition to fluorine transfer to give tris(dimethylamino)-difluoro-A5-phosphane (18) as the main product. In contrast, the reaction with tris(methyl-sulfanyl)phosphane does not give a straightforward fluorination extensive Arbuzov-type rearrangements and fluorination reactions occur.220... 

L = Dihexylsulfoxides trimethylamine l,eu-diaminoalkane(n = 2-4) l,2-bis-(dimethylamino)ethane. tet a lethylpiperid ne pyridine, 4-methyIpyridine 2-methylpyridinc, pyridine 1-oxide 2-, 3-. and 4-methylpyridine 1-oxides triphenylphosphane triphenylphosphane oxide, sulfide, and selenidc " tributylphosphane selenide , tris[4-methoxyphenyl]phosphane selenide, 1,2-bis(diphenylphosphano)ethane f -diselenide, thiourea, letramethylthiourea, dithioxamide dimethylacetamide ... 

A coordinatively unsaturated 14-electron palladium(O) complex, usually coordinated with weak donor ligands (usually tertiaiy phosphanes), has meanwhile been proven to be the catalytically active species [5]. This complex is mostly generated in situ. Tetrakis(triphenylphosphane)palladium(0) [6J, which exists in an equilibrium with tris(triphenylphosphane)palladium(0) and free triphenylphosphane in solution, is frequently employed. The endergonic loss of a second phosphane ligand [7] leads to the catalytically active bis(triphenylphosphane)palladium(0). However, palladium(D) complexes such as bis(triphenylphosphane)palladium dichloride or palladium acetate, which are easily reduced (e.g. by triarylphosphanes see below) in the reaction medium, are more commonly employed for convenience, as they are inherently stable towards air. The mechanistic situation is a little more complicated with palladium acetate, in that anionic acetoxypalladium species Pd(PPh3) (AcO ) (n = 2, 3) are formed in the presence of acetate ions [5], and these actually participate in the oxidative addition step and the following coupling reaction. 

Reaction of tris(2-pyridyl)phosphane (8) with chlorine in methylene dichloride or acetonitrile gave chlorotris(2-pyridyl)phosphonium chloride or its covalent isomer tris(2-pyridyl)phosphonium dichloride (20). Treatment of the dichloride derivative with dilute HCl afforded the coupling product, 2,2 -bipyridine (16), whereas tris(2-pyridyl)phosphine oxide (9) was isolated from the reaction with sodium hydroxide. 

Treatment of tris(2-pyridyl)phosphane or phosphine oxide with chlorine in acetonitrile in the presence of a small amount of water or an alcohol gave the 5-chloro-2,2 -bipyiidine (21) as the major ligand coupling product. 

Au(I) can form uninuclear complexes with tris(dimethylamino)phosphane (98), or can form trinuclear cluster cations with oxide (99) or imido (100) divalent anions. The P—Au—X atoms are nearly collinear in complexes 99 and 100, the O and N atoms are at die apex of a pyramid with AU3 basis198. See also items N-3 and N-4 above. 

Commercial stick P was purified by dipping it into CS2 until the outer oxide layer became detached, and then transferring it under a C02 atmosphere to the reaction vessel where it was dried in vacuo. In a typical experiment, trifluoroiodomethane (2.94 g, 15 mmol) was sealed in vacuo in a C arius tube containing purified P (3 g. 97 mmol). There was no reaction after 24h at 100 C. but after 48 h at 220 C the tube contained a red solid and a liquid less volatile than tris(trifluoronicthyl)phosphane. Fractionation gave unchanged C F31 (30%), spontaneously flammable tris(trifluoromcthyl)phosphane [yield. 0.7g (84%)]. iodobis(trifluoromethyl)phosphanc [yield 0.11 g (15%)]. bp 72 78 C. and diiodo(trilluoromethyl)phos-phane lyield 0.05 bp 69 C/29 Tori. Yields are based on the amount of trifluoroiodomethane... 

Huttner obtained molybdenum complex 215 upon treatment of ligand 115 with butyllithium, followed by BHs THF, tris(acetonitrile)tricarbonylmolybdenum, iodine, and l,4-diazabicyclo[2.2.2]octane (DABCO), in 76% yield as a mixture of two isomers (Scheme 37). Irradiation of 215 with a mercury high-pressure lamp caused ligand exchange with chelation of the remaining phosphane sidearm to give 216 in 72% yield. Oxidation of 215 with O2 under irrradiation resulted in a decarbonylation to give cationic oxomolybdenum complex 217 in 65% yield. 

Alkylation at Phosphorus. Phosphines and phosphites undergo easy quaternization. Thus methylation of tris(2,6-dimethyl-phenoxy)phosphine with MeOTf, followed by treatment of the product with sodium 2,6-dimethylphenoxide, gave methyltetrakis (2,6-dimethylphenoxy)phosphane. Methoxyphosphonium tri-flates are relatively stable intermediates in Arbuzov reactions Phosphine oxides and sulfides are alkylated. S-Methylation of chiral phosphine sulfides, followed by treatment with hexam-ethylphosphorous triamide, has been advocated as a general synthesis of optically active phosphines. ... 

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