Phosphine, tris spectroscopy

A number of silylated bismethylenephosphoranes (6) have been prepared and characterized by n.m.r. spectroscopy and X-ray structural analysis.6 X-ray analysis reveals that the novel ylide structure (7) is formed in the reaction of tri-(n-butyl)phosphine... 

Benzannulated NHPs are straightforwardly accessible from AUV-disubsti luted o-phenylenediamines either via base-induced condensation with substituted dichlorophosphines [25] or PC13 [26], or via transamination with tris(dialkylamino) phosphines [13, 14, 27], respectively. An analogous NH-substituted derivative was obtained in low yield via transamination of o-phcnylcncdiaminc with ethoxy-bis(diethylamino)phosphine [28], and condensation of o-phenylenediamine with excess tris(diethylamino)phosphine furnished a l,3-bis(phosphino)-substituted heterocycle [29], Intermediates with one or two NH functions were detectable by spectroscopy but could not be isolated in pure form under these conditions. However, 2-chloro-benzo-l,3,2-diazaphospholene and the corresponding 1-phenyl derivative were prepared in acceptable yield via condensation of PC13 with o-phenylenediamine under microwave irradiation [30], or with A-phenyl-o-phenylenediamine under reflux [27], respectively, in the absence of additional base. The formation of tetrameric benzo-NHPs during transamination of A-alkyl-o-phenylenediamines with P(NMe2)3 has already been mentioned (cf. the section entitled 1,3,2-Diazaphospholes and 1,3,2-Diazaphospholides ). 

The formation of both 12 and 13 during the reduction of 4 in the presence of triphenylphosphine indicated not only that one-half of an equivalent of the added phosphine was taken up, but also that the intermediate formed is the bisphosphine complex, (< 3P) JRhCl, proposed as the reactive intermediate in hydrogenation runs using 1 as the catalyst (1). This assumption is further supported by the fact that the product stereochemistry (cis/trans = 2.0) and lack of double bond isomerization observed on hydrogenation of 7 with this reaction mixture corresponds directly with the data obtained on hydrogenation of 7 using pre-hydro-genated 1 (3). When the reduction of 4 was repeated in the presence of tri-p-tolyphosphine, the carbonyl complex formed was isolated and shown by PMR spectroscopy to contain 1.5 equivalents of triphenylphosphine and 0.5 equivalent of the tri-p-tolyphosphine, as expected. 

Introducing a chiral center in the amide functionality renders all 32 potential isomers diastereomeric and thus discernable (in principle) by NMR spectroscopy. In practice, the lanthanide complexes formed (Eu, Gd and Tb) with macrocyclic monoamide tris(phosphinate) ligands bearing a chiral center on the amide group exist as only two non-interconverting diastereomers in a ratio of 2 1 and 4 1 for the a-phenylethyl and a-l-napthylethyl derivatives, respectively (DOTMP-MPMeA and DOTMP-MNaphMeA) [114]. The configuration at... 

Neutral Ti(CO)6 is an extremely unstable compound which decomposed even below -220 °C, as shown by matrix isolation spectroscopy [165]. The much more stable phosphine derivatives Ti(CO)3(dmpe)2, Ti(CO)5(dmpe), Ti(CO)5(PMe3)2, Ti(CO)4(PMe3)3 have been isolated [166-168]. In contrast, the dianionic salt [Ti(CO)6] (53) is thermally much more stable and decomposes only above 200 C. Complex 53 was obtained by reductive carbonylation of Ti(CO)3(dmpe)2 by alkali metal naphthalenides in the presence of cryptand [169]. Carbonylation of 79 also produces 53 [170]. The naph-thalenide-assisted reductive carbonylation of the zirconium tetrachloride afforded the zirconium analog [Zr(CO)6] (54) [171], which was also derived by carbonylation of the tris(diene) dianion 45 [150]. One anion [R3Sn] effectively stabilizes Ti(CO)e as an air stable monoanionic salt, [R3SnTi(CO)J [172]. 

As in past years, there have been reports of the reactions of quinones with phosphites. It has been supposed that these reactions initially involve transfer of an electron from the phosphite to the quinone. Support for this postulate has come from the observation of the formation of paramagnetic species in the reactions by e.s.r. spectroscopy. A quantitative study has now shown that the rate of the electron process correlates with the reduction potential of the quinone. The actual structures of the radicals produced in some of these reactions have also been elucidated. For example, triethyl phosphite reacts with 2,7-dinitrophenanthraquinone to give the quinone radical ion and ethyl radicals. Tris(dimethylamino)phosphine reacts with phenanthraquinone to give the radical cation (56). This was identified by use of... 

Chromium(I) complexes, 702 alkyl isocyanides, 704-709 aryl isocyanides, 704-709 2,2 -bipyridyl, 709 electrochemistry, 713 electronic spectra, 712 ESR spectra, 712 IR spectra, 712 magnetic properties, 710 synthesis, 709 cyanides, 703 fluorophosphine, 716 isocyanides crystallography, 708 electrochemistry, 709 spectroscopy, 708 synthesis, 707 1,10-phenanthroline, 709 electrochemistry, 713 electronic spectra, 712 ESR spectra, 712 IR spectra, 712 magnetic properties, 710 synthesis, 709 tertiary phosphines dinitrogen, 713 tris(bipyridyl)... 

Stereospecific ring closure. 2/ -Azido-3a-iodocholestane in benzene added to tri-methyl phosphite, allowed to stand at room temp, until spectroscopy shows disappearance of the IR-azide band, solvent and most of the excess trimethyl phosphite removed in vacuo, the ethereal soln. of the residue added to a stirred soln. of LiAlH4 in anhydrous ether at a rate to maintain reflux, and stirred 2 hrs. at room temp. 2, 3i -iminocholestane. Y 16%. - This convenient reaction sequence may be successful in cases where other methods fail. F. e., also isolation of the intermediate, and ring closure with other phosphorus(III) nucleophiles such as phosphines, s. A. Hassner and J. E. Galle, Am. Soc. 92, 3733 (1970). 

Other triorganotin phosphinates self-assemble into chain-like, supramolecular helical arrays, 176 these include trimethyltin dimethylphosphinate, Me3Sn02PMe2, and dichlorophosphate, Me3Sn02PCl2 [529], and tri-n-butyltin diphenylphosphinate, Bu3Sn02PPh2 [530]. The self-assembly of tributyltin derivatives of phosphorus oxyacids (orthophosphates, phosphonates, and phosphinates), (Bu3Sn) 0 P(0)-Ph3 , n = 0-2, has been investigated by " Sn and P NMR and " Sn Moss-bauer spectroscopy results are indicative of intermolecular association both in solution and in the solid state [531]. On the basis of spectroscopic evidence associated structures in the solid state and in solution have also been suggested for tri-... 

E- (32a) and (32b) isomers which have been characterized by NMR spectroscopy and X-ray crystallography. The P NMR chemical shifts of both Z- and E- isomer sets were found to differ by about 60 ppm, with Ssip - 63.0 and 126.9 for (31a) and (32a), and 8 P - 87.3 and - 138.5 for (31b) and (32b) respectively. Theoretical studies indicate that the low field position of 83 ip for the Z isomer is due to reduced P pyramidalisation caused by steric congestion around the phosphorus atom and strong electronic interaction of the phosphorus lone pair with the 7 double bond. The results from semiquantitative MP2 calculations have provided a more systematic understanding of the structural influences on P chemical shielding. Three molybdenum-N2 complexes [Mo(N2)(Ll)(L2)] (33), each containing a combination of a bi- (L2 = depe, dppe, and 1,2-dppp) and a tri-dentate (LI = dpepp) phosphine ligand, have been prepared and characterized by... 

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