P NMR spectra

All borophosphonates obtained so far are air and thermally stable (m.p. >210 °C). They are soluble in all common organic solvents if they carry bulky groups either on phosphorus or on boron. Borophosphonates that contain only methyl or phenyl groups show poor solubility [140]. H-, B-, and P-NMR spectra are in agreement with the highly symmetric silasesquioxane-type structure in solution [140, 141]. 

While it is relatively easy to show that the two calculations are equivalent in simple systems, it is not so easy with more comjj plex in vivo systems, as when these equilibria are studied with P NMR spectra from perfused or intact organs. We recently (3) became involved in a controversy where a 4-fold difference in magnesium ion level was calculated from substantially identical NMR spectra as a result of such differences in definition. Our experience indicates that an intelligent program to supervise such calculations would be quite useful. 

The concentrations of 6, 7 and 8 are determined by integration of their characteristic P nmr spectra (Sec. 3,9.5) and their variations with time are shown in Fig. 1.8. These curves illustrate some general features of the system (1.66). At the maximum concentration of 7,... 

Fac and mer isomers of IrH3(CO)(Ph3P)2 were characterized by H and P nmr spectra. Their rates of interconversion in CH2CI2 at 25 °C... 

Pl.l pro-Rp phosphoryl oxygen-sulfur substitution consistent with Mg + interactions seen in the Scott crystal structure (PDB 301D) obtained at pH 8.5, because the preceding NMR experiments were conducted at this pH. In the same NMR experiment conducted at pH 5.5, no Cd + shifts of the P NMR spectra were seen for the substrate Pl.l pro-Rp phosphoryl oxygen-sulfur substitution. 

Fig. 17. NMR spectrum obtained using a single 90° pulse without H decoupling in pure DPPC bilayers at 50 °C and 1 bar (a) and P NMR spectra obtained using a fully phase-cycled Hahn echo sequence with inversely gated H decoupling in pure DPPC bilayers at 50 °C and 1 bar in the LC phase (b), 1 kbar in the GI phase (c), 1.75 kbar in the interdigitated Gi gel phase (d), 2.5 kbar in the GII gel phase (e), 3.7 kbar in the GUI gel phase (f), and 5.1 kbar in the GX gel phase (g) (after Refs. 4, 18).

The P-NMR spectra of the homogeneous solutions in this phase of the reaction show only the formation of (MesSiljP and LiP(SiMe3)2, as... 

An extensive review appeared on the configurational stability of enantiomeric organolithium reagents and the transfer of the steric information in their reactions. From the point of view of the present chapter an important factor that can be evaluated is the ease by which an inversion of configuration takes place at the metallation site. It happens that H, Li, C and P NMR spectra of diastereotopic species have been central to our understanding of the epimerization mechanism depicted in equation 26, where C and epi-C represent the solvated complex of one chiral species and its epimer, respectively. It has been postulated that inversion of configuration at the Li attachment site takes place when a solvent-separated ion pair is formed. This leads to planarization of the carbanion, its rotation and recombination to form the C—Li bond, as shown in equation 27, where Li+-L is the solvated lithium cation. An alternative route for epimerization is a series of... 

The quality of the system identification results is strongly dependent on the manner in which the spectroscopic measurements are made. In this regard, the time-scale of the individual spectral measurements Tgpect is crucial. Many good resolution FTIR, Raman, UV-VIS, fluorescence and H, F,"P NMR spectra can be obtained in 100 s or less. Also, many VCD, ECD, and 2D NMR spectra can be obtained in 1000 s or less. 

A compilation of P NMR data is available for heterophospholes complete up to mid-1987 <88PS(36)217>, and for anellated heterophospholes up to 1993 <94T7675>. Some characteristic data is also found where more generally the P NMR spectra of two-coordinate phosphorus compounds are treated [Pg.779]

RuCl(PNNP)KPF ) and [RuCl(H,0)(PNNP)](PF ) (PNNP=tetradentate chiral ligands, e.g.iV,A -[bis(o-diphenylphosphino)-benzylidene]-(15, 25)-di-iminocyclohexane (Fig. 1.42) [928,929] andiV,iV -[bis(o-diphenylphosphino)-benzylidene]-2,2-di-imino-l, F-(S)-binaphthylene) [928], These complexes were made from the ligands and RuCljCPPhj) in CH Cl P NMR spectra were measured [929]. 

The pH values of quenched autoclave contents are recorded prior to dilution with water for product recovery. Thermogravimetric analyses (T6A) were performed in air on a DuPont 951 thermogravimetric analyzer. A Siemens 12 X-ray diffractometer was used to collect X-ray powder diffraction data with CuKa radiation. Magic angle spinning P NMR spectra were recorded on a Bruker MSL 300 spectrometer. The P NMR spectra were taken at a frequency of 121.496 MHz and a spinning rate of 3-5 kHz. Chemical shifts are reported relative to 85 wt% H3PO4. 

The P spectra were recorded on a Brucker MSL-300 spectrometer operating at 121.4 MHz s. The P NMR spectra were obtained under MAS conditions by use of a double bearing probehead. A single pulse sequence was used in all cases and the delays were chosen allowing the obtention of quantitative spectra (typically the pulse width was 2 ms (10°) and the delay was 10 to 100 s. The number of scans was 10 to 100. Spectra were refered to external H3PO4 (85%). 

Figure 14. Palladium reagent, different analytes (7/10), and P-NMR spectra of the diastereomeric complexes formed by reaction of the Pd-reagent with samples of 8 (C6D6, 101.3 MHz)80,...

Mg(II) forms a complex with adenosine triphosphate (ATP, 45), which at pH 7.2 and 37 °C has dissociation constant Kj = 3.8 x 10 molL-. The fraction of the total ATP which did not nndergo complexation present in a cell, (p, can be estimated on the basis of P NMR spectra by means of equation 5, where the snbscripts afi denote the chemical shift of P relative to that of P and the superscripts denote the valne measnred for... 

From the foregoing discussion, it is evident that a variety of isomers are possible for unsymmetrically substituted cyclophosphines P NMR spectra are informative for distinguishing between these isomers. For example, two isomers of the cyclic trimers cyclo-(PR)2(PR ) are observed. The symmetrical isomer with identical substituents on the same side of the ring exhibits an A2B spin system, whereas the asymmetric isomer gives rise to an ABC spin system (Figure 11.5) (see Section 3.4.3). 

The two BH3 groups are coordinated to two adjacent phosphorus atoms of the P5 ring in cyclo-1,2-(BH3)2(cyclo-P5Ph5) (Figure 11.7). Only one dia-stereomer is present in the unit cell, corresponding to two enantiomers related by the crystallographic centre of symmetry. In solution, however, a complex mixture of isomers is evident from P NMR spectra. 

---