Phosphorus-31, heteronuclear

Fe—Fe bond can be assigned structures 201 or 202 based on spectral data. The other product of this reaction is 193 (R = r-Bu), however, it is produced in minor amounts. Complexes 199 (R = R = r-Bu, R = Ph, R = r-Bu) were obtained. Reaction of 146 (M = Mo, R = Ph, R = R = Ft, R = r" = Me) with (benzyli-deneacetone)iron carbonyl gives rise to the bimetallic complex 200 (M = Mo), which reacts further with the free phosphole to form the bimetallic heteronuclear sandwich 203. The preferable coordination of the molybdenum atom to the dienic system of the second phosphole nucleus is rather unusual. The molybdenum atom is believed to have a greater tendency to coordinate via the trivalent phosphorus atom than via the dienic system. 

As we have already pointed out in the section dealing with heteronuclear coupling that it is not always necessary to confirm the presence of a particular hetero atom by acquiring the NMR spectrum of that nucleus. More often than not, the hetero atom will have a clear signature in the proton or carbon spectrum. Fluorine and phosphorus are both examples of nuclei that couple to protons over two, three, four and even more bonds. 

The use of phosphonodifluorodithioacetate as a 2ji component in cycloadditions with a variety of dienes provides simultaneous direct access to fluorine and phosphorus containing 3,6-dihydro-2/7-thiopyrans, for example, 217 and their 3-ones 218. Complex signals result from the heteronuclear couplings <2002TL2033>. 

One of the common 2D SS NMR approaches employed for investigation of phosphoro-organic and bio-organic samples is based on high-resolution heteronuclear correlations (EIETCOR). In solution-state NMR, this technique is the basic method that allows assignment of proton and phosphorus to the molecular structure. In the solid state, the assignment is more complex because of the very... 

During the introduction of this review, reference was made to the classical rule of the double bond. The theory, which in its original predictions supports the exceptional position for the elements boron, carbon, nitrogen, and oxygen, has lost its validity and needs modifications, as can be seen from the erratic increase in the numbers of compounds that contradict the rule that have been discovered within the last 12 years. These compounds are not found only as low-valent phosphorus-carbon species, but also increasingly as heteronuclear and even homonuclear molecules built up by heavier elements of the fourth to sixth main groups, such as Si, Ge, As, Sb, S, and Se. 

The 31P NMR spectrum of (89) includes a resonance due to the Pd-coordi-nated phosphorus at high field (8 33.92 ppm).418 Detailed 1- and 2-D homo-and heteronuclear NMR spectra, including 1H, 13C, 1H-111 COSY, 1H-I 3C COSY, were reported for trans-PdL2X2, where X = Cl, Br L = 2- or 8-diethylquinolyl methylphosphonates.419 Similar experiments were reported to give full assignments of [Pd(p-K2-OAc)(p-K1-OAc)(KP, KC14-phenop)]2, where... 

Both types of experiments detect magnetization arising from mutually coupled heteronuclear spin-triples. Even if the spectra can in principle be displayed in a 3D-cube representation (Rg. 10), the analysis of 2D slices or projections is often preferred for the interpretation. Important features can be derived as is demonstrated in the example shown in Fig. 10, e.g. from inspection of H,C planes taken at the chemical shift of an individual phosphorus atom, which give a two-dimensional H,C correlation of all signals... 

Figure 6.1. The four general schemes to produce 2D heteronuclear shift correlation spectra. The relative sensitivities of these approaches are compared for proton correlation experiments with phosphorus-31, carbon-13, and nitrogen-15.

A two-dimensional heteronuclear correlation experiment [94] using crosspolarization is performed by preparing the aluminum spins with a 90° pulse and then encoding the evolution frequencies of the aluminum spins in an initial time period. The aluminum polarization is subsequently transferred to the phosphorus spins with a spin lock, and a phosphorus free induction decay is accumulated... 

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