The disecondary phosphines [PhHP(CH2)nPHPh] (n = 2-4, 6): improved syntheses, NMR spectra and complexation behaviour with group VI Transition metal hexacarbonyls

Kimpton, Bryan R; McFarlane, William; Muir, Alan; Patel, Pallavi G; Bookham, Jonathan L.

doi:10.1016/s0277-5387(00)83079-x

Cited by 27 publications

(17 citation statements)

References 34 publications

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“…Mynott published spectra for the Ru (4) and Ni (5) compounds in a review, but only discussed the Ru case; nevertheless the Ni case also appears to contain one ABX resonance (12). Two cases involving Pt bisdiphenylphosphinopropane complexes (6) were mentioned in the paper's Supplementary Material (13), and the two most recent cases involving the diphosphorus compounds 7 (14) and 8 (15) were described in detail. In what is perhaps testimony to the difficulty in tracking down these examples in a rational manner, none of these papers cite any previous cases.…”

Section: Research: Science and Educationmentioning

confidence: 99%

False AA'X Spin-Spin Coupling Systems in 13C NMR: Examples Involving Phosphorus and a 20-Year-Old Mystery in Off-Resonance Decoupling

1997

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It is common in both NMR textbooks and journal articles to loosely describe certain ABX spin systems as AA′X spin systems (1)(2)(3)(4)(5). For purposes of illustration, consider the 13 CH 2 spin system of maleic anhydride shown in Figure 1. One of the AB pair of hydrogen atoms is attached to a 13 C atom, the X-nucleus in the spin system, but the other is attached to a 12 C atom, the NMR-inactive isotopomer of the Xnucleus, and so the symmetry of the molecule is broken. Rigorously, the different isotopes split the chemical shifts of the "false" AA′ pair, and the properly designated AB hydrogen atoms are chemically as well as magnetically inequivalent.In practice, however, the chemical shifts normally are indistinguishable, and many of those same textbooks and journal articles point out that while rigorously the system is ABX, for all practical purposes it can be analyzed as AA′X (1,6). The danger of all of this is that when the chemical shifts are not the same, one may fail to recognize that fact owing to the assumption that the isotopomer shift is always insignificant. Results and Discussion P ExamplesA number of authors have noted that diphosphines and transition metal complexes with two phosphine ligands represent interesting test cases of such false AA′X systems (6-8), as shown for diphos (1) in Figure 2. Here the AA′ nuclei are the 31 P atoms, and the X-nucleus is the lone 13 C atom anywhere in this molecule. Detailed descriptions of the expected appearance of AA′X systems have been published (3,4,6), and except for the few cases to be described below, the AA′X description suffices for diphosphorus compounds (2, 6, 7). Representative multiplets from 1 and 2 are shown in Figure 3 for illustration. A common feature of AA′X spectra is that each exhibits a peak at the center of a 3-or 5-line multiplet (for J AA′ ≠ 0); the relative heights of the lines are dependent on the relative values of J AA′ , J AX , and J A′X . The separation of lines 1 and 3 (Fig. 3a,b) or 2 and 4 ( Fig. 3c) is equal to |J PC + J P′C |. The coupling constant J PP′ (if relatively large) can be obtained from the outer "wings" at approximately ± J PP from the central peak (Fig. 3c), or (if relatively small) from matching the height of the central line with that in simulations of the observed spectrum (Fig. 3a). These multiplets are examples of "virtual coupling" (9), because even though the longer range coupling constant J P′C ≈ 0, lines due to the second phosphorus atom are present in the 13 C NMR spectrum caused by the strong coupling of the phosphorus atoms-hence the second phosphorus is "virtually" coupled to carbon. It is important to recognize, especially in the case of the deceptively simple "triplet", that the coupling constants cannot be extracted on the basis of familiar first-order analyses.In contrast to the AA′X patterns seen above, the multiplets due to the ipso and bridging carbon atoms of diphos exhibit split central lines in the 100.6 MHz 13 C NMR spectrum (Figure 4a,b). The spectra are readily modeled if one drops the AA′X ...

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Section: Research: Science and Educationmentioning

confidence: 99%

False AA'X Spin-Spin Coupling Systems in 13C NMR: Examples Involving Phosphorus and a 20-Year-Old Mystery in Off-Resonance Decoupling

1997

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“…The P-P coupling of the PϪCϪCϪP fragment was observed only in the 1 H-NMR [22] spectra of 7 and 9. For 10, the coupling constant of the PϪMoϪP fragment ( 2 J PP ϭ 19 Hz) was observed in the 1 H-NMR spectrum [27] . However, due to line broadening in the proton-coupled 31 P-NMR spectra, only P-H coupling was observed for 9 and 10, and for 7 only one broad signal (ν 1/2 ഠ 600 Hz) was present.…”

Section: Discussion Of 31 P-and 1 H-nmr Data Of 1 7 9 and 10mentioning

confidence: 99%

Reactions and Coordination Properties of the First Secondary Carbaboranyldiphosphane: 1,2-Bis(phenylphosphanyl)-1,2-dicarba-closo-dodecaborane(12)

Balema

Somoza

Hey‐Hawkins

1998

Eur. J. Inorg. Chem.

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“…The requisite diphosphane 8e was prepared according to Brookham et al by reductive cleavage of dppe with lithium at 0°C (Scheme 13). [21] In the reaction between the dianion of 8e and the enoate, the diphosphide could not be used in excess because of the formation of the undesired monoaddition product. Good results were obtained using either of the following methods: Scheme 13.…”

Section: Double Conjugate Addition Of Secondary Diphosphanesmentioning

confidence: 99%

Syntheses of New Chiral Phosphane Ligands by Diastereoselective Conjugate Addition of Phosphides to Enantiomerically Pure Acceptor‐Substituted Olefins from the Chiral Pool

et al. 2005

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A variety of new chiral phosphanes were prepared by highly diastereoselective additions of phosphanes to α,β-unsaturated carbonyl compounds and related acceptor-substituted olefins derived from myrtenal as ex chiral pool source. Monophosphanes with astereogenic as well as stereogenic phos-[a] Organisch-Jansen and Feringa who employed this approach for a synthesis of the ligand chiraphos using as key steps diastereoselective addition of lithium diphenylphosphide to a γ-alkoxybutenolide and trapping of the resulting enolate with PPh 2 Cl (Scheme 2). [6] Scheme 2. Asymmetric synthesis of chiraphos via conjugate addition.Afterwards, the concept of the diastereoselective conjugate addition of phosphides as a simple route to novel ligands was further elaborated in our group. In contrast to Jansen and Feringa we directly used the addition products as ligands and selected the chiral starting materials from ex chiral pool sources in order to assure enantiomeric purity and relative configuration of the new phosphane ligands. In this way it was possible to obtain enantiomerically pure trans-3-(diphenylphosphanyl)myrtanic acid [7] in only two steps: addition of lithium diphenylphosphide to tert-butyl myrtenate which is easily accessible from commercial, cheap myrtenal followed by cleavage of the ester (Scheme 3). [8] In the meantime related diastereoselective conjugate additions to EWG-substituted olefins to give enantiomerically pure P,N-ligands were described by Knochels group. [9] Further-New Chiral Phosphane Ligands FULL PAPER more, enantioselective additions of phosphanes under control of asymmetric catalysts have been achieved by Togni et al. [10] Scheme 3. Synthesis of trans-3-(diphenylphosphanyl)myrtanic acid, an excellent ligand for Pd-catalyzed allylic substitutions, by diastereroselective conjugate addition.trans-3-(Diphenylphosphanyl)myrtanic acid is an excellent ligand for Pd-catalyzed allylic substitutions. [11] Minami et al. described an alternative approach to enantiomerically pure β-phosphanylcarboxylic acids via a multi-step synthesis of a racemate followed by enantiomer resolution by crystallization of diastereomeric salts. [12] Both the butenolide-derived as well as the myrtane-based system impressively demonstrate that phosphane additions on such rigid, cyclic cores proceed with a high degree of diastereoselectivity and at a high reaction rate. The almost unlimited availability of a large variety of enantiomerically pure enones, enoates and enals, therefore, offers the possibility to generate libraries of structurally diverse ligands. This consideration and the high efficiency of trans-3-(diphenylphosphanyl)myrtanic acid as ligand in Pd-catalyzed allylic alkylation reactions [8] prompted us to examine the conjugate addition more thoroughly. To begin with, the following aspects were most relevant:1. The torsion angle between the phosphanyl and the carboxyl group of phosphanylcarboxylic acids can be systematically varied by choosing appropriate conjugated acceptors. As shown in Scheme 4 phosphanylcarbo...

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The disecondary phosphines [PhHP(CH2)nPHPh] (n = 2-4, 6): improved syntheses, NMR spectra and complexation behaviour with group VI Transition metal hexacarbonyls

Cited by 27 publications

References 34 publications

False AA'X Spin-Spin Coupling Systems in 13C NMR: Examples Involving Phosphorus and a 20-Year-Old Mystery in Off-Resonance Decoupling

False AA'X Spin-Spin Coupling Systems in 13C NMR: Examples Involving Phosphorus and a 20-Year-Old Mystery in Off-Resonance Decoupling

Reactions and Coordination Properties of the First Secondary Carbaboranyldiphosphane: 1,2-Bis(phenylphosphanyl)-1,2-dicarba-closo-dodecaborane(12)

Syntheses of New Chiral Phosphane Ligands by Diastereoselective Conjugate Addition of Phosphides to Enantiomerically Pure Acceptor‐Substituted Olefins from the Chiral Pool

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