| Abstract
| - The scalar coupling constants between protons, nitrogens, andphosphorus in the metal complex chloro(triphenylphosphine)bis[bis(1-pyrazolyl)methane]ruthenium(II)chloride,[RuCl(PPh3)(BPM)2]+Cl-(1), were measuredwith a set of specially adapted NMR experiments. The absolute signof the coupling constants was determined byrelating the signs of the measured couplings to that of a one-bondproton−carbon coupling constant. A complete setof coupling constants >|0.4| Hz was obtained with use of a singlesample with 99% 15N-labeled bis-pyrazolylligands.The data show that the two-bond 15N−15Nand 31P−15N couplings across the metal centerare significantly larger,if the two metal-ligating atoms are trans rather than cis with respectto one another. Furthermore, all trans couplings2JPN and2JNN are positive, while thecorresponding cis couplings are negative or too small to be measured.Theconformation dependence of the scalar coupling constants supports therapid structural characterization of catalyticallyactive organometallic complexes by NMR spectroscopy. The proposedset of NMR experiments includes HSQCexperiments with small flip angles, a quantitative long-range15N−15N correlation experiment, and DQ/ZQexperimentsfor the determination of the sign and size ofJNN and JPN couplingconstants in linear spin systems.
|
