Trihalides coupling

Table 12. Halogen quadrupole coupling constants and p-orhital populations in trihalide ions (A —B—C)...

Treatment of epoxides with SOCI2, Ph3P and CCI4 or Ph3PCI2 0-76 Reduction of trihalides 0-87 Coupling of halides with trihalides... 

Identification of most mixed boron trihalide adducts, and all information on rates and equilibria of halogen redistribution in these systems, depends on correct NMR peak assignments. The reliability of these is assured by a combination of two or more of the following distinctive heteronuclear NMR coupling patterns systematic variation of peak areas as the ratio of two halogens is changed identification and consistent behavior of peaks due to the same species in spectra of two or more of 1H, 19F, UB, and 13C nuclei agreement of observed parameters with values calculated from "pairwise interaction parameters (76,123). Fine points of structure can also be determined by... 

Pairwise interaction parameters can perhaps be interpreted in chemical bonding terms (76, 80,123, 182). Pairwise terms involving fluorine are often anomalous and this may be related to some surviving multiple bonding in the boron-fluorine bonds in the adducts (20). Pairwise interaction parameters of the Me3N mixed trihalide adduct system are reported to correlate consistently for 41, 13C, 19F, and nB chemical shifts and for nB—19F coupling constants (123). It is perhaps surprising that even the proton shifts can be correlated in this way. 

As is the case with the trihalides, loss of a halogen ion is the dominant reaction channel and loss of a halogen atom is next. A small amount of CI2 loss is also seen. Ligand coupling reactions like reaction 8c will be discussed in the next section. 

The complexes of boranes and boron trihalides with simple phosphorus compounds have been extensively investigated, possibly because of the presence of B- P coupling. Reaction of phosphine with diborane gave the monomeric complex H3P.BH3 with a B signal - -60 8 p.p.m. [from (MeO)3B] which was a quartet of doublets with B- P coupling of 27 c./sec. and the B- H coupling of 103... 

Trihalide cations MFs", MCl3 and MBrJ, M = B, Al, Ga pseudo Jahn-Teller coupling, electronic spectra and ionization potentials... 

Keywords Trihalide cations Pseudo Jahn-Teller effect Double minima in C2V symmetry Coupled cluster and... 

In the reduced binary and ternary halides of the lanthanoids, the f electrons are well localized on the metal atoms. The coupling between the magnetic moments is weak in the case of insulators as can be seen from the low ordering temperatures of the saltlike trihalides whereby, for example, GdQj orders ferromagneti-cally at 2.2K. In the presence of extended M-M bonding, the conduction electrons provide a very efficient mechanism for coupling the moments via a RKKY... 

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