The basicities of the triarylphosphines P(4-XC6H4)3 (X = Cl, F, H, CH3, CH3O, (CH3)2N), P(3-CH3C6H4)3, and P(2-CH3C6H7)3 as well as the trialkylphosphines P(t-Bu)3 and PCy3 have been measured by the nitromethane titration method. The range of basicity available by aryl substitution is very large, being pKa = 8.65 for X = (CH3)2N to 1.03 for X = Cl. The most basic phosphine is P(t-Bu)3 whose pKa = 11.40. The measured basicities correlate well with σp, [Formula: see text], and ν as well as with the lone pair ionisation potentials of the triarylphosphines. Generally the 1H, 31P, and 13C nmr spectral parameters of the free and protonated phosphines do not correlate well with pKa.

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23399-62-4; a,a/-bis(methylamino)-m-xylene (formamide derivative), 59276-03-8; oija'-diamino-m-xylene, 1477-55-0. Supplementary Material Available: Listings of anisotropic temperature factors and observed and calculated structure factors (29 pages). Ordering information is given on any current masthead page.

A section-selective three-dimensional phosphorus-31 chemical shift imaging (CSI) experiment was evaluated as the spatial localization method for spectroscopy in an integrated clinical magnetic resonance (MR) imaging and spectroscopy examination. The results of a CSI experiment can be displayed as either spectra related to specific voxels or "metabolite maps," in which the relative concentration of a given metabolite is displayed as an overlay of the MR image. This method was applied to the study of a soft-tissue mass and to a meningioma. The total imaging time in each case was 17 minutes with a voxel size of 27 cm3 in the extremity and 64 cm3 in the brain. The total time to set up this part of the study was about 10 minutes. No additional shimming was necessary when the center of the field of view selected for the CSI experiment was located at or near isocenter. The promising results obtained with this approach make the CSI method an attractive choice of spatial localization method.

Triphenylphosphine reacts with mercury(II) acetate and fluoroacetates to form complexes of the types Ph3PHg(O2CR)2, (Ph3P)2Hg(O2CR)2, and (Ph3P)3Hg(O2CR)2, where R = CH3, CH2F, CHF2, or CF3. The 1:1 and 2:1 have been isolated and characterized by elemental analysis, molecular weight, and conductance measurements and by vibrational and nmr spectroscopic studies. The formation of the 3:1 complexes is inferred by 31P nmr spectral measurements at 183 K. Both the 1:1 and 2:1 complexes are indicated to be monomeric molecular species in which the O2CR groups are bidentately bonded to mercury. The Hg—O and Hg—P stretching frequencies for these complexes have been assigned by infrared and Raman spectral measurements. The 199Hg–31P spin–spin coupling constants and the 31P coordination chemical shifts for the 1:1 as well as the 2:1 complexes increase in the order: O2CCH3 < O2CCH2F < O2CCHF2 < OCCF3 Correlations between 1J(199Hg–31P) values, 31P coordination chemical shifts, and the pKa values for the carboxylic acids are discussed.