31P nmr has been used to show that, in MeNO2, M(SbF6)2 (M = Sn or Pb) forms 1:1 complexes with Ph2P(CH2)2PPh2, PhP[(CH2)2PPh2]2, MeC(CH2PPh2)3, [Formula: see text][Formula: see text]P[(CH2)2PPh2]3, and Ph2P[(CH2)2PPh]2(CH2)2PPh2. The phosphonium ligands are formed in situ. Spectra characteristics of slow inter- and intramolecular exchange were obtained in all cases except, perhaps, those involving the last two ligands, which may be involved in rapid intramolecular exchange. For the first five ligands, the maximum denticity is achieved and unambiguous one-bond M(II)—31P (M = 117/119Sn or 207Pb) coupling constants are reported and discussed. In the presence of M(SbF6)2 (M = Sn or Pb). PPh3 is protonated in MeNO2, while in acetone Sn(SbF6)2 forms a 1:1 complex with PPh3 which appears to be solvent-inserted, [Sn—O—CMe2PPh3]2+.Reduced temperature 31P nmr spectroscopy has allowed the detection of 1:2 and 1:3 (M:L) complexes of OPPh3, and 1:1 complexes of Ph2P(O)(CH2)2P(O)Ph2, PhP(O)[(CH2)2P(O)Ph2]2, and (O)P[(CH2)2P(O)Ph2]3, with both tin(II) and lead(II). The 1:1 complexes with polydentate ligands are isolable; nmr shows that the maximum denticity occurs except with the last ligand which behaves in a tridentate manner. Several two-bond M—O—P coupling constants have been obtained. Also, the changes which complexation produces in the P—P couplings are compared with changes produced in the analogous phosphine complexes.The synthesis and characterization of Ph2P(E)[(CH2)2P(E)Ph]2(CH2)2P(E)Ph2 (E = S or Se) and (Se)P[(CH2)2P(Se)Ph2]3 are reported. The 31P nmr spectra of these compounds are compared with those of the parent tetraphosphines and other members of the corresponding tetraoxide–tetrachalcogenide series.

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amount of water present) during the titration. Therefore, all titrations were carried out at 0.005 M concentrations. The pKa point was always in the desired flat portion of the titration curve. The e.m.f. at half neutralization was taken as one-half the calculated stoichiometric end point. As mentioned above, the latter was always very close to the observed inflection point, and resulted in a maximum error of e.m.f. values of about 5 mv. Runs were carried out in duplicate. Repeat determinations were always within 10 mv. and generally within 5 mv.The collected Ae.m.f. values at half neutralization ( values, referred to N,N'-diphenylguanidine) are given in Table III. A plot of these values vs. literature pKj(H:0) values for several of these bases (diphenylguanidine, triethylamine, pyridine, acetamide, and urea) indicated a straight-line relationship, and so the p/Guno) values for the series of N,N-disubstituted amides are interpolated from this line (Tables I and III).The least-squares calculation of pifa(H¡o) vs. was pATa(HiO) = 10.10 -0.0118 , with a standard deviation of 33 mv.