Carbon-13 NMR Spectra of Some Phosphorane=AminoCompounds? zyxwvuts zyxw Fabio Costanzi, Maurizio Pianca, Marco Tato" and Giovanni Moggi zyxwvutsrq zyxwvuts zyxwvutsrq C.R.S. MonteRuos, Via Bonfadini 148, 20138 Milan, Italy The 13C NMR spectra of a series of compounds of the type R1P(NR2),Phs,, X- are reported. A net trend toward larger 'J(PC) values with an increasing number of diakylamino substituents is observed. INTRODUCTION Table 1. 13C chemical shifts of phosphorane-amino compounds of the series R'P(NR,z),&.,X- Despite the fact that aminophosphines have been widely investigated by 13C NMR,' compounds of the type R'P(NR,"),Ph:-,Xhave received little attention. This paper describes a structural investigation of some new phosphorane-amino compounds of industrial interest., EXPERIMENTAL Phenyl C-1 Compound Benzyl CH2 C-1 CH-P 28.3 29.6 29.0 29.6 28.9 29.1 28.0 1 I+CHzP(NMe,)31'CI2 I+CHzP(NEtz)3l'CI- 3 I+CH,P(NMe,)z+l'CI4 I+CH,P(NEt,),QI+CI~ 5 [+CHzP(NMez)+21'Cl~ 6 [+CHzP(NEt,)+zl+CI7 [+CH,P+sl+CI- 120.0 121.4 119.5 120.0 117.8 Amino CHs CHz 129.6 36.7 129.9 39.2 128.9 37.3 129.2 40.1 128.3 38.2 128.1 41.3 128.0 zyxwvu 8 [MeP(NMe,),l'l9 [MeP(NEt,),l'l10 [MeP(NMe,),dJI+l11 lMeP(NEtz)z+l'l- The NMR spectra were recorded in the FT mode on a Varian XL-200 spectrometer operating at 50.31 MHz for 13C. All the spectra were recorded in 10 ~ ~tubes l ~ as dilute (5-10%) solutions in DMSO-d6 (used also as internal lock) at 21 "C. The chemical shifts are reported relative to internal TMS and are accurate to +0.1 ppm. A memory of 32K data points was used for a spectral width of 11000 Hz, with h4LEV-163 as a 'H decoupling pulse sequence. A pulse repetition time of 1.5s, a flip angle of 30" and 2500 scans were typically used. All the compounds were prepared as reported in Ref. 2. l l 12IMeP(NMeJ+,I+I~ 13 IMeP(NEt2)+z1'1~ 14IMePdJJ'I- Table 2. -C-"'P 122.7 123.9 121.5 122.2 119.8 6.7 10.0 9.0 10.7 8.6 9.6 7.3 35.8 38.8 36.7 39.8 37.6 41 .I one-bond coupling con- stants" of phosphorrmoe-amino comof pounds R'P(NR,Z),&,XCompound the Phenyl c-1 Benzyl (CHJ 118.3 121.8 96.8 96.4 85.4 103.9 105.4 79.0 78.4 59.0 60.0 46.3 series Methyl zyxwvuts 1 2 3 4 5 6 RESULTS AND DISCUSSION 7 The assignments of the different signals are based on chemical shift correlations, P-C couplings and literature data.4 Tables l and 2 and Fig. l summarize the 13 C chemical shifts and the one-bond P-C coupling constants for the carbon atoms of major interest. The NMR parameters of the remaining carbon atoms (e.g. in the phenyl groups) are not reported. They do not differ significantly from those reported4 for the phenyl groups in a series of triphenylalkylphosphonium salts. Triphenylmethylphosphonium iodide and triphenylbenzylphosphonium chloride are included for comparative purposes. * Author to whom correspondence should be addressed. i.Presented at the Sixth International Meeting on NMR Spectroscopy, Edinburgh, Scotland, 1983. 8 9 10 11 12 13 14 a 120.3 120.5 100.0 99.8 88.2 111.2 110.7 85.6 85.1 66.6 66.5 55.8 The diaital orecision is aooroximatelv 0.34Hz. Chemical shifts Apart from a small (1-2ppm) deshielding for the phenyl C-1, PhCH,-P and CH,-P on replacement of a phenyl group with a dialkylamino group, the only noticeable effect in the series is the upfield shift for N-GH, and N-GH2CH, with increasing NR,, substitution. This feature might reflect the higher steric CCC-0030-4921/84/0022-0705$01 .00 0Wiley Heyden Ltd, 1984 ORGANIC MAGNETIC RESONANCE, VOL. 22, NO. 11, 1984 705 z zyxwvuts zyxw zyx F. COSTANZI, M. PIANCA, M. TAT0 AND G. MOGGI '301 compression between the bulky NR2' groups, as observed in aminophosphines.'" 0 P-C-I (Ph) / 0 One bond P-C couplings Figure 1. One-bond coupling constants in the series [MeP(NMe,),~,-,l'l-. Similar curves are obtained for the other series of compounds. The regular trend towards larger P-C couplings with an increasing number of dialkylamino substituents is reported in Fig. 1. This may be qualitatively explained on the basis of Bent's rule (i.e. the s character of the phosphorus orbitals is concentrated in bonds with the most electropositive substituents)lb as well as by a dominating contribution of the Fermi contact interaction to the spin coupling m e ~ h a n i s m . ~ , ~ A decrease in d,-p, bonding on replacement of a phenyl group (caused by the weak, back-bonding from nitrogen to phosphorus, compared with phenyl), together with the increased electronegativity of the substituents, seems to lead to an isovalent rehybridization Of the phosphorus atom hence, to the Observed trend of the P-C coupling constants. zy zyxwvutsr zy zyxwvutsrqp REFERENCES 1. (a) G. A. Gray and J. H. Nelson, Org. Magn. Reson. 14, 8 (1980); (b) J. P.Van Linthoudt, G. V. Van Den Berghe and G. P.Van Der Kelen. Spectrochim. Acta, PartA35.1307 (1979); 36, 315 (1980). 2. Montedison S.p.A., U.S. Pat. 4259463 (1981). 3. M. H. Levitt, R. Freeman and T. Frenkiel, J. Magn. Reson. 47, 328 (1982). 706 ORGANIC MAGNETIC RESONANCE, VOL. 22, NO. 11, 1984 4. T. A. Albright, W. J. Freeman and E. E. Scheizer, J. Am. Chem. SOC.97, 2942 (1975). 5. G. A. Gray, J. Am. Chem. SOC.93, 2132 (1971). 6. T. A. Albright, Org. Magn. Reson. 8, 489 (1976). Received 19 January 1984; accepted 20 March 1984