J . Phys. Chem. 1990, 94,6515-6516
are mostly blurred in the spectrum of solid P4S9, probably due to site inequivalencies in the monoclinic crystal giving rise to overlapping multiplets. A close examination of molecular distortions in phosphorus sulfides reveals that these are often associated with crystal packing due to intermolecular S . 4 or S.-PII1 nonbonding interactions. Thus, four kinds of P=S-S=P short contacts, down to 3.41 3 A, occur in the crystal of P4S103*9*10 with A values of 0.4-2.4’ and P=S bond length varying from 1.890 to 1.916 these interactions probably account for the unexpected low symmetry (triclinic) of the crystal of P4Slo,contrasting with the high symmetry of the adamantanoid molecule. No P-S-.S=P or P=S-P short contact exists in cubic P4Sg; the closest intermolecular distance is 3.59 A between S atoms of P1l1-S-PtV bridges, Le., only 0.1 A less than the normal van der Waals distance. Monoclinic P4S7only displays weak P=S-S< and >S-S< interactions (nonbonding distance 3.52-3.65 and 3.65-3.68 A, respectively). By contrast, P=S.-PII1 short contacts, with nonbonding distances of 3.29 and 3.41 A, take place between both Pill sites of each molecule and one of the two inequivalent exocyclic S atoms [referred to as S(3)9] of a neighboring molecule (Figure I ) . It is noteworthy that the P(4’)-S(3’)-P(1 or 2) angles are close to 90’ while S(3’)-P( I)-S(4) and S(3’)-P(2)-S(5) are close to 180’; this may be viewed as an incipient formation of two phosphoranide anions PIv- (distorted trigonal bipyramids with an equatorial lone pair on P12,13)by coordination of negative S(3’) with acceptor P( 1) and P(2) (eq I), a step toward the disproportionation of P4S7to p-P4S614and P4SSs(eq 2) through detachment of S(3’) and insertion in the P(l)-P(2) bond:
6515
TABLE I: Updated Compilation of Intracage Bond Angle Values A (in degrees) with Solid-state N M R Asymmetry Parameters r) for Phosphorus Sulfides comvd site unit A.. denn 0.2 0.8 4.3 2.2 0.7 2.7 6.3 7.1 0.9 2.1 2.4 0.4
0.09‘ 0.16‘ 0.14 0.92 0.51“ 1. O P 0.69’ 0.97’ 0.P 0.15‘ 0.15“ 0.0’
’Tentative assignments based on an assumed correlation. p4s3
P--9 p4s5 II
Lc
6
- - ___ - -.-;K
‘
’
L.6
P4S3
:z z - = z 11
-1 0
3.2
3.3
3.4
3.5
3.6
3.7
3.8
dinter[Al
(2)
t 8‘ I
It is significant that in monoclinic P4S7 the P-P bond is exceptionally long: 2.326 The ability of P4S7to dissociate with production of fl-P4s6 has previously been ~uggested,’~J~ especially to explain that the orthorhombic form of P4S7 is always sulfur deficient.l7-I9 The fact that the P=S--PII1 interaction in P4S7 is stronger with P(2) than with P( 1) (see Figure 1) is reflected in the A values of the PI1’ sites (2.7 and 0.7’, respectively) and supports the assignment made by Eckert1-P(2) upfield to P(I)-rather than the reverse.* Thus, the higher the conversion of Pill to PIv- (eq I), the higher its N M R shielding, a result that is consistent with literature data on phosphoranides.12 Registry No. P&, 1314-85-8; P4S7, 12037-82-0; P4SI0, 15857-57-5; P&, 25070-46-6.
Institut National des Sciences AppliquPes Laboratoire de Chimie Organique 20 Avenue Albert Einstein F-69621 Villeurbanne Cedex. France
Michel C. D h ” q
Received: November 28, 1989
Reply to Comment on “‘‘P NMR Spectroscopy of Solid Phosphorus Sulfides” Sir: M. C. Dgmarcq is correct; the statement regarding cubic P4S9-II,made in ref 1, is in error. Furthermore, since our paper appeared, new solid-state N M R results obtained by us (on P4S5 ( I ) Eckert, H.; Liang, C. S.; Stucky, G . D. J . Phys. Chem. 1989, 93,452.
Figure 1. Plot of the chemical shift difference between the solution state and the solid state for individual P atoms in phosphorus sulfides against the closest intermolecular distances occurring in their crystal structures. Diamonds indicate that this closest intermolecular distance involves the P atom under consideration directly, while squares indicate that the closest approach involves an atom (S or P) bonded to the P atom under consideration. Dashed lines indicate assignment uncertainties. In spite of these assignment uncertainties, the figure indicates that there is no discernible correlation.
and p-P4s312)2reveal that there appears to be no simple correlation between the asymmetry parameter v and the range of intracage bond angles A for PS312groups. Table I gives an updated overview of the data; the 7 values are recalculated here from the published 6, values’V2 according to the convention q = - 6111/1833- 6iJ, where the 6ii are the principal shielding tensor components defined such that - 6i, I 2 lblI - Siml 2 1622 - 1 5 ~ ~ 1 . In his Comment, M. C. Dimarcq draws attention to the influence of intermolecular nonbonding interactions upon molecular distortions and, possibly, 31PN M R chemical shifts. If such interactions are of general significance, they should manifest themselves in systematic chemical shift changes between the solution and the solid state. Inspection of published N M R data reveals that, among all of the phosphorus sulfides, a-P4S3shows the largest shift difference. However, no close intermolecular contacts exist in its crystal ~tructure.~The case of P4S7mentioned by D i m a r q merits some further discussion: Two SIP groupings exist in this m o l e c ~ l e :S(2)=P(3) ~ and S(3)=P(4) (using the nomenclature of ref 4). Of these, S(3) forms two short intermolecular contacts of 3.407 and 3.288 A (with P( 1) and P(2)), whereas S(2) is not involved in any such contacts with distances below 3.5 A. Nevertheless, despite the significant differences between S(2) and S(3), the solid-state chemical shifts of P(3) and P(4) are in very close proximity of each other and of the solution-state value. In contrast, a much larger difference is seen, (2) Tullius, M.; Lathrop, D.; Eckert, H. J . Phys. Chem. 1990, 94, 2145. (3) Leung, Y. C.; Waser, J.; van Houten, S.; Vos, A.; Wiegers, G . A.; Wiebenga, E. H. Acta Crystallogr. 1957, 10, 574. (4) Vos, A.; Othof, R.; Van Bolhuis, F.; Botterweg, R.Acta Crystallogr. 1965, 19, 864.
0022-3654/90/2094-65 15%02.50/0 0 1990 American Chemical Society
6516
The Journal of Physical Chemistry, Vol. 94, No. 16, 1990
for the same connectivity type, in P4Sl0, where at least two of the four inequivalent P=S groups engage in much weaker intermolecuiar contacts. Figure 1 shows an attempted correlation of sWolid- d,,i with the shortest intermolecular distances present in the crystal structure. These distances involve either the P atoms under consideration directly (diamonds) or their first nearest P or S neighbors (squares). Data for P4S3,P4Ss, P4S7,P4SI0, and P4S312 are included; solution-state shifts are taken from the table of Harris et ala5 Assignment uncertainties are indicated by dashed lines. Figure 1 shows that there is no obvious correlation. Two explanations are possible: ( I ) the strength of the intermolecular interaction (and its impact upon NMR chemical shifts) is insufficiently quantified by a distance parameter and also depends on ( 5 ) Harris, R. K.; Wilkes, P.J.; Wood,
P.T.;Woolins, J. D.J . Chem. Soc.,
Additions and Corrections orientation, the type of P atoms studied, and the type of contact present, or (2) even though the intermolecular distances are shorter than the sum of van der Waals radii (3.75 A), these interactions are generally of little significance. The large differences between solution-state and solid-state chemical shifts observed in some cases could be alternatively explained in terms of local magnetic fields arising from the diamagnetic anisotropy of neighboring groups without the necessity of invoking close intermolecular approaches. Further experimental work to settle this question is under way in our laboratory. Registry No. P4S3, 1314-85-8; P& 12037-82-0; P,S,,, 15857-57-5; P4S9, 25070-46-6.
Department of Chemistry University of California, Santa Barbara Goleta, California 931 1 7
Dalton Trans. 1989, 809.
Received: January 1 I, 1990
ADDITIONS AND CORRECTIONS 1990. Volume 94
A. A. Viggiano,* Robert A. Morris, and John F. Paulson: Kinetic Energy and Temperature Dependences of the Rate Constants for Electron Detachment of NO- by N 2 0 ,C02, Nz, CH,, C2H6,and C3H8.
Page 3290. The use of the reference superscript 23 in the text is incorrect; superscript 22 is the correct citation at that point in the text. The previous use of superscript 23 on page 3288 is correct.
H. Eckert
