2887
Bromobis (2-(2-aminoethyl)pyridine) copper (11) Bromide by Phirtu Singh, Vicki C. Copeland, William E. Hatfield, and Derek J. Hodgson" Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 87514
(Received March I S , 1978)
Publicatjon costs assisted by the iMaterials Reaearch Center of the University of North Carolina
bromobis(2-(2-aminoethyl)pyridine)copper(II) bromide, [Cu(C,NzH&Br]Br, has been prepared by the reaction of copper(I1) bromide with excess 2-(%aminoethyl)pyridine (AEP) in 95% ethanol, and its crystal and molecular structure has been determined from three-dimensional X-ray data collected by counter methods. The material crystallizes in theomonoclinic space group C2/c with four formula units in a cell OF dimensions a = 8.883(6) 8, b = 11.853(13) A, c = 16.940(14) 8 and p = 67.57(3)'. The observed and calculated densities are 1.87(2) and 1.885 g cm-a, respectively. The structure has been refined by least-squares methods to a final value of the R factor (on F) of 0.044 for 1620 independent data. The complex consists of five-coordinate [ C U ( , ~ E P ) ~ Bcations ~ ] + which are well separated from discrete Br- anions. The copper atoms and both bromine atoms lie on a twofold rotation axis in the cell, and the geometry a t the copper atoms is intermediate between tetragonal pyramidal and trigonal bipyramidal, The pyridine nitrogen atoms are trans, the N-Cu-N angle being 178.0(2)', while the N(amine)-Cu-N(amine) and, Br-Cu-N(amine) angles are 149.4(3)" and 105.3(1)", respectively. The Cu-Br bond length of 2.702(2) A is very long, but does not appear to result from intramolecular contactu. The monomeric nature of the complex, which i s in contrast to the structure of Ch(AEP)Brz,is consistent with its magnetic properties.
Introduction The preparations oi complexes of the types Cu(AEP)zXzand Gu(AEP)Xz, where AEP is 2-(2-aminoel hyljpyridine, have been reported by Uhlig and Maaser,' and these workers suggested that the complexes Cu(AEP)XZ are dimeric with five-coordinate geometry a t the copper atoms while those of formulation C U ( A E P ) ~ Xare ~ monomeric and six coordinate. Our recent report of the structure2 of Cu(AEP)Br2, homever, shows that this complex is polymeric, containing both Cu-Br-Cu chains and dimer-type CuBr-Cu-Br linkages, and that the copper atoms are six coordinate. The magnetic properties of the complex of formulation Cu(AEP)J3r2 are consistent with a monomeric structure, since the Curie-Weiss law is obeyed to 2,9' but weak dirneric or polymeric interactions cannot be ruled out on the basis of magnetic susceptibility data alone. The great water solubility of this complex, h o ~ w e r did , not, seem to us to be consistent Qith any polymeric model, but suggested that the complex might be ionjc Such an ionic species could not be ruled out in view of the known, five-coordinate geome t r y of the complex Cu(bipy)JZ (where bipy = 2,2'bipyridine), in which there are [Cu(bipy),I]+ cations and discrete I- ~ I ~ ~ O I I S . ~ In order t o further our studies of the relationship etween strric turd and magnetic proper tie^,^^^ j-l0 and especially t o make a comparison between the complexes CU(AFP)~X.arid Cu(AEP)Xz, we have under-
taken a precise three-dimensional structural investigation of the complex Cu(AEP)2Br2.
Experimental Section The preparations of complexes of formulation Cu(AEP)2X2.HzO, where AEP is 2-(2-aminoethyl)pyridine and X is chlorine or bromine, have been reported by Uhlig and nlaaser.I These authors report that the complex Cu(AEP)2Br2.Rz0, for example, is formed by the reaction of CuBrz with excess AEP in aqueous solution, and assumed that the complex i s probably a tetragonally distorted octahedron with trans bromine atoms, analogous to the known structure'l of Iransdinitrotetraamminecopper(I1). (1) E. Uklig and 31. Maaser, Z . Anorg. A&. C'hem., 322, 25 (1963). (2) V. C. Gopeland, P. Singh, W. E. Hatfieid, and D, J. Kodgson, Inorg. Chem., 11, 1826 (1972). (3) D. Y. Jeter, R. E. Hatfield, and D. J. llodgson, J , P h y s . Chem., 76, 2707 (1972). (4) G. A. Barclay, €3. F. Hoskins, and C. €3. L.Kennard, J . Chem. Sac., 5691 (1963). (5) D. L. Lewis, W. E. Hatfield, and D. J. Hodgson, Inorg. Chem., in press. (6) J. A. Barnes, D. J. Hodgson, and W. E. Hatfield, ibid., 11, 144 (1972). (7) D. J. Hodgson, P. K. Hale, and W. E. I-Iatfield, ibid., 10, 1061 (1971). (8) D. Y . Jeter, D. J. Hodgson, and W. E. Hatfield, Inorg. Chim. Acta, 5, 257 (1971). (9) D. Y . Jeter, D. J. Ilodgson, and W. E. Eatfield, Inorg. Chem., 11, 185 (1972). (10) J. A. Barnes, W.E. Hatfield, and D. J. Hodgson, Chem. Commun., 1593 (1970).
The Journal of Physical Chemistry, Val. '76, No. 10,1078
(11) M. A. Porai-Koshits alid $4. Butio-cislca, Kr,isla,llog:t4)%?6a,6 , 381 (leel), (12) Analyses were performed by Gal braith Laboratories, Inc., Knoxville, Tenn. (18) W. R. Busing and H. A. Levy, Acto. Crystdlogr., 22, 457 (1967). (14) P. W. R. thrfield, R. a. Doedens, and J. A.Ihws, Inorg. Chem., 6, 197 (1967). (15) W. R. Busing and H . A. Levy, J . Chem. Phys , 2 6 , 583 (1957). (16) The programs for the T13.M 3GO/75 used in tliis analysis were local modifications of Ilamilton's W N O absorption correction program, Ibers' NUCLEI leastsquares program, Busing, Martiit, and Levy's O B F ~Ei.inction and error progmrn, Zalkin's F O ~ A Fourier P program, Doedens' 1tsc.m program, and various local programs. (17) D. Orr.Cromer and J'. T. Waher, Acta L'a.gistcdZoar., 18, 1.04 (1965). (18) R. P. Stewart, E. E.Davidson, and W . T. Biinpsciu, 1.Cham. Pihyy~,,42, 3175 (1965). (1 9) J. A. Ibers, "'Znlernational Tablcs for X-Ray Crystallography," Vol. 'ZIP, Kynocli Press, Birmingham, England, Tabla 3.3.18. (20) J. A. Ibers and W. C. T-Pa,mili;oii, Acta C?-yataZlogr., 17, 781 (1964). (SI) D. T. Cromer, ibid., 18, 17 (1965).
The Jowrnd os .Wfy3d4:aj Ghsmistry, Vnl. 76, N o . BO, 1972
B R O M O B I 8 ( 2 - ( % A M I N O E ) P Y R I D I N E ) C O P P E R ( ~ ~ )BROMIDE
estimated standard deviationa were run. The nonhydrogen atoms were sasigned variable anisotropic thermal parameters and the hydrogen atoms were assigned variable isotropic thermal parameters, and all positional and thermal parameters (including the hydrogen parameters) were refined. The final values of R, and RZwere 0.044and 0.056, respectively. A final difference Fourier map was featureless, with no peak higher than 0.6 e the peak height of a nitrogen atom in this analysis was about 7 e A-a. Examination of the data suggested to us that no correction for secondary extinction was necessary. I n the final cycle of leasesquares refinement, no parameter experienced a shift greater than one-half of ita estimated standard deviation, which was taken 89 evidence that the refinement had converged. The positional and thermal parameters derived from the last cycle of leasesquares refinement, along with their sasociated standard deviations as estimated from the inverse matrix, are presented in Tables I and 11. A table of observed and calculated structure amplitudes is available.zz
Table I: Positional Parameters for [Cu(GNtH1&Br]Br z
Y
'h
0.38308 (6p
'/s
0.15509(5) 0.72343 (6) 0.3801 (3) 0.4282 (4) 0.4351(3) 0.4190 (4) 0.3519(4) 0.2978(4) 0.%134(4) 0.5103 (4) 0.4492 (4) 0.458(4) 0.357(4)
'/l
0.4590(4) 0.2672 (5) 0.3379 (5) 0.3086 (6) 0.4062 (6) 0.5342 (6) 0.5548 (5) 0.2314(6) 0.1526(5) 0.241(7) 0.393 (6) 0.597(7) 0.620(6) 0.129(7) 0.299(7) 0.070 (7) 0.127 (6) 0.293(9) 0.266 ( 8 )
0.264(4)
0.284(4) 0.538 (5) 0.577(5) 0.507(6) 0.370 (5) 0.491(9) 0.344(9)
1/4
'/. v 4
0.3784(2) 0.2725(3) 0.4393(3) 0.5250(3) 0.5496(3) 0.4864(3)
0.4034(3) 0.4122 (3) 0.3608 (3) 0.554(4) 0.604(3) 0.498(3) 0.373(3) 0.467(4) 0.379(4) 0.359(3) 0.384(3) 0.246(4) 0.240(4)
aThe numbers in parentheses here and elsewhere in this paper are the estimated standard deviations in the least significant digit. The numbering scheme for the nonhydrogen atoms is shown in Figure 1. a The H atoms are numbered with reference to the C or N atoms to which thev are bonded. Thus. H(4) is bonded to C(4), H(61) and H(62jto C(6). H(N1) and H(N2) to N(2).
Description of the Structure The complex consists of monomeric, five-coordinated [ C U ( A E P ) ~ B ~cations ]+ and discrete Br- anions. The
2889
Figure 1. View of the coordination geometry around the copper(I1) in [Cu(AEP)*Br]+. Hydrogen a t o m have been omitted for clarity, and the thermal ellipsoids are drawn at the 40% probability level. The Cu and Br atoms lie on a twofold rotation axis, and atoms designated by a prime are related to the reference atom by the twofold rotation.
copper and both bromine atoms lie on a twofold rotation axis, and the geometry of the cation is shown in Figure 1. The coordination around the copper atoms is intermediate between trigonal bipyramidal and tetragonal pyramidal, the observed bond angles being within two standard deviations of the average of the values for the two idealized forms; thus, for example, the N(2)-Cu-N(2)' angle of 149.4(3)' is approximately the average of the values of 120 and 180" calculated for trigonal bipyramidal and tetragonal pyramidal geometries. The five-coordinate, ionic nature of the complex is analogous to that found' in [ C ~ ( b i p y ) ~ I but ]I, the geometries at the copper atoms in the two structures are very different since in [Cu(bipy),I]+ there are only small deviations from trigonal bipyramidal g e ometry.' The bond distances and angles found in ICu(AEP)*Br]+ are listed in Table 111. The complex is clearly monomeric, which is con& tent with the observation* that its magnetic susceptibility follows the Curie-Weiss law to at least 2.9'K; the closest Cu-Cu approach is 7.408(2) A. The nonbonded bromide ion is 4.034(2) A from the copper in the direction trans t o the bonded bromine atom. The Cu-N(1) bond length of 2.065(3) A is similar to the values reported for other Cu(I1) complexes of pyridine and substituted pyridines. Thus, it is slightly longer than the values of 1.980(6) and 1.985(6) A in dibromobi~(2-methylpyridine)copper(II),~~2.000) A in dichlorobis(4-ethylpyridine)copper(II),z4 2.021(5) A in dibrom0(2-(2-aminoethyl)pyridine)copper(II),~ 1.98(1) and 2.02(1) & . in dichlorobis(2-methy1pyridine)copper(II)," and 2.02 A in dichlorobis(pyridine)cop(22) A liating of etructure factors will appear following these p w s in the micro6lm edition of this volume of the journal. Single copies may be obtained from the Business Operations Office. Books and Joumala Division. American Chemical Society. 1155 Sixteenth St.. N.W., Washington. D . C. 20036. by referring to code number JPC-7%2887. Remit cheek or money order for 13.00 for photooopy or S2.M) for miero6ehe. (23) P. Singh. D. Y. Jeter. W. E. Hatfield. and D. J. Hodgaon. Inmo. Chm... 11.. 1657 (1972). . . (24) M. Lainr and G . Carr. J . Chm. Soc. A . 1141 (1971) (25) V. F. Duckworth and N. C. Stephenson, A d o Cw8ldlom..
Sed.E . 25. 1795 (1960).
nr P,t>oru
Pzr
paa
0.00586 (6) 0.00486 (4) 0.00944 (7) 0.0047 (2)
0.00220 ( 3 ) 0.00311 ( 3 ) 0.00405 (3) 0.0021 ( 1) 0.0031 ( 2 )
qj
cia
iD ,IDOSI. ( 1)
Br(:l) Br(12) N(1) N(2)
0.114153(I) hb , ICi I%4( 1) 2) IiIkOi. ( 5 ) O.'O.LCI% (6)
e(:[)
0 13114 ( 7 ) )"I.Y (8)
C(2) C(3) C(4) C(5) C(6) C(7)
0.008I (3) 0.0043 (3) 0.0061 (3) 0.0073 (4) 0.0060 ( 3 ) 0.0037 (3) 0.0053 (3%) 5). 0072 (4)
0.0026 (2) 0.0022 (2) 0.0021 (2) 0.0038 (2) 0.0029 (2) 0.002s (2) 0.0031 (2)
PlZ
Bra
0 0 0
- 0.00076 (4) - 0.00276 (4)
0.000~7(3) 0.0018 ( 3 )
- 0 . 00lO ( 2 ) -0.0014 (2) --0,0010 ( 3 )
0.0001 (3) 0.0002 (4) - 0.0004 (4)
0.0010 (4)
--.0.0026l(S)
o.oooo(3) -0.0017(3) -.I
0.0082 ( 3 )
0.0016 (4)
0.0027 (4) 0.0017 (4)
Be3
Q 0 0 -0.0001 (1) - 10.0002 (2) - 0.0002 (2) -0,0002(2) 0.0002(2)
--0.0002 ( 2 ) - 0 . 000s ( 2 ) 0.0000 ( 2 ) 0.0008( 2 )
H(2)
H(,3) n(4)
2
~
a ( 1.0)
H(5) H(61) R(62) B(7l) H(72) H(NI) H(N 2) a
5 . I ! 13) 4 " :?, ( 118 4.3(Ilj
913) 113 ( 2 )
+
+
The form of the misotropic thermal ellipsoid is exp[ - (&h2 PlzkZ 4- @d22Pizhk 4-2plahE 4- 2Pz3kZ)].
Table 111 : Internuclear Distances and Angles in [Ca(C7W2H1")213r ,-----,
Dista nee,
Gu-Br( 1) Cu~Br(2) Cu.--N( I )
w---.----? 2 702 (2) 4.034 (4) 2.065(3) 7 (4) 2(5> ~
2(5) C(l)-C(Z) c(4)-C(5) C(I)-C(6) C(B)-C(7) C(2)-H(2) 6(3)-H(3) C(4)-H(4) 6(5)-lH( 5 ) C(6)-.B(BI j 6:(6).-13(62) C(7)--1X('71) C(7)-"(%2) N(B)-H(NA: K(B)-H(6\12:
5 (6) 1,.388(6)
(7) (7) 1.:;!;9 ( 7 j l.493(6) 1.495 ( 7 ) 0.79(6) 0.89 ( 5 ) 0.7:' '5j 0.70
---Angle,
N (l)-Cu-N( 1)' N(2)-.Cu-N(2)' N(I)-Cu-N(2) N(l)-Cu-N(2)' Br(l)-Cu-N(l) Br(l)-Cu-N(2) C(l)-N(l)-C(5) N(I)-C(l)-C(2) W(1)-C(l)-C(6) c(a)-C(l)-c(o) C(I)-C(2)4(3) C(2)-C(3)-C(4) C(3)-C(4)-C(5) N(l)-C(5)-C(4) C(I)-C(6)-C(7) C(S)-C(7)->T(Z)
deg---
178.0 (2) 149.4 ( 3 ) 92.8(2) 87.7 (2) 89.01 (9) 105.3 (1) 117.6 (4) 120.9(4) 118.1 (4) 121.0 ( 4 ) 121.1(4) 117.8 (4) 119.0 (5) 123.7 (4) 112.4 (4) 112. I ( 4 )
l.08 ( 8 ) I.03 (8) ]I 02 ( 7 ) 1.138 (5) 0 . m (10) E . 14 (9) I
Atoms ties:g-nateiS. wiih a prime are related to the reference atom by .the twofold rotation,
per(~II),26 but is shorter than the value of 2.16(1) 8 found in 2-metii~lpyridinecopper(II) chl ~roacetate.~' Similarly, the Cii--N(2) bond length of 2.027(4) A is The Journal of'PhUsicul Chcmistyy, Vol. 76, No. 20, 1979
consistent with the copp:r(II)-amine bond lengths of 1.971(2) and 1.984(2) A in earbonatocliamminc.,copper(II),282.012r9) and 2.017(9) A irr selenatotetraamminecopper(I1) , 2 9 2.031(6) and 2.032 A in sulfatotetraa m m i n e c ~ p p e r ( l I )and , ~ ~ in many other related ~ y s t e m ~ , ~ O all - ~ jof which fall in the range 1.97-2.07 8. The bonded Cu-Br(1) disi,ance is longer tlian any terminal Cu-Br bond that could be found in the literature. In dibromobis(2,3-dixnethylpyridine)copperC U ( A E P ) B ~and ~ , ~ dibromobis(2-m.etbylpyridine)copper(II) , 2 3 the terminal Cufall in the range 2.888-2.413 A, which migh"., therefore, be considered 'hormal" for systems of this type. In CuBr2-, the Cu-Br distances are372.450(2) and 2.519( 2 ) A, and this latter is the longest terminal Cu-Br bond length found in the literature; the sum of the (26) J. D. Dunitz, Acta Crystallog?., 10, 307 (1957). (27) G. Davey and F. 8. Stephens, .I. @h.ern, 8006. A. 2803 (1970). (28) M. H. Meyer, P. Singh, W. E. Matfield, and D. J. Iilodgson, Acta Cryst., Sect. B , 28, 1607 (1972). (29) B. Morosin, Acta Crystdloyr., Sect. B , 25, 29 (1969). (30) M. B. Cingi, C. Guastini, A. Musatti, and M. Nard.elli, ibid., 26, 1836 (1970). (31) I. Agrell, Acta Chem. Scand., 20, 1281 (1966). (32) T. Distler and P. A. Vaughan, Inorg. C h e m , 6 , 126 (1967). (33) Y . Iita.ka, K. Bhimieu, and T. Kwan, Acta Cryst., 20, 803 (1968). (34) B. W. Brown and E. C , Lingafelter, i b i d . , 17, 254 (1.964). (35) Y . Komiyama and E. C. Liagafeiter, ibid., 17, 1145 (1964). (36) W. Stiihlin and W. R. Ostwald, Acta C~ystaZEoyr.,Sed. B , 27, 1368 (1971). (37) 8. A. Goldfield and K. N. Raymond, Inorg. Chem., 10, 2604 (1971).
covalent radiisMof Cu(B%)(1.35) and Br (1.14) leads to a single bond valnc of 2.49 in good agreement uith these values. The bond length of 2.702(2) 8 found ~ ~ than c aall~of ~these ~ examples, , ~ here 1s s i ~ ~ ~greater and is very similar to the value of 2.70 found for the Ch-1 Land" 111 ~~~~~~~~y~~~~~~ the sum of the covalent r d i i @of Cu(lQ>and k is 2 68 KKL an att,empt to discovw the cause of this anomalous Cu-Rr bond leng!h, we made a series of calculations in which the Br(1,1atom m s bonded more closely to the C h atom bill, the other atoms maintained their obst:rwe,l posi$ons. When the Cu-Br bond length was set to 2.41 A t h ~ s ewere Rr. -hrand Br. . . C contacts of 3.848 and 3.235 & respectively, and with a Cu-Br b o d length of 2.52 -4 these contacts were 3.230 and 3.2901 A, respeclivcly; in the observed molecule, the c i o s e 4 separnt1on.s are 3.272 and 3.388 While these Bs. s:ondacts are Iess than the sum of the atomio van der ‘iVa,akiradii reported by P a ~ l i n gnone ,~~ of them can be ~~~~:~~~~~ as severe since in dibromobis(2-Pna:tkijrlpyridieia) copper(1H) there are four Br separai,iona 111 the range 3 118(7)-3.1$8(7) 8 , 2 3 in CU( A ~ ~l h )e r ~~ia ra 2~2 ~ . .N distance OS 3.195 8,2and in dibrornobiu(&3-~ ~ ~ e t R ~ ~ p ~ there r ~ darei nBr. e ). .K coritaols of 3.10 L(9) and 3.105(9) I n none of these cases cited is the apparent contraction of the Br. . eepassd,ions due 1 o hydrogen bonding, since the nitrogeri ~ t ~ m involved s ore pyridine nitrogen atoms and have PIO hydrogen dm-n attached. Hence, the lengthening of the Cu -Br b o d cannot be attributed to intramolecular contacts. There is no evidence of any h y ondmp, iaivol ving this bromine; t ( 2 ) ~~~a~~~~~~~ ia 3.702(3) 8, with a correseparation of 3.11 8 and an as1-3 (2) angle of 112”. These values d u d e any kiycciirogen bond since the * N s q x “ in oonaiderably larger than the sum of t k i ~van der W a d s radii and the Br. . .El[ distance i n hydrogen brmcdcd system Raa been reported to be etpproximalely 2 . ~ ~A,40 3 41 ‘ICB-te geornetry of the wubytituted pyridine ring is norxxd ‘The C-N(I) bond lengths of 1.342(5) and 1 .tkEi:i) in tYir A E P Isgarrd are in excellent agreement with ?he nnem value of a.342(11) 8 in dibroniobis(2~ ~ ~ t ~ ~ ~ ~ ~andyther values i ~ of~ 1.33(1) n e sind 1.342(9) ,&. in the AEP ligand in Cu(AEP)Br2,2 rind also -\vntla the mean value of 1.352 8 reported for laeberoeyclia c:ompounds by 6utt011.~~Whilc there are wide variations ir: the C-G bond lengths in the ring, it is evident thal, the U’I>-C(2) bond, which is 8djacmt 1 o t h cxo~yclia: ~ por1ic.n of the ligand, is slightly longe: (1388(6) A) than the merage length of 1.367(13) A for the otlier ring 6-42bonds, The exocyclic 6-C \ ~ K lengths I of 1.493(6) 1 2 ~ i d l1.495(7) 8, however, are
x.
I
A.
-
I
a
relatively short. This shortening of the exocyclic 6-6 bond and lengthening of the adjacent ring @-C bond have been observed in analogous systems,223-25 and can be ascribed to a drift of electron densjty from the ring toward the exocyclic moiety.23 The bond angles in the ring are normal, Falling in the range of P17.6(4)L23.7(4)”. The pyridine ring ia planar, ~ i t no h titorn deviating from the least-squares plane by more than
A.
B>.UIS
The geometry at the copper(1l) atoms is quite different from Lhat proposed by Uhlig and lBIaaser,l and we hare made some calculations of the intramoiecular contacts which would result if the AEP ligands niaiiitained their observed geumptrj and position but the nom bonded Br(2) ion were within bonding distance of the nzetal. In these models as in the prewous calculations inudving Br(l’r (vide s u p ~ a the ) brorishe atom 71 as constrained to lie on the tclofold axis. With a normal bonded Cu-Br separation o f 3.41 there n o d d be 1 3 ~ .. eN(’2) coiitaci,s a9 short a 6 2.709 and when the Cu-Br distance 18 increased to %.FJ~ A. lhere are still Br. ’N(2) jnteractions of 2.7&6 A; ihis contact is increafied to only 2.919 .k when the Cu-IDr(2) bond length is set equal to the very long @u-Br(l) value of 2.702 A. ATP of these Br. ‘ N contacts mfouPcB muse severe strain in the molecule and are significantly shorter than any Br. . .E\J ~ . , o ~ > ~~hiclb. t ~ l s c o d d LW i ’ o ~ in ~ ~t hde literalure. While lbese calculated coubacts do explain 13, hy the Hr(2) ion cannot bond to the [Cu\AEP)&]+ moiety if the cation maintains i t 3 present geometry, there is no obvious reason v-hj the AEP liqands could nut move upward (in the direction o i Bril)) to reduce this strain. If ~vouldbe of great interest i o compare this structure with those of the correrumndtng iodo and chloro cornpPcxe~i o see 15 hcther arny iurthrr light can bc shed on Ihns problein.
K,
e
Acknowledgments. This research was supported by the Materials Research Center o€ the University of Ic’orth Carolina under Contract KO.DL4HC-% 5-67-C0223 with the Advanced Resc!aerch Projects Agency, and by the Xatioizal Science Foundation under Grant Xo. GP-110300. W c are grateful for this continuing support. ~ c ~ ~ ~ e ~ ( ~ ~ ~ ~ ~ (38) L. Pauling, “The Nature of the Chemical Bond,” 3rd ed, Cornell University Press, Ithaca, K.Y., 1960. (39) W. C. Hamilton and J. A. Ibers, “Hydrogen Bonding in Solids,” W. A. Benjamin, New York, N, Y., 1968. (40) M. A. Levy and 8. W. Petersen, J. Anaer. Chem. Soc., 75, 1536 (1953). (41) H. S. Gutowsky, G. E. Kistiakowsky, G. E. Pa.lie, and E. M. Purcell, J . Chem. Phys., 17, 972 (1949). (42) L. E. Sutton, “‘Tables of Interatomic Distances and Configurntioris in Molecules and Ions,” The Chemical Society, London, 1958.
The Journal of Physical Chemistry, Vol. 76, N o . 90, 1SYW
