2294
J. Phys. Chem. 1994,98, 2294-2297
Ab Initio Characterization of Gaseous (COzP)+ Species X. Lopez,? F. P.Cossio,t J. M. Ugalde,'+t C. Barrientos,$ and A. Largos Kimika Fakultatea, Euskal Herriko Unibertsitatea, P.K. 1072, 20080 Donostia, Euskadi, Spain, and Departamento de Quimica-Fisica y Analitica, Universidad de Oviedo, 33006 Oviedo. Spain Received: September 20, 1993"
Ab initio molecular orbital theory has been used to characterize both gaseous singlet and triplet (COzP)+ species. Five stable molecular structures have been found for each of the spin multiplicities, at the MP2/6-3 lG* level of theory, one planar cyclic, two ion-molecule complexes, and two ion molecule-molecule complexes. Only the triplet states of the (OP-CO)+ complexes have been found to have substantial hemibond character. For all other complexes studied, an electrostatic type of interaction is found to dominate. The electrostatic singlet 'A' state of the OP+-CO complex has been predicted to be the most stable of all. However, our calculations demonstrate that the P+-OPO ion-molecule complex has the greatest binding energy. Finally, vibrational spectra of these species, which may help in their detection, are discussed.
Introduction
Computational Methods
In recent years considerablework has been done on both neutral and charged small phosphorus oxide complexes. Thus, neutral phosphorusdxygen complexes of the form (P2)x(02)y( x = 1,2; y = 2-5) were found to be involved in the reaction of P2 with 0 2 in argon matrices initiated by the ultraviolet photoexcitation of dipole-forbidden excited states of P2.l On the other hand, the reaction of P2with O3in argon2during condensationat cryogenic temperatures is spontaneous and produces PO and PO2 radicals and linear P20 as primary reaction products. Then, secondary reaction products like PO3, P2O5, and P402 are formed during the matrix condensationprocess. Also, photolyzing or annealing the matrices leads to two structural isomers of P204 and to the five-membered-ringisomer P40. Someof these phosphorus oxide species have been characterized by ab initio calculations.3~Both open and bipyramidalstructures have been discussed from the standpoints of both structural chemistry and vibrational spectroscopy. Calculations reveal that the cyclic D2h symmetry structure of the (02P2) species is the most stable one, but it has a large biradical character which may prevent its experimental isolation.5~~However, several 0pen~3~ and bipyramida14structures have been suggestedas possible P20, detectable structures. Charged complexes of P+ have been found to form with relative ease in experimentson ion-molecule reactions of PH,+ (n = 0-4) with some neutral molecule^.^^* In particular the complexes PNH3+,9POH2+,10 PCH4+,lland PSH2+ l 2 are predicted, on the basis of ab initio calculations, to be neatly stabilized species. Also, the OPO+ has been suggested to be considered as a possible synthetic target," with some reservation about its experimental isolability due to the large electron affinity14 of its short-lived neutral parent OPO (2Al). Finally, a recent15ab initio study of the (02P2)+species has predicted the planar 0 2 1 symmetry cyclic structure to be the most stable one. Hemibonded trans OP-PO+ and PO-OP+ structures have also been characterized along with two bipyramidal ones. However, the P+-OPO ion-molecule complex which lies higher in energy than even hemibonded structures is predicted to have the greatest binding energy. This paper presents ab initio results for the geometries, energies, vibrational frequencies, and intensities of the (C02P)+ species. A total of 10 equilibrium structures will be discussed from the standpoints of structural chemistry, stability, and vibrational spectroscopy.
Ab initio molecular orbital calculations have been carried out using the GAUSSIAN-92I6 package. Geometries have been optimized, allowing for part of the electron correlation using the Maller-Plesset second-order (MP2) with the split-valence plus polarization 6-3 1G*basisset.17 Harmonicvibrationalfrequencies have been computed at the HF level with the 6-3 lG* basis on their corresponding optimized structures at the same level of theory. Zero-point vibrational energies were also obtained at this level. In order to ascertain the stability order of the different species, we have computedtheir energy using fourth-order Maller-Plesset (MP4) perturbation theory. We have checked on the basis set superpositionerror (BSSE). Calculations with the function counterpoise method of Boys and BernardiI'J indicated that the BSSE was negligible.
Euskal Herriko Unibertsitatea. Universidad de Oviedo. 0 Abstract published in Aduonce ACS Absrrocrs, February 1, 1994. f
0022-3654/94/2098-2294%04.50/0
Structures Figure 1 shows the MP2/6-3 1G*-optimized geometries for the five stable molecular structures that we have characterized on both the triplet and thesinglet (in parenthesis)potential energy hypersurfaces of (C02P)+. These structures can be classified into three categories,namely: ion-molecule complexes P+-OCO and P+-C02, ion molecule-molecule complexes (OP)+-(CO), and cyclic molecules POCO+. Ion-Molecule Complexes. Indeed, the triplet state of the P+OCO ion-molecule complex has been found to be the most stable of all the isomers on the triplet potential hypersurface. This structure shows a remarkable electrostatic character for both its triplet 3A' and its singlet 'A' states. Thus, the P+ moiety bears almost a full unit charge, namely +0.82 e- for the triplet and +0.76 e- for the singlet, which along with the long P+-0 distance precludes this complex to be held by the electrostatic interaction between P+ (3P, ID) and C02 ('E:) for the triplet and singlet states, respectively. Notice that the C02 moiety is only slightly bent with respect to its isolated linear structure. However, the C-0 distances are found to be substantially modified as a consequence of the interactionwith P+;namely, relative deviations of 0.06 and 0.07 have been found for the triplet and singlet states, respectively. The other ion-molecule complex that we have characterized, namely P+-C02,is found to be the less stable one of all on both the triplet and the singlet hypersurfaces. Its long carbon terminal oxygen bond length and the acute C-0-C bond angle, 8 1.6O for the triplet and 76.2' for the singlet, which renders an oxygen-xygen length of 1.69 A for the triplet and 1.63 A for the singlet, are remarkable. 0 1994 American Chemical Society
The Journal of Physical Chemistry, Vol. 98, No. 9, 1994 2295
Characterization of Gaseous (C02P)+ Species (1.15)
P
-- - - - -
Figure 3. Valence-bond structure of the POCO+ cyclic 'A, state.
(1 88) 1.83
I
II
(1.14)
&:
,'
175.4
(102.2)
,'(2.69)
(147) 1.65
IV
Ill
V
Figure 1. MP2/6-31G*-optimizedgeometries for the triplets and singlets and, in parenthesis, states of the (C02P)+ species.
Figure 2. Resonant valence-bond structures of the POCO+ cyclic
state.
Ion Molecule-Molecule Complexes. Structures III and IV can best be viewed as ion molecule (PO+)-molecule (CO) complexes. Indeed, the (PO) moiety bears in all cases almost a full unit charge. Also, the geometry of the (CO) moiety remains rather unchanged irrespective of the multiplicity, in both of the complexes. However, both the P-0 bond length and the intermoiety distance are found to differ markedly between the singlet and the triplet states. The 1 . 4 7 4 length found for the P-O bond is the same as the bond length of the PO+ in its IC, ground state at the same level of theory.I9 Hence, the singlet states are dominated by the balance between the Pauli's repulsion between the PO+, IC, and CO, IC, closed shells and the electrostatic attraction between the PO+ and the CO molecule. This accounts for the very long intermoiety distance, of the order of 2.6 A, as seen from Figure 1. However, for the triplets a decrease of the intermoiety distance and an increase of the P-0 bond length are observed. The calculated P-0 bond length of 1.63 A (1.65 A) for the OP+-CO (OP+-CO) compares well with the bond length of 1.65 A of the PO+ 3A state.Ig In addition, inspection of the molecular orbitals of the structures 111 and IV reveals that the PO+ 3A state's (37r*)1 HOMO interacts with the lone pair of the carbon atom (oxygen atom) of the CO moiety of structure 111(IV), thus rendering a two-center three-electron (2c, 3e) hemibond, responsible for the shrinkingof theintermoiety distancewith respect to the singlet states. The (I-P-C and 0-P-O angles of structures III and IV, respectively, are dictated by the maximum overlap disposition and as expected are found to be close to 90°. This also accounts for the lower energy of structure 111with respect to structure IV, for in the former the interaction of the (37r*)1 HOMO of PO+ occurs with the lone pair of the carbon atom which lies higher in energy than the lone pair of the oxygen atom of the CO moiety; hence a closer match of the orbital
energies is obtained, and therefore a larger interaction energy is achieved, which renders an extra energy stabilization. Cyclic POCO+. The long P-C bond length calculated for both singlet and triplet states precludes P-C cross-bonding. This is further confirmed by the analysis of the charge density p(r), whose gradient shows only a ring critical point on the P-C path, for both singlet and triplet structures. However, appreciably different P-0 and C-0 bond lengths and 0-P-0 and 0-C-O bond angles are predicted, depending upon the spin multiplicity. Thus, the MP2/6-31 G*level of theory predicts a shrinking of 0.2 A for the P-O bond length and an increase of 0.17 A for the C-0 bond length of the singlet state with respect to the triplet state. The partial electron density donation from the lone pairs of the oxygens to the phosphorus, reflected in the Mulliken overlap population, may be responsible for these bond length deviations. A total overlap population of 0.053 electrons between the lone pair of each oxygen and the vacant 3p orbital of the phosphorus is calculated from the 'Al state. However, due to the occupancy of this 3p orbital in the 3B1 state, the electron donation from the lone pair of the oxygen is hindered, and thus a negligible overlap population of 0.007 is now found. This could account also for the C-0 bond length increase. Analysisof the Mulliken charges indicates that the phosphorus bears almost the whole charge unity of the molecule for both states, while the spin density on both carbon and phosphorus have comparable values for the triplet. Hence, a likely valencebond representation for the triplet may be given by the resonant valence-bond structures shown in Figure 2, while the singlet might be representedby thevalence-bondstructureof Figure 3. Finally, it should be mentioned that the other possible cyclic structure, namely POOC+, was not found, although an extensive search of the potential energy surface was carried out.
Vibrational Spectra The calculated vibrational spectra are summarized in Table 1. The theoretical vibrational transitions should be greater than the experimental values, as the calculated spectrum is harmonic whereas the experimentalincludes anharmonicity. Also, it should be mentioned that in many cases, discrepancies between computed and observed vibrational frequenciesarise due to approximations in the harmonic force constant calculations. However, it has been established17that the discrepanciesbetween theoretical and experimental frequencies reveal systematic differencesthat may be corrected empirically. Thus, Pople et al.20 suggested that presumably correct frequencies can be found by scaling the frequencies calculated at the HF/6-31G* level of theory by the empirical factor 0.8929, and so this has been done in this paper. Inspection of Table 1 reveals that for both singlet and triplet structures I the modes with largest IR intensity correspond to the asymmetric stretching of the C02 moiety, namely its last two a' modes. The P+-0stretching modes at 328 cm-l for the singlet and at 292 cm-1 for the triplet appear to have significant IR intensity, Le., 173.5 and 161.7 kcal/mol for thesinglet and triplet states, respectively. However, for both singlet and triplet structures I1 the P+-C a l stretchingmode has small IRand Raman intensities. These structures have only one mode with appreciable IR intensity, namely, their symmetric C-0 stretching al mode at 1542 cm-1 in the singlet and at 1646 cm-1 in the triplet. The largest frequency mode of structure 111 is associated with the C-0 stretching, and for the triplet it is the only mode with appreciable IR and Raman intensities. It is worth noting that the P-0 stretching modes of both the singlet, at 1474 cm-', and
Lopez et al.
2296 The Journal of Physical Chemistry, Vol. 98, No. 9, 1994
TABLE 1: Vibrational Freauencies (in cm-l) and Intensities (in kcal/mol) for (COIp)+ at the HF/6-31C* Level of Theory singlet triplet struct svmm mode V IR Raman mode V IR Raman 0.4 106 7.5 0.8 93 5.6 I CS a’ 0.5 328 173.5 1.o 292 161.7 a’ a”
a’ a’ a’ bz
C2,
bi 81
a1 b2
111
CS
IV
C,
V
C2”
al a’ a’ a“ a’ a’ a’ a’ a“ a’ a’ a’ a’ bi bz
a1 b2
al a1
TABLE 2 Basis Set
607 654 1212 2341 262 389 520 794 935 1542 89 136 174 232 1460 2267 72 95 110 146 1474 2083 187 440 129 945 1015 1056
0.4 1.5 11.8 6.9 3.1 3.8 8.8 18.9 2.0 35.4 0.4 2.1 0.1 0.6 24.0 20.1 1.4 0.9 0.4 1.3 17.9 35.3 0.6 1.o 3.6 0.6 3.6 14.5
618 643 1317 2354 215 355 375 798 883 1646 168 310 345 439 813 2300 96 115 218 262 839 1998 426 49 1 585 893 1384 1428
bz bi
al al a1 b2
15.9 76.9 241.3 1383.0 7.6 34.8 3.8 33.5 14.9 252.4 13.1 18.3 7.8 27.9 44.8 163.6 3.5 4.6 37.9 116.3 81.1 668.9 24.1 31.9 137.6 54.8 91.2 266.4
0.1 1.2 11.6 4.3 3.1
0.7 0.2 22.6 2.9 84.4 2.4 0.0 1.o 1.4 5.9 106.8 9.1 0.1 1391.4 39.8 95.2 962.3 2.9 0.1 7.7 2.6 10.9 1.o
Ab Initio Energies (in au) and Energy Differences (in kcal/mol) in Parenthesis for (C02P)+with the 6-31C* II
I ‘A’
HF//HF MP2 PMP2 MP3 PMP3 MP4SDQ MP4SDTO PMP4
74.5 87.2 271.9 1262.8 11.3 12.1 0.1 63.1 18.9 405.8 5.1 75.1 0.2 26.7 72.1 65.6 1.4 7.2 11.4 79.0 64.7 365.6 0.2 12.1 143.2 178.9 320.1 45.9
3A‘
521.924 446 528.001 375 528.469 603 528.531 638 528.533 565 528.465 822 528.525 518 528.526 826 528.487 655 528.545 988 528.514 450 528.512 088 52a.573 397 (77.0) (40.0)
‘AI
527.753 613 527.801 665 528.333 804 528.364 105 528.366 964 528.329 841 528.354 259 528.355 694 528.352 654 528.381 a57 528.285 245 528.415 661 528.411 102 (156.6) (136.5) (0.0)
the triplet, at 8 13 cm-1, compare well with the stretching modes of PO+ (IE)at 1405 cm-l 21 and PO+ (3A) at 916 as expected. Also, the P-C stretching has larger vibrational frequency in the triplet, 345 cm-I, than in the singlet, 136 cm-I, reflecting the stronger intermoiety interaction for the former, as anticipated in the preceding section. For the structure IV, the central P-0 bond stretching mode is found in the range of small frequencies, namely at 110 cm-I for the singlet and 218 cm-l for the triplet. However, the large Raman scattering activity of the latter, Le., 1397.4 A4/amu, may help in its detection. Also, the C-0 stretching mode is predicted to have a measurable Raman scattering activity of 962.3 A4/ amu. With respect to cyclic structure V we have found that the singlet has three modes with appreciable IR intensity, Le., a breathing al mode at 729 cm-1, an antisymmetric breathing bz mode at 945 cm-I, and a bending mode of the COz end of the moleculeat lOl5cm-1. However,forthetriplet,onlyitsbreathing a l mode at 585 cm-I and its antisymmetric stretching b2 mode of the COz end of the molecule have appreciable intensity. In either case, the Raman scattering activities are predicted to be small.
Energies Single-point calculations were made at the full MP4/6-31G* level of theory on the previously optimized MP2/6-3 l G *
V
IV
I11 )A2
‘A‘
3A”
528.006 733 521.913 053 528.511 176 528.399 461 528.403 072 528.560 961 528.416 110 528.419 083 528.594 504 528.436 526 528.621 053 528.455 690 538.510 853 528.458 063 (77.7) (4.2) (109.5) (93.5)
528.497 480 (81.5)
molecular structures. It has been found22 that comparison of relative energies of open-shell species which differ in the amount of spin contamination may be misleading. In such cases, projected Maller-Plesset energies,23which are listed in Table 2,are needed. Inspection of these figures reveals that the electron correlation does not change the energy ordering; however, it does affect substantially the relative energies. Singlet OP-CO+ is found to be the most stable structure at the highest level of theory, with singlet OP-OC+ lying only 4.2 kcal/mol above. It is worth noting that unlike the (OzP2)+ species,15the cyclic structure V is very high in energy with respect to both singlet ion moleculemolecule species OP-(CO)+. Indeed, even the P-OCO+ ion-molecule complex is found to be more stable than the cyclic structure V, for both the singlet and triplet potential energy surfaces. Binding energies of the various (CO*P)+structures are collected in Table 3. Hence, calculations predict that structures II are largely endoergic with respect to their corresponding P+ COz dissociation products. All others are found to be exoergic. It is worth noting that the P-OCO+ ion-molecule complex appears to have the largest of all the calculated binding energies for the singlet states. The sameresult has been also found for the (02Pz)+ system.15 However, the ionized phosphorus oxide interacts more favorably, by 4.85 kcal/mol for the singlet and 33.13 kcal/mol for the triplet, with the carbon end of CO with respect to the oxygen end of CO.
+
The Journal of Physical Chemistry, Vol. 98, No. 9, 1994 2297
Characterization of Gaseous (C02P)+ Species
TABLE 3: Binding Energies with the 6 3 1 V Basis Set singlet
triplet
binding energy (kcal/mol)
I I1 III IV
dissociation products
binding energy (kcal/mol)
36.10 -44.98 11.86 7.02
3 1.88 -66.20 53.97 20.84
P-Cz2.23
Figure 4. Optimized geometry of the 2 B ~state of the Ca symmetry POCO cyclic neutral molecule a t the MP2/6-31G* level of theory.
TABLE 4 Energy and Vibrational Spectra of the Neutral CZ,Cyclic POCO Neutral vibrational spectra UHF//UHF PUHF MP2 PMP2 MP3 PMP3 MP4SDQ MP4SDTQ PMP4
energy(-E)
mode
Y
IR
Raman
528.220831 528.223 957 528.775 563 528.777 627 528.789 527 528.782723 528.798 291 528.820 373 528.821 569
bl b2
306 617 675 964 1013 1181
3.1 5.2 110.0 34.5 169.5 118.6
34.0 3.5 10.1 7.0 0.3 5.5
a1
a1 b2 a1
We have calculated also the electron affinity of the POCO+ cyclic structure V. For completeness, Figure 4 and Table 4 summarize the results obtained for the neutral POCO molecule. We have found that its ground state is the 2B1state of Ca symmetry withboth MP2/6-31G* P-OandO-CbonddistancesandO-P-O and 04-0bond angles intermediate with respect to those of its singlet and triplet cationic species. Its vibrational modes are predicted to have small intensities, the one with the largest IR absorption intensity being the b2 mode which corresponds to the antisymmetric stretching of the C02 end of the molecule. The data of Table 4 allow the estimation of electron affinity for both singlet and triplet POCO+ cyclic cations. Inclusion of ZPVE correction renders an electron affinity of 9.16 eV for the singlet and 8.79 eV for the triplet. This high electron affinity may hinder its experimental isolation,for it will easily trap an electron to give the neutral species.
Conclusions Five stable molecular singlet and triplet (C02P)+ structures have been characterizedby ab initio molecular orbital calculations. For each spin multiplicity we have found one planar cyclic structure, two P+-(C02) complexes, and two (OP)+-(CO) complexes. Analysis of their geometry and molecular orbitals revealed that only the triplet states of the OP+-(CO) complexes 111and IV have substantial intermoiety hemibond character. For all other complexes the electrostatic type of interaction between the moieties dominates. On the singlet surface, the O p t 4 0 complex was found to be the most stable species; however, the P+-OCO ion-molecule electrostatic complex was found to be the most stable species on the triplet surface. Conformational energy differences are found to be small for the OP+-(OC) complexesIII and IV on the singlet surface, namely
dissociation products P+CP) + CO2VZg) P+(3P) + C02(1Z OP+(~A) co(lb OP+(~A)+ co(1~)
+
level of theory MP4/ / MP2 MP4//MP2 MP4//MP2 MP4//MP2
4.2 kcal/mol, and large for the P+-(C02) ion-molecule complexes I and 11,965 kcal/mol for the triplet surface and 79.6 kcal/mol for the singlet. Inspection of the binding energies calculated at the MP4SDTQ//MP2 level for the singlets and at the PMP4/ IMP2 level for the triplets, with the 6-31G* basis set, reveals that the ion-molecule complex I has the largest binding energy for both singlet and triplet surfaces. This result comes along with that found for the (OzP2)+ system, in which also the P+OPO complex was calculated to have the largest binding energy, and suggests that electrostatic P-0 interactions are favored in the primary interactions between phosphorus cation and oxides. The singlet ground states of the ion-molecule moleculecomplexes III and IV are predicted to have small binding energies, and the P+-CO* complex II is predicted to be very endoergic; therefore it will not be formed spontaneously.
Acknowledgment. This research has been supported by the Spanish Officeof Scienceand Education (Ministeriode Educacion y Ciencia), Grant PB91-0456, and the Provincial Government of Gipuzkoa (Gipuzkoako Foru Aldundia). X.L.gratefully acknowledges a grant from the Basque Government (Eusko Jaurlaritza). References and Notes (1) (2) (3) (4)
McCluskey, M.; Andrews, L. J. Phys. Chem. 1991, 95, 2679. McCluskey, M.; Andrews, L. J. Phys. Chem. 1991, 95, 2988. Lohr, L. L. J. Chem. Phys. 1990, 94, 1807. Lohr, L. L. J. Chem. Phys. 1992, 96, 119. (5) Bruna, P. J.; Miihlluser, M.; Peyerimhoff, S. D. Chem. Phys. Lett. 1991, 180, 606. (6) Lopez, X.;Sarasola, C.; Lecea, B.; Largo, A.; Barrientos,C.; Ugalde, J. M. J. Phys. Chem. 1993, 97,4078. (7) Thorne, L. R.; Anicich, V. G.;Huntress, W. J. Chem. Phys. Lett. 1983, 98, 162. (8) Smith, D.; McIntosh, B. J.; Adams, N. G. J. Chem. Phys. 1989.90, 6213. (9) Largo, A.; Flores, J. R.; Barrientos,C.; Ugalde, J. M. J . Phys. Chem. 1991, 95, 170. (10) Largo, A.; Redondo, P.; Barrientos,C.;Ugalde, J. M. J . Phys. Chem. 1991, 95, 5443. (1 1) Largo, A.; Flores, J. R.; Barrientos,C.; Ugalde, J. M. J. Phys. Chem. 1991, 95, 6553. (12) Lopez, X.; Ugalde, J. M.; Barrientos, C.; Largo, A,; Redondo, P. J . Phys. Chem. 1993, 97, 1521. (13) PyykkO, P.; Zhao, Y.-F. Mol. Phys. 1990, 70, 701. (14) Lohr, L. L., Jr. J. Phys. Chem. 1984,88, 5569. (15) Sarasola,C.; Lopez, Xi;Arrieta, A.; Barrientos, C.; Largo, A.; Ugalde, J. M. J. Phys. Chem. 1993, 97, 5860. (16) Frisch, M. J.; Trucks, G.W.; Head-Gordon, M.; Gill, P. M. W.; Wong, M. W.; Foresman, J. B.; Johnson, B. G.; Schlegel, H. B.; Robb, M. A.; Replogle, E. S.;Gomperts, R.; Andres, J. L.; Raghavachari, K.;Binkley,
J.S.;Gonzalez,C.;Martin,R.L.;Fox,D. J.;Defrees,D.J.;Baker.J.;Stewart, J. J. P.; Pople, J. A. Gaussian 92, Revision C;Gaussian, Inc.: Pittsburgh, PA, 1992. (17) A complete discussion of the basis and methods used in this paper may be found in: Hehre, W. J.; Radom, L.; Schleyer, P. v. R.;Pople, J. A. Ab Initio Molecular Orbital Theory; Wiley Interscience: New York, 1986. (18) Boys, S. F.; Bernardi, F. Mol. Phys. 1970, 19, 553. (19) Redondo, P. Ph.D. Thesis, University of Valladolid. 1992. (20) Pople, J. A.; Schlegel, H. B.; Krisham, B.; DeFrees, D. J.; Binkley, J. S.; Frisch, J. S.;Whiteside, R. A,; Hout, R. F.; Hehre, W. J. Inr. J . Quantum Chem. Symp. 1981, 15, 269. (21) Butler, J. E.; Kawaguchi, K.; Hirota, E.J. Mol. Spectrosc. 1983, 101, 161. (22) McKec, M. L. J. Phys. Chem. 1986, 90, 2235. (23) M a , C.; Schlegel, H. B. Inr. J . Quantum Chem. 1986, 29, 1001. Schlegel, H. B. J. Chem. Phys. 1986, 84. 4530.
