1682 Inorganic Chemistry, Vol. 17, No. 6, 1978 Table I. Assignments of Raman Spectra’ of (SBr,)’(AsF,)-
,
(SBr )‘(AsF,)Solid AsF, s o h
130gb 872.5
685 sh 674 573 562
676 560 436 p 421 d p
429 414 39 1 367.5 375 175 128
378.5 p 174 p 124 d p
(SBr,)+(SbF,)-
so, soh
Solid
Notes and (SBr,)+(SbF,)PBr,‘ gas
867.5
675 sh 642 562.5
643.5 560 434 p 417 d p
42 1 41 0.5 277
711 686
:ii
400
280h
379 175 127.5
(SF,h+(As-
F6)- solid C S A S F , ~ LiSbF,e
376.5 p 175.5 p 124 d p
38 1
161 116
Assignment
685 576
668 558
Iu,(MF,)-
372
294
IY,(MF,)- or us(MF,)v 4 (MF, 1-
922
iii
942 5 34 40 3
(SBr3)’
VI
v, (SBr,)+ v4(SBr,)l
‘
Frequencies (in cm-’) accurate to ca. i 2 cm-’. See Solvent peaks and Br, stretch omitted. These are, however, marked in Figure 1. Correref 14. See ref 6. e See ref 13. Tentative assignment assuming Oh and C, symmetry for (MF,)- (M = A s or Sb) and (SEI,)+. Could b e an impurity. sponds t o u3(PBr,) o r v3(SF3)I in appropriate column. a
b I I
I
I
‘ IL I
broadened in the order 436 > 872 > 1309 cm-’ and therefore is likely a resonance Raman spectrum. It was least intense for (SBr3)+(SbF6)-in sulfur dioxide solution using the 6471-A (red) exciting frequency and no overtones were observed. We are presently attempting to determine the nature of this species. Acknowledgment. We thank the National Research Council of Canada for financial support and a fellowship (E.K.R.). Registry No. (SBr3)+(AsF6)-,66142-09-4; (SBr3)+(SbF6)-, 66142-10-7. References and Kotes 0. Ruff, Chem. Ber., 37, 4513 (1904). J. W. Mellow, “Comprehensive Inorganic and Theoretical Chemistry”, Vol. X, Longman and Green, London, 1930, pp 646-647. F. A. Cotton and G. Wilkinson, “Advanced Inorganic Chemistry”, 3rd ed, Wiley, Toronto, 1972, pp 437, 440. H. A . Mayes and J. R. Pardington, J . Chem. Soc., 2594 (1926). J. P. Marino in “Topics in Sulfur Chemistry”, Vol. I , A. Senning, Ed., G. Thieme. Stutteart. 1976. OD 51-53. and references therein. D. D. Gibler, C. J.kdarns, M.’&cher, A. Zalkin, and N. Bartlett, Inorg. Chem., 11, 2325 (1972). W. Sawodny and K. Dehnicke, Z . Anorg. Allg. Chem., 349, 169 (1967), and references therein. J. Passmore and P. Taylor, J . Chem. Soc., Dalton Trans.,804 (1976). T. Birchall, P. A. W. Dean, B. Della Valle, and R. J. Gillespie, Can. J . Chem., 51, 667 (1973). J. Passmore and P. Taylor, 1976, unpublished data. J . Passmore, P. Taylor, T. K. Whidden, and P. White, J . Chem. Soc., Chem. Commun., 689 (1976). J . Passmore and E. K. Richardson, 1976, unpublished data. G. M. Begun and A. C. Rutenburg, Inorg. Chem., 6, 2212 (1967). A. T. Kozulin, A. V. Gogolev, V. I. Karmanov, and V. A. Murtsovkin, Opt. Spektrosk., 44, 1218 (1973). J. A. Evans and D. A. Long, J . Chem. SOC.A , 1688 (1968). G. Herzberg, “Molecular Spectra and Molecular Structure”, Val. 11, Van Kostrand, New York, N.Y., 1945, p 285. H.Stammreich, R. Forneris, and Y. Tavares, Spectrochim. Acta, 17, 1173 11961). C. La;, H. Lynton, J. Passmore, and P. Y . Sew, J . Chem. Soc.. Dalton Trans., 2535 (1973). ~~
1300 900
700
I
1
I
500
300
100
F R E 0 U E N C Y (c m -I)
R a m a n spectra of t h e (SBr3)+ cation: (a) solid (SBr3)+(SbF6)-(6471-A line); (b) solid (SBr3)+(AsF6)-(5145-A line); (c) (SBr3)+(SbF6)-in SO2 solution (5 145-A line); (d) (SBr3)+(AsF6)in AsF3 solution (5145-A line). Slit width 8 cm-’ except in (b), which was a t 4 cm-’. X indicates solvent peaks. 0 indicates t h e Br, peak. indicates impurities.
Figure 1.
+
The spectra support an essentially ionic formulation for the two salts. The peaks attributed to SBr,’ are similar in solution and in the solid state, except Y, (SBr,’), the antisymmetric stretching mode, (e), is split in the solid state. The four Raman active bands (two polarized and two depolarized) expected for SBr3+ are observed, and as expected,6,18they are a t higher frequencies than the corresponding bands for the isoelectronic molecule PBr3 except for v l (SBr,’) which is not significantly different fromv, (PBr,). The peaks designated v ( X ) in Table I were observed in solution spectra and varied in intensity from sample to sample. The most intense was observed for (SBr,)+(AsF,)- made in situ in arsenic trifluoride and (SBr3)+(SbF6)-in dilute sulfur dioxide or arsenic trifluoride solution with the 5 145-A (green) exciting wavelength. The intensity decreased, and the peak
Contribution f r o m t h e Chemistry Department, University of Tasmania, H o b a r t , Tasmania, 7001, Australia
Polarized Crystal Electronic Spectrum of Bis(ethy1ammonium) Tetrachlorocuprate(I1) and an Application of the Angular Overlap Model to the Bonding in Chlorocuprate Complexes Michael A. H i t c h m a n * a n d Peter J. Cassidy Receiced October 24, I977
The chlorocuprates exhibit a wide variety of stereochemistries and it is probably for this reason that they have often
0020-1669/78/ 1317-1682$01 .OO/O @ 1978 American Chemical Society
Inorganic Chemistry, Vol. 17, No. 6, 1978 1683
Notes
Table I. Spectral Transition Energies Calculated by a Least-Squares Procedure for Various Chlorocuprate Complexes Using the Angular Overlap Modela Bond Energies, cm-' X lo-' lengths, Comad Tvveb A Ref Transit ion Calcd Calcdf Obsd 2.30 2.39 2.24' 2.22d
11
8.25 10.23 5.97 6.59 7.83 9.70 6.97 9.72 13.38 10.68 8.07 14.60 11.10 10.5 3 14.43 11.01 10.72 15.17 15.65 11.45 12.91
18
2.256e
19
2.32 2.78
20
(EtNH,),CuCl,
TO
2.29 3.04
5
(n-PrNH& ,CuCl,
TO
2.281 2.975
6
(C,H,CH,CH2NH,CH3),CuCl,
P
2.248 2.281
21
7.94 10.31 5.70 6.33 8.19 9.4 1 6.68 9.35 12.98 10.90 7.48 14.15 11.46 9.76 13.97 11.33 9.93 14.72 15.09 11.86 11.87e
Ref
8.70 10.80 4.80 5.55 1.90 9.05 5.92 8.85 12.93 10.00 8.30 13.30 12.39 11.13 13.50 12.30 11.30 14.15 14.40 12.50 16.90
22 3
4 23 g
g
2
Complex stereochemistry: TB, trigonal bipyramid: T, distorted tetrahedral; TO, a See text for the "best fit" ligand field parameters. elongated tetragonal octahedral; P, square planar. 'ClCuCl= 131.2'. ClCuCl= 127.1". e ClCuCl= 132.5". f In this calculation the fitting procedure was carried out without including the 2Bl(dX2,y2) + 'Al(dZ2) transition of (C,H,CH2CH2NH2CH3),CuC1,. g Present work. been used to test the application of bonding models of transition-metal complexes.' The definite assignment of the excited-state energies of typical complexes with each type of geometry is therefore important, and these have been established for the C U C ~ ion ~ ~in- a square-planar2 and a distorted tetrahedral g e ~ m e t r y . ~The , ~ present study reports the polarized crystal spectrum of bis(ethy1ammonium) tetrachlorocuprate [ (EtNH3)2CuC14], which contains planar C U C ~ groups ~ ~ - linked by long axial bonds to produce a centrosymmetric, distorted octahedral coordination geometry.5 The low-temperature mull spectrum of bis(n-propylammonium) tetrachlorocuprate(I1) [(a-PrNH3)2CuC14],which has a similar ligand arrangement about the Cu2+ ion6, is also reported. Experimental Section The complexes were prepared by the method of Remy and Laves' and had satisfactory analyses. (EtNH3)*CuCI4belongs to the orthorhombic space groupPbca and crystallized as thick plates with the (100) face best developed. The crystal structure is such5 that when the electric vector lies in the (100) plane the electronic spectrum is essentially an average of the xy and z molecular spectra (with z defined parallel to the long Cu-C1 bond directions). A section containing the (001) plane was therefore obtained by grinding, and the spectrum was measured at 8 K with the electric vector of light along the a and b crystal axes using a Cary 17 spectrometer (Figure 1) and an Oxford Instruments cryostat. The a spectrum corresponds to the pure xy molecular spectrum, while the b spectrum corresponds to the proportions 0.53(xy) + 0.47 (2); the pure z spectrum was readily obtained by subtracting out the xy component and normalizing to a unit projection of the electric vector along z. Discussion and Comparison with Other Compounds The spectrum consists of three peaks, the central one being almost absent in z polarization. The ligand arrangement approximates closely to D4* ~ y m r n e t r y ,and ~ the only electric dipole transition forbidden by vibronic selection rules for a copper(I1) complex belonging to this point group is 2Bl,(dd-9) 2B2,(d,) in z polarization. The peak a t 12 390 cm-' may therefore be assigned as this transition and, as virtually all bonding models require a higher energy for the transition 'BIg(dxz-,,z) ZEg(dxzyz), this may be assigned to the band at 13 300 cm-', leaving the peak at 11 130 cm-' as 2Blg(d,z-,,z)
-
-
I
10
I
I
12
I
I
I
Figure 1. Electronic spectra at 8 K of the (001) crystal face of (EtNHJ2CuC14with the electric vector parallel to the a and b crystal
axes. The a spectrum corresponds to the xy molecular spectrum, while the b spectrum corresponds to 0.53(xy) + 0.47(z); the "pure" z spectrum is also shown, as is the mull spectrum of ( r ~ - P r N H ~ ) ~ c u C l ~ measured at 77 K.
-
2Alg(d,2). This overall assignment agrees with that generally assumed for tetragonally distorted octahedral copper chloride complexes,' and with the E P R parameters of (EtNH3)2CuC14and related complexes.',2 It is interesting to note that except for the 2Blg 2A,, transition, the z spectrum of (EtNH3)2CuC14is somewhat more intense than the xy spectrum. This is in contrast to planar CuC142-2and most other tetragonally distorted copper(I1) complexes.* Presumably in (EtNH3)2CuC14the presence of axial ligands is somehow instrumental in inducing intensity into the z spectrum. The spectrum of (n-PrNH3)2CuC14(Figure 1) measured as a mull at 77 K closely resembles the b spectrum of (EtNH3)2CuC14, and the three bands may be assigned in analogous manner (see Table I). It is interesting to compare the d-orbital energies in the tetragonal octahedral chromophores with those in chloro-
-
1684 Inorganic Chemistry, Vol. 17, No. 6, 1978
Notes
cuprates having other geometries and to see how well these orbital in the ground-state wave function of planar CuCld2-. may be rationalized for the series of complexes using simple While this has not been confirmed directly for the copper(I1) bonding models. Several attempts have been made to apply complex, EPR spectral measurements of the isotropic hyperfine crystal field theory to the chlorocuprates, but more sophisconstants of low-spin planar cobalt(I1) complexes with Alg(dzz) ticated calculations suggest that such a model is quite unground states suggest molecular orbital coefficients of realistic.’ Perhaps the best simple bonding model currently 0.15-0.25 for the 4s orbital in these complexes alsoI5 and that available for metal complexes is the angular overlap model the participation of this orbital in the ground state decreases ( A O M ) of Jorgensen and S ~ h a f f e r This . ~ has recently been on axial ligation.15J6 It would, thus, seem that while the AOM successfully applied to the interpretation of the spectral is adequate to describe the bonding in metal complexes having properties of a variety of metal The A O M significant ligand interactions along each of the Cartesian suggests that the energy e by which a metal d orbital is raised molecular axes, in the case of planar compounds it is necessary to include the metal 4s orbital in the bonding scheme. upon interaction with a ligand orbital is given by e = S2K, where S is the diatomic overlap integral and K is a constant. Acknowledgment. The receipt of a grant from the AusThe total energy of each orbital is obtained by summing the tralian Research Grants Commission is gratefully acknowleffects of all the ligand orbitals using the angular overlap edged. matrix appropriate to the geometry of the complex. Both u Registry No. [(EtNHJ2CuCI4],55940-27-7; [(n-PrNH,)PCuC14], and T effects are included, and as the Cu (3d) and C1 (3p) 55940-28-8. overlap integrals have been reported as a function of Cu-C1 References and Notes bond lengthI2 the AOM allows the d-orbital energies of a whole For a recent discussion of these calculations and other aspects of series of complexes of different geometries to be expressed as chlorocuprate chemistry see D. W. Smith, Coord. Chem. Reu., 21, 93 a function of just two parameters, K , and K,. In its simplest ( 1976). P. Cassidy and M. A. Hitchman, J . Chem. Soc., Chem. Commun., 837 form, the A O M predicts that for a spherical ligand such as (1975); Inorg. Chem., 16, 1568 (1977). C1- the condition K , = K , should be satisfied. In practice, it J. Ferguson, J . Chem. Phys., 40, 3406 (1964). has been proposed that the model may need to be extended C. Furlani, E. Cervone, F. Calzona, and B. Baldanza. Theor. Chim. Acta, in several ways, e.g., by the inclusion of electrostatic effects 7, 375 (1967). J. P. Steadman and R. D. Willett, Inorg. Chim. Acta, 4, 367 (1970). or ligand-ligand interactions,1° bonding with ligand s orbitals, F. Barendregt and H . Schenck, Physica (C’trecht), 49, 465 (1970). or the admixture of metal s or p orbitals with the d f ~ n c t i o n s . ’ ~ H. Remy and G. Laves, Ber Dtsch. Chem. Ges., 66, 401 (1933). The equations relating the d-orbital energies to K, and K, have B. J. Hathaway and D. E. Billing, Coord. Chem. Rea., 5, 143 (1970). C. Schaffer and C. K. Jgrgensen, Mol. Phys., 9,401 (1965); C. E. Schaffer, been given elsewhere for square-planar, tetragonal-octahedral, Struct. Bonding (Berlin),5,85 (1968); C. K. Jgrgensen, “Modern Aspects distorted tetrahedral, and trigonal-bipyramidal ligand coorof Ligand Field Theory”, North-Holland Publishing Co., Amsterdam, d i n a t i ~ n . ~These ~ , ’ ~ were used to fit the electronic transition 1970. D. W. Smith, Struct. Bonding (Berlin), 12, 49 (1972), and references energies observed a t low temperature for 7 copper(I1) comtherein. plexes of accurately known molecular geometry including all M. A. Hitchman, Inorg. Chem., 11, 2387 (1972); 13,2218 (1974); M. these stereochemistries by a least-squares technique, and the A. Hitchman and T. D. Waite, Inorg. Chem., 15, 2150 (1976). D. W. Smith, J . Chem. Sot. A , 1498 (1970). results are shown in Table I. Except for the transition ’B,D. W . Smith, Inorg. Chim. Acta, 22, 107 (1977). (dX2~y2) 2A1(d,2) in planar CuC14’- the calculated and P. Ros and G. C. A. Schmit, Theor. Chim. Acta, 4, 1 (1966). observed energies agree quite well, the “best fit” ligand field A. Rochienbauer, E. Budb-Zikonyi, and L. J. Sinlndi, J . Chem. Soc., Dalton Trans., 1729 (1975); P. Fantucci and V. Valenti, J . A m . Chem. parameters being K , = 1.01 X lo6 and K, = 1.21 X lo6 cm-l. Soc., 98, 3832 (1976). Removal of this transition from the calculations gave “best B. R. McGarvey, Can. J . Chem., 32, 2498 (1975). fit” parameters K , = 0.94 X lo6 and K, = 0.93 X lo6 cm-l K. N . Raymond, D. W . Meek, and J. A . Ibers, Inorg. Chem., 7, 1111 with the only discrepancies greater than 1000 cm-’ occurring (1968). J. A. McGinnety, J . Am. Chem. Soc., 94, 8406 (1972). for the zBlg(dx2Ly2) 2Alg(d,2) transitions of the tetragoN.Bonamies, G. Dessy, and A. Vaciago, Theor. Chim.Acta, 7,367 (1967). nal-octahedral chromophores in (EtNH,),CuCI, and (nA. W. Schuetler, R. A. Jacobson, and R. E. Rundle, Inorg. Chem., 5, PrNH,),CuCI4. Considering the wide range of stereo277 (1966). R. L. Harlow, W. J. Wells, G . W. Watt, and S. H . Simonsen, Inorg. chemistries covered, the agreement between the calculated and Chem., 13, 2106 (1974). observed transition energies is remarkably good. Moreover, G . C. Allen and N. S. Hush, Inorg. Chem., 6, 4 (1967). in agreement with the simple model K , K,. Participation R . Laiko, M . Natarajan, and M. Kaira. Phys. Status Solidi A , 15, 31 1 (1973). of ligand s orbitals in the bonding or the presence of ligand-ligand interactions should cause K , to differ from K,, as well as produce systematic discrepancies in the spectral fits of complexes with differing stereocherni~tries.~~~’~ However, the ZBlg(d+$) 2A1,(d,2) transition energy in planar C U C ~ ~ ~ is underestimated by -5000 cm-’. Smith has recently Contribution from the Istituto di Chimica Generale, proposed13that in this complex the alg(dr2)orbital is lowered Universitg di Pisa, 56100 Pisa, Italy in energy by configuration interaction with the a1,(4s) orbital. In D4hsymmetry these two orbitals are mixed by an amount Synthesis, Properties, and X-Ray Structure of dependent on the difference in ligand interaction along the x (Diethylenetriamine)copper( I) Carbonyl: a Highly and z axes. Because the 4s orbital is so diffuse, its interaction Thermally Stable Copper(I) Amine Carbonyl with the ligand orbitals is large even a t the long axial bond lengths in the tetragonally distorted octahedral ~ o m p l e x e s , ’ ~ Marco Pasquali, Fabio Marchetti, and Carlo Floriani” and it is only in the rigorously planar C U C ~ ion ~ ~that - the Received August 3, 1977 alg(dz2)orbital is lowered drastically in energy. The overall spectral fit (see Table I) suggests a depression of -5000 cm-’ Notwithstanding that copper(1) amine carbonyl chemistry in planar CuC142-, -1400 cm-’ in (EtNH&CuCI4 and (nis one of the oldest areas of carbonyl chemistry,’,’ no thermally PrNH3)2CuC14 (axial bond lengths -3 A), and -800 cm-’ stable solution or solid-state copper(1)-amine carbonyl in CsCuCI3 (axial bond lengths 2.78 A). Assuming an energy complexes have been isolated until r e ~ e n t l y .The ~ stabilization of 150 000 cm-’ for the 4s orbital,I4 simple perturbation of the Cu-CO bond was variously ascribed to the electronic theory suggests a molecular orbital coefficient of -0.2 for this effect of the ancillary ligands around Cu(1) and/or to the
-
-
-
-
0020-1669/78/13 17-1684$01 .OO/O
0 1978 American Chemical Society
