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The raman spectra of ruthenocene
Volume 6. number 5
CHEMlCAL PHYSICS LETTERS
THE
RAMAN
SPECTRA
OF
1 September1970
RUTEENOCENE
J. BODENHEIMER Microwave Division, Department of Physics, The Hebrew Universily, Jerusalem, Israel
Received 6 July 1970
man spectra of ruthenocene single crystals are presented. Assignment in terms of the molecular normal modes is given.
The ruthenocene molecule (C585)2Ru has a
sandwich structure similar to that of ferrocene. The molecule has 21 x 3 - 6 = 5’7 vibrational degrees of freedom, which give rise to 34 modes, of which 15 are Raman-active. Ruthenocene c stallizes in the orthorhombic space group % with four molecules per unit cell [l]. The Dab, cyclopentadienyl rings lie in an eclipsed configuration, so that the local symmetry of the molecule is D5h, rather than D5d in ferrocene. Unlike ferrocene, no phase transition has so far been reported in ruthenocene. Vibrational spectra of ruthenocene in solution have been studied by Lippincott +d Nelson i2], and assignments have been given No crystal Raman spectra have been reported. In the crystal one expects 228 modes from the intra-molecular vibrations, of which 114 are Raman-active: each non-degenerate vibration in the molecule gives rise to two Raman-active vibrations in the crystal, whereas each degenerate vibration gives four Raman-active vibrations. This includes a!so those modes which are inactive in the Dsh symmetry *. Thus ruthenocene crystal Raman spectra are useful in testing assignments, since the inactive molecular normal vibrations may be expected to show up in the crystal Raman spectrum. Single crystals were grown from solution in tolueue at room temperature. Crystals of suitable dimensions were.obtained without difficulty. Spectra were taken at room temperature and at 80’9, with a HeNe laser (6328A) as well as an Argon ion laser (5145A and 488OA). The accuracy of the measured frequencies is better than _, f 2 cm-l. * A d&&d
The results are given in table I. The frequencies observed by Lippincott and Nelson, in Raman and infrared, are fisted in the first and second columns respectively. The assignment in the third column is in general an extension of that given by those authors for their observed lines tn solutions, corrected for D5h symmetry, except for the line at 1353 cm-1 which we have assigned to CC stretching. Lippincott and NeIson assign this line as a combination, and the CC stretching mode is assigned by them to a Itne at 1560 cm-l, which has not been observed in ruthenocene by them or by us. The last column gives the experimental results of our present study. It is obv-iaus that one observes many more lines and detailed structure in the particular assignments, as expected for single crystals. The frequencies Ifsted are those measured at 80°K. The temperature shifts are mostly negligible; the main effect in reducing the temperature is in the line narrowing, thus improving resolution of this complex spectrum. A notable exception is the ring-metal-ring deformation at 130 cm -1. This frequency appears to shift at room temperatures to 111.5 cm-l. The explanation for thts effect must be sought in the nature of the vibration. Several weak bands near 2740 cm-1 have been observed at room temperature only, and are assigned to difierence bands. Studies on mixed crystals of ferrocene-ruthenocene are in progress. The advice and assistance of Professor W. Low, and the technical assistance of Mr. A. Gabay knci Mr. L Wagner, are gratefully acknowiedged.
analysis will be published.
519
--V6lqme 6, nuinber 5:: ,_-‘. ‘.
CHE$IICAT; PHYaCS :
-. .
,_
-402
._(I . ~2 mpg-m+zL-ring
’
‘:
Raman in crystals (SOOK) (Present work)
Moleculae dkription
_--
330 cm-1
Ai metal-ring
-.
deform
-i30 cm-l,
stretch
329,
stretch
400.
407
602.
607
E; ring tilt 446
A; metal-ring
528
E; E&
804.
392. 394(T),
Eg ring deform
Ai,
Ai CH deform
(I)
818
835
Ey.
Ei CH deform’ (I)
832,
Ei,
Ei ring deform
896. 909
Ei CR deform (a)
996
1002
Ez,
1056
1050
Eb, Ei CH deform
1360 1412
(I)
806.
1193
1413 1622 1651 1684 1727 1774
(I)
3089
404
841,
996.
1049,
846,
S%(7),
1062.
;003,
1065,
A;), Ah CH deform (11)
1092
A;.
Ai ring breath
1099,
E;.
E; CH d&form (H)
1169(?). 1176(?), 1194, 1203. 1208
E;.
Eg CC stretch
1359,
13$5
Ey, Ei CC stretch
1404,
1407.
868 1012
1068
1101 1184,
1411,
1414
Overtone and combination banda, involving CH modes
’
.-,
Ey, Zi
3104
634.
991;
(I)
2736, 2739, 2746, temperature only
difference bands :
403.
ring tilt
A; + Ai combination
1103
Iarge temp. shift
336
763
_--
1104
1 September 1970
:.
:. 901ut@l $ipncc$ a@ Nelson) -. .i .-
-,
Table 1 spectra of rutbenotiene
Vibrational
Infrared
:
LETTERS
3100
CH stretch
3076,
3083,
3085
E& Es CH stretch
3052,
3098,
31GZ
Ai, A; CH stretch
3104.
3112,
3113
at room
REFERENCES [I] G. L. Hardgrove and D. H. Templeton,
12 (1959) 28.
[2] E.R.Lippincott 10 (1958) 30’7.
and R.D.Nelson,
Acta Cryst.
Spectrochim.Acta
.. : .,: -.
:
‘.
,-.
;
..,
:
’ ,.:
520
. .
_. -
_,
,‘; -_,_
. , - ;:
,.
: _, .,
‘.
CHEMlCAL PHYSICS LETTERS
THE
RAMAN
SPECTRA
OF
1 September1970
RUTEENOCENE
J. BODENHEIMER Microwave Division, Department of Physics, The Hebrew Universily, Jerusalem, Israel
Received 6 July 1970
man spectra of ruthenocene single crystals are presented. Assignment in terms of the molecular normal modes is given.
The ruthenocene molecule (C585)2Ru has a
sandwich structure similar to that of ferrocene. The molecule has 21 x 3 - 6 = 5’7 vibrational degrees of freedom, which give rise to 34 modes, of which 15 are Raman-active. Ruthenocene c stallizes in the orthorhombic space group % with four molecules per unit cell [l]. The Dab, cyclopentadienyl rings lie in an eclipsed configuration, so that the local symmetry of the molecule is D5h, rather than D5d in ferrocene. Unlike ferrocene, no phase transition has so far been reported in ruthenocene. Vibrational spectra of ruthenocene in solution have been studied by Lippincott +d Nelson i2], and assignments have been given No crystal Raman spectra have been reported. In the crystal one expects 228 modes from the intra-molecular vibrations, of which 114 are Raman-active: each non-degenerate vibration in the molecule gives rise to two Raman-active vibrations in the crystal, whereas each degenerate vibration gives four Raman-active vibrations. This includes a!so those modes which are inactive in the Dsh symmetry *. Thus ruthenocene crystal Raman spectra are useful in testing assignments, since the inactive molecular normal vibrations may be expected to show up in the crystal Raman spectrum. Single crystals were grown from solution in tolueue at room temperature. Crystals of suitable dimensions were.obtained without difficulty. Spectra were taken at room temperature and at 80’9, with a HeNe laser (6328A) as well as an Argon ion laser (5145A and 488OA). The accuracy of the measured frequencies is better than _, f 2 cm-l. * A d&&d
The results are given in table I. The frequencies observed by Lippincott and Nelson, in Raman and infrared, are fisted in the first and second columns respectively. The assignment in the third column is in general an extension of that given by those authors for their observed lines tn solutions, corrected for D5h symmetry, except for the line at 1353 cm-1 which we have assigned to CC stretching. Lippincott and NeIson assign this line as a combination, and the CC stretching mode is assigned by them to a Itne at 1560 cm-l, which has not been observed in ruthenocene by them or by us. The last column gives the experimental results of our present study. It is obv-iaus that one observes many more lines and detailed structure in the particular assignments, as expected for single crystals. The frequencies Ifsted are those measured at 80°K. The temperature shifts are mostly negligible; the main effect in reducing the temperature is in the line narrowing, thus improving resolution of this complex spectrum. A notable exception is the ring-metal-ring deformation at 130 cm -1. This frequency appears to shift at room temperatures to 111.5 cm-l. The explanation for thts effect must be sought in the nature of the vibration. Several weak bands near 2740 cm-1 have been observed at room temperature only, and are assigned to difierence bands. Studies on mixed crystals of ferrocene-ruthenocene are in progress. The advice and assistance of Professor W. Low, and the technical assistance of Mr. A. Gabay knci Mr. L Wagner, are gratefully acknowiedged.
analysis will be published.
519
--V6lqme 6, nuinber 5:: ,_-‘. ‘.
CHE$IICAT; PHYaCS :
-. .
,_
-402
._(I . ~2 mpg-m+zL-ring
’
‘:
Raman in crystals (SOOK) (Present work)
Moleculae dkription
_--
330 cm-1
Ai metal-ring
-.
deform
-i30 cm-l,
stretch
329,
stretch
400.
407
602.
607
E; ring tilt 446
A; metal-ring
528
E; E&
804.
392. 394(T),
Eg ring deform
Ai,
Ai CH deform
(I)
818
835
Ey.
Ei CH deform’ (I)
832,
Ei,
Ei ring deform
896. 909
Ei CR deform (a)
996
1002
Ez,
1056
1050
Eb, Ei CH deform
1360 1412
(I)
806.
1193
1413 1622 1651 1684 1727 1774
(I)
3089
404
841,
996.
1049,
846,
S%(7),
1062.
;003,
1065,
A;), Ah CH deform (11)
1092
A;.
Ai ring breath
1099,
E;.
E; CH d&form (H)
1169(?). 1176(?), 1194, 1203. 1208
E;.
Eg CC stretch
1359,
13$5
Ey, Ei CC stretch
1404,
1407.
868 1012
1068
1101 1184,
1411,
1414
Overtone and combination banda, involving CH modes
’
.-,
Ey, Zi
3104
634.
991;
(I)
2736, 2739, 2746, temperature only
difference bands :
403.
ring tilt
A; + Ai combination
1103
Iarge temp. shift
336
763
_--
1104
1 September 1970
:.
:. 901ut@l $ipncc$ a@ Nelson) -. .i .-
-,
Table 1 spectra of rutbenotiene
Vibrational
Infrared
:
LETTERS
3100
CH stretch
3076,
3083,
3085
E& Es CH stretch
3052,
3098,
31GZ
Ai, A; CH stretch
3104.
3112,
3113
at room
REFERENCES [I] G. L. Hardgrove and D. H. Templeton,
12 (1959) 28.
[2] E.R.Lippincott 10 (1958) 30’7.
and R.D.Nelson,
Acta Cryst.
Spectrochim.Acta
.. : .,: -.
:
‘.
,-.
;
..,
:
’ ,.:
520
. .
_. -
_,
,‘; -_,_
. , - ;:
,.
: _, .,
‘.