- Email: [email protected]
Chemistry of the metal carbonyls
371
PRELIMIX_%RY SOTES
absorbs at 243 rnp [e = 1x,150!. Replacing meth_vl groups with chlorine atoms has little effect on the ultraviolet spectra (Table 3). The only other group which has so far been found to be effective in altering the band position is the vinyi group. Thus, r.z&divinyItetramethyIdisilane and I~~vinyloctametltetrasilane possess ultraviolet spectra with maximum absorption at 225 and 243-5 rnp, respectively. From the foregoing discussion it can be seen that the unique spectral properties of poiysilanes are due to the silicon+ilicon bond acting as a chromophore, probably through the use of vacant d-orbitals of the silicon atom. Substituents such as phenyl and vinyl with their _z-electron systems are apparently able to be conjugated with polysilane chains through suitable overlap of d- and z-orbitals. The authors wish to espress their sincere gratitude to Professor X I
of Chemistry,
_imcs, lo-da
lo-sa
Statz
C&z*ersify.
HESRS GILXAX \I-ILLIAM H. _~-AVELL
(U.S.A.)
GERALD I ID.S. HMXE AXD R. H. PRISCE. 2 H. GILX~S, \\-_ H. AI-WELL ASD 3 I<.\\-.HAUSSER. R. KUHS ASD _i 11. IIADA 5 H. H. JAFFE
L.SCHWEBKE
Proc. Chcm. SOG.. (1961) 3oo_ G. L. SCHWEBKE, Chen:. Id. (London). (1964) A. SW=.I~UL~. 2. Phm_ Chem.. Bzg (1935) 354.
ASD 11. ISHIKAI\-A, J. Or~anonzefat. Ck?m. .ISD IL. ORCHIS;. Theo?? acd =Ipplicalions
1063.
I (1964) 153_ of ~ltraziolet Spectroscopy,
\Viiey,
Sew
York, 1962
Receiv-ed JuI>- 29th. 1964
Chemistry XXVII.
of the metal
carbonyls
The infrared spectra of organomanganese organorhenium pentacarbonyls *
and
Recent interest in CO stretching modes in manganeseeJ. technetium3 and rhenium3 pentacarbonyls prompts us to report observations which appear to confirm a theoretical prediction”. Complexes of subgroup seven metals of t_vpeLM(CO), should show three CO fundanrental infrared bands, classified as two A r and one E stretching modes The generaht- of this deduction has been confirmed esperimentall~~~6, but it has been pointed out” that in addition to the normal frequencies, splitting of the intense E transition and appearance of a low intensity B, transition might be observed in the complexes if the @-and-metal group lacks axial symmetry. Xany manganese and rhenium complexes LM(CO), (where L is an asymmetric fluorocarbon group) have been prepared’. We are currently measuring their infrared spectra under conditions of high resolution. When the organic group in the manganese pentacarbonyls is not atiall\- symmetric. spectra in which the E band is split, such *
For
Pzrt XXVI
ofthls series. see ref.I. J. Orgarrometa!. Chem.. 2 (1964) 371-372
37”
PRELIMIS_XRl’
SOTES
as the one shown in the fig. I(a) have been observed. The magnitude of the splitting of the E band varies. As expected. manganese pentacarbonvk show the effect more stror@y than the rhenium pentacarbon-ls -+othat in the latter it is sometimes not _xen Tig_ r(b):_ Complexes which show- a splitting of the E absorption and, in agreement with theoryg sinmitaneous appearance of the 23, mode io their infrared spectra
[cl-cIoh,i-sar?e solutioni inclcde: HCCI,CF,l\IniCOj, IG cm-l), HCCI,CF,Rc(CO!5 i~-cm-~!, C,F,COMnJCO& (’ cm-‘) and C,F,COJInlCOj, (13 cm-l]. The eticct is not condition; with more symmetrical compounds 1il-x obserx--ed under similar CH,(CFI_;:4Re{CO),,
C6H3Mn(CO~~3, or CHzCF,CF,Jin(CO~,. In the gns-rilrnsz spectrum howe\-er, an E band splittin, * of 2 cm-l is jusz detectable.
of CH,CF,CF,MniCO~)s, 11-e zxc indebted
to the donors of the Petroleum
Research
Fund,
administered
b>
the _-Jmerican Chemical Society, for a grant for the support of this work. \\‘e thank the Dep-tment of ScieAk and Industs% Research for the award of a studentship to J.IS.X1-_, and Dr. E. \V. _bEi for helpful discussions.
PRELIMIX_%RY SOTES
absorbs at 243 rnp [e = 1x,150!. Replacing meth_vl groups with chlorine atoms has little effect on the ultraviolet spectra (Table 3). The only other group which has so far been found to be effective in altering the band position is the vinyi group. Thus, r.z&divinyItetramethyIdisilane and I~~vinyloctametltetrasilane possess ultraviolet spectra with maximum absorption at 225 and 243-5 rnp, respectively. From the foregoing discussion it can be seen that the unique spectral properties of poiysilanes are due to the silicon+ilicon bond acting as a chromophore, probably through the use of vacant d-orbitals of the silicon atom. Substituents such as phenyl and vinyl with their _z-electron systems are apparently able to be conjugated with polysilane chains through suitable overlap of d- and z-orbitals. The authors wish to espress their sincere gratitude to Professor X I
of Chemistry,
_imcs, lo-da
lo-sa
Statz
C&z*ersify.
HESRS GILXAX \I-ILLIAM H. _~-AVELL
(U.S.A.)
GERALD I ID.S. HMXE AXD R. H. PRISCE. 2 H. GILX~S, \\-_ H. AI-WELL ASD 3 I<.\\-.HAUSSER. R. KUHS ASD _i 11. I
L.SCHWEBKE
Proc. Chcm. SOG.. (1961) 3oo_ G. L. SCHWEBKE, Chen:. Id. (London). (1964) A. SW=.I~UL~. 2. Phm_ Chem.. Bzg (1935) 354.
ASD 11. ISHIKAI\-A, J. Or~anonzefat. Ck?m. .ISD IL. ORCHIS;. Theo?? acd =Ipplicalions
1063.
I (1964) 153_ of ~ltraziolet Spectroscopy,
\Viiey,
Sew
York, 1962
Receiv-ed JuI>- 29th. 1964
Chemistry XXVII.
of the metal
carbonyls
The infrared spectra of organomanganese organorhenium pentacarbonyls *
and
Recent interest in CO stretching modes in manganeseeJ. technetium3 and rhenium3 pentacarbonyls prompts us to report observations which appear to confirm a theoretical prediction”. Complexes of subgroup seven metals of t_vpeLM(CO), should show three CO fundanrental infrared bands, classified as two A r and one E stretching modes The generaht- of this deduction has been confirmed esperimentall~~~6, but it has been pointed out” that in addition to the normal frequencies, splitting of the intense E transition and appearance of a low intensity B, transition might be observed in the complexes if the @-and-metal group lacks axial symmetry. Xany manganese and rhenium complexes LM(CO), (where L is an asymmetric fluorocarbon group) have been prepared’. We are currently measuring their infrared spectra under conditions of high resolution. When the organic group in the manganese pentacarbonyls is not atiall\- symmetric. spectra in which the E band is split, such *
For
Pzrt XXVI
ofthls series. see ref.I. J. Orgarrometa!. Chem.. 2 (1964) 371-372
37”
PRELIMIS_XRl’
SOTES
as the one shown in the fig. I(a) have been observed. The magnitude of the splitting of the E band varies. As expected. manganese pentacarbonvk show the effect more stror@y than the rhenium pentacarbon-ls -+othat in the latter it is sometimes not _xen Tig_ r(b):_ Complexes which show- a splitting of the E absorption and, in agreement with theoryg sinmitaneous appearance of the 23, mode io their infrared spectra
[cl-cIoh,i-sar?e solutioni inclcde: HCCI,CF,l\IniCOj, IG cm-l), HCCI,CF,Rc(CO!5 i~-cm-~!, C,F,COMnJCO& (’ cm-‘) and C,F,COJInlCOj, (13 cm-l]. The eticct is not condition; with more symmetrical compounds 1il-x obserx--ed under similar CH,(CFI_;:4Re{CO),,
C6H3Mn(CO~~3, or CHzCF,CF,Jin(CO~,. In the gns-rilrnsz spectrum howe\-er, an E band splittin, * of 2 cm-l is jusz detectable.
of CH,CF,CF,MniCO~)s, 11-e zxc indebted
to the donors of the Petroleum
Research
Fund,
administered
b>
the _-Jmerican Chemical Society, for a grant for the support of this work. \\‘e thank the Dep-tment of ScieAk and Industs% Research for the award of a studentship to J.IS.X1-_, and Dr. E. \V. _bEi for helpful discussions.