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Mass spectra of vinyltriphenyl derivatives of fourth main-group elements
InternatGnd
3ournal of i%&ss Spectrometry
ad
Ton Physks
J5kevier PubIishing Company, Amsterdam .- Printed in the NetherIands
MASS SPECTRA OF VINYLTRIPHENYL MAIN-GROUP ELEMENTS
P. N. PRESTON,
P. 3. FUCE AND
DERIVATIVES
303
OF Ff)URTH
N. A. WEIR
DqwtmeJd of Chemist~_v_ Seriot- Wurt
Urticxr.sitys IGiinL!wghtJicotland)
(ReceivedJuneMI, 1968)
Electron-impact induced fragmentation of organometallic compounds of fourth main-group elements has received considerable attention’-4, but little has been reportedS-’ on the spectra of compounds containing functional groups attached to the metal atom; Djerassi et aI.’ have investigated the mass spectra of trimethylsilyl-ethers, -am&s. and -sulphides. Recently we noted’ sign&ant d%‘erences between t%e mass spectra of tetraphenyl derivatives of carbon, silicon, and germatium and tentatively sngg&ed that certain fragment ions from tetraphenylsiianedecomposition might be stabilised by “through conjugation” incorporating &-pn effects, a weg authenticatedg~‘o resonance concept in organosiiicon chemistry. Thus in the spectrum of tetraphenylsilane, ions at m/e 286,208 and 130 may conceivably contain silicon attached to unsaturated moieties within strur;tures of the type Cr8H15SiCH-CH,~+, C12HL ISiC=CH+, and C,H,SiGCH’ respectivelyThe unusual nature of the bonding in vinyl and alkynyl derivatives of silicon, germanium, and tin as manifested in chemical reactivity9 and spectroscopic properties’ OS13 prompted us to compare the mass spectra of compounds of the type Ph,MCH=CH2, M = C (I), Si (Ii), Ge (III), and Sn (IV). In the fragmentation diagrams (Schemes 1-5) metaxable transitions are denoted by an astetik, and for II-IV figures quoted are m/e values based on the most abundant metal
PhteGHz C227
-hH,
t 12.01
SCHEME
%Ge*
_ph-
P$Ge-+
mo5,20_01
1
(228,
I
-52%
1
PhGe+ (%51,2QO)
--c312 f
Gt?C,Hf n25,
2-9)
3x5)
-
P. N. PRESTON,
P. J. RICE,
N, A,
WEIR
isotope; %orrected” abund.anc& are given as percent ion current of ah metalcontaining ions (for Z&TV), and as percent ion current for I. The spectra of III and TV arc the simpkst, and relate mainly to the reported1s2 fragmentation of Ph_+Zef and Ph,Sn+ reqect.ively_ A noteworthy aspect of the spectrum of IE (Scheme 1) is the appearance of ions in which the gernxnium atom reMns the vinyl gr&p; the ion at m[e 178 assigned as PhGeCH=CHz-t arises from_the moleCular ion but the origin of Ph2GeCH=CH2 + at m/e 255 is uncertain_ The important fragmentation reactions of N are shown in Scheme 2.
C3Gl)
lo.4)
l
-
-sH;
__I
Z274.2G.S)
SCHEME
2
PhSn+ (197,
-Ph.
22.2)
f
One interesting fature is formation of the ion at m/e 301 assigned as Ph,SnCH-CHt + which provides a second route to Ph,Snst ; apparently’ ring fragmentation processes of PhsSnt do not occur and the ion at m/e 301 must arise by loss of phenyl radical from the molecular ion, _~hc~/rzjz~
Ph2Si-• ~182,lc3
GH$i*
- Ph. ----,,5::‘,,
*
*
-
+
-Hz l
(257,091
I,-=6H6
t PhSiCgHz (181,129)
J. M4ss S’ctromwy
and Ion Physkr,
SCHEME
1 (1968) 303-308
3
_
%Hdi+ (255.0.4)
WNYLTRIPHENYL
C, Si, Ge AND
OF
DERIVATIVES
Sn
305
The behavionr of II on electron impact is significantly diEem& from III and IV, the most striking aspects being the intense molecular ion and the presence of ions which result fro& ring fragmentation, A large part of the spectrum can be assigned (Scheme 3) on the basis of the reported3 decomposition of Ph,S?. Important features based on decomposition of the molecular ion are as follows (Scheme 4): Fr@ICH=cH~ (209
-Ph‘
a 3.7)
PhJScH=CH;+
Ph2SiCH=CH‘*
-p
(208,
-H2
l
(a3,481
PMiiC6H~
_
-ii-
PhSGH; (180,
081,129)
Ql)
3.9)
~1
f -c&2 SCHEME
1
4
PnSiC,H2 Z-55,
4.
28)
An additional ion appears at m/e 130 (4.0) which might’ be assigned as PhSi-CXH~. The ion at m/e 209 does not arise3 from Ph$i* and must originate from loss of phenyl radical from the molec&r ion; loss of acetylene from this ion produces Ph2SiHC, a process without analogy in the fragmentation of III and IV. The decomposition of I (Scheme 5) is more complicated than II-IV and in many respects is strikingly different from its nearest analogue, II. The molecular ion is of high abundance and decomposes by six routes of which losses of C,H, and C&I,- are important processes. Ions produced by loss of methyl radical involved in the transitions m/e 270 --, 255,243 --+ 228, 193 + 178, and 167 -N 152 involve unusual decomposition modes; the mechanism of some similar processes has recently bren elucidated by Johnstone and MillardI using labelled PhCH,CHClPh, PhCHBrPh and PhCH=CHPh. In marked contrast related transitions, i.e. losses of CH3. or MHz- (M = Si, Ge, or Sn) are absent in the spectra of II-IV. An unusual feature is the formation of tropylium ion at m/e 91 from I but not from II-IV. An attractive route to this ion, as well as to the ion at m/e 179, involves isomer&.&on of the molecular ion to V followed by two subsequent fragmentation modes_ An additional conclusion indicated is that transitions in which hydrogen molecules are eliminated (e.g. for I, m/e 243 --, 241, 241 + 239, 191+ 189, 167 + 165 and for II, 259 + 257, 257 + 255, 183 + 181) are more important for the organic compound than for the orgauometallic analogues; transitions of this type have recently received extensive theoretical treatment by Johnstone and WardIs_ 1,l .l-Triphenylcropene eliminates a styrene molecule in a direct process, supported by the evidence of a metastable ion arising from the transition J. Mass Speclrometryand IOR Physics, 1 (1%8) 303-308
P. N.
PRESTON,
P.
Js RICE,
-PnCfip* l
A_ WEIR
Rt2C=CH ~179,
l
lal)
I
-C,H'
/\ -
PhpP 067,7_6,
Ph /
8
N.
\
CSCH
-
171
I165,17.4
/-\+/ /\ P
1 052.2.5)
-4
089, 331
\
\
(239,
YHEME
5
3.1)
270 --+ 166, Similar mass differences were noted for the other three compounds (II: 286-182; IKI: 332-228; TV: 378-2741, and, aItho11ghcorresponding metastable peaks were not observed, the possible elimination of styrene has been imiicated in Schemes 1,2 and 3. The considerabIe differences in the spectra of I-XV are of some interest; l Je increasing potisabiity of the metal atom coupled with increasing metalcarbon bond dissociation energies in the order IV > III > II are obviously important directive effects, The formation of tropylium ion may be unique to I because of steric inhibition of cyclisation of U-IV which wouid provide analogucs of V; we have initiated Inbelling studies to investigate the mechanism of this transitioti.
VINYLTRIPHENYL
OFXIVATIVES
OF
C, $i+ Ge
AND
Sn
307
I=, II”* IIIf8, and IV19 were either prepared by literature methods or kindly donated to us by J. J. Eisch, J. G. NoItcs and D. Seyferth. Mass spectra were obtained using an A.E.I. MS.9 instrument operating at 70 eV aud an accelerating voltage of 8 kV with the ionisation chamber at 20°; sampIes were intro_ duced using a direct insertion probe.
ACKNOWLEDGEMENT
We thank Micirand Silicones Ltd. for a gift of organosilicon compounds.
The electron-impact
induced frsgmentation
carbon, silicon, gemxmium,
of vinyltriphenyl
derivatives of
and tin has been studied at 70 eV under high resolu-
tion. The fiagmentztion modes of the gersn~nium and tin compounds are assigned mainly on the basis of the knowvn’p2decomposition of Ph3Ge+ and Ph$n*, respectively. The behaviour of vinyltriphenylskne on electron impact is nearer to the organic member of the series than to the organometak members. Unique features in the series are the observatioc of tropylium ion in the spectrum of 1,1,1--triphenylpropene, and transitions in the spectrum of the ratter in which methyl radicak are eliminated; a possible mechanism of fxmation of tropylium ion is suggested. .
REFERENCES
1 D. B. CHAMBERS, F. GLOCKLING AND M. WESTON, J. Chem. Sot. (A), (1967) 1759. 2 F. GLOCKLING XND J. R. C. LIGHT, J. C&m. Sot. (A), (1968) 717. AND F. GLOCKLIXG, J. Chem. Sot. (A), (19683 735. 3 D. B. C4 A. M. D-, C. D-, P. MAZEROLIES, 3. DUBEC AND G. Mruurru, f. Organomeial. Chem., 12 (1968) 123. 5 J. D-. J. B. --hiOMSON AND C. D-, J. Org. Ckm., 32 (1967) 3904. 6 W. DA VIDSOHNANE, M. C. HENRY, 3. Organometal. Chem., 5 (1966) 29. mu M. D. ? R. A. =!m’-rxn, A. A. POLY~OYA~ A. A. l’nzov, F. A. MmST~MC~VK, Zh. 01&h. Khim., 35 (1965) 773, C. A., 63 (1965) 681la. 8 P. N. pREsr0~ AND N. A. Wfznt, Inorg. Nucl. Chem. Letters, 4 (1968) 279.* 9 D.S MERM, G. S~~GEZAVD R. Suz~, Organosificon Chemistry, International Sympos+mt, Prague* ip6.5, Butterworths, London. p-159. 10 v. CHvArovs?zY, &;a, p. 231.
l
The ion at m/e 147 discussed in this note has now barn sham to be due to impurity. J. Mass Specrro~
-.
and I+n Physks, 1 (1968) 303-308
.
308 II 12 13 14 15 16 17 18 19
P.
N.
PRESTON,
P. J. RICE,
N.
A.
WEIR
D. 1 BLEW, S. S. DAHYLVK AND S. CAWLEY, II 0~gmwmetaL Chem., 6 (1966) 284. D. SEXFERTU AXD L. G. VAUGIMN, L Oq&mmrcruL Client., I (1963) 138 C S. m 15~~ M.. L LQSFJZ,J_ O~gaszwnezat_ Chem_. 10 (1967) 427. R k w. 30~~ AND B. J. F&n, 2. Nurfbrdt., 21 (1966) 604. R. A. We Jo HSSIVNE, private communi~on; CT. R. A_ W_ JOHXST~XE AND S. D- WARD. J. Ckem sac. (A), (1963) in press. F. 3. F%IEL mm W. G- BRO’WN, J. Am Chem. SOC. 75 (1953) 502% 3.3. EE.QX AXD J. T. T~USMXZ, L Org. Client.. 28 (1963) 487. M. C HENRY AND _i_ G_ NOLZIX%,L Am. Chem. Sot_, 82 (1960) 555. D. %YFsRTU AND F. G. A. STOFZ, .L Am. Chenr. Sot-. 79 (1957) 515.
J. MQSS Specrrometr~ and Ion Phyjics.
I (1968) 303-308
3ournal of i%&ss Spectrometry
ad
Ton Physks
J5kevier PubIishing Company, Amsterdam .- Printed in the NetherIands
MASS SPECTRA OF VINYLTRIPHENYL MAIN-GROUP ELEMENTS
P. N. PRESTON,
P. 3. FUCE AND
DERIVATIVES
303
OF Ff)URTH
N. A. WEIR
DqwtmeJd of Chemist~_v_ Seriot- Wurt
Urticxr.sitys IGiinL!wghtJicotland)
(ReceivedJuneMI, 1968)
Electron-impact induced fragmentation of organometallic compounds of fourth main-group elements has received considerable attention’-4, but little has been reportedS-’ on the spectra of compounds containing functional groups attached to the metal atom; Djerassi et aI.’ have investigated the mass spectra of trimethylsilyl-ethers, -am&s. and -sulphides. Recently we noted’ sign&ant d%‘erences between t%e mass spectra of tetraphenyl derivatives of carbon, silicon, and germatium and tentatively sngg&ed that certain fragment ions from tetraphenylsiianedecomposition might be stabilised by “through conjugation” incorporating &-pn effects, a weg authenticatedg~‘o resonance concept in organosiiicon chemistry. Thus in the spectrum of tetraphenylsilane, ions at m/e 286,208 and 130 may conceivably contain silicon attached to unsaturated moieties within strur;tures of the type Cr8H15SiCH-CH,~+, C12HL ISiC=CH+, and C,H,SiGCH’ respectivelyThe unusual nature of the bonding in vinyl and alkynyl derivatives of silicon, germanium, and tin as manifested in chemical reactivity9 and spectroscopic properties’ OS13 prompted us to compare the mass spectra of compounds of the type Ph,MCH=CH2, M = C (I), Si (Ii), Ge (III), and Sn (IV). In the fragmentation diagrams (Schemes 1-5) metaxable transitions are denoted by an astetik, and for II-IV figures quoted are m/e values based on the most abundant metal
PhteGHz C227
-hH,
t 12.01
SCHEME
%Ge*
_ph-
P$Ge-+
mo5,20_01
1
(228,
I
-52%
1
PhGe+ (%51,2QO)
--c312 f
Gt?C,Hf n25,
2-9)
3x5)
-
P. N. PRESTON,
P. J. RICE,
N, A,
WEIR
isotope; %orrected” abund.anc& are given as percent ion current of ah metalcontaining ions (for Z&TV), and as percent ion current for I. The spectra of III and TV arc the simpkst, and relate mainly to the reported1s2 fragmentation of Ph_+Zef and Ph,Sn+ reqect.ively_ A noteworthy aspect of the spectrum of IE (Scheme 1) is the appearance of ions in which the gernxnium atom reMns the vinyl gr&p; the ion at m[e 178 assigned as PhGeCH=CHz-t arises from_the moleCular ion but the origin of Ph2GeCH=CH2 + at m/e 255 is uncertain_ The important fragmentation reactions of N are shown in Scheme 2.
C3Gl)
lo.4)
l
-
-sH;
__I
Z274.2G.S)
SCHEME
2
PhSn+ (197,
-Ph.
22.2)
f
One interesting fature is formation of the ion at m/e 301 assigned as Ph,SnCH-CHt + which provides a second route to Ph,Snst ; apparently’ ring fragmentation processes of PhsSnt do not occur and the ion at m/e 301 must arise by loss of phenyl radical from the molecular ion, _~hc~/rzjz~
Ph2Si-• ~182,lc3
GH$i*
- Ph. ----,,5::‘,,
*
*
-
+
-Hz l
(257,091
I,-=6H6
t PhSiCgHz (181,129)
J. M4ss S’ctromwy
and Ion Physkr,
SCHEME
1 (1968) 303-308
3
_
%Hdi+ (255.0.4)
WNYLTRIPHENYL
C, Si, Ge AND
OF
DERIVATIVES
Sn
305
The behavionr of II on electron impact is significantly diEem& from III and IV, the most striking aspects being the intense molecular ion and the presence of ions which result fro& ring fragmentation, A large part of the spectrum can be assigned (Scheme 3) on the basis of the reported3 decomposition of Ph,S?. Important features based on decomposition of the molecular ion are as follows (Scheme 4): Fr@ICH=cH~ (209
-Ph‘
a 3.7)
PhJScH=CH;+
Ph2SiCH=CH‘*
-p
(208,
-H2
l
(a3,481
PMiiC6H~
_
-ii-
PhSGH; (180,
081,129)
Ql)
3.9)
~1
f -c&2 SCHEME
1
4
PnSiC,H2 Z-55,
4.
28)
An additional ion appears at m/e 130 (4.0) which might’ be assigned as PhSi-CXH~. The ion at m/e 209 does not arise3 from Ph$i* and must originate from loss of phenyl radical from the molec&r ion; loss of acetylene from this ion produces Ph2SiHC, a process without analogy in the fragmentation of III and IV. The decomposition of I (Scheme 5) is more complicated than II-IV and in many respects is strikingly different from its nearest analogue, II. The molecular ion is of high abundance and decomposes by six routes of which losses of C,H, and C&I,- are important processes. Ions produced by loss of methyl radical involved in the transitions m/e 270 --, 255,243 --+ 228, 193 + 178, and 167 -N 152 involve unusual decomposition modes; the mechanism of some similar processes has recently bren elucidated by Johnstone and MillardI using labelled PhCH,CHClPh, PhCHBrPh and PhCH=CHPh. In marked contrast related transitions, i.e. losses of CH3. or MHz- (M = Si, Ge, or Sn) are absent in the spectra of II-IV. An unusual feature is the formation of tropylium ion at m/e 91 from I but not from II-IV. An attractive route to this ion, as well as to the ion at m/e 179, involves isomer&.&on of the molecular ion to V followed by two subsequent fragmentation modes_ An additional conclusion indicated is that transitions in which hydrogen molecules are eliminated (e.g. for I, m/e 243 --, 241, 241 + 239, 191+ 189, 167 + 165 and for II, 259 + 257, 257 + 255, 183 + 181) are more important for the organic compound than for the orgauometallic analogues; transitions of this type have recently received extensive theoretical treatment by Johnstone and WardIs_ 1,l .l-Triphenylcropene eliminates a styrene molecule in a direct process, supported by the evidence of a metastable ion arising from the transition J. Mass Speclrometryand IOR Physics, 1 (1%8) 303-308
P. N.
PRESTON,
P.
Js RICE,
-PnCfip* l
A_ WEIR
Rt2C=CH ~179,
l
lal)
I
-C,H'
/\ -
PhpP 067,7_6,
Ph /
8
N.
\
CSCH
-
171
I165,17.4
/-\+/ /\ P
1 052.2.5)
-4
089, 331
\
\
(239,
YHEME
5
3.1)
270 --+ 166, Similar mass differences were noted for the other three compounds (II: 286-182; IKI: 332-228; TV: 378-2741, and, aItho11ghcorresponding metastable peaks were not observed, the possible elimination of styrene has been imiicated in Schemes 1,2 and 3. The considerabIe differences in the spectra of I-XV are of some interest; l Je increasing potisabiity of the metal atom coupled with increasing metalcarbon bond dissociation energies in the order IV > III > II are obviously important directive effects, The formation of tropylium ion may be unique to I because of steric inhibition of cyclisation of U-IV which wouid provide analogucs of V; we have initiated Inbelling studies to investigate the mechanism of this transitioti.
VINYLTRIPHENYL
OFXIVATIVES
OF
C, $i+ Ge
AND
Sn
307
I=, II”* IIIf8, and IV19 were either prepared by literature methods or kindly donated to us by J. J. Eisch, J. G. NoItcs and D. Seyferth. Mass spectra were obtained using an A.E.I. MS.9 instrument operating at 70 eV aud an accelerating voltage of 8 kV with the ionisation chamber at 20°; sampIes were intro_ duced using a direct insertion probe.
ACKNOWLEDGEMENT
We thank Micirand Silicones Ltd. for a gift of organosilicon compounds.
The electron-impact
induced frsgmentation
carbon, silicon, gemxmium,
of vinyltriphenyl
derivatives of
and tin has been studied at 70 eV under high resolu-
tion. The fiagmentztion modes of the gersn~nium and tin compounds are assigned mainly on the basis of the knowvn’p2decomposition of Ph3Ge+ and Ph$n*, respectively. The behaviour of vinyltriphenylskne on electron impact is nearer to the organic member of the series than to the organometak members. Unique features in the series are the observatioc of tropylium ion in the spectrum of 1,1,1--triphenylpropene, and transitions in the spectrum of the ratter in which methyl radicak are eliminated; a possible mechanism of fxmation of tropylium ion is suggested. .
REFERENCES
1 D. B. CHAMBERS, F. GLOCKLING AND M. WESTON, J. Chem. Sot. (A), (1967) 1759. 2 F. GLOCKLING XND J. R. C. LIGHT, J. C&m. Sot. (A), (1968) 717. AND F. GLOCKLIXG, J. Chem. Sot. (A), (19683 735. 3 D. B. C4 A. M. D-, C. D-, P. MAZEROLIES, 3. DUBEC AND G. Mruurru, f. Organomeial. Chem., 12 (1968) 123. 5 J. D-. J. B. --hiOMSON AND C. D-, J. Org. Ckm., 32 (1967) 3904. 6 W. DA VIDSOHNANE, M. C. HENRY, 3. Organometal. Chem., 5 (1966) 29. mu M. D. ? R. A. =!m’-rxn, A. A. POLY~OYA~ A. A. l’nzov, F. A. MmST~MC~VK, Zh. 01&h. Khim., 35 (1965) 773, C. A., 63 (1965) 681la. 8 P. N. pREsr0~ AND N. A. Wfznt, Inorg. Nucl. Chem. Letters, 4 (1968) 279.* 9 D.S MERM, G. S~~GEZAVD R. Suz~, Organosificon Chemistry, International Sympos+mt, Prague* ip6.5, Butterworths, London. p-159. 10 v. CHvArovs?zY, &;a, p. 231.
l
The ion at m/e 147 discussed in this note has now barn sham to be due to impurity. J. Mass Specrro~
-.
and I+n Physks, 1 (1968) 303-308
.
308 II 12 13 14 15 16 17 18 19
P.
N.
PRESTON,
P. J. RICE,
N.
A.
WEIR
D. 1 BLEW, S. S. DAHYLVK AND S. CAWLEY, II 0~gmwmetaL Chem., 6 (1966) 284. D. SEXFERTU AXD L. G. VAUGIMN, L Oq&mmrcruL Client., I (1963) 138 C S. m 15~~ M.. L LQSFJZ,J_ O~gaszwnezat_ Chem_. 10 (1967) 427. R k w. 30~~ AND B. J. F&n, 2. Nurfbrdt., 21 (1966) 604. R. A. We Jo HSSIVNE, private communi~on; CT. R. A_ W_ JOHXST~XE AND S. D- WARD. J. Ckem sac. (A), (1963) in press. F. 3. F%IEL mm W. G- BRO’WN, J. Am Chem. SOC. 75 (1953) 502% 3.3. EE.QX AXD J. T. T~USMXZ, L Org. Client.. 28 (1963) 487. M. C HENRY AND _i_ G_ NOLZIX%,L Am. Chem. Sot_, 82 (1960) 555. D. %YFsRTU AND F. G. A. STOFZ, .L Am. Chenr. Sot-. 79 (1957) 515.
J. MQSS Specrrometr~ and Ion Phyjics.
I (1968) 303-308