1417
In the case of the tungsten system, an ion, probably [(CH3)2N]2PWNHCH3+,is observed at 14 mass units less than the [(CH3)2N]3PW+ion, suggesting that the first step involves loss of a CH2 fragment. This may be followed by loss of the methyl group to give the ion [(CH3)2N]2PWNH+which is unstable with respect to loss of ammonia by means of the N H group attached to the tungsten atom abstracting two protons from the remaining methyl groups. The net result of these successive losses of methylene, methyl, and ammonia fragments would be loss of 46 mass units and formation of the (CH&NP(CH2NCH2)W+ion (I, M = W). Despite the well-established presence9 of metalphosphorus rather than metal-nitrogen bonds in the metal carbonyl complexes of tris(dimethy1amino)phosphine, some fragments in the mass spectra of these compounds clearly contain metal-nitrogen bonds. These include the ions (CH3)2NCrCH2NCH3+ (Table I), (CH&NCr+ (Table I), (CH3NCH&Fe+ (Tables I11 and IV), (CH&NFe+ (Tables I11 and IV), and CbH5V( C H Z N C H ~ ) N ( C H ~(Table ) ~ + V). In addition the ions of the type [(CH&NI4PM+ (M = Cr, Mo, W, and Fe) observed in the metal carbonyl complexes containing two tris(dimethy1amino)phosphine ligands probably are [(CH3)2N]3PMN(CH3)2+ with one metal-nitrogen bond, since bonding of four dimethylamino groups and a
metal atom to a single phosphorus atom appears unlikely. Such ions containing metal-nitrogen bonds appear to be formed by elimination of the phosphorus as phosphine, PH3, since the metastable ion at m/e 114.6 in the mass spectrum of the tris(dimethy1amino)phosphine complexes of the iron carbonyls corresponds to the reaction
+
[(CH&N]*PHFe+--+ (CH3NCH2),Fe+ PH, mle 176 m/e 142
Substituted phosphines may also be eliminated to form ions with metal-nitrogen bonds as demonstrated by the metastable ion at m/e 92.2 in the mass spectrum of [(CH3)2N]3PFe(CO),corresponding to the reaction [(CH&NI:PFe+ m/e 219
+(CH3NCH2)*Fet+ (CH&NPH? m/e 142
Metastable peaks corresponding to the formation of the other ions believed to contain metal-nitrogen bonds have not been observed. Acknowledgment. I am indebted to the U. S. Air Force Office of Scientific Research for partial support of this work under Grant No. AF-AFOSR-580-66. I am also indebted to Mr. R. E. Rhodes and Mr. J. R. Boa1 for running the mass spectra.
Mass Spectra of Organometallic Compounds. 11. Some Cyclopentadienylmetal Carbonyl Derivatives' R. B. King2 Contribution from the Mellon Institute, Pittsburgh, Pennsylvania, and the Department of Chemistry, University of Georgia, Athens, Georgia. Received July 20, I967 Abstract: Mass spectra of cyclopentadienylmetal carbonyl derivatives exhibit not only stepwise loss of their carbonyl groups but also extrusion of C2H2from the CjH5Mf ions to give C3H3M+ions. Compounds of the type RFe(C0)2C5H5also exhibit ions in their mass spectra arising from ferrocene and substituted ferrocene pyrolysis products. Sufficient metastable ions have been observed in the mass spectra of the iron compounds CH3COFe(C0)*CsH5and CH30COCH2Fe(C0)2C5H6 to establish degradation pathways from'the molecular ion down to the bare metal ion Fe+. The mass spectra of the latter iron compound and of the related molybdenum compound C2H50COCH2Mo(C0)3C5H5 exhibit processes involving fragmentation of ketene (CHCO, mass 42). This molybdenum compound as well as the iron compound CsH5COFe(CO)2C5H5 and the tungsten compound CH2=CHCOW(C0)3C5Hjdo not exhibit the parent ions in their mass spectra. Instead, the highest mass ion in their mass spectra occurs 28 mass units below the expected value for their parent ions, suggesting facile decarbonylation within the mass spectrometer. The mass spectrum of the n-allyl derivative CBH5M~(CO)PCSHj exhibits the carbonyl ions CSH~MO(CO),C~HS+ (n = 1 or 2) but not the carbonyl-free allyl ion C3HSMoChH5+.Instead, the carbonyl-free cyclopropenyl ion C8H3MoC5H5+is observed in high abundance.
A major
portion of the recent synthetic work in transition-metal organometallic chemistry has dealt with cyclopentadienylmetal carbonyl derivatives. However, the mass spectra of relatively few such compounds have been studied. Winters and Kiser3 report (1) For part I of this series, see R. B. King, J . A m . Chem. Soc., 90,1412 (1968). (2) Department of Chemistry, University of Georgia, Athens, G a ; Fellow of the Alfred P. Sloan Foundation, 1967-1969. (3) R. E. Winters and R. W. Kiser, J . OrganometaL Chem. (Amsterdam), 4, 190 (1965).
the mass spectra of the simple mononuclear cyclopentadienylmetal carbonyls of the first transition series CsH3M(CO), (M = V, n = 4; M = Mn, n = 3 , M = Co, n = 2). Schumacher and Taubenest4 describe the mass spectra of a few other cyclopentadienylmetal carbonyls including the binuclear [GH~Mo(C0)312 and [CjH5Fe(C0)2]2; the trinuclear (C5H5)3Ni3(C0)~; and the bromides C6HjFe(C0)2Brand C5HjMo(C0)3Br. (4) E, Schumacher and R. Taubenest, Hele. Chim. Acta, 49. 1447 (1966).
King J Cyclopentadienylmetal Carbonyl Derivatives
1418
11111
Y
I
4
0
..
1
.Id1
..I
50 I
1111.
'
'
~
.. ...
100
'
/
.I1 I. ,,...I,.,
l
i
.I
'
,I.
150 '
C H3OC 0C H2Fe(C0)zC5H5
I. I./. ILI,
,
/
'
'
200 '
I, I
'
/
'
'
250 '
'
l
'
300
'
'
'
~
Figure 1. Mass spectra of four of the compounds discussed in this paper. The ions designated by an asterisk are drawn half their relative heights in order to fit on the scale.
Very recently Bruce5 reported the mass spectra of CaH5CH2Fe(C0)2CbH5 and CeF5CHzFe(CO)K5Hs. This paper discusses mainly the mass spectra of a few representative cyclopentadienylmetal carbonyl derivatives also containing in addition either a-bonded or T bonded organic groups. Experimental Section The mass spectra were run on a standard M S 9 mass spectrometer located at the Mellon Institute. They are reported in Tables I-XII, inclusive. In addition Figure 1 depicts the mass spectra of four representative compounds. The standard conditions used were a 7Gev ionizing potential, 200-230' inlet temperature, resolution of IOOO, and 8-kv accelerating voltage. Samples were introduced directly into the ion source using a metal probe. The relative peak intensities were estimated by measurement of the heights of the peaks on the galvanometer recorder chart with a millimeter rule. Values relative to an arbitrary value of 100 for the i o n CsH5M+ are reported in the tables. The m/e values reported in the tables are for the ions containing the isotopes W, s@Fe,Q@Mo, and/or lSdW.6 The compounds used in this study were prepared by methods already adequately described in the literature.' ( 5 ) M.I. Bruce, Inorg. Nucl. Chem. Leffers,3, 157 (1967). (6) In the cases of ions containing molybdenum or tungsten, the
characteristic multiline patterns containing the ions of the several isotopes of these metals were observed. In the mass spectra of the molybdenum and tungsten compounds, the relative abundances of the ions containing the metals and of the ions not containing the metals are not directly comparable because the total abundance of the ions of a given type containing the multiisotopic metals will be divided over several
Journal of the American Chemical Society J 90:6
In the mass spectra of the iron and vanadium compounds metastable ions were observed. These ions provide excellent corroboratory evidence regarding suggested modes of fragmentation of certain of the observed ions.8 In the cases of CH3COFe(CO)zC5Hs(Figure 2) and CHaOCOCHzFe(CO)zC5Hs (Figure 3), metastable ions were observed corresponding to nearly all of the proposed fragmentation steps from the molecular ion down to the bare metal ion Fe+. ions of relative intensities corresponding to the isotopic abundances whereas the total abundance of ions of a given type containing no multiisotopic metals such a s molybdenum or tungsten will be essentially concentrated in one ion. The relative abundances of the ions containing molybdenum and tungsten cited in the tables are for those containing their most abundant isotopes SUMO and l*'W, respectively. (7) The following references give the preparations of the compounds used in this study: (a) CHaCOFe(CO)zCsHs, R. B. King, J. Am. Chem. SOC.,85, 1918 (1963); (b) CaHsCOFe(CO)zCsH6, C E H S F ~ ( C O ) Z C ~ H ~ , CMHSCH=CHCOF~(CO)ZCSHS, and CHz=CHCOW(CO)aCsHa, R. B. King and M. B. Bisnette, J . Organornefal. Chem. (Amsterdam), 2 , 15 (1964); (c) CH~OCOCHZF~(CO)ZCSHS and CzHsOCOCHzMo(C0)aCsHs, R. B. King, M. B. Bisnette, and A. Fronzaglia, ibid., 5, 341 (1966); (d) Br(CHz)4Mo(CO)aCsHs, R. B. King and M. B. Bisnette, ibid., 7, 311 (1967); (e) CsHsW(CO)aH, T. S. Piper and G. Wilkinson, J . Inorg. Nucl. Chem., 3, 104 (1956); (f) CSHSMO(CO)ZCIHT, R. B. King and M. B. Bisnette, Inorg. Chem., 3,785 (1964); (9) C~HSW(CO)ZC~H~, R.B. King and A. Fronzaglia, ibid., 5, 1837 (1966); (h) CsHsMo(C0)zCHzC6Hs,R. B. King and A. Fronzaglia, J. Am. Chem. SOC.,88, 709 (1966); (i) CaHsMo(CO)zCsHa, M. Cousins and M. L. H. Green, J . Chem. Soc., 889 (1963); !j) CsHsV(CO)d, R. P. M. Werner, A. H. Filbey, and S . A. Manastyrskyl, Inorg. Chem., 3, 298 (1964); (k) CsHsRe(CO)a, E. 0. Fischer, and W. Fellmann, J . Organomeral. Chem. (Amsterdam), 1, 191 (1963). (8) For a further discussion of metastable ions, see H. Budzikiewicz, C. Djerassi, and D. H. Williams, "Interpretation of Mass Spectra of Organic Compounds," Holden-Day, Inc., San Francisco, Calif., 1964, p xiii, and references cited therein.
March 13, 1968
'
1419
CHaCsH4FeC5H5 I
+
(CjH&Fe
mle 220 -CO
CHGH4FeC5H5+
(C5H5)zFe+
i
m* 167.5
CHaFe(CO)zCsHs+
mle 186
m/e 200
-
CH3COFe(C0)2C~Hs+-CHI
-2e-
I
mle 192
I
1
-CrHr m* 7 8 . 1
-CO m* 140
C5H5Fe+
CH3FeCOC5H5+ mle 164
m/e 121
I
-CrHr m* 2 5 . 8
-CO
I
m*113
Fe+
CHsFeC5Hs+
mle 56
mle 136
I
- H Z m* 1 3 2 . 5
CsHsFe(C0)af mle 205
I I
-CO m* 152.7
C&We(CO)r+ mle 177
-CO m* 1 2 5 . 3
CaH5FeCO+ mle 149
1
-CO m* 9 8 . 3
CsH5Fe+ mle 121 -CrHr
I
m*25.8
CaHsFe+
Fe+
mle 134
mle 56
- CsHa m* 2 3 . 4
I
Fe+ mle 56
Figure 2. Fragmentation scheme of CHsCOFe(CO)&5Hs.
CH3OCOCHzFe(CO)zCsH5
COCHzFe(CO)zCsHs+ m/e 219
-2e-
CH~OCOCHZF~(CO)~C~HG+
/
I
mle 250
CsH5Fe(C0)zf mle 177
J
-CO m* 125.5
t
CH30COCH~FeCOC5HS+
m/e 149
mle 222 -CrHr
J
-COlm* 9 8 . 2
m*78.5
C5HsFe+ mle 121
C5H5Fe+ mle 121
CH~OCOCH~FeCbHs+ mle 194
I
-GH,
-CHzCO m* 119.2
Fe+ mle 56
CsHsFeCO+
1
m* 2 5 . 8
Fe+
C5HsFeOCH3+ m/e 152
mle 56
1 1
- H Z m* 148.5
CsH5FeCOH+ m/e 150 -CO m* 9 9 . 2
C5H5FeH+ mle 122
1
-OH6 m* 2 5 . 6
Fef mle 56
Figure 3. Fragmentation scheme of CHaOCOCHzFe(CO)zCsH5.
Discussion A. General Comments. Features observed in previous studies3v4of the mass spectra of cyclopentadienylmetal carbonyl derivatives also were observed in this study. These include particularly the stepwise loss of carbonyl groups and the tendency for extrusion of the elements of acetylene (GH2) from C5HsM+
ions to give the corresponding C3HaM+ ions. The hydrocarbon fragment ions arising from the r-cyclopentadienyl ligand invariably include C5He+, C5H5+, and C3Ha+. The mass spectra of all of the cyclopentadienyliron dicarbonyl derivatives exhibited the ion (CsH5)zFe+. A comparison of the mass spectra of CH3COFe(C0)2CbH5at inlet temperatures of 70 and 200" (see below) King
Cyclopentadienylmetai Carbonyl Derivatives
1420 Table I. Mass Spectrum of CH&ZOFe(C0)2C5H6
Relative intensity a b
Ion 220 205 200 192 186 177 164 149 136 134 121 95 94 93 84 81 71 66 65 56 39
CH3COFe(CO)zC5HS' C&Fe(C0)3+ C5H5FeCsH4CH3+ CH3Fe(C0)2C6H5 + (C5H&Fe CJ%Fe(CO)z+ CH3FeCOC5H5+ C5H5FeCO+ CH3FeC5H5+ C6HeFe+ C5H5Fe+ C3H3Fe+ C3H2Fe+ C3HFe+ FeCO+ CH3Cr,He+ CH3Fe+ C&+ CsH5 Fe+ C3H3+
2 0.8 0.2 36 22 4 29 14 18 52 100 13 6 3 3 6 3 5 3
Table 11. Mass Spectra of CBH~COF~(CO)&H~ and CsHrFe(COXCd-L
9c 2
5
Metastable ions
152.7
Process - 28 220 +192 - 28 205 +177
140
192 +164
132.5
136 ---f - 28 177 ----f - 28 164 ---f - 28 149 ---f - 65 186 ----f
mle
167.5
125.3 113 98.3 78.7
- 28 -2
-1
co co co
134
Hz
149 121
co co co
121
CsH5
136
64.5
66 ----f 65
25.8
121 + 56 - 78 13456
23.4
Neutral fragment lost
- 65
mle
173.5
CsH6
AEI MS-9 mass spectrometer, standard conditions, source pressure 4.7 x 10-6 mm, inlet temperature -200". Japan Electron Optics Laboratory JMS-OlSG mass spectrometer, 75-ev electron energies, inlet temperature 70". c Assignment confirmed by exact mass measurement to three decimal places. a
22 46 148 275 157 93 82 40 237 200 22 18 100 82 14 11 7 14 19 21 14 42 129 37 24 22 24 197 26 37 25 50
23 56 116 226 48 52 32 16 190 120 21 13 100 53 10 6 23 3 16 11 8 15 53 24 8 8 8 97 11 16 8 16
Neutral fragment lost
Ion
Hz
- 28 226 +198 - 26
co
198 +172
CzHz
140
142 +141 - 56 198 +142 - 26 141 --+ 115 - 65 186 +121
H
102 94 76.5 56.6 25.8 (1
198 -+- 196
149.5
78.6
Journal of the American Chemical Society / 90:6
