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Oxidative Addition to a Quadruple Bond. The Complete X-ray Structure of [Mo2Cl8H]3

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of two ester methyl signals (6=3.70 and 3.75 in pyridine,
3.85 and 3.88 in CDCI3) demonstrates the limited rate of
equilibration['!
Yet another equilibrium was indicated by the transformation
of (7) in acetonitrile into orange crystals of C18Hz8N4(24 %
yield), probably the azo-bis(enamine) (1 2). We suspect a dissociation of ( 7 ) , with prototropic shift, into the anion (10)
and the cation ( l l ) , which combines with ( 6 ) , formed in
the other dissociative equilibrium, to give (12). Dimethyl
(7) 2
+
HzC(COzCH3)a
L
(12)
fI1)
malonate could be detected. Such azo-bis(enamines) have been
observed on reaction of dimesyl- and bis(phenylsulfony1)diazomethane with substituted a-m~rpholinostyrenes[~~.
Azo coupling of m-diazo carbonyl compounds with N-( 1-cyclopenteny1)amines can be described in terms of M O perturbation theory by combination of the H O M O and LUMO centers
with the greatest atomic orbital coefficients (cf. ['I ) . According
to the 13C-NMR spectra, C-4 has a somewhat greater charge
density in cyclopentenylamines than in cyclohexenylamines.
It could not be predicted, however, that this would lead to
such drastic differences in reactions with a-diazo carbonyl
compounds: azo coupling in the case of N-(I-cyclopenteny1)and 1,3-dipolar cycloaddition with N-(1 -cyclohexenyl)dialkyIamines.
Mo:'(OzCCH3)4
+ 8 HX + [Mo:IIXgHI3- + 3 H + + 4 CHsCOzH
(1)
This reaction appears to be quantitative when carried out
(a) at temperatures of 60°C and above, and (b) with exclusion
of 02.It had earlierl4' been shown that at 0°C a simple
metathesis takes place according to:
M O Y ( O ~ C C H+~8) HX
~ --* [Mo:IXS]~-+ 4 H
+
+ 4 CHjCOzH
(2)
Reaction (1) constitutes the first unambiguous recognition
of oxidative addition to a well-defined metal-metal multiple
bond.
The [ M O ~ C I ~ H ]anions
~ - have since been shown to have
interesting chemical properties[51;however, their characterization remained incomplete in two respects: Direct structural
evidence for the bridging hydrogen atom was lacking, and
the conformation of the anion, when not constrained to occupy,
in a disordered fashion, a position of D3h symmetry, was
unknown.
We report here experimental results that supply the above
information. We have found that by modifying the reaction
conditions and using cations other than those of the alkali
metals, a great variety of well-crystallized salts of the
[ M O Z X ~ H ] ~anions
can be easily prepared. One of these
new salts, the pyridinium salt [C5NH6]3[Mo2ClSH], has been
studied by X-ray crystallography and a complete structural
characterization of the anion (including the location of the
hydrogen atom) was achieved for the first time.
Received: February 6, 1979 [ Z 174b IE]
German version: Angew. Chem. 91. 147 (1979)
CAS Registry numbers:
(1 ). 936-52-7; ( 3 ) , 69631-56-7; r 4 ) , 69631-57-8; s j n - ( S ) , 69631-58-9;
anti-(5), 69631-59-0; (6), 7148-07-4; ( 7 ) , 69631-60-3; ( 8 ) , 69631-61-4; (9),
69631-62-5; ( 1 2 ) , 69631-63-6; methyl diazoacetate, 6832-16-2; dimethyl
diazomalonate, 6773-29-1
[l] R . Huisgen, H.-U. Reissig, Angew. Chem. 91. 346 (1979); Angew. Chem.
Int. Ed. Engl. 18, 330 (1979).
[Z] The rate phenomena i n the H, D exchange are informative; H.-Li. Reissig,
Dissertation, Universitat Miinchen 1978, pp. 35-49.
[3] U . Schdllkopj; E. Wiskatt, K . Riedel, Justus Liebigs Ann. Chem. 1975,
387.
Oxidative Addition to a Quadruple Bond. The Complete
X-ray Structure of [Mo2ClsHl3- [**I
By Aoi Bin0 and F. Albert Cotton"]
The preparation of the [ M O ~ C I ~ H ]anion
~ - was first described about ten years ago['] although the presence of the
hydrogen atom was not then recognized. A few years later
the bromo analog, [ M O ~ B ~ ~ Hwas
] ~ - reportedrz1. In
1976 the coordinated hydrogen atom was demonstrated by
a combination of chemical observations, isotopic labeling
experiments and infrared spectra[3! The chemical process by
which these ions are obtained was thus shown to be represented
by eq. (1):
[*] Dr. A. Bino, Prof. Dr. F. A. Cotton
Department of Chemistry
Texas A & M University
College Station, Texas 77843 (USA)
[**I This work was supported by the Robert 4.Welch Foundation under
Grant No. A-494.
332
Fig. 1. The structure of the [ C I ~ M O ( ~ - C ~ ) ~ ( ~ - H ) M
ionO C
asI it~ ]occurs
~~
in [C5NH6]3[Mo2ClsH]. Atoms are represented by their ellipsoids (sphere
for H) of thermal vibration at the 50 % probability level.
The pyridinium salt crystallizes in the space group PT with
Z = 2; the anion has no crystallographically imposed symmetry
(Fig. 1). After a structural model omitting hydrogen atoms
had been refined to convergence a difference electron density
map revealed peaks corresponding to hydrogen atoms, one
of which was in a bridging position in the anion. Hydrogen
atoms for the three independent [C5NH6]+ cations were
placed at calculated positions and not refined, while the H
atom in the anion was refined isotropically and the other
atoms were all refined anisotropically. Using 2786 reflections
with I > 3 o(I) and 257 variables final discrepancy indices
of R 1= 0.026, R2 =0.040 and a goodness-of-fit parameter equal
to 1.008 were obtained.
It is clear that in the previous structures the fact that the
[Mo2X8H]'- anions were constrained to disordered occupation of sites of am2 (D3h)symmetry obscured important details
of their structure. The virtual symmetry of the [ M o z C I ~ H ] ~ anion is mm (Czv),where the mirror planes intersect at the
p-H atom; one contains the Mo atoms and the other the
p-Cl atoms. The terminal atoms trans to p-H have a mean
Mo-CI bond distance (Table 1) significantly longer (0.10 A)
0 Vrrlag Chemre, GmbH, 6940 Weinhelm, 1979
0 Vrrlag Chemre, GmbH, 6940 Weinhelm, 1979
0570-0833179 0404-03,1 '$ 0 2 5 0 / 0
0570-0833179 0404-0332 $ 025010
Table 1 . Dimensions of the [Mo2X8H],- anion in the Rb' and pyridinium
salts.
Mo-MO [>]
Mo-CI, [A]
Mo-Clb [A]
< Mo-Clb-Mo'
Q CI,-Mo-CI;
Mo--H [A]
Mo'-H [A]
Q Mo-H-Mo'
2.371(1)
2.39(1) [a]
2.49(2) [b]
2.497(2)
56.82(2)
92.7(16)
1.74(1)
1.62(1)
89.6(3)
2.38(I )
2.38( 1 )
["I
r]
["I
2.'5Q2)
56.8(9)
93.1(14)
-
iminium salts in the presence of hydrogen chloride. The unstable carbamoyl chlorides ( I ) formed as intermediates suffer
electrophilic attack by either phosgeniminium chloride [dialkyl(dichloromethy1ene)ammonium chloride] (PI)" o r by the
Vilsmeier-Haack-Arnold reagent (VHA)['I with simultaneous
loss of phosgene.
Thus, trichlorovinyl isocyanate ( 3 ) reacts smoothly both
with PI and VHA/HCI to give the new N'-(trichlorovinyl)chloroformamidines (2) and N',N'-dimethyl-NZ-(trichloroviny1)formamidine ( 4 ) , respectively. An equally useful alternative route to (2) and ( 4 ) consists in using dichloroacetonitrile
( 5 ) as starting materialc31.
[a] Bonds trans to pCI. [b] Bonds trans t o p-H
C1.
than those trans to pC1. The Mo-Mo and Mo-Clb distances
and the mean Mo-Clb-Mo'
are the same as those found
before.
The p-H atom refined as well as can be expected using X-ray
data[6,7].The mean Mo-H distance, the Mo-H-Mo'
angle
(Table 1 ) and an isotropic temperature parameter of 3.0A2
for this atom are reasonable values and are consistent with
the view that a symmetrically bridging hydrogen atom with
appreciable hydride character is present.
Received: January 16, 1979 [Z 191 IE]
German version: Angew. Chem. 91. 356 (1979)
CAS Registry numbers:
Rbj[M02ClsH], 57719-39-8; [ C ~ N H ~ ] , [ M O ~ C I ~ 69706-30-5
H],
[l] M . J . Bennett, J . V Brrncic, f. A . Cotton, Inorg. Chem. 8, 1060 (1969).
[2] F. A . Cotton, B. A . Freni, Z . C. Mester, Acta Crystallogr. B29, 1515
(1973).
[3] F . A . Cotton, B. J . Kalhacher, Inorg. Chem. I S , 522 (1976).
141 J . I/ Brencic, F. A. Cotton, Inorg. Chem. 8, 7 (1969).
[5] A . Bino, M . Ardon, J. Am. Chem. SOC.99, 6446 (1977); J . Sun Filippo,
Jr., M . A . Schaefier King, Inorg. Chem. 15, 1228 (1976).
[6] M . R. Churchill, Adv. Chem. Ser. 167, 36 (1978); M. R. Churchill, R.
A . Larkewgcz, Inorg. Chem. 17, 1950 (1978).
[7] A more precise study using neutron diffraction will be undertaken if
suitable crystals can be grown.
,Cl
Like trichlorovinyl i~ocyanate'~]
both (2) and ( 4 ) are valuable 1,3-biselectrophilic reagents, especially for heterocyclizations.
Thus ( 2 a ) (R=CH3) reacts with benzamidine to give the
trisubstituted triazine ( 6 ) in 80 % yield, while reaction of
( 4 ) with m-methoxyaniline affords the quinazoline (7) (50 %),
and with hydrazine hydrate the triazole (8) ( 5 5 %).
+HN=C:
/C1
ClzC=C,
/C1
ii=C
C H
NHI
Cl2CH-f
CHCI,
C6H5
VN
N
4
N2-(Trichloroviny1)amidines-New 1,3-Biselectrophilic
Reagents[**]
ClZC=C;
By Didier Van Broeck, Zdenek Janousek, Robert Merknyi, and
Heinz Giinter Viehe[']
Dedicated to Professor Horst Pommer on the occasion of his
60th birthday.
Isocyanates and vinyl isocyanates behave as masked primary amines and vinylamines towards strongly electrophilic
,H
H
Some physical data are listed in Table 1
Table 1. Physical data of the compounds (2a), (4), (4)-HCI, (6).HCI,
(7) and (8).
Q
P I = R2N=CC12 C l O ;
0
VHA = (CH,),N=CHCl
C1°
~~
['I
Prof. Dr. H. G. Viehe, Lic. Chim. D. Van Broeck, Dr. Z. Janousek,
Dipl.-lng. R. Merenyi
Laboratoire de Chimie Organique, Universite de Louvain
Place Louis Pasteur 1, B-1348 Louvain-La-Neuve (Belgium)
[**I Phosgeniminium Chemistry Part 25.- Part 24: B. Stelander, J . P . Dedrry,
M . Van Meersschr, G . Grrmuin, H . G . Viehe, Bull. SOC. Chim. Belg. 86,
291 (1977).
(2a), 'H-NMR (CDCI,): 6=3.2 (s); ' C N M R (CDCI,): 39.5 (4.
' J = 1 3 9 . 9 H ~ ) , 107.1 (S, =CCI2), 132.7 (s, =CCl), 144.6 (s, N=CCIN; IR
(CHzC12): P=1630, 1600cm-'; MS: m/r=234, 236, 238 ( M + ,four CI atoms),
199, 201 (M' - CI)
(4), 'H-NMR (CDCI,): 6=3.05 (s, 6H), 7.65 (s, 1 H); IR (CH2C12):8=2925,
1635, 1595, 1365, 1100, 945, 880 c m - l ; MS: m/e=200, 202 ( M i , three CI
atoms), 165, 167 ( M + - C l )
(41.HCI.m.p. 121°C; 'H-NMR(CF,COOD): ij=3.4, 3.6 (s, 6H), X.2 (s, 1 H),
11.2(s,lH)
(6).HCI, m.p. 142-143°C; 'H-NMR (CDCI,): 6=3.45 (s, 6H), 7.4 (m,
3 arom. H), 7.85 (s, 1 H), 8.5 (m, 2 arom. H), 12.1 (s, 1 H)
(7), m.p. 170-171 "C; ' H - N M R (CDCI,): 6=3.95 (s, 3H), 6.75 (s, 1 H),
7.2(m,2arom.H),7.67(d,1arom.H,J=9Hz),9.1S(s,larom.H)
(S), m.p. 166-167°C; 'H-NMR ([D6]-acetone): 6=7.25 ( s , I H), 8.6 ( s , 1 H),
12 (s, br., 1 H)
333
Aiiyew. Chem. lnr. Ed. Engi. 18 (1979) No. 4
0 Vrrlay Chemie, GmbH, 6940 Weinheim, 1979
0570-0833/79~0404-0333 $ 02.50/0
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