close

Вход

Забыли?

вход по аккаунту

?

Intermediates in Nitrogenase Models N2H3 and N2H4 as 2-Coordinated Ligands.

код для вставкиСкачать
[l] K. C. Nicolaou, D. G. McGarry, P. K. Sommers, J. Am. Chem. Soc. 112
(1 990) 3696.
[21 K. C. Nicolaou. C. V. C . Prasad, W. W. Ogilvie, J. Am. Chem. Soc. 112
(1990) 4998.
[3] Y. Shimizu, H. N. Chou, H. Bando, G. Van Duyne, J. Clardy, J. Am. Chem.
SOC.108 (1986) 514. See also: M. Pawlak, M. S. Tempesta, J. Golik, M. G .
Zagorski. M. S . Lee, K. Nakanishi, T. Iwashita, M. L. Gross, K. B. Tomer,
J. Am. Chem. Soc. 109 (1987) 1144.
141 K. C . Nicolaou, C.-K. Hwang, B. E. Marron, S . A. DeFrees, E. A. Couladouros, Y. Abe, P. J. Carroll, J. P. Snyder, J Am. Chem. Soc. 112 (1990)
3040.
151 K. C. Nicolaou, M. E. Duggan, C.-K. Hwang, J. Am. Chem. Soc. 108
(1986) 2468.
[6] K . C. Nicolaou, C. V. C. Prasad, P. K. Somers, C.-K. Hwang, J. Am.
Chem. SO<.111 (1989) 5330.
[7] K. C. Nicolaou, C.-K. Hwang, M. E. Duggan, J. Am. Chem. Soc. 111
(1989) 6682.
[8] All new compounds exhibited satisfactory. spectral
and analytical. and/or
_
exact mass data. Yields refer to spectroscopically and chromatographically homogeneous materials. Selected physical properties of compounds 67.
72. and 82: 67: oil; R, = 0.5 (20% ether in petroleum ether); IR (neat)
= 3080, 3040, 2980, 2940, 2880, 1480, 1440, 1260, 1100, 840, 710,
680cm-';'H NMR (500 MHz. CDCI,) 6 =7.7-7.2 (m, 20H, aromatic),
5.7-5.9 (m. 4H. olefinic), 5.39 (s. 1 H, benzylic), 4.72 (d, J = 12.5Hz, 1 H,
benzylic). 4.58 (d. J = 12.6 Hz, 1 H, benzylic), 4.33 (d, J = 8.3 Hz, 1 H,
Intermediates in Nitrogenase Models:
N,H, and N,H, as q2-CoordinatedLigands **
By Sabine Vogel. Annette Barth, Gotffried Huttner,*
Thomas Klein, Laszlo Zsolnai, and Reinhard Kremer
Dedicated to Professor Dieter Sellmann
on the occasion of his 50th brithday
Dinitrogen ligands of the type N,H, are important intermediates in all models which attempt to explain the activity
of nitrogenase.['] The hydrazido(1-) ligand, N2H,e, plays a
key role. Only in one case recently was it possible to stabilize
this ligand on a organometallic complex fragment.['] Organo(m 2 1) of the parent compound
derivatives R,N,H(,-,,
N2H,, however, have been known as ligands for some
time.I3l We report here the synthesis and properties of
[(tripod)Co(q2-N,H,)]@ (tripod = CH,C(CH,PPh,),), 1, the
first non-organometallic N,H, complex. The protonation of
1 led to [(tripod)Co(q2-N,H4)]'@,2. The q2-coordinationof
the N2H4ligand, which is as important in the interpretation
of nitrogenase activity, could be proven for the first time by
CHO).4.13im,2H.CHO),3.95-3.6(m,8H,CHO),3.55(t,J=10.4Hz.the X-ray structure analysis of this complex.
1 H. CHO). 3.41 (m.I H, CHO). 3.15 (m, 2H, CHO), 2.88 (dd. J = 6.0.
In the presence of tripod, [Co(BF,), .6H,O] reacted with
4.2 Hz. 1 H, CH,), 2.78 (m, 1H, CH,), 2.67 (m, 4H, CH,), 2.48 (m, 2H,
N2H4aq to cation 1 (Fig. I), which precipitated as the dark
CH,). 2.26 (m. 2H. CH,), 2.01 (m. 1 H, CH,), 1.87 (m, 2H. CH,), 1.74(t,
green, air-sensitive BPh, salt. The analytically pure, crysJ = 12.7 Hz. 1H. CH,). 1.7 (series of multiplets, 4H, CH,), 1.31 (t,
J = 7 . 1 Hz. 3H, CH,), 1.25 (t, J = 7 . 1 Hz, 3H, CH,), 1.10 (s, 9H, fBu),
talline salt l-(BPh,). 2THF has a magnetic moment of
0.89 ( s . 9 H , IBu), 0.08 (s, 3H, CH,Si), 0.04 (s, 3H, CH,Si); MS: mi;
1.8 lB,
corresponding to a low spin d 7 configuration at C O ~ ~ .
(intensity) 1135 (24), 1106 (64), 1074 (100). 942 (33), 662 (90); HRMS
Figure 1 shows the results of the X-ray structure analysis of
Calcd forC6,H,,0,S,Si,: ( M + H)@:1135.564, found: 1135.560. 72: oil;
this salt.
R, = 0.35 (30% ether in petroleum ether); [ E ] ~+ 186" (c = 0.34, CDCI,);
IR (neat)<,,, = 3090.3040,2950,2885.1600,1460,1430.1400,1105,1070,
The coordination geometry of cobalt lies between the two
940.740.710cm-'; 'H NMR(500 MHz,CDC1,)6 =7.91-7.22(m,20H,
extremes of square pyramid and trigonal bipyramid. The
aromatic), 5.83 (dd, J = 10.0. 6.6Hz, I H , olefinic). 5.77 (dd, J = 10.9,
best description of the geometry of 1 is as an ideal tetrahe6.2 Hz. 1 H. olefinic), 5.69 (m. 2H, olefinic), 5.41 (s, 1 H, benzylic), 4.72 (d.
dron around the cobalt atom, where the N,H, unit, as a
J=12.6Hz,1H,benzylic),4.61(d,J=12.6Hz,lH,benzylic),4.36(t,
J =7.4 Hz, 1 H , CHO), 4.17 (dd, J = 9.4, 3.8 Hz, 1 H, CHO), 4.00 (d.
whole, occupies one tetrahedral site.[41
J = 5.7 Hz. 1 H, CHO), 3.90 (m, 1 H. CHO), 3.86 (dt, J = 10.6, 4.4 Hz,
The only moderate quality of the crystals[51did not permit
1H,CHO),3.80(dd,J=9.3,4.4Hz,1H,CHO),3.76(t,J=8.4Hz,1H,
the
crystallographic location of the hydrogen atoms attached
CHO). 3.70-3.58 (series of multiplets, 5H, CHO), 3.18 (m. l H , CHO).
to nitrogen. The identification of the ligand as an N,H, unit
3.15(dd,J=9.6,2.5Hz,1H,CHO),3.06(m,1H,CHO),2.74(m,2H.
is, however, unambiguous: in the IR spectrum three NH
CH,CH=CH), 2.37 (dd.J= 14.2, 7.0 Hz, IH,CH,),2.25 (m, 3H. CH,),
2.11 (dd, J = 12.0, 4.3 Hz, l H , CH,), 1.88 (bs, 2H, CH,), 1.71 (t,
stretching frequencies are observed (d = 3290, 3217,
J = 11.9 Hz. 1 H, CH,), 1.61 (m, 3H, CH,), 1.44 (dd, J = 11.3, 11.3 Hz,
3130 cm-') as expected for N,H,; these bands do not ap1H. CH,). 1.21 (s, 3H, CH,), 1.04 (s, 9H, IBu); I3C NMR (125 MHz,
pear
when deuterated reagents are used for the synthesis.
CDCI,) 139.23, 138.76, 137.66, L35.52, 134.06, 131.83, 129.46, 128.91,
The magnetism of 1 mentioned above corresponds to one
128.91, 128.23. 128.17, 128.09, 127.55, 127.11, 127.06, 126.14, 124.10,
101.61, 85.92, 82.30, 82.14, 81.04, 77.67, 77.58, 76.84, 72.99, 72.33, 72.39,
unpaired electron per cobalt atom. This only allows the for72.26. 70.30. 69.76, 63.73, 62.65, 44.57, 35.70, 32.98, 32.64, 30.24, 29.85,
mulation of 1 as [(tripod)Co(N,H,)]@, where x = 2n + 1 .
28.69, 26.86. 19.20, 16.80; MS m/z (intensity) 913 ( M + H, 40), 856 (55),
Furthermore, the structure of 1 points to the existence of the
808 (52). 748 (loo), 688 (49), 627 (45), 464 (62); HRMS Calcd for
N2H, unit: the N-N distance of 138.4(14)pm lies in the
( M + H)@: 913.471, found: 913.469; Anal. Calcd for
C,,H,,O,Si:
C , 73.68; H, 7.45, found: C , 73.88; H, 7.63. 82: oil;
C,,H,,O,Si:
range observed for the N-N bond lengths of q2-organoR , = 0.6 (30% ether in petroleum ether); [ E ] +
~ 108" (c = 0.19, CHCI,);
hydrazido ligands in R,N,H(, - ,,,,.I3]
IR (neat) tmSx
3080, 3040, 2940, 2880, 1600, 1440, 1390, 1100, 840,
Similarly the different Co-N distances (Fig. 1 ) reflect the
710cm-I; 'H NMR (500MHz, CDCI,) 6=7.66-7.22 (m, 15H,
familiar pattern[31 of the q'-coordinated R,,,N,Ho ),- liaromatic), 5.71 (dd, J = 10.8, 5.4 Hz, 1 H, olefinic), 5.62 (m, 1 H, olefinic),
4.71 (d. J = 12.6 Hz, 1 H, benzylic). 4.61 (d, J = 12.6 Hz, 1H, benzylic,
gands. The shorter metal-N distance agrees with those for
4.46 (m. 1 H. CHO), 3.90 (d, J = 2.7Hz, 1 H, CHO), 3.86 (dt,
the nitrogen atoms which carry only one substituent (H or
J = 10.4, 4.7Hz. 1 H, CHO), 3.79 (dd, J = 9.4, 4.1 Hz, 1 H, CHO), 3.72
R).[,' The same pattern is also observed for [(tripod)Co(q2(m, 1 H. CHO), 3.68 (t, J = 6.0 Hz, 2H, CH,OSi), 3.56 (m, 1 H, CHO),
NHNMe,][BPh,] . 1.5THF: Co-NNMe2= 205(2), Co-N,, =
3.31 (m. 3H,CH0,CHz),3.15(m, 3H,CHO,CH,), 3.05(m, l H , CHO),
196(2) pm.I7l
2.68(m. 1 H,CH,CH=CH), 2.4-1.4(seriesofmultiplets, 19H,CH,), 1.21
<,Ax
(s, 3H. CH,). 1.04 (s, 9H, tBuSi), 0.89(s, 9H, tBuSi),0.09 (s, 3H, CH,Si),
0.04 (s. 3H. CH,Si); MS m/r (intensity) 1065 ( M + H, 5). 809 (7), 199
(100); HRMS Calcd for C,,H,,O,Si,I:
( M + H)": 1065.459, found
1065.463.
This mixture was taken through the next two steps, at which point the cis
isomer 69 was separated chromatographically.
a) S . Hanessian, P. Lavallee, Can. J. Chem. 53 (1975) 2975. b) S . Hanessian. P. Lavallee, Cun. J. Chem. 55 (1977) 562.
The structure of thisepoxide was tentatively assigned on the basis of NMR
studies.
K. B. Sharpless, M. A. Umbreit, M. T. Nieh, T. C . Flood, J. Am. Chem.
Soc. 94 (1972) 6538.
This X-ray crystallographic analysis was carried out by Dr. Patrick
C a r r d of the University of Pennsylvania. Details are published elsewhere.
Angew. Chem. hi.Ed. Engl. 30 (1991) No. 3
0 VCH
[*] Prof. Dr. G. Huttner, Dipl.-Chem. S. Vogel, Dipl.-Chem. A. Barth,
Dipl.-Chem. T. Klein, Dr. L. Zsolnai
Anorganisch-chemisches Institut der Universitat
Im Neuenheimer Feld 270, W-6900 Heidelberg (FRG)
Dr. R. Kremer ['I
Max-Planck-Institut fur Festkorperforschung
Heisenbergstrasse 1, W-7000 Stuttgart 80 (FRG)
['I Magnetic measurements
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
Verlugsgesellschufi mbH. W-6940 Weinheim, 1991
0570-0833/91/0303-0303S 3.50
+ .25/0
303
Further evidence for the identity of 1 is provided by its
protonation to 2. The dark green BPh, salt of 1 is converted
into the light green hydrazine complex 2 in THF with 40 O h
HBF, a q , which is obtained as the analytically pure, crystalline salt [(tripod)Co(N,H,)][(BPh,)(BF,)] . T H E
According to the X-ray analysis, the best description of
the coordination geometry around the cobalt atom of 2 is a
distorted square pyramid (Fig. 1) in which the phosphorus
atoms PI and P2, and the two nitrogen atoms of the hydrazine ligand form the base of the idealised square pyramid.
In agreement with this geometry, the Co-P bond to the apical
phosphorus atom P3 is margianally longer than the other
Co-P bonds. The magnetism of 2-(BPh,)(BF,) . T H F (solid
state) of 3.84 pB corresponds with the spin-only value for
three unpaired electrons.['] Compound 2 may therefore be
described formally as a high spin d7 C O complex.
~ ~
Experimen fa1 Procedure
All work was performed under argon to exclude air and moisture. Before use
all glassware was heated with a hot-air blower, evacuated several times on a
vacuum line (oil pump) and flushed with inert gas. Solvents were dried under
inert gas and freshly distilled. The IR spectra were taken as Nujol mulls.
1 : Equimolar amounts of the tripod ligand (624 mg, 1 mmol) in 15 mL THF
and carefully dried (over P,O, in a desiccator) Co(BF,), ' 6H,O [ll] (340 mg,
1 mmol) in 15 mL ethanol were mixed at 20°C. To the orange-red solution was
added dropwise 0.5 mL (1 mmol) 64 % N,H, (immediate color change to dark
green). After addition of 342 mg (1 mmol) sodium tetraphenylborate in 5 mL
ethanol, the mixture was stirred for 2 h at 20°C and then filtered through a G4
frit. Concentration to half the volume (lo-' mbar, 20°C) caused black-green
crystals of 1-BF, . THF to separate within 24 h. Decantation, washing of the
crystalline product with ethanol till the washings were colorless and then with
petroleum ether, and drying under high vacuum gave an analytically pure
product. Yield: 435 mg (42%. based on Coze salt); correct C,H,N,P analyses.
2: To an equimolar mixture of the tripod ligand (624 mg, 1 mmol) in 15 mL
THF and Co(BF,), .6H,O [ l l ] (340 mg, 1 mmol) in 15 mL ethanol is added
dropwise 0.05 mL (1 mmol) 64% N,H, at 20°C. The solution is stirred for 1 h
(20°C). after which 4 drops of 40% HBF, (ca. 1 mmol) is added to the dark
green reaction mixture (no color change); addition of a solution of 684 mg
(2 mmol) sodium tetraphenylhorate in 10 mL ethanol, 1 h stirring at 20°C and
filtration (G4) gives, after workup as for 1, dark green crystals of 2(BPh,)(BF.,). TH E Yield: 450 mg (40%. based on Co2@salt): correct elemental analyses (C,H.N,P.Co.F.B).
Received: November 9, 1990 [Z 4271 IE]
German version: Angew. Chem. 103 (1991) 325
1
CAS Registry numbers:
l-(BPh,), 131761-28-9; l-(BPh,) ' 2 THF, 131761-29-0; 2-(BPh,)(BF4) . THF,
131761-32-5: nitrogenase, 9013-04-1.
-
217.7(4)
227.6(4)
1
2
Fig. 1. qZ-Bonding(top) and structure characterization (bottom) of the cations
1 and 2 (phenyl groups of the tripod ligands omitted). Numerical data: distances in pm; underlined values: distances to cobalt: values in parentheses:
standard deviations of the last decimal place.
D. Sellmann, Angen. Chem. 86 (1974) 331 ; Angen. Chem. Int. Ed. Engl. 13
(1974) 639; J. Chatt, J. R. Dilworth, R. L. Richards, Chem. Rev. 78 (1978)
589; J. A. McCleverty, Chem. Soc. Rev. 12 (1983) 331; D. J. Lowe, R. N.
Thorneley, B. E. Smith in P. M. Harrison (Ed.): Metalloproreins. Vol. I.
VCH, Weinheim 1985, p. 207.
R. R. Schrock, A. H. Lium M. B. ORegan, W. C. Finch, J. F. Payack.
lnorg. Cl,em. 27 (1988) 3574.
J. Carroll, A. Sutton, J. Chem. SOC.Chem. Commun. 1979. 1058; J. Chatt.
J. R. Dilworth, ibid. 1980, 786; I. A. Latham, G. J. Leigh, J. Chem. SOC.
Dalton Trans. 1986. 385.
Note added in proof: G . SiiJ-Fink et al. report a p3-q2-NHNH, ligand in
HRu,(CO),(N,H,): T. Jenke, H. Stoeckli-Evans, G . SuD-Fink, J.
Organomefal. Chem. 391 (1990) 395.
M = 1178.17,
Crystal structure of l-(BPh,). 2THF: C,,H,,N,O,P,CoB,
monoclinic. space group P2Jc (No. 14), a = 9.960(2), b = 28.509(7), c =
23.039(5) pm, p = 92.33(2)', V = 6253(2) . lo6 pm', Z = 4, T = 298 K, 6
range 2" < 20 < 50'. scan speed ["min-']2.3 < < 29.3,11 072 independent reflections, 6581 observed reflections (I 2 2a), 545 refined parameters. R , = 11.01 %, R, = 9.63%. Crystal structure of Z-(BPh,)(BF,)
M 1193.8, triclinic, spacegroup PI (No. 2).
THF: C,,H,,N,OP,CoB,F,,
a = 12.73(1), b = 13.86(1), c = 19.80(1)pm, a =71.61(6), 0 = 82.55(6),
y = 87.46(7)", V = 3287(5). lo6 pm', 2 = 2, T = 200 K, 8 range 2' <
20 < 47", scan speed [" min-' - 11 2.3 < ci, < 29.3, 9783 independent reflections, 6518 observed reflections ( I > 20), 596 refined parameters,
R , = 12.13%. R, = 10.84%. Measurement on a Siemens(Nico1et-Syntex)
R3m/V diffractometer, Mo,, radiation, graphite monochromator, solution and refinement: SHELXTL PLUS [6]. Further details of the crystal
structure investigation may be obtained from the Fdchinfotmationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Information mbH, W-7514 Eggenstein-Leopoldshafen 2 (FRG) on quoting the
depository number CSD-55033, the names of the authors and the journal
citation.
G. M. Sheldrick, SHELXTL PLUS, Universitat Gottingen 1988.
S. Vogel, Diplomarheif. Universitat Heidelberg 1990.
See also: L. Sacconi, J. Chem. SOC.A 1970,248.
N. A. Bailey, P. D. Frisch. J. A. McCleverty, N. W. Walker, J. Williams,
J. Chem. SOC. Chem. Commun. 1975, 350; J. Bultitude, L. F. Larkworthy, D. C . Povey. G. W. Smith, J. R. Dilworth, G. J. Leigh, ibid. 1986.
1748.
R. S . Dickson, J. A. Ibers, J. Am. Chem. Sor. 94 (1972) 2988; C . Kriiger,
Annen. Chem. 23 (1973) 1051: Anpew. Chem. Inr. Ed. End.
Y.-H. Tsav.
~"
- 12
(1973) 998; K. Jonas, D. J. Brauer, C. Kriiger, P. J. Roberts. Y-H. Tsay, J.
Am. Chem. Sor. 98 (1976) 74.
[ l l ] H. Funk. F. Binder. Z . Anorg. Allg. Chem. 155 (1926) 327.
~
The experimentally determined magnetism of three unpaired electrons confirms the N,H,, x = 2n, ligand composition for the dication 2. The bond lengths suggest a formulation with x = 4: the N-N bond distance of 144.6(17)pm falls
into the range found for q2-coordinated organohydrazines
R,N,Ho-,,
(m 2 I)['] and precludes the formulation N,H,
or N2["l as ligand unit for 2.
The Co-N distances in 2 are equal within experimental
error, which confirms that both nitrogen atoms have the
same substitution pattern (in contrast to I). In the NH
stretching region of the IR spectrum, 2-(BPh,)(BF,) . THF
shows a broad band at 3229 cm-' with shoulders at 3310
and 3275 cm-', and a sharp band at 3148 cm-'. These four
IR-active NH valence frequencies are expected for a N,H4
ligand in 2.
In nature phosphane ligands do not form part of enzymes,
neither does cobalt occur as the active metal center in the
known nitrogenases. Nevertheless, the hypothesis that the
specific coordination geometry imposed by the tripod ligand
stabilizes the elusive N,H, intermediates in complexes 1 and
2, possibly throws some light on the subject.
304
0 VCH
Verlagsgesellsrhafi mbH, W-6940 Weinheim, 1991
0570-0833/91/0303-0304$3.50+ ,2510
~I
Angen. Chem. Inr. Ed. Engl. 30 (1991) No. 3
Документ
Категория
Без категории
Просмотров
1
Размер файла
286 Кб
Теги
model, nitrogenand, intermediate, coordinated, n2h4, n2h3, ligand
1/--страниц
Пожаловаться на содержимое документа