вход по аккаунту


Monomeric Molybdenum and Tungsten Complexes That Contain a MetalЦPhosphorus Triple Bond.

код для вставкиСкачать
[7] We use 'H NMR routinely to inonitor reactions involving *H-labeled paraand
magnetic complexes such as [Mo(NRAr),] (1); see: N M R u/ P r r r r r n i ? u ~ n ~ / i ~ ~
M ~ I(Eds.:
~ G.~ N . La
~ Mar,
~ ~ D.~ Horrocks
~ . Jr..~ R. H. Holm), Academic
Press. New York, 1973.
[XI a) A suitable crystal of 2.THF, of approximate dlmensions 0.28 x 0.24 x
0.12 mm. was obtained by cooling a T H F solution of 2 to -35 C. The crystal
Nadia C. Zanetti, Richard R. Schrock,* and
was mounted on a glass fiber in a stream of cold N,. Data were collected at
M. Davis
- 8 6 ' C on an Enraf-Nonius CAD-4 diffrdctometer with graphite monochromated Mo, radiation. A total of 2109 reflections were collected to a 20 value
of 45.0'. The structure was solved by direct methods. Non-hydrogen atoms
Monomeric complexes of the type [ (N,N)Ta=PR]
were refined anisotropically except for the T H F atoms: the THI: molecule is
(N,N = [(Me,SiNCH,CH2),NI3-; R = Ph, cyclohexyl, tBu)
disordered about a symmetry element. The final cycle of least-squares refinecan be prepared by treating [(N,N)TaCI,] with two equivalents
ment was based on 1585 observed reflections (/ > 3.00a(/))aiid 263 variable
LiPHR.[" A crystal structure of [(N,N)Ta=P(cycloparameters and converged with R = 0.058 and R , = 0.062. A final difference
Fourier map showed no chemically significant features. Crystal data are
hexyl)] showed that the Ta=P bond length is 2.145(7) 8, and the
u=11.434(1). c =18.051(3)A. Y = 2043.7(5)A3. space group P6,. Z = 2.
Ta-P-C angle is 170(1)", consistent with strong donation of the
M , =719.80. and { I ~ , , ,=1.169gcm-3.
b) Further details of thecrystal strucphosphorus lone pair to give a Ta-P pseudo triple bond. More
ture Investigation may be obtained from the Director of the Cambridge Crysrecently we have shown that tungsten-carbon triple bonds form
tallographic Data Centre, 12 Union Road. GB-Cambridge CB2 1EZ ( U K ) , on
remarkably readily by ejection of dihydrogen from d2 alkyl
quoting the full journal citation.
191 The P = P distance in gaseous P, is 1.895 A: N . N . Greenwood, A. EarnshaN.
complexes of the type [(N,N)W(CH,R)].[21 even when proChmnirrr~u / / / ? cEieiniwts, Pcrgamon, Oxford. 1984. The M o = M o distance in
tons are present in the alkyl ligands, which suggests that the
[Mo,(NMe,),] is 2.214 A: M. H. Chisholm. F. A. Cotton, B. A. Frenz, W. W.
W = C bond in this type of do alkylidyne complexr3] is highly
Reichert. L. W. Shive, B. R. Stults, J. Am. C'hrin. S w . 1976, YN, 4469. The sum
favored thermodynamically. Therefore we speculated that for
of Mo and P triple bond covalent radii may therefore be taken as 2.055
[iO] A. R. Johnson. P. W. Wanandi. C. C. Cummins. W. M . Davis, Orgrmoin[,frr//ir.~
both steric and electronic reasons, and because of the diagonal
1994, 13. 2907.
relationship between some C and P chemistry,r41[(N,N)W=P] ,
[I 11 C. E. Laplaza. W. M. Davis. C. C. Cummins, OrgunonieruNics 1995. 14, 577.
a monomeric compound containing the heretofore unknown
[I21 We prepared mesityl azide (caution! organic azides arc potentially explosive)
transition metal to phosphorus triple
would be a
according to the procedure given in the following paper: I . Ugi, H. Perlinger.
L . Behringer. Chmn?.Ber. 1958, 91. 2330.
worthwhile and achievable goal. We describe here the synthesis
[I31 Y. G. Gololobov. L. F. Kasukhiii. Glruheilron 1992, 4N. 1353.
of [(N,N)W=P] and [(N,N)Mo=P] by an unconventional
[14] C . E. Laplaia, W. M. Davis. C. C . Cunimins, unpublished results. See reference
route. These results should be compared with the synthesis and
[I] above for the synthesis of [Mo(NO)(NRAr),].
reported by Cumstructure of [{3,5-Me,C,H3)(zBu)N},MorP]
[I 51 D. C. Bradley, C. W. Nehing. J. CIie117. Soc., C h m . Cominun. 1970. 21 9.
[I61 A crystal of 3 having approximate dimensions 0.38 x 0.29 x 0.12 mm was
mins et al. in the preceding article in this issue.[']
mounted on a glass fiber in a stream of cold N,.Data were collected at - 86 'C
The slow reaction between [ (N,N)WCI][*] and two equivaon an Enraf-Nonius CAD-4 diffractometer with graphite monochromated
of LiPPhH (toluene/tetrahydrofuran, 4/1, two days) yields
Mo,, radiation. A total of 5628 reflections were collected to a 20 value of 54.9
yellow, crystalline. pentane-soluble, diamagnetic [(N,N)WrP]
The structure was solved by direct methods. Non-hydrogen atoms were refined
either anisotropically o r isotropically. Aromatic rings were refined as rigid
in approximately 50 % yield [Eq. (a)]. An X-ray study revealed
groups. Because of poor crystal quality we regard this structure as a confirmation ofatom connectivity only. and offer no detailed discussion of bond lengths
and angles at this time. The final cycle of least-squares refinement was based
on 1943 observed reflections ( I > 3.0Oo(l))and 160 variable parameters and
conkerged with R = 0.095 and R, = 0.084. A final difference Fourier map
showed no chemically significant features. Crqstal data are u = 22.626(1).
V=4416(2)A3. space group Piiu3,, 2 = 4 .
[17] The free "monophosphadiazoiiium" cation [PNAi*]+ (Are = 2.4.hrBu,C,H2) has been isolated aiid structurally characterized as its tctrachloroaluminate salt: E. Niecke, M. Nieger, F. Reichert, Ai?gcw. C'liivn. 1988. 100.
1781; "itigrlt'. CIieiii. / t i / . Ed. Eiigl. 1988, 27, 3715
a structure (Fig. 1) that is unremarkable for heavy metal mono[18] We believe this to be the first example of a terminal PS ligand. For discussions
meric complexes of this general
except for the presence
ofcomplexed phosphorusmonoxide see: 0 .J. Scherei-, J Braun, P. Walther. G.
of a terminal phosphorus ligand 2.162(4) 8, from tungsten, a
Heckmann. G. Wolmershiuser. Angcvv. C h o i i . 1991. 103, 861 ; Arigcii,. Clicrii.
In/.E d Engl. 1991. 30. 852: W. A. Herrmann, ihid.. 1991. 30. 818: 1991, /03.
metal-P distance that is essentially the same as that in
835: J. F. Corrigan. S. Doherty, N. J. Taylor. A. J. Carty. J A f t ! . Chcw. S m
The 31P N M R signal of
1994, 116. 9799.
[(N,N)W=P] is found at 6 =1080. but J(P,W) is only
1191 A. H. Cowley, A. R. Barron. 4 c r . Chcm. Rrs. 1988. 21. 81.
138 Hz (Table 1 ) . This value for J(P,W) should be compared
[20] A. H. Cowley, B. Pellerin, J. 1.Atwood. S. G. Bott. J. An?. C'hen?. So(,.1990.
with that of 410 Hz for the planar phosphido phosphorus in
1211 C'. C . Cummins. R. R. Schrock. W. M . Davis, Angmi,. C h m . 1993. 105. 758;
in which the metal also can be
A n g w . CAeiii. h i . Ed. Efigl. 1993. 32, 756.
said to be d@.and J(P.W) =719 Hz in [(N,N)W(PPhH)] (see
(221 Z . Hou, T. L. Breen, D. W. Stephan. Orgmornetullics 1993, 1-7. 3158.
below). Such a low value for J(P,W) in the W-P bond could be
[ 2 3 ] J. B. Bonanno, P. T. Wolczanski. E. B. Lobkovsky. .I h i . Clieiii. Sm.. 1994,
indicative of a low YOs character in the CF portion of the bond.
[24] P. B. Hitchcock, M . F. Lappert. W:P. Leung, J C/icmir.Sor. Cheni. Curiiiiiiui.
if the relationship that is so well-known for C-H bonds were to
1987. 1282: P. Bohra, P. B. Hitchcock. M. F. Lappert. W:P. Leung. Poldiedron
hold also for W - P bonds. The IR spectrum of [(N,N)W=P]
1989. 8 , 1884.
1251 M. H. Chisholm. K . Folting, J. W. Pastcrczyk, Inorg. Clieni. 1988. 27, 3057.
[*] Prof. D r R R. Schrock, Dr. N. C. Zanetti. Dr. W. M. Davis' "
[26] M. H. Chisholm. J. C. Huffman. J. W. Pasterczyk. /iiorc. C h h . A d o 1987, 133,
Department of Chemistry 6-331
Massachusetts Institute of Technology
Cambridge, MA 02139 (USA)
Telefax: Int. code + (617)253-7670
c-mail: rrs!ii'
[ '1 X-tray structure analysis.
[**I This work is an extensioii o f a program supported by the National Instilutes of
Health (GM 31978) desizned to elucidate chemistry of N,N complexes relevant
to the reduction of dinitrogen.
Monomeric Molybdenum
Complexes That Contain a Metal-Phosphorus
Triple Bond**
VCH ~ e r / u ~ s g e s r l / . ~ c hnihH,
u f t 0-69451 Wrin/ieini, 1YY5
$ /f/.OO+ .-75;0
Angtw. ('hem. I n t . Ed. EngI. 1995, 34. Nu. I N
threefold symmetric species in more than 60 'YO yield that has
N M R parameters similar to those for [(N,N)W(PPhH)]
(Table 1) and which was shown in an X-ray study (Fig. 2) to
contain a planar phenylphosphido ligand in which Mo-P distance is 2.227(3) A and the Mo-P-C and Mo-P-H angles are
129.7(2)" and 134(1)". respectively. The distance between M o
Fig. I . A Cheni 3Ddrauingofthestructureof[(N,N)WmP].Selected bond lengths
I' 2.162(4). W N,, 1.975(6). W -NAY
Tahle 1 Selected NMR data for compounds with M(PPhH) and M = P units.
nH(.I(H,P) J(H.W))
hlH value [a]
[ ( N ,N)W(PPhtl)]
91 (719)
18.68 (300.36)
12.16 (283)
to80 (138)
3.37 (t. CH,)
2.21 (t. CH,)
0.33 is. TMS)
3.38 (t. CH,)
2.35 (1. CH,)
0.28 (s. TMS)
3.52 (t. CH,)
1.69 (t. CH,)
0.72 (s. TMS)
[ ( N ,N) M o 'PI
[a] N , N Iigand. TMS
3.36 (t. CH,)
1.77 (1. CH,)
0.73 (s. TMS)
above 550 c n - l is similar to that of [(N,N)WCI] except for a
medium strength peak at 935 cm-', but we are cautious about
ascribing this to the W = P stretch until further studies are carried out. Since examples of M E E (M = M o or W) stretching frequencies include v(Mo=N) at 991 cm-'
and v(W=C) at 911 cm-' in
[CI(Me,P),WrCH] .[121 we would expect the value for v(W=P)
to be lower than 935 cm-'.
Before the reaction shown in Equation (a) is complete a diamagnetic threefold symmetric species can be observed by N M R
spectroscopy along with [(N,N)W=P] and paramagnetic
[(N,N)WCI]. We propose that this intermediate is [(N,N)W(PPhH)] (Table 1 ) by analogy with the N M R data for the crystallographically characterized [(N,N)Mo(PPhH)] (see below).
[(N,N)W(PPhH)] is diamagnetic because the lone pair on phosphorus is donated to the metal and the d,,/dy, orbital degeneracy
thereby is split, but it still has C , symmetry on the N M R time
scale. The N M R data for the PPhH ligand in [(N,N)W(PPhH)]
should be compared with those for the PPhH ligand in [W(C~BU)(PP~H)(PE~,),CI,~I'O]
(6P = 233, 6 H = 10.0, J(P.W) =
410 Hz, J(P.H) = 362 Hz, and J(H,W) = 65 Hz). Reactions between [(N,N)WCI] and on(' equivalent of LiPPhH also give
mixtures that contain [(N,N)W=P]. [(N,N)WCI], and
I(N3N )W(PPhH)I.
The reaction between [(N,N)MoCI] and one equivalent of
LiPPhH [Eq. (b)] yields an orange, crystalline diamagnetic
50 O C
Fig. 2 . A Chem 3D drawing of the structure of [(N,N)Mo(PPhH)]. Selected bond
lengths [A] and angles [ 1: Mo-P 2.22713). Mo-N,, 1.992(5). 7.014(5), 2.010(5),
Mo N,,, 2.25115); Mo-P-C 129.7(2). Mo-P-H 134(1).
and H (3.23(1) A) is too great to invoke any bonding interaction. These data are consistent with a Mo-P pseudo double
bond being formed by using one of the two available n-type
orbitals pointing toward P along the N-Mo-P ( 2 ) axis. An electron pair must be present on Mo in the remaining n-type orbital
that lies approximately in the C-P-H-Mo plane. It is interesting
to note that a hydrido(ph0sphinidene) analog of the recently
characterized cyclopentylidene hydrido complex, [(N,N)W(C,H,)(H)],['31 is disfavored. Note also that thc Mo-N,,,,, distance in [(N,N)Mo(PPhH)J is shorter (2.26 A) than the
W-Naxia,distance in [(N,N)W=P] (2.34 A), consistent with a
larger trans effect for the W - P triple bond than for the Mo-P
pseudo double bond.
Addition of two equivalents of LiPPhH to [ (N,N)MoCI]
(tolueneiTHF, 80"C, 12 h) or one equivalent of LiPPhH to
[(N,N)Mo(PPhH)] (toluene/THF, 25 'C, 2 days) yields yellow
crystalline [(N,N)Mo-PI in about 75% yield in which the ,'P
N M R signal is found at 6 = 1346, A8 = 266 further downfield
than the corresponding signal in [ (N,N)WrP].
The mechanism of formation of [(N,N)M=P] complexes is
not clear at this stage. So far we know that [(N,N)Mo-PI
is not observed when a [D,]toluene solution of pure
[(N,N)Mo(PPhH)] is heated at temperatures up to 120 "C for up
to three days, even though a solution of pure [(N,N)Mo-PI
remains unchanged after being heated to 120 C for three days.
We also have found that [(N,N)Mo(PPhH)] does not react with
butyllithium in [DJtoluene at 25 'C over a period of one day.
Preliminary experiments suggest that the reaction between
[ (N,N)WCI] and two equivalents LiP(cyclohexy1)H also yields
[(N,N)W=P] in more than 50% yield.
The results reported here demonstrate that d" terminal phosphido complexes can be formed readily in the sterically protected C , environments found in [{(Me,SiNCH,CH,),N)M] complexes. In future studies we will attempt to elucidate the
mechanism of forming terminal phosphido complexes and explore their reactivity patterns. and attempt to prepare analogous
terminal arsenido complexes by similar techniques.
Experimental Procedure
M. H. Chisholm, J. C . Huffman. J. W. Pasterczyk, fnorg. Cliitn. A m 1987.133,
Mulliple Bondi mid Loii C'oorilinurion in P1iosphuru.s C/wmi,rtr.v(Eds.: M. Regitz, 0 ..! Scherer) Thieme. New York. 1990.
M . H. Chisholm. K . Folting, J. W. Pasterciyk. fnorg. Cl~eni.1988. 27. 3057.
C . E. Laplara. W. M. Davis, C. C. Cummins. Angcw. C'hrni. 1995. (07. 2181:
Angciv. Chm. b i t . Ed. EngI. 1995, 34, 2042.
Z. Duan. J. G. Verkade. Inorg. C h m . 1995. 34, 1576.
S. M. Rocklage. R. R Schrock. M. R . Churchill. H.!.
O ~ g r i n o m ~ ~ t a1982,
l l i ~ ~I .. ~1332.
W. Plass, .! G. Verkade. 1 A m . C h w i Soc. 1992. 114, 2275.
J. Manna. R. J. Kuk. R. F. Dallinger, M. D. Hopkins. J. Ani. Chov. So(.. 1994.
116. 9793.
R. R. Schrock. K.-Y. Shih. 0 . A. Dobbs. W. M. Davis. J Am. CIicw~.So<. 1995,
All operations were performed under dinitrogen using appropriately dried and
degassed solvents. N M R data are reported in [D,]benzene at 20 C unless otherwise
noted. See Table 1 for selected N M R data.
[(N3N)W-P]: A mixture oT[(N,N)WCl] (164 mg. 0.28 mmol) and LiPPhH (66 mg,
0.57 mmol) in a mixture of toluene (20 mL) and tetrahydrofuran (5 mL) w a s heated
for 2 days at 80'C. The color changed from orange to deep red. The solvent was
removed in viicuo and the residue was dissolved i n pentane ( 1 00 mL). The mixture
was filtered and the solvent was removed from the filtrate in vacuo. The resulting
orange residue was recrystallized from ether at -40 C ; yield X7 mg ( 5 3 % ) . Anal.
calcd (found) for WC,,H,,N,P: C 31.36 (31.54). H 6.84 (6.55). N 9.75 (94X)
[(N,N)Mo(PPhH)]: A solution of[(N,N)MoCI] (135 mg. 0.27 mmol) and LiPPhH
(38 mg. 0.33 mmol)in a mixtureof toluene (15 mL)and tetrahydrofuran (5 mL) was
heated for 12 h at 50'C. The solvent %its removed in vacuo and the residue was
taken up in pentane (50 mL). The mixture was filtered and the solvent was removed
from the filtrate in vacuo. The orange residue was recrystallized from cther at
-40°C; yield 109 mg (70%).
[(N,N)Mo-P]: A solution of[(N,N)MoPPhH] (60 mg) and LiPPhH ( I 6 mg) in a
mixture of toluene (20 mL) and tetrahydrofuran (5 m L ) was heated to 70 C for
12 h. The color changed from orange to yellow. The solvent was removed in vacno
and the residue was dissolved in pentane (50 mL). Concentration of the pentane
solution in vacuo produced a yellow crystalline solid; yicld 4 2 m g ( X l % )
[(N,N)Mo=P] also can be prepared directly from [(N,N)MoCI] in 11 manner
analogous to that used to prepare [(N,N)W=PJ. Anal. calcd (found) for
MoC,,H,,N,P: C 37.02 (36.80). H 8.08 (7.85). N 11.51 (11.53).
X-ray diffraction study of [(N,N)W=P]. WC,,H,,N,Si,P. M = 574.58. A yellow.
cubic cry?tal (0.280 x 0.280 x 0.280 mm) was determined to possess cubic metric
symmctry (25 reflections. 14.0-22.0' in 2 0 ) : 11 =17.166(4) A. I / = 505X(I) A,.
P . . , ~ ~=1.509 gem-,, space group PUS (no. 205). Z = 8. F(000) = 2304,
p(MoKJ = 48.72 cm-I. Data were collected on an Enraf-Nonius CAD4 diffractometer, Mo,, (2. = 0 71069 A) radiation, at 187 K . Reflections were memured with
widths of (0.80 + 0.35 tan())'. in (11 in the w-20 mode at a rate of between 1.9 and
Ih.O'.min-' in (II to a 28,,\, of 44.9 . A total of 3693 reflections were collected, of
which 1239 were unique (R,,, = 0.08). Lorentz-polarization, absorption (trans. factors: 0.93-1.06), and secondary extinction (0.30939 x 10.') corrections were applied. The structnre was solved by standard Patterson and difference Fourier techniques. Full-matrix least squares converged at R(R,) = 0.028(0.025) and
GOF = 1.05 using neutral atom scattering factors and anomalous dispersion terms
for all non-hydrogen atoms. Hydrogen atoms were placed in calculated positions.
Final cycles based upon IF1 with 683 observations (1>3u(1)) and 74 variables gave
rise to residual electron density of 0.69 e k 3 . All calculations were performed with
TEXSAN crystallographic package.
X-ray diffraction study of [(N,N)Mo(PPhH)]. MoC,,H,,N,Si,P.
M = 564.78. An
orange, prismatic crystal (0.280 x 0.140 x 0.2XO mm) was determined to possess
monoclinic metric symmetry (25 reflections, 20.0-30.0'' in 2 0 ) : u = 16.32(2),
h = 9.82(2), c=19.55(2).& fl=110.7(1)-.
V = 2 Y 3 2 ( 7 ) A s . pcx,cd=1.279gcm-'.
space group P2,:n (no. 14), Z = 4, F(OO0) = 1192, p(MoK,J= 6.25 cm- I . Data were
collected on a Rigaku AFC6S diffractometer, Mo,. (A = 0.71069 A) radiation, at
173 K. Reflections were measured with widths of (1.31 + 0.30 taiiU) in iw in the
0 ~ 2 mode
at a rate of 16.0' inin-' in (I) (8 rescans) to a 20,,, of 45.2 . A total of
4193 reflections were collectcd of which 4025 were unique (R,,, = 0.125). LorentLpolarization, absorption (trans. factors: 0.91 - 1.06). and secondary extinction
(0.16781 x lo-') corrections were applied. The structure was solved by standard
Patterson and difference Fourier techniques. Full-matrix least squares converged at
R(R,) = 0.040(0.037) and G O F = 1.75 using neutral atom scattering factors and
anomalous dispersion terms for all non-hydrogen atoms. Hydrogen atoms were
placed in calculated positions. Final cycles based upon 1 FI with 2889 observations
( I > 3 o ( I ) )and 272 variables gave rise to residual electron density of 0 35 e k 3 . All
calculations were performed with TEXSAN crystallographic package. Further details of the crystal structure investigations may be obtained from the Director ofthe
Cambridge crystallographic Data Centre. 32 Union Road. GB-Cambridge CB2
IEZ (UK). on quoting the full journal citation.
Cerium(rr1) Chloride Promoted Nucleophilic
Addition of Organolithium Reagents to
a-Alkyl-P-Ketophosphine Oxides:
A New Protocol for the Synthesis of
Stereochemically Defined Trisubstituted Olefins
Giuseppe Bartoli,* Enrico Marcantoni, Letizia Sambri,
and Monica Tamburini
Given the importance of stereochemically defined carbon carbon double bonds, extensive effort has been devoted over the
years to their stereoselective construction.['] Nevertheless, while
efficient procedures are available for the synthesis of stereochemically defined disubstituted alkenes,['] a general method
for trisubstituted compounds is still needed. The classical
Horner method offers poor stereocontrol in the formation of the
key phosphine oxide intermediates with a tertiary hydroxyl
group in the /&position.[' - 4 1 An efficient access to trisubstituted
olefins has been recently proposed by Denmark et al.,L4]who
succeeded in adapting the Warren variant of the Horner-Wittig
method[$] for the highly stereoselective construction of cedialkyl-8-hydroxyphosphineoxide intermediates by using the chiral reagent 1 as starting material (Scheme 1). The method is
Received: April 28. 1995 [Z7941 IE]
German version: A i i g ~ w Chcw.
1995, 107, 2184-2186
Keywords: complexes with phosphido ligands molybdenum
multiple bonds
phosphorus compounds *
tungsten compounds
[ l ] C. C. Cummins. R. R. Schrock, W. M. Davis, A n g m . Chcm. 1993, 105. 758:
Angeic. Cllem. Inl. Ed. Engi. 1993. 32. 756.
[2] K.-Y. Shih. K. Totland. S. W. Seidel. R. R. Schrock. J. A m . Chem. Sot,. 1994.
116, 12103.
131 .! S. Murdzek, R. R. Schrock in Higlr 0.sidurron Srurr~A/ky/i[/j,ffc, Cm,ip/c.xcr.
VCH. New York. 1988.
[4] 0.J. Scherer, Angehr. Chem. 1990. f02,1137; Angcw. ('liem. fnt. Ed. Ef7gl. 1990.
2Y. 1104.
VCH Verlugsgesellschufi m b l f , D-69451 Weinhrim. 1YY5
Scheme 1 . Denmark synthesis of a-dialkyl-l/-hydroxyphosphamidates. a) Diisobutylalurninum hydride (DIBAL). b) CeCI,. NaBH,, or LiBHEt, or
LiBHsBu 1.
Prof. Dr. G. Bartoh. Dr. L. Sambri. Dr. M. Tamburlni
Dipartimento di Chimicd Organica
"A. Mangini". v. le Riaiorgimento, 4, 1-40136 Bologna (Italy)
Telefax: Int. code (51)6443654
Dr. E. Marcantoni
Univcrciti di Camerino (MC) (Italy)
0570-0833iY.5:341N-_70463 /O.fJO+ .-7S:O
Angcw. chi^. Inr. Ed. E ~ R I 1995.
34. No. 18
Без категории
Размер файла
442 Кб
bond, monomeric, metalцphosphorus, contain, triple, complexes, tungsten, molybdenum
Пожаловаться на содержимое документа