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An Unconventional Intermolecular Three-Center NЦH Е H2Re Hydrogen Bond in Crystalline [ReH5(PPh3)3]╖indole╖C6H6.

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An Unconventional Intermolecular Three-Center
H,Re Hydrogen Bond in Crystalline
[ReH,( PPh,),] indole * c6H6
Jeremy Wessel. Jesse C. Lee, Jr., E d u a r d o Peris,
Glenn P. A . Yap, Jeffrey B. Fortin. John S. Ricci,
Gjergji Sini. A l b e r t o Albinati,* T h o m a s F. Koetzle,*
Odile Eisenstein,* Arnold L. Rheingold,* and
Robert H . Crabtree*
In the hope of' introducing ideas from molecular recognition
into transition metal complexation and catalysis, we have been
studying hydrogen bonding"] i n metal complexes. H-bonding is
common between a weak acid A-H and one or two weak bases
B, to give a 2-center ( I ) or three-center H-bond (2). In a number
of recent caseb.[" for example 3.LZa1intramolecular H-bonds of
would be adopted in the absence of geometrical constraints such
as those present in the chelate system 3.
We chose indole because it is a good H-bond proton donor
but does not self-associate significantly because it has no good
H-bond proton acceptor site. We now find that the polyhydride
[ReHJPPh,),] cocrystallizes with indole to give jReH,(PPh,),]
.C,H,NH.C,H, (4) as large yellow crystals. A n X-ray crystal
structure clearly showed that the N-H hydrogen atom of indole
is close to two of the rhenium hydrides, forming a three-center
H-bond of type 2. A subsequent neutron diffraction study
(Fig. 1 ) confirmed this result, and both studies located the hydrogens in positions similar to those found"] for free
[ReH,(PMePh,),] by neutron diffraction.
C105 C104
an unconventional kind have been discovered in which the weak
base component is a metal hydride. Structural and spectroscopic
data12' suggest H - . . H distances of about 1.7-1.9A and Hbond strengths of 3-6 kcalmol-I. If the Ir-H bond in 3 is
replaced b y l r - X ( X = F,CI, Br,or I),conventionalN-H"-X
H-bonds arc formed, but surprisingly, these are weaker for
X = CI. Br, and I, and only marginally stronger for X = F.131We
wanted to find out if intermolecular H-bonding was possible
with a suitable H-bond donor AH, and if so, what geometry
Fig. 1 The ORTEP diagram of the neutron diffraction structure (20 K ) o f 4 with
ellipsoids dra6n at 50% probability. The metric parameters of the N-H . . . H , R e
unit are given in Figure 2. Selected distances [A] and angles [ 1. Re P1. 2.396(3);
Re-P2.2.387(4); Re-P3.7.376(3).Pl-Re-P2.
IlO.0(1): P?-Re-P3. 105.6(1): PI-ReP3. 133.9(1): Re H1. 1.683(6); ReeH2. 1.683(5): Re - H i . 1.686(5); Re-H4.
1.683(6): Re-H5. 1.681(6); Hl-Re-H2. 79.33).
Prof, Dr. R H . Crahtree, J. Wessel. Dr. J. Lee, Jr.. Dr. E. Peris
Y'ile C'henii\tr! Department
211 Prospect Street. New Haven. CT 06511 (USA)
Telslax. Inr code + (203)432-6144
c'-niail: cr,ihtrcerir
Prof. L)r. A . 1.Rheingold. Dr. G. P . A . yap
Uni\crsit\. of Delaware Chemistry Department
Newrark. Llb 1Y716 (USA)
Tclefiih- 1111 code + (302)-831-6335
e.iii:iil : iirni hcinitr
P r d Dr. A Alhinati
In\titute ol' Pharmaceutical Chemistry
L ' n i c c r ~ i t i . of Milan. 1-20131. Milan (Italy)
Dr. T. I- K o e r ~ l e
Bi-ookhavcii National Laboratory
Upton. hY. 11973 (USA)
1clet"i.x l i l t . code + (516)282-5815
c-moil koctzle;(
Prof. I)r 0 Eiaenstein
1 ~ x h o r ; i t ~ ~de
i i eChimie Theorique. (URA 506) B i t 490
Uni\,ersitG de Paris-Sud. 91405 Orsay (France)
T e l c h x : l n i . code + (1)60-19-33-0?
e-mail odile.cisenatein~~i
1 H. Fortin. I'rof. Dr. J S. Ricci
I3NL. Upton. and liniversity of Southern Maine. Portland. M E (USA)
r1r.G Sin
itc de Cergj-Pontoise (France)
T h i s w o r k wiis supported by the NSF. the CNRS (URA 506) and Fellowships
irom the NSF and W, R. Grace & Co. to J. W. The neutron study was carried
o u t a t the I-tieh Flux Beam Reactor at Brookhaven National Laboratory under
contrlict I)E-.AC02-76CH00016 with the US Department of Energy. Office of
B:isic Encrx! Sciencec. Division of Chemical Sciences.
(Cyttp =
[Cy,P(CH,),],PPh) can be protonated with HSbF;C,H,
give [ReH,(Cyttp)]SbF, .['I In our case, [ReH,(PPh,),] cocrystallizes with a much weaker acid, indole. to give crystals in which
the L,H,ReH,. . H-NC,H, interaction is strong enough to
hold the two components together in the crystal without complete proton transfer. A molecule of benzene was also found. but
apart from the ReH, . . H -N interaction. there are no other
close contacts in the structure.
The unusually precise neutron diffraction study161shows that
the two short H " . H distances in 4 are vety asymmetric
( H l A . . . H I , 2.212(9) A; H l A . . . H 2 , 1.734(8) A ) , the shorter
being similar to the distances foundr2](1.7-1.9A) in the intramolecular N - H ' ' . H--M examples. Nonbonding H ' . . H
contacts are normally about twice the van der Waals radius"' of
H, or 2.4A; all other N H . . . H R e distances found here are
greater than 2.6A. The finding that the N H proton lies at a
distance of only 0.066(7) A from the plane defined by N1, H I ,
and H2 fulfills the usual criteria[lc1for three-center H-bonding
(2). The N - H bond points towards the closer metal hydride. H2
(N-H-H2 = 163.1(6), N-H-HI =130.9(5).), which implies that
the dominant interaction is with Re-H2 (Fig. 2). H2 is unique
in that it is the only hydrogen in the structure occupying a B-site
I683(5)A ,,
I18.9(4)..\.-__ I63 l(6)
I .683(6)A"\P7.2(3),
*'* 12(9)A
0,Fig. 2 . The detailed structure of the N H . . . H,Re unit from the neutron diffraction
on a very flat potential surface, of the relative positions of the
two molecules gives a structure similar to that of4. In particular,
a three-center H-bond is preferred over the two- or four-center
types, and the asymmetry of the experimental structure is reproduced ( H . . . H distances: 1.92w (H2) and 2.48 A (Hl)). The
interaction energy of 8 kcal mol- ' is in reasonable agreement
with experiment (4.3 kcal mol- '). In the theoretical study, the
N - H is slightly closer to P1 than is found in 4 ; steric effects may
be responsible. As is well known." the lone pair in a d Zdodecahedral complex is perpendicular to both trapezoidal planes. Although in this complex it is not far from H2, it does not point
towards the N H bond and so is unlikely to contribute much to
the stabilization of the hydrogen bond. This emphasizes the
electron donor power of the M H bond, which is also apparent
in the ready formation of H, complexes by protonation of metal
hydrides (even in competition with protonation at the metal),[*]
in the ability of M-H in such complexes as [Cp2Zr(H),(CO)]["1
to engage in back donation, and in the M - H/H, "cis effect".[I3'
Our studies show that the presence of indole as crystallizing
agent for [ReH,(PPh,),] allows rapid formation of much larger
(ca. 5 mm3) crystals than in its absence, but that the structure of
the complex is not significantly altered by H-bonding. Indole
may be a useful agent whenever a compound that is a potential
H-bond acceptor fails to crystallize satisfactorily for crystallographic or other single-crystal studies; it complements the
Ph,PO agent suggested by Etter114]for compounds having Hbond donor groups.
of a dodecahedron (Fig. 3), and so is sterically the least hindered.
In order to eliminate the possibility that nonspecific crystal
packing forces are responsible for the structure, we attempted to
grow crystals using indene,
which is isosteric with indole
but lacking the N H bond. If the
N - H . . H interaction were not
important for holding the
supramolecule together, indene
ought to cocrystallize just as
well as indole. However, only
small crystals could be grown
under conditions identical to
those used for 4 but substituting
for indole. and these
F , ~ 3.
. The dodecahedra] coordinaExperimental Procedure
tion geometry in the same molecular
contain only [ReH,(PPh,),]
orientation as Figure 1 showing A
and no indene (from N M R and
The general synthetic and spectroscopic methods were previously described [2a].
and B sites and the two orthogonal
IR evidence). This suggests that
Pentahydrido(tristriphenylphosphane)Re".indole: A 0.8 mL aliquot of a filtered
BAAB trapezoids (dotted).
solution of the complex 1151 [ReH,(PPh,),] (1.1 g, 1.1 mmol) in benzene (10mL)
the N - H . . H interaction is inwas added to a test tube containing indole (50 mg. 0.4 nimol). Hexanes were added
deed important in holding the
to form a supernatant layer. and the sample tube refrigerated at 5 "C. After 1 day,
assembly together and that the very short H . . H distance is a
large yellow crystals formed (18 mg. 21 "A).
result of the H-bonding. Weak aromatic stacking interactions
between PPh, and indole may well also contribute to the stabiReceived: January 18, 1995
Revised version: August 1. 1995 [Z76391E]
lization of the supramolecular assembly, however.
German version: A n g w . Clwn. 1995. 107. 271 1-271 3
The IR spectrum (KBr pellet) shows a shift in the N-H band
from 3437 cm-' in free indole to 3242 cm-' in crystals of 4.
Keywords: hydrogen bonding . hydrides . indoles . rhenium
According to the Iogansen equation,['] which relates the bond
strength to the shift in I R frequency, the H-bond strength in this
case is 4.3 kcalmol-', close to the values (3-6 kcalmol-') determined for intramolecular M - H . . . H - N interactions.l2I
[ l ] a) G. A. Jeffrey, W. Saenger. Hwlrogrn Bonding in B i O / O g f C o / Structure3,
Figure 2 shows the structural details of the ReH, . . H N
Springer, Berlin, 1991. b) ref.[la], p. 110: c) ref.[la]. p. 22.
[2) a) J. C. Lee. E. Peris, A L. Rheingold. R. H. Crabtree. J. A m . Chrm. SOC,
interaction. The N-H ' . H angles are comparable to those
1994. 116. 11014. G. P.A. Yap, A. L. Rheingold. P. Das, R. H. Crabtree,
seen"] in standard three-center H-bonds, but the Re-H . . . H N
Ifiorg. Clwm. 1995,34, 3474: b) S. Park, R. Ramachandran. A. J. Lough, R. H.
angles (97.2(3) and 118.9(4)") are strongly bent. A nonlinear
Morris, J. Chrm So[. C h m . Conimim. 1994. 2201. c) A much weaker interacM-H . . H N arrangement was already apparent[,"] in 3
tion of the same type is also known: R. C. Stevens. R. Bau. D. Milstein. 0.
Blum, T. F. Koetzle, J. Chwn Soc. Dulron Trans. 1990, 1429.
(Ir-H . . H = 132") and related species[2b1but could have been a
[3) E. Peris, J. C. Lee, J. Rambo, 0. Eisenstein, R. H. Crabtree, J. Am. Clzem. SOC.
result of she constraints of chelation. Now we see that in an
1995. 117. 3485.
unconstrained system like 4, a strongly nonlinear ReH . . . H N
[4] a) T. J. Emge. T. E Koetzle. J. W. Bruno. K . G . Caulton. fnorg. Chum. 1984. 23,
arrangement is still preferred. This may be because an elec4012; b) T. F. Koetzle. K G. Caulton. hid.1984, 23, 4012.
[S] Y. Kim. H . Deng. D. W. Meek. A. wojcicki, J. Am. Clirm So<.1990, 112.2798.
trophile tends to attack a (T bond in a side-on manner.181In this
16) a) Neutron diffraction structure of 4 ( M , = 1173.3), triclinic, space group Pi;
view, 4 can be considered to represent the earliest stages of
T = 2 0 K ; a=13.037(3), h=13.410(4), t.=19.221(5)A. a=91.67(2).
protonation of the Re-H2 hydride to give an H, complex,
/j =107.79(2). j. =119.02(2), V = 2733(1)A3, Z = 2 . Q.~,,,, = 1 . 4 2 5 g ~ m - ~ .
which would be bound side-on. This picture suggests other types
mm3; 2H,,,
91"; p =1.952cm-';
crystal dimensions 3 . 4 1.9x0.72
= 1.0462 A; scan mode w:20, 12394 independent reflections observed,
of CT bonds should show H-bonding behavior; indeed, we have
all of which were used for refinement: conventional R ( F ) ,[ R >3o(F)] = 0.052.
now found similar intramolecular B-H . . . H-N interactions,
Measurements carried out at the Brookhaven High Flux Beam Reactor. The
with bent B-H . . . H-N angles, in a number of amine- b ~ r a n e s . ' ~ ]
crystal was sealed in an Al can under He. mounted in a DISPLEX refrigerator.
Theoretical work confirms that the interaction is attractive.
and placed on the diffractometer. A hemisphere of reciprocal space was Sampled. to a limit of sin O I L = 0.67 k'.
The 4 2 0 step-scan profiles were reduced
The model compound [ReH,(PH,),].NH, was studied by ECP
to inkgrated intensities. assuming the first and last tenth of each scan to be
ab initio calculations with functional density theory."'] Free
background. Lorentz factors and absorption corrections (range e-U' = 0.702ReH,L, was first optimized and found to be in close agreement
0365). calculated by means of an analytical procedure [6b], were applied. The
with the neutron structure.[41It was then frozen, and NH, was
crystal was approximated by seven boundary planes, as follows: (010). (001).
( i l l ) . ( i l i ) , ( l i ? ) , (1iO). Initial coordinates for all atoms were taken from the
placed in the vicinity of H I and H2. Geometrical optimization,
'f: VCH
W~rlagsgasel/schufirnhH, D-694Sl Wrinheim, 1995
OS70-OX331YSi3422-2SOX $ 10.00+ ,25111
Angew. Clzeni. Int. Ed. Engl. 1995, 34, No. 22
X-ray resiilts. Refinernenis were carried out by a least-squares procedur-e [bc].
miniiiii~ing1 1 1 (F:- L'b-:)2 using all independent data. Weights were assigned
ii\ 11 = 0 I. uhere 0' = (OF,+ (0.015)fi:)2). The structure model included
ad~u.;tahlepositional kind anisotropic thermal parameters for all 136 iitorns. a
\tale l"ictor k . and ii parameter for an isotropic-type I extinction correction
u i t h Lorenman mosaic spread [6c]. The maximum extinction correction was
lo"<). for I l k (T23) reflection. Neutron scattering lengths were taken irom a
recznl coiiipilAion by Sears [6b]' h, = 0.66484. b,, = - 0.3741, h, = 0.936.
/I,, = 0.511. hKL= 0.920 (all x l o - " crn). Further details of the crystal strucion are available on request from the Director of the Cambridge
Iiic Data Centre. 12 Union Road. GB-Cambridge CB2 IEZ
ling the full journal citation. b) J. DeMeulenaei-, H. To
~ ' i ) . s r d / o g r1965.
/Y. 1014: L. K. Templeton, D. H . Templeton. Am.
y r . ~ W K I. l ~ y, Storrs. C'T Abstract E10. 1973: c) J . 4 . Lundgren.
, y r u p l i i ~( ' o i i i / ) i t i e w Pm,qrfii~i.s
in Report UUIC-Bl3-4-05, Institure of Chemistry.
Iliiivcrsit). ot'IJppsa1,i. Sweden, 1982. d) P. Becker. P. Coppens. Ae,ru Cr)wdbirr S i w .A 1974. 30. 129. i h i d 1975. 3 I . 417: e) V. F. Sears in Iriteriie~tioniil
X r I ) / c , \ / o r ( ' r ~~ / u / / r > g r o p / i Vr ,d . C' (Ed.: A. J. C . Wilson). Kluwer. .4c;ideniic
Puhlishei-h. Dordreclit. 1993.
S. (i K ; ~ ~ ~ i r i ; iPi i ,A . Hamley. M. Poliakoft J. A i r i . C/wir. SIK 1993. 1 1 5 ~
4 069
R H . ('rahlree. Aiigcw (1/1wr7. 1993. 105. 828: Aiigeii. Ciwni. / t i / . Ed. Eiijii.
1993. 32. 7 X c l
T Richard.;(in. S. deG;ila. P. E M . Siegbahn. R. H. Crabtree. J. A m C/irn?
.So, . ~ u h i n i t ~ c d
i i ) C~aiissiaii92 DFT. Revision F.4: M. J. Frisch, G. W. Trucks. H. B. Schlegel,
P. M. W. G i l l , B G. Johnson. M . W. Wong. J. 8 . Foresman. M . A. Robb. M.
Replogle, R Gomperts. J. L Andres. K. Raghovxhari.
inzale,. R. L Martin. D. J. Fox. D. J Deft-ees. J. Baker.
Poplc. Gaussian Inc.. Pittsburgh. PA, 1992 For further
tion see ret'[lOb] b) For Re. a relativistic ECP [IOc] wa.
shell of Re includes the 5s. 51, w t h a basis set of triple
CP of Stevens and Biisch [IOd] was chosen with 'I doubl
riz:ition. Indole was represented by a planar N H ,. The
h y r l i ideb iiic ieprescnted by a triple basi, set with poliiriration and the H of
PH h!
\iiiglc ;basis set. For tlic functional density. we used the hqbrid
luiic'tioii\ o l Bccke (B3LYP) [loel. c ) D. Andrae. U. Hausserrnann. M. Dolg.
H Sroll. ti l%xiss.?liiwr. C ' h h Acrrr 1990. 77. 123: d) W. J. Stevens. H. Bash.
M. Kraus\. ,/ C/wiri. Pii~..\. 1984. I?. 6016. e) A. D. Becks. J. (1Ii~w.P/I).S.1993.
YS. i64X: P I Ste\cns. F. .I. Deblin. C. F. Chablowski. M. J. Frish. ;bid 1994,
YH. I I h l i .
J. K Hurderl. K . Hollmmn. R. C . Fay. /rrorg CIiiw71 1978. 17. 2553.
J M Manriclue/, D. R. McAlistei-. R. D. Sanner. J. E. Bercaw. J A I I I .C ~ P I I I .
1978. 100. 2716: flljd. 1976. 98. 6733.
L S Van
Slugs. I . Eckert. 0 . Eisenstein. J. H. HAl. J. C. Huffmiin. S. A.
Koctrle. Ci. J Kubas. P. J. Verganini, K. G. Caulton, J A m
<'/wnr. Sor 1990. 112. 4831.
M . ( l-.ttt.i. . 4 < < .( ' / i < ~ . Rcs. 1990. 33. 120.
_I ('h;itl. R 5. ('oft'eg. .I ('II~wI.
So<..4 1969, 1963
'r t.'.
chalcogenide chemistry have yielded several new "polymeric" materials: [Mo,Se,Js-. [Mo,Se,,]' -. [Mo, ,Se,,]" -,
[MO,S,,]~-, and [ M O , S ~ , , ] ~ - . ~I n~ this
- ~ I paper we report the
formation of a novel puckered Set, ring. stabilized by
[Mo,S,,]' - clusters through interchalcogen interactions. This
new form of selenium fits into the Q, sequence [Q = chalcogen)
of homoatomic sulfur ring structures, S,, Slo. S,,, . . . Szo.r5]
Large ring systems of polyselenides and polytellurides have
been examined as parts of metal complexes.[6. For example, it
has been known that selenium and tellurium ions can form
complex rings since the isolation of an S e i + ring in
[Se,][AICI,], .[*I Kanatzidis has found isolated Sef; rings in
(Ph,P),[Se, l ] . These rings comprise two Set- ions and one Se2+
ion and link to form a cluster of corner-sharing "cyclohexanelike" rings of selenium.[91Very recently, Sheldrick reported that
the structure of Cs,Tez, contains a two-dimensional 4, network
of tellurium Tei- ions as well as discrete Te, rings."'
The synthesis of the above-mentioned polychalcogenides has
been achieved through moderate temperature reactions of the
elements with oxidizing agentsc8]-in the case of polyselenide
ions with a mild oxidant["I---or through methanothermal reactions with the elements.'"] We have had some success in preparing large polysulfide clusters by hydrothermal reactions.[4. 'I
and we used this synthetic route to prepare the title compound 1.
The hydrothermal reaction of (NH,),MoS, with A$,
(A = Na, K: .Y = 2-6) generally resulted in the formation of a
new phase of (NH,),[Mo,S
Replacing the polysulfide salt
with A,Se, (A = Na, K ; s = 2-4) yielded primarily selenium
metal, molybdenum metal. and some soluble polychalcogenides. By preparing a new heteropolychalcogenide salt,
Na,S,Se, ,[''I whose redox potential lies between the polysulfide
and poly~elenide,"~.
14] we were able to tune the chemistry of the
redox reaction and isolate compound 1.
The solid-state structure of 1 is shown in Figures 1 and
'I Double layers (AB packing) of trinuclear molybdenum
Richard A. Stevens, Casey C. Raymond, and
Peter K. Dorhout*
Since their discovery!'] the [MO,S,,]~- core clusters have
spurred researchers on to further study. Electron-poor, trinuclear molybdeniim chalcogenides. sulfides in particular. have
aroused considerable interest because of their hydrodesulfurization activity.I2I New ventures into trinuclear molybdenum poly[*I Prof Dr. 1'. K . L h r h o u t , R . A. Stevens. C. C . Raymond
L)ep.irlmeiit 01' ('hemistry. Colorado State University
I-ort Collins. c'o 80523 (USA)
Telet'ix: Int. cude + (303)401-1801
[**I Fin:inci;il hupport w a s provided by the American Chemical Society. Petroleum
Rehcarcli F(itiiidstion. and the Research Corporation, Cottrell Fellowship.
Addilional help provided by C. M Zclenski (EDS). S . M. Miller (X-ray diff raction).
and Di-. H. Murray. Exxon Kescarch. for providing some molyhden u n \tarting iiiLitcriiils.
Fig. 1 Crystal structure of I viewed along the c axis [15]. Only halfthe cell is shown
forclarity. 6 :
N iitoms. 0:
Moatoms. 0 : S a t o m s . 0:
Seatom\ These-Sebonds
within the Se,, ring are nearly all identical: 2.335(2) and 2.327t2) A. The internal
Se-Se-Sc ring angles are consistent with those found for Se, and re8 [?I. alternating
between 105.14(4) and 102.94(7)'. Instead of [Mo,S,, .,Se, ,] the simplified structure of [Mo,S,,] is shown.
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hydrogen, bond, crystalline, c6h6, unconventional, three, nцh, h2re, reh5, intermolecular, pph3, indole, center
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