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Direct MetalЦMetal Bonds Between High and Low Valent Complex Fragments The Reaction of Metal Bases with the Metal Acids [Re(NR)3]+ and [Mo(NR)2]2+.

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resemble those of 3 and 4.In view of the similarity of the N M R
data of 6 and 7 as well as the band-to-band analogy of the IR
spectm. an almost identical structure may be assumed for the Fe
analogue 6.
The general applicability of the concept of Ti-M bond stabilization by use of Ti complex fragments containing polydentate
ainido ligands was demonstrated by the synthesis of the Ti -Co
species 5 and 8. Stable dinuclear compounds with this structural
element have been elusive until r e ~ e n t l y ” ’ due
~ to their extreme
thermal lability. Both 5 and 8 can be readily handled in solution
and were found to be sufficiently stable at ambient temperature
to enable ;I systematic investigation into their reactivity.”81 In
general. type A and B Ti amides therefore appear to “do the
trick” i n stabilizing Ti-M (M = late transition metal) heterobimetallics.
E.xperiiiwtiu1 Procedure
2 : A 7.5 hi solution ofii-butyllithium in hexanes (5.72 mL) was added to a mixture
of HC(SiMc,NHC,H,CH,), (2.41 g. 4 72 mmol) [Sb] in pentane (30 niL) and diethyl ether ( 2 mLJ. ~ h i c huiis cooled at -50 C The reaction mixture was subsequently u;iriiicd and stirred at room temperature for 2 h. The resulting lithium
ainide \uspension was then cooled to -50 C, solid [TiBr,(thf),] (2.69 g =
idded. and the reaction mixture warmed to room temperature over
20 h Evaporatioii ofthrsolvciit.exti-action ofthe residue with toluene(20 mL). and
liltralion ~ieldedii deep red filtrate. which was concentrated to 10 mL and stored at
-40 C to kield 2 ‘is red crystals. Yield: 1.65 g (55%).
3 8 : Solid .ilkall carbonyl rnetalate (1 mmol) was added to a solution of 1 or 2
(1 minol. l b r I458 mg. for 2 631 mg) in toluene (30 mL) cooled at -70 C. and the
reaction iiiixtiii-c uarmcd to rooin temperature over a period of 20 h . Evaporation
of tlic solbcnt. extraction of the residue with pentane (20 mL), and subsequent
filtration 4 ieldcd ).cllo\v-orange solutions of the heterobimetallic complexes. Evaporation 01the solvent yielded the reaction products a s inicrocrystalline solids, which
Mere u,ished with cold pentane. isolated yields: 3 59%, 4 68%. 5 48%. 6 61 %.7
73?b, 8 3Y‘!,,. Single crystals suitablc for X-ray crystaiiography were obtained by
slou coolitif of wlutioiis of the compounds in toluene.
Received: Octobcr 13. 1993 [Z 6414 IE]
German version: A i i p i . Chciii. 1994. 106. 705
[I] W. M P B Menge. J. G. Verkade. /iiorg. Chon. 1991. 30. 4628: A. A. Naiini,
W. M . P. B. Menge. J. G. Verkadc, ihid. 1991. 30. 5009: J. G. Verkade, Acc.
C.heiii KP\ 1993. 36. 483.
[2] <’. C Cuinmins. R . R. Schrock. W. M. Da\ia. Orguiioiiieiri//i~,.s1992. I f , 1452;
c‘. C. Cumrnins. J Lee. R. R. Schrock. W. M . Davis. Angrw.. Choin. 1992, 104,
1510: .Iri,cy11. ( h r i i i . / i i r . Ell. h g l . 1992. 31, 1501: C . C . Cummins, R . R.
Schrock. W. M . Davis. i M . 1993, 105, 758 and 1993. 33. 756
131 D. W Stephan. C ~ r dChrm.
.
R E V .1989. Y j , 41.
[4] a ) C P Cascy. J Orgunoinet. Chivii. 1990. 1/10, 205 and references therein:
b) W J. Sxtaiii. J. P. Selcgue. OIXuitoiiic.rrri/i[T 1987. 6. 181 2.
[S] a ) L H Gade. N. Mahr, J C / w n .SOC.Udtoii Truii5. 1993.489: b) L. H. Gade.
C. Bcchcr. J. bb! Lauher. /nor.q. C ’ h o n 1993. 33,2308.
[6] a ) S. Friedrich. L H. Gade. A. J. Edwards. M. McPartlin. Chein. B w . 1993.
/ ? . 1797:h ) .I Chriir. So(,. Uulron Traii,. 1993. 2x61.
[ 7 ] Burger sl al h \ e reported the unsuccesafiil attempt to coordiiiate the in situ
1ithi;ited HC(SiMe,NHMe), to titanium(iv) centers: a ) H. Burger, R. Mellies.
cl. J Oi-,quiioiiiet. C/wiii. 1977. 142. 55. We have found that the use of
iryl-wbstituted amines of this type lcads to stable titanium complexes:
h) H. Mrmniler. L. H. Gade. J W. Lauher. I ~ O VChrvrr..
K.
submitted.
[ X I The o n l y knouii example of a titanium compound of thnt type. Selegur‘s
[Cp(C‘O)l~eTi(NMe,),].was reported to decompose rapidly i n solution at
ambient temperature [4b]. Case). et al. reported the synthesis of
[ C p i Z i - ( K ) I ~ e ( C O ) z C (pR/ ]= C H , . OtBu) and [Cp,Zr(Fc(CO),Cpl,]. The
latter I \ only stable in solutioii at temperatures below -20 C : C. P. Caaey.
R. E .lordmi. A . I.. Rheingold. J. .Am. Chc,iii. SOL..1983, 10.5. 665. O ~ g ~ i i ? o n w r i i / / I ( , \ 1984. .?. 504.
[9] M. Broohhai-t. W B. Studabaker. R. Husk, ~ V g u i i ~ i i i ~ , / [ i / /1987.
i C , \ 6. 3141.
[I01 Crybrala o f 3 ruitablc for X-ray studies were difficult to obtain and diffracted
onl) poorlq. This resulted in relatively high standard deviations o n all parameters. hut (he iniiin features of the structure are well established. Crystal data of
3 ( ,,H,,N,O,Si,TiFe, monoclinic, spacc group P l , ‘ 1 1 . (I =15.496(3).
1. = 29.219(3) /i= 104.518(2) ,M =555.57. I , = 5690 71
=1.297
F(000) = 2352, R = 0.0699.K, = 0.0709 for 2301
reflcctiuiis with /,‘o(/)
> 3.0 corrected for absorption [p(MoKr)= 9.1 cm-’1.
Crystal data of‘ 4: C,,H,,N,OISi,TiRu,
monoclinic. space group P2,:c.
L I =12.Y77(3)./1 =12.084(3).( =18.217(3) A,/) = 91.33(2)‘.M = 600.73. I’=
2855 Y I A I, Z = 4. pcdlUd
= 1 397 g c r C 3 . F(000) = 1248. R = 0 0484;R, =
A.
.
A’.
0.0518 for 2903 reilections with lo(/)>3.0 corrected for absorption
[Ir(Mo,,) = 9.0cm-’].
[ I l l a) W. S. Sartain. .I.P. Selegue, ./. h i . Cheni. S O ( . 1985. 107. 5818:
h) Or.quiioriri,/ri//ii.s1989, 8. 21 53.
[I 21 Cambridge Structural Database, Cambridge University. 1993.
[13] Whether d,-d, backbonding plays a role in these heterobimetallics a s invoked
for the ligund-bridged Zr- Rh complex [Cp*Zr(p-OCH2Ph,P),RhMe2][d(ZrRh) = 2.444(1) A](G. S. Fcrguson, P. T, Wolcranski. L. Piirkiiiiyi. M . C. Zonnevyllc. Orjianonw/u//ics1988, 7. 1967) remains to be investigated in MO cLiIciilations of appropriate model systems.
[14] See. for example. F. A. Cotton, P m g . /iiorg. Chcwi. 1976, 21. I . F. A. Cotton.
J. M. Troup, J. Ain. Chem. Soc 1974. 96, 1233; W. I. Biiiley, D. M Collins,
F. A. Cotton. J. Orgunoiiic/. Chem. 1977. 13.5, C53.
1151 Crystal data of 7 : C,,H,,N ,O,Si,TiRu. monoclinic. space group 12:c.
( I = 24.4733). h =15.417(3). c = 20.783(4) A, /<=104.20(2) , :M =772.92.
l’=7h01.X4A3. L = 8. ocrlLd=1.351 gcm-’. F(000) = 3200. R = 0.0663’
R , = 0.0667 for 1904 reflections with /‘o(/)> 3.0 corrected for absorption
[ii(MoKI)= 6.9 cin-’1. Further details ofthe crystal structures :ire available on
request froin thc Director o f the Cambridge Data Centre. 17 Union Road.
Cambridge CB2 1 EZ. U K on quoting the full journal citation.
[I61 A preliminary X-ray structure analysis of the aterically less crowded precursor
2 has revealed a similar arrangement of the tolyl groups [7 b]. \*hich is therefore
not to be interpreted as solely a consequence of the steric inter;iction w i t h the
Ru complex fragment.
[I71 D. Selent. R. Beckhaus, J. Pickardt. Or~jiliiic’”i[,rii//i~,\1993. 12. 2857. The only
other structurally characterized example o l a compound containing a n unsupported Ti-Co bond was reported by G . Schmid. B. Stuttc. R. Boese. C h m .
Brr. 1978, I l l . 1239.
[18] I f solutions o f 5 or 8 in benzene ;ire stirred at room teinperaturc over ii period
of .stveru/ r i c i j x slow decomposition sets in and generates [ jCo(CO),(PPh,)l,]
which precipitates from the solution.
Direct Metal-Metal Bonds Between High and
Low Valent Complex Fragments: The Reaction
of Metal Bases with the Metal Acids [Re(NR),j
and [Mo(NR)J* **
+
+
Jorg Sundermeyer,* Diane Runge, and John S. Field
Dedicated to Professor Wolfgang S u n d e r n q w
on the occccsion of his 65th hirthduj
The synthesis of heterobimetallic complexes in which a metal
center deficient in d-electrons (f block element, metal of the
group 4 or 5 ) with a complex fragment rich in d-electrons (typically a metal of group 8) fixed in close proximity is enjoying steadily
growing interest. The combination of antipodes of the periodic
system (early-late heterobimetallics)[’I holds the promise of cooperative behavior on the part of the metal centers in the activation of smaller molecules,[2’ an increased catalytic activity in the
homogeneous phase, or at least an insight into the interaction of
immobilized catalysts with oxide support materials.[31 Comparable synergistic effects could also be achieved by the combination of the same metal, or of two metals close to one another
[*I Dr. J. Sundermeyer. DipLChem. D. R u n g
lnstitut fur Anorpanische Chemie der Universitlt
Am Hubland
D-97074 Wurzhurg (FRG)
Telefax. Int. code (931)888-4605
Prof. J. S. Field
Department of Chemistry and Chemical Technology
University of Natal
P. 0 Box 375. Pietermaritrburg 3200 (South Africa)
[**I Hohervalente Derivate der d-Metall-Siuren, Part 9. This uork was supported
by the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie. the South African Foundation for Research Development. and the Univeraity of Natal. We would like to thank Prof. Helmut Werner for his support
and Dr. Lutr Gade for his expert debates. Part 8 : J. SundermeSer, K . Weber.
K. Peters. H. G . von Schnenng. Orgunoinr~tu//ic.s.submitted.
+
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in the periodic system. A prerequisite for this, however, is that
one metal center may be considered as electron-deficient because of its formally high oxidation state (> + 5 ) . the other as
low valent and electron-rich (oxidation state 1.0). Unequivocal
evidence of it direct interaction between the metal atoms would
be a M -M' bond wholly unsupported by bridging ligands. The
only compound which, to our knowledge, fulfills these criteria,
is the complex [Cp*W(O),-W(CO),Cp*] (Cp* = qs-C,Me,),
which was synthesized by autoxidation of [ iCp*W(CO),),] by
H. Alt et al.i"l This was reason enough for us to search for
svnthesis strategies for the isoelectronicallv related comDounds
0-f the type ~L,(0),M]-[Mr(CO)n,Lrn].and [L,(RN),M][M'(CO)",L',,I
Nucleophilic substitution reactions compete with electrontransfer processes in the reaction of electron-deficient 0x0 complexes with potentially reducing nucleophiles as a matter of
course. The selectivity in favor of the substitution increases when
the 0x0 function. 0' is replaced by the isoelectronic, yet more
strongly n-basic iinido function, ( R N ) ' ~ .A very fruitful branch
of organometallic chemistry has developed in the last few years,
in which reactions of high valent imido complexes with carbanand phosphorus ylides [*I, as well as the activation of
C-H bonds,['] stand in the foreground. The imido function
continued to prove itself as a useful protecting group in the masking of 0x0 functions, for example in the synthesis of organometallic functionalized oxometalates, such as NBu,[Cp*MO,] (M =
Mo, W)"] through selective hydrolysis of the imido precursors.
For this reason. we directed our attention primarily at metalated
imido complexes.
Recent works by R. R. Schrock,['" G. Wilkinson,["] and
M . L. H. Green['21report that, in the reduction of high valent
imido complexes with Na/Hg or [Co,(CO),], Re-Hg, Re-Co
and Mo-Hg bonds can be formed. A first early-late heterobimetallic complex containing bridging iniido ligands has just
been described by R. G. Bergman et aI.[l3] In the following we
report on a series of bimetallic compounds which have been
prepared in good yields in targeted syntheses by reactions of
[Re(N IBU),CI]['~~
and [Mo(NtBu),C1,]["l with carbonyl metalates of groups 6-8 (Schemes 1 and 2). Compounds l a - e and
+
The absence of a tendency for the complexes to fbrm clusters
of higher nuclearity by loss of carbonyl groups under normal
conditions, as is observed in the reaction of [Re(NtHu),CI] with
[Co,(CO),].I'' I is rather surprising. Onty rotamers can be identified spectroscopically; no isomers with bridging carbonyl, iso~ a r b o n y l , "o~r ~
imido ligands can be identified even at low temperatures. This explains why no spontaneous redox reaction takes
place through inti-amolecular ligand exchange under normal conditions." 51
-.
le
Id
Scheme I . Renction of [(/BuN),ReCI] wi t h the carbonyl metalates
2a-e were obtained in adequate purity for analytical purposes
after workup by sublimation. crystallization, or column chromatography. A selection of spectroscopic and analytical data is
shown in Table 1 ,
2a
2c
CI/Mo\ CI
J
2e
\
2d
Scheme 2. Reaction or [(!BuN),MoCI,] with the carbonyl metalate.;.
Compounds l a - e and 2a--e are formed by metalation of the
formally heptavalent and hexavalent cationic Lewis acids,
[Re(NR),]+ and [Mo(NR),]'+ respectively, with carbonyl complex fragments isolobal with CH,-. The compounds I a--e can
be described as a combination of a 16VE (valence electron) and
an 18VE building block. The donor and acceptor centers are
connected to one another by a polar metal-metal bond, which
is not supported by ligand bridges. The recently reported homobinuclear d' -d' dimer [(ArN),Tc-Tc(NAr),] (Ar = 2.6iPr,C,H,)[161 is comparable in its overall electron balance. In
contrast, 2 a-e are electronically unsaturated. Even if both imido
ligands are considered as using their donor capability to the full
extent, that is, one and two n bonds each. only 16 VE can be
assigned to the central molybdenum atom in each case. The difference A6 in the 13C resonance signals of the quaternary and
primary carbon atoms in tert-butylimido complexes is a useful
spectroscopic probe for the estimation of the electron density on
the metallic center." 'I The Ab values for 1a-e and 2a --ecorrelate
with the M'H acidities of the corresponding metal carbonyl
hydrides.["] As the metal basicity and a-donor ability (nucleophilicity) of metal carbonyl fragments are influenced to varying
extents by steric factors. a tendency.["' but not a linear correlation of A6(M =NtBu)/pK,(M'H), can be recognized (Table 1 ) .
Additional evidence for the structures given in Schemes 1 and
2 is provided by the results of crystal structure analyses o n single
crystals of 1 a (Fig. I ) and 2 a (Fig. 2).["' The molecular framework of l a has C- symmetry in the crystalline state. A mirror
plane runs through the atoms Re, Mo, C2, 0 2 , C 8 , N 1 . and
C9. The Re-Mo distance of 2.844(1) 8, is considerably shorter
than comparable Re-Mo single bonds. The metal-metal bond
of 3.12 8, in [(OC),Re-Mo(CO),Cp][Z'l for example, in which
none of the ligands plays a bridging role, or the asymmetrical
CO-bridged bond of 2.959( 1) 8, in [CpRe(p-CO),MoCp2]I'z1 are
significantly longer. Considered separately. neither of the metal
COMMUNICATIONS
Table 1 Experimental data froin 1 and 2.
Compound ( R = rBu)
W,)
S(C,)
Ad [c]
pK, [d]
M [el
( M ' - CO)
Color.
Yield. M.p.
68.65
30.90
37.75
13.9
645.0
68.61
30.78
37.83
16.1
(705.1)
69.03
31.00
38.03
15.1
594.8
61 63
31.34
36.29
19.4
577.2
69.0.;
30.71
38.32
8.3
570.9
71.99
30.96
41.03
l 3.9
731.7
yellow. 72%.
121 C [ f ]
>elloh. 64?6.
134 C
> C l l O h . 34%.
56 corange-yellow. 83 "'",
105 c
oranpe. 91 "4.
63 c
oranpe. 43 %.
171 'C [f]
1242 s
1204 \
71.62
30.66
40.96
16.1
(876.0)
1231 s
1200 s
12.16
31.43
40.73
15.1
1747 s
1204 s
68 7X
31.83
3695
19.4
593.8
123Y s
72.84
30 97
41.87
ti..:
58 1.7
v(C0) [a]
v(M
1993 vs. 1924 s,
1228 s
1211 s
1226 s
1211 5
1227 s
1209 s
I229 5
1912 \'b
1092 vs. 1916 5 .
1909 vs
2079 in. 1997 vs,
1990 5
1994 vs. 1949 vs
=
NC) [bl
1211 s
1225 )I
120s s
1240 s
I202 s
2072 s. 201 I s~
1994 vs
2023 m. 1982 kb.
1946 s. 1912 m,
1888 m
2022 s. 1962 s.
1939 VI. 1913 s.
1903 ni
2079 in. 2054 s.
2019 m. 1989 vs.
1971 vs. 1926 m
1978 5 , 1969 v\.
1926 vs
2078 m. 2059 vs
2039 5 , 2017 b. 1999 1;s
oi-mge. 31 "4.
199'C[f]
dark red. 63 %.
64 c [f]
orange. 71 YO
144 C [f]
red. 66%.
68 C [f]
I202 s
[a] In cm-'. l a - e . 2 c - e in ii-herane. 2a.b in methylcyclohexane. [b] In c m - ' , nujol mull. [c] "C['H] NMR (100.6 MHz): l a e. 2d i i i CDCI,: 2 a - c . e in C,D;
C, = CMe,. C,= CMc,. A6 = diC,)-b(C',). [d] pK. of M'H [18]. [el El-MS (70 eV): most intemive signal shown, correct isotope distribution. [f] decomposition.
C14
5
C l 2 G
c10
Fig. 1. Crystal structure of 1a (SCHAKAL image [20d]): View perpendicular to the
mirror plane: selected distances [A] and angle5 [ 1: Re-Mo 2.844(1), Re-Nl
1.720(13). Re-N2 1.7.37(14). Re-N3 1.760(15). Mo-C1 2.01(2), Mo-C2 1.97(2).MoC3 1.96(2); Mo-Re-NI 108.8(4). Mo-Re-N2 103.4(4), Mo-Re-N3 104.0(4). NI-ReN2 111.9(7). NI-Re-N3 Il2.1(7). N2-Re-N3 115.7(7). R e - N I X 9 165.6(12). ReN2-Cl3 164.0(11). Re-N3-C17 164.2(13). CI-Mo-C3 105.2(7). Re-Mo-C2 128.9(4).
are [C~(CO),MO-M~(CO),C~]~*~~
(3.235(1) A) and [CpMo(CO),M~-MO(CA~,)(NNCA~,)C~]'~~~
(3.052(1j A).
We assume that the very short M-M distances are due to
coulombic forces; more precisely, due to the electrostatic attraction in the dipolar structural unit Ms+ -Mo'-. The smaller radii
of Re7'lRe6' and Mo6+/Mo4+as compared to the zero valent
and monovalent metal centers also contribute to the shortening
of the M-M bond. Just how large the difference between formal
oxidation state and the distribution of real charge density actually is in these simply built, symmetrical molecules remains a
domain reserved for the analysis of photoelectron spectra and
quantum mechanical calculations.
The electronically unsaturated character and the low coordination number of the central diimido unit in compounds 2a-e
promises further interesting chemistry when these are used as
starting materials. We have these reactions currently under investigation with particular attention to the linking of imido and
10
A
complex fragments is found to deviate characteristically from
known structures of the respective homonuclear complexes.[sh,231
Compound 2 a has crystallographically imposed C, symmetry.
The M o 1 center has distorted tetrahedral coordination; the twofold screw axis bisects the extended angles M o 2-Mo 1-Mo 2' and
and 114.6(6)', respectively). Thecarbonyl
N-Mo l-N'(124.7(1)"
groups C 1 - 0 1 and C 2-02 formally fulfill the criteria[241for
semibridging CO ligands. This can be regarded as a possible
mechanism by which the molecule compensates the different
charge densities on the Mo 1 and M o 2 centers. The interactions
are so weak. however, that they can equally plausibly be explained by the forced spatial proximity of four CO groups to the
sterically shielded Mo 1 center. The M o 1 -Mo2 distance of
2.875(1) A is considerably shorter than other known Mo-Mo
single bond values in the absence of ligand bridges. Examples
680
'(-'
VC'H V~rlu,~~jirsclls~/iu/i
inhtf. 0-69451 We~nlieini,1994
"I
3
C6
Fig. 2. Crystal structure o f 2 a (SCHAKAL image [20d]): Vie% perpendicular to the
crystd~lographicallyimposed C , axis; selected distances [A] and angles ['I: M o l Mo2 2.875(1), M o l - N 1.721(8). Mo2-CI 1.983(12), Mo2-C2 1.939(11). M o 2 - G
1.999(13); Mo2-Mol -N 101.9(3). Mo2-Mol - M o 2 I24.7(1). N-Mol-N' 114.6(6).
Mol-N-C9 166.5(8): Mol-Mo2-C3 127.6(3). CI-MoZ-CZ 102.2(5).
U57U-U833iY4/0606-06~0B 1 0 . 0 U f .?5:U
Angru-. Chtvn. hi.Ed. En,qI. 1994, 33, No. 0
COMMUNICATIONS
E. J. Moore. J. M. Sullivan. J. R. Norton. J. A m . (%en?. So(. 1986. /OX. 22572263.
As expected, the weakest metal base [Co(CO)J led to the largest A& value.
and the strongest metal base [CpFe(CO)J to the smallest. When the pK,
values show only small differences from one another. the c-donor capability I \
found to be largely dependent on the steric requirements of Ihc metal carhonyl
fragments.
a ) Crystal structure analysis of l a : CL,H,,MoN,O,Re. ,M = h44.64gmol I .
orthorhonibic, space group: Phca, (i = X.866(2). h = 17.262(3). c =
33.519(6) A, V = 5130(2) A3, Z = 8, pralrd= 1.669 gem-'. crystal siLe = 0.75
x 0.15 x 0.19 mm. {(MaK,) = 54.94cm-'. Intensity measurement: Enruf-Nonius CAD4 diffractometer. Mo,, radiation, 22 C. 20.,,, = 46 ,2864 rellectioiis
measured. of which 1953 observed (I> 0,).semi-empirical absorption correction ( l scan). Structure refinement: H atoms were not found. C atoms of the
rBu group were input as part of a rigid group. All atoms other than hydrogen
were refined anisotropicically. R = 0.0409, R , = 0.0423. 11 = I![o'(~') +
0.0007F2] max. shiftks.d. = 0.518. 235 parameters. remaining clectron denhity = 0.86 e k " b) Crystal structure analysis of 2 a : C,,H,,Mo,N,O,,.
.M =
742.33 gmol-I, monoclinic, space group. C
u =17.715(3). h = 16.107(3).
c = 9 . 5 8 8 ( 3 ) A . p = 9 1 . 9 5 ( 3 ) . V = 2 7 3 5 ( l ) A 3 . Z = 4 . [ ~ ~ , , , ~X~0,3=g cl m ~ ' .
crystal size = 0.42 x 0 31 x 0.25 mm, ji(MoKJ = 13.72 c m - ' Intensity incasiirement : Enraf-Nonius CAD4 diffractometer. Mo,, radiation. 22 C.20,,,, =
46 ,2488 reflections measured. of which 1425 observed ( I > 30,). semi-cmpirical absorption correction ( p c a n ) . Structure refinement: H atom positions
were calculated. Methyl C and H atoms %ereinput as part o f a rigid group. All
atoms other than hydrogen were refined anisotropicically. H atoms were refined isotropically. R = 0.0491. R, = 0.04X1. 11' = I:[c'(f') + 0.1)l)ll)F2]
max.
shift:e.s.d. = 0.128, 187 parameters. remaining electron density = 1.0 e A '.
The programs SHELX-86 and SHELX-76 were used to solve and refine both
structures [2Oc]. Further details of the crystal structure investiptions may he
obtained from the Fachinformationszentruin Karlsruhe. V-76344 EggensteinLeopoldshafen ( F R G ) o n quoting the depository number CSD-57X67 m d the
journal citation. c) G. M. Sheldrick. SHELX-86. Universitit Giittingen, 1986.
SHELX-76, University ofcambridge. 1976: d) E. Keller. S < ' / / , 4 K AL. Universitat Freiburg. 1990.
Y.T. Struchkov, K. N. Anisimov, 0 . P. Osipova, N. E . Kolohova. A. N. Nchineyanov. Duki. Akad. iVoiiA SSSR Scr. K h i m 1967. 173. 107: G Wilkinson,
F. G. A. Stone, E. W. Abel. Coinpreheir.rilc Or~~rrnoriicruliiiC/iiviii\iri., W. 6 .
Pergamon, Oxford, 1982, p. 802f.
R. I . Mink. J. J. Welter. P. R. Young, G. D. Stucky. .I A i i i , ('Iiiwi Soi.. 1979.
I t > / . 6928 ~6933.
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carbonyl ligands through the mediation of the metal centers to
give isocyanates. It is also hoped that selective hydrolysis or
metathesis reactions will provide a general preparative route to
mixed metal carbonyl -ox0 complexes containing M-M' bonds.
Furthermore, the especially volatile compounds 1a-e, 2c, and
2 e are promising starting materials for the deposition of thin
layers [M,,,M',,N,] from the gas phase using the metal-organic
chemical vapor deposition technique.
Recei\'ed: October 15, 1993 [Z6424IE]
German ver5ion: Ari,q.aii, Cheni. 1994. 106. 679
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78'10 7x91
[I41 Iwcarbonyl bridges [M']-C=O-[M] are often found for very hard Lewis acids
[MI, or for [MI fragments with high steric requirements. They are a result ofthe
aiiihidmt char;icter ofthe metal nucleophiles. For a representatibe example. see
ilton. Jr W. S. Willis. G. D. Stucky. J. Am. Chen?. Sol.. 1981. 103.
.
~
Tetrakis(hypersilyl)dithallium(TI- TI):
A Divalent Thallium Compound**
~
.
1151 Intcrc\tinyly. bridging nnido and carbonyl ligands were recently identified in
homohinuclear M o and W complexes with more strongly balanced charge
dcn\itics on both metal centers: M. D. Curtis. M. S. Hay. W. M. Butler. J.
Kaiiipf. A L. Rheingold, B. S. Haggerty. Or~mioiiit~ru//r~.~
1992. / I . 28842802
[I61 a ) A K Burrell. J. C. Bryan. Angi,it.. Chem. 1993, 105, 85-86; A,i,qw. Cheni.
l n i Ed. Eiix/. 1993. 32. 94-95: b) In contrast, the combination of two 17VE
[(rBu,N),ReJ radicals led to the formation of a d i - - d i dimer with bridging
iinido IignnJs (two edge-sharing tetrahedra). See also [5b]
1171 W A Nugent. R J. McKinneg. R. V. Kasovski. F. A. Van-Catledge, Iuor,q.
C ' h r n j . ..lc./a 1982. 6.5, L91 -L93.
S o n j a Henkel, Karl Wilhelm K l i n k h a m m e r , *
and Wolfgang Schwarz
Molecular compounds with divalent boron have been known
for a long time in the form of diboranes(4), whereas Uhl et al.
achieved the first preparation and unequivocal characterization
of element-homologous dialuminum, digallium. and diindium
compounds only a few years ago."] Hitherto, only for the heaviest element of the third main group, thallium. were no analogous
compounds known.[*]We report here on the synthesis and structural Characterization of one such dithallium compound.
Organothallium(1) compounds with o-bound substituents and
corresponding derivatives with TI-Si bonds have so far not been
sy~ithesized,~~]
in contrast, the related trivalent thallium com-
[*I
["I
Dr. K. W. Klinkharnmer. Dr. W. Schwarr
Institut fur Anorganische Chemie der Universitit
Pfaffenwaldring 5 5 . D-70550 Stuttgart ( F R G )
Telet'dx: Int. code + (711)685-4241
S. Henkel
Institut fur Orgdnische Chemie der Universitit Stuttgart (FRG)
For the term '-hypersilyl" bee ref. [ 5 ] .
68 1
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