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The 30-Electron Rule for Triple-Decker Complexes ЦVanadium Niobium and Tantalum Complexes as Illustrative Examples.

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3 . 5 7 ( q , J = 7 . 0 H ~ , 2 H ) , 2 . 6 7 ( q , J = 7 . 0 H ~ , 2 H 1) ,. 0 6 ( t , J = 7 . 0 H ~ , 6 H ) ;
lb:S=7.28-7.18(m,lOH),5.82(~,2H),3.32(q,J=7.1
Hz,2H),2.94(q,
J=7.1 Hz, 2H),0.81 (t, J=7.1 Hz,6H).
[6] l a : monoclinic, P2,/c, a = 1734.7(4), b=797.9(7), c=2023.7(5) pm,
13=93.16(2)", Z = 4 ; 2683 reflections, R=0.048. Ib: monoclinic, P2,/c,
a = 1460.0(2), b=844.1(7), c=2240.2(5) pm,f?=91.87(1)", Z = 4 ; 3509 reflections, R =0.031. Further details of the crystal structure investigations
can be obtained from the Fachinformationszentrum Energie, Physik,
Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen 2, on quoting
the depository number CSD-53297, the names of the authors, and the
journal citation.
[7] UV spectroscopic monitoring of the equilibration shows an isosbestic
point during the first 10-15 min. Thereafter, the system becomes unclean
due to decomposition. This decomposition also makes a quantitative interpretation of the IR data impossible.
[XI Cf. L. J. Todd, J. P. Hickley, J. R. Wilkinson, J. C. Huffman, K. Foltig,
1. Organomer. Chem. 112 (1976) 167.
[9] H. Vahrenkamp, A d a Organornet. Chem. 22 (1983) 169.
1101 A. Albini, H. Kisch, Top. Curr. Chem. 65 (1976) 105.
The 30-Electron Rule for Triple-Decker Complexes
-Vanadium, Niobium and Tantalum Complexes
as Illustrative Examples**
they show the typical pattern of three CO bands for
M(CO), groups with highly perturbed local C4,symmetry
(Table 1). Their NMR data, with I'B and I3C NMR signals
L
L
* y o
OCJ
V
oc/'
Fe
V
0
[*] Prof. Dr. G. E. Herberich, Dr. I. Hausmann, Dipl.-Chem. N. Klaff
I**]
Institut for Anorganische Chemie der Technischen Hochschule
Professor-Pirlet-Strasse1, D-5100 Aachen (FRG)
Triple-Decker Complexes, Part 6. This work was supported by the
Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.-Part 5: [I].
Angew Chem. Inr. Ed. Engl. 28 (1989) N o . 3
0c::
c
0
0
1
5
6
c
0
2.M.V
3.M = Nb
4. M = Ta
Table 1. C(C0) values in hexane.
Compound
C(C0) [cm
~
2022 m, 1974 w,
2030 m, 1964 w,
2033 m, 1949 w,
2035 m, 1939 w,
By Gerhard E. Herberich, * lngeborg Hausmann, and
Norbert Klaff
The number of valence electrons in the triple-decker
complexes thus far isolated[21lies between 26 in [(p-q6C6H6)(VCp),]131
and 34 in [(p-Cp)(NiCp)2]@.[4'
R . Hofmann
et al. have demonstrated in a definitive treatise on the MO
scheme of triple-decker complexes that closed electron
shells are achieved with 30 and 34 valence electrons;15a1
this conclusion has often been cited as the 30/34e rule.
Wade's cluster rules[5b1lead to a narrower statement for triple-decker complexes : the magic number of valence electrons is 30.15c1
The many triple-decker sandwich complexes with one or
two outer Cp ligands often have a valence electron count
deviating from 30.[21For instance, in the case of vanadium
the 26e systems [(~-~66-c6H6)(vcp),~"'
and [(p-$-P6)(V(C,Me,R),),] (R = Me, Et)[31are known, but no 30e systems. On the other hand, it can be seen from the general
MO scheme for triple-decker complexes that: a rigid 30e
rule should apply when strong o-donor-n-acceptor ligands
such as carbon monoxide are present in the outer complex
fragments. As illustrative examples for this assertion, we
describe here some 30e complexes containing M(CO),
fragments, where M is an element of the fifth subgroup
(vanadium, niobium, tantalum).
1-Phenyl-2,5-dihydro-lH-borolereacts with V(CO)6 in
hexane with dehydrogenative complexation to give red,
crystalline 1. The electrophilic stacking of the hydride 5[61
with V(CO)6 in hexane affords red needles of 2. The complexes 1 and 2 are the first 30e triple-decker complexes of
vanadium. The higher homologues 3 and 4 are obtained
as deep-red needles by electrophilic stacking of sodium
borataferrocene 6I6]with 7 or 8, respectively['] in THF;
they are the first triple-decker complexes of niobium and
tantalum.
The new complexes[81are sensitive to light and extremely
sensitive to nucleophilic
In the IR spectrum
oc/'
x-:.c' o
c
c
iCpfeH(~$C,H,BPhll
Na[CpFe(q'-C,H,BPh)I
Na[(p-CII, (M(CO),l, I
7.M=Nb. 8.M=Ta
&B--Ph
M
'1
1943 s
1932 s
1929 s
1920 s
at comparatively high field, confirm the presence of a
bridging IH-borole ligand; the AA'BB' system in the 'H
NMR spectrum shows the small coupling constant
N = 3J23 4J24 of only 3.9-4.2 Hz which is typical for the
triple-decker structure.[91The closely related triple-decker
+
[NMe3Ph][(p-q5-C,H,BPh)(Cr(CO),)(FeCp)]
9
complex 9 has been characterized by X-ray crystallography;"'"' here again, as in the case of the molybdenum and
tungsten homologues,"ObJthe outer carbonyl ligands enforce a 30e configuration.
Experimental
1: A mixture of I-phenyl-2,5-dihydro-lH-borole
(2.0 g, 14 mmol) and V(CO),
(1.00 g, 4.6 mmol) in hexane (20 mL) was heated to 55°C for 16 h. Filtration
and chromatographic work-up (silica gel, -20°C) of the hexane filtrate afforded a yellow zone containing 7.3 mg (32 p o l ; 0.7%) of [V(CO)nCp]and a
second, carmine-red zone, from which 9.6 mg (21 pmol; 0.9%) of red crystals
of 1 were obtained by threefold crystallization. M.p. 68°C. decomp. 74"C,
soluble even in pentane, light-sensitive in solution.--'H NMR (80 MHz,
[Ddacetone):6=7.66(m,2H,),7.36(m,2H,+H,),5.72(m,H-3,4),4.29(m,
H-2,s); N = 'Jz3+4J24=4.2 Hz. "B NMR (32.08 MHz, CDCI,, ext.
BF3.OEt2): 6=21.
2: A solution of 5 (345 mg, 1.32 mmol) 161 in hexane (100 mL) was treated
with a solution of V(CO), (361 mg, 1.65 mmol) in hexane (25 mL) at -25°C
and the mixture stirred for 7 d at room temperature. Chromatographic workup (A1201 with 7% water, -35°C) afforded a first runnings of V(CO), with
pentane, then a red zone with pentane/toluene (I/]), from which 228 mg
(0.54 mmol; 41%) of red needles of 2 were obtained after removal of the
eluent and crystallization from hexane at -30°C. M.p. 140°C (decomp.),
light- and air-sensitive, soluble even in pentane.-'H NMR(80 MHz, CDCI,,
in!. TMS): 6=7.72 (m, 2H,), 7.34 (m, 2H,+Hp), 4.08 (s, Cp), 4.48 (m,H3,4), 3.43 (m, H-2,s); N = 3Jz3+4J24=4.0Hz. "B NMR (32.08 MHz, CDCI,,
ext. BF,.0Et2): S= 11.4. "C-NMR (67.88 MHz, CDCI,, -70°C): 6=255
(br., CO), 140.9 (s, C,), 132.5 (dm, 'JCH=155Hz, Co), 127.4 (dd, 'Jcn=158
Hz, C,,,), 126.9 (dt, ' J c n = 159 Hz, Cp), 68.6 (dm, ' J c H = 177 Hz,Cp), 66.6 (d,
'Jcn=165 Hz, C-2.5). 65.0 (d, 'JcH=183 Hz, C-3,4).
3: A solution of the salt 7 (prepared from 2.00g (3.62 mmol) of
[ N ~ ~ O ( C H Z C H , O M ~ ) ~ ~ ~ ~and
[ N 0.72
~ ( CgO(7.3
) ~ ]mmol) of CuCl [7]) in 250
m L of EtzO was treated dropwise at -70-C with a solution of 6 (prepared
from 0.85 g (3.25 mmol) of 5 by deprotonation with NaH 161) in 120 m L of
Et20 and the mixture stirred for ca. 12 h at room temperature. Filtration,
0 VCH VerlagsgesellschafrmbH. 0-6940 Weinheim, 1989
0570-0833/89/0303-0319 $ 02.50/0
3 19
drying under vacuum, extraction with hexane and crystallization at -30°C
afforded 300 mg (0.64 mmol; 20% referred to 5 ) of deep-red, light- and airsensitive needles of 3. M.p. 143°C (decomp.), soluble even in pentane.-'H
NMR (80 MHz, CDCI,, int. TMS): 6=7.67 (m,2H,), 7.35 (m,2H,,+H,),
~ ~"B
=~.~
4.18 (s, Cp), 4.93 (m, H-3,4), 3.72 (m, H-2,5); I V = . ~ J ~ , + ~ JHz.
NMR (32.08 MHz, CDC13, ext. BF3.0Et2):6= 13.8. ''C NMR (67.88 MHz,
CDCI,, -70°C): 6=251.6 (s, CO), 141.4 (s, C,), 132.9 (dm, 'JCH=157 Hz,
= Hz, Cm), 127.2 (dt, ' J C H = 160 Hz, C,,), 69.9 (dm,
C,,), 127.7 (dd, ' J c H 154
IJC.H= 177 Hz, Cp), 66.4 (d, 'JcH=167 Hz, C-2.51, 66.2 (d, ' J C H = 183 Hz,
C-3,4).
4 : Synthesis and work-up as described for 3; 1.95 g (3.05 mmol)
[Na10(CH2CH20Me)212][Ta(CO)61,
0.60 g (6.1 mmol) CuCl and 0.79 g (3.02
mmol) 5 give 430 mg (0.78 mmol; 26% referred to 5 ) deep-red, almost airstable needles of 4. M.p. 164°C (decomp.), soluble even in pentane.--'H
NMR (80 MHz, CDCI,, int. TMS): S=7.66 (m, 2H,), 7.34 (m,2H,+H,),
4.21 (s, Cp), 4.85 (m, H-3,4), 3.63 (m, H-2.5); N = 3J23+4J24=3.9Hz. "B
NMR (32.08 MHz, CDCI,, ext. BF3.0Etz): 6 = 12.8. "C NMR (67.88 MHz,
CDCI,, -7O'C): 6=246.7 (s, CO), 140.6 (s, C,), 133.0 (dm, IJCH=157 Hz,
C,,), 127.8 (dd, 'JCH=
160 Hz, C,,,), 127.4 (dt, ' J C H =154 Hz, Cp), 70.9 (dm,
' J c H = 178 Hz, Cp), 64.3 (d, 'JcH=
156 Hz, C-2,5), 64.7 (d, ' J C H = 190 Hz,
C-3,4).
Received: September 6, 1988;
revised: November 28, 1988 [ Z 2957 IE]
German version: Angew. Chem. 101 (1989) 328
CAS Registry numbers:
1, 118657-21-9; 2, 118657-22-0; 3, 118657-23-1; 4, 118657-24-2; 5, 103432.559; 6, 118657-25-3; 7, 84821-59-0; 8, 118657-26-4; V(CO)6, 14024-00-1;
[NaiO(CH2CH20Me)2)2][Nb(CO)61, 12189-43-4; [NajO(CH,CH20Me)2)2][Ta(CO),]. 12 189-44-5; I-phenyl-2,s-dihydro- 1 H-borole, 84017-49-2.
[I] G. E. Herberich, U. Biischges, Chem. Ber.. in press.
121 For further references see: a) W. Siebert, Angew. Chem. 97 (1985) 924;
Angew. Chem. Int. Ed. Engl. 24 (1985) 943; b) 0. J. Scherer, J. Schwalb,
H. Swarowsky, G. Wohnershauser, W. Kaim, R. Gross, Chem. Ber. 121
(1988) 443.
(31 a) A. W. Duff, K. Jonas, J. Am. Chem. SOC.105 (1983) 547; b) P. T.
Chesky, M. B. Hall, ibid. 106 (1984) 5186: c) K. Angermund, K. H.
Claus, R. Goddard, C. Kriiger, Angew. Chem. 97 (1985) 241; Angew.
Chem. Int. Ed. Engl. 24 (1985) 237; d) K. Jonas, W. Riisseler, K. Angermund, C. Kriiger, ibid. 98 (1986) 904 and 25 (1986) 927.
141 H. Werner, A. Salzer, Synfh. Inorg. Met. Org. Chem. 2 (1972) 239; A.
Salzer, H. Werner, Angew. Chem. 84 (1972) 949: Angew. Chem. Int. Ed.
Engl. I 1 (1972) 930; Synth. Inorg. Met. Org. Chem. 2 (1972) 249; H.
Werner, B. Ulrich, A. Salzer, J. Organornet. Chem. 141 (1977) 339; E.
Dubler, M. Textor, H. R. Oswald, G. B. Jameson, Acfa Crystallogr. Sect.
8 3 9 (1983) 607.
[5] a) J. W. Lauher, M. Elian, R. H. Summerville, R. Hoffmann, J . Am.
Chem. Soc. 98 (1976) 3219; b) K. Wade, Adv. Inorg. Chem. Radiochem.
18 (1976) 1; c) further theoretical studies: [3b]; E. D. Jemmis, A. C. Reddy, Organometallics 7 (1988) 1561.
161 G. E. Herberich, B. Hessner, D. P. J. Koffer, J. Organornet. Chem. 362
(1989) 243.
[7] F. Calderazzo, G. Pampaloni, J. Organornet. Chem. 303 (1986) 1 I I.
[8] Correct C,H analyses. The molecular ions and successive cleavage of 8
(in the case of 1) and 4 (in the case of 2-4) CO groups are observed in
the mass spectra.
191 G. E. Herberich, B. Hessner, R. Saive, Organomel. Chem. 319 (1987) 9.
[lo] a) G. E. Herberich, B. Hessner, J. A. K. Howard, D. P. J. Koffer, R.
Saive, Angew. Chem. 98 (1986) 177; Angew. Chem. Inr. Ed. Engl. 25
(1986) 165; b) G. E. Herberich, K. Peters, unpublished.
NaBH, Reduction of Ketones in the Solid State
By Fumio Toda,* Koji Kiyoshige, and Minoru Yagi
Previously we reported that Baeyer-Villiger oxidations
of ketones with rn-chloroperbenzoic acid proceed much
faster in the solid state than in solution."] We have now
found that reductions of ketones with NaBH, also proceed
in the solid state (Table 1). In addition, the formation of
1 : 1 inclusion complexes can be exploited to carry out regio- and enantioselective reductions leading to products
[*I
Prof. F. Toda, K. Kiyoshige, M. Yagi
Department of Industrial Chemistry, Faculty of Engineering
Ehime University, Matsuyama 790 (Japan)
320
0 VCH Veriagsgeseiischaji mbH, 0-6940 Weinheim, 1989
such as 2a and 4, which are of interest as synthetic building blocks but only accessible with difficulty by other
routes.
A mixture of the ketone and a tenfold molar amount of
NaBH4 was finely powdered using an agate mortar and
pestle and kept in a dry box at room temperature for five
days, being stirred once a day. The reaction mixture was
extracted with ether, and the dried ether solution was
evaporated to give the corresponding alcohol in the yields
shown in Table 1. Almost the same results were obtained
by shaking the mixture for a day using a test-tube shaker.
Table 1. Reduction of simple ketones in the solid state by NaBH.,.
Ketone
Alcohol
Yield
Ph2CH-OH
Ph2C0
trans- PhCH=CHCOPh
[Oh]
100
trans- PhCH=CHCHPh
100 (1 : 1)
PhCH2CH2CHPh
I
OH
B r n C O P h
B r eC HIP h
100
OH
53
m
C
O
M
e
PhCHCOPh
I
OH
meso -PhCH-CHPh
PhCH2COPh
PhCH2CHPh
I
OH
62
1
OH
63
I
OH
OH
tB"C)-;O
t B u e 0 H
92
PhCOCONiPr2
PhCHCONiPr2
24
I
OH
Treatment of a 1 : 1 inclusion ~ o m p l e x l *of
, ~ ~(R)-1 and
(R,R)-5 with NaBH4 in the solid state for 3 days gave
(R,R)-2a of 100% ee ([a],-192.8 (c=0.24, benzene)) in
54%yield. The corresponding reaction of a 1 :1 complex of
(S)-1 and (S,S)-5 gave (S,S)-2a of 100% ee. Treatment of
the racemic diketone 1 with (R,R)-5 results in selective
formation of an inclusion complex with (R)-1 : decomposition of the complex gives (R)-1 of 100% ee. Since the hydride attacks the carbonyl carbon at the 7-position from
the side opposite the methyl group,14] (R)-1 should give
(R,R)-2a of 100% ee, as was found. The IR spectrum and
[a],value of the product were comparable to those of an
authentic sample ([a],- 203 (c= 1.545, benzene)) prepared
by biological reduction of rac-1 .Is1
The enone moiety of (R)-1 is presumably masked by
forming a hydrogen bond with the hydroxyl group of
( R , R ) - 5 ,so that the other carbonyl group is reduced selectively. When the reduction of (R)-1 is carried out in the
presence of (R,R)-5 in a suspension in water, the diol 2b is
obtained as a mixture of diastereomers.
0570-0833/89/0303-0320 $ 02.50/0
Angew. Chem. Int. Ed. Engl. 28 (1989) No. 3
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