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Borole Dianions Metalation of 1-(Dialkylamino)-2 5-dihydro-lH-boroles and the Structure of Li2 (C4 H4 BNEt2)╖TMEDA.

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A crystal suitable for the crystal structure analysis of 4 was obtained by
sublimation in vacuo. Monoclinic, P2,/c, a = 654.6(5), 6 = 963.1(6), c =
1171.1(5)pm.fl= 1 0 3 . 5 2 ( 5 ) " , ~ =
~ ~1.88gcm-'.
,~~
R=0.029,RW=O029
(Mo,, = 71.069 pm), 1256 crystallographically independent reflections,
1142 with Fo z 3 u(Fo),anisotropic temperature factors, starting coordinates by Patterson methods (SHELXS-86) [20], full-matrix least squares
refinement (SHELX-76) [21]. 100 refined parameters, max. shiftierror
0.002, residual electron density 0.29 e k ' , empirical absorption with the
Program DIFABS by D. Sruart and N. Walker 1221. Further details of the
crystal structure investigation are available on request from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische
Information mbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-54273, the names of the authors, and the
journal citation.
W. P. Griffith, G. Wilkinson, L Chem. SOC.1555, 1629.
K . D. Grande. A. J. Kunin, L. S. Stahl, Inorg. Chem. 22 (1983) 1791
J. A. J. Jarvis, A. Johnson, R. J. Puddephatt, J. Chem. Soc. Chem. Cummun.
1973, 373.
C. J. Gilmore. P. Woodward, J. Chem. Soc. (0)
1571 1233; C. Mitchel,
F. G. A. Stone, Chem. Cummun. 1970, 1263.
J. Cleemens. M. Green, M.-C. Kuo, C. J. Fritchie Jun., J. T. Mague,
F. G. A. Stone. J. Chem. SUC.Chem. Commun. 1972, 53.
R. S . Dickson, S . H. Johnson, H. P. Kirsch, D. J. Lloyd, Acta Crysrallogr.
Ser.c. 5 3 3 (1977) 2057.
J. W. Bixler. A. M. Bond, R. S . Dickson, G. D. Fallon, R. S . Nesbit, H.
Pateras, Organumerallics 6 (1987) 2508.
W. Beck, M. Schweiger, G. Miiller, Chem. 5er. 120 (1987) 889.
R. Anschutz. Q. Wirtz, Ber. Drsrh. Chem. Ges. 18 (1885) 1947; W. H.
Perktn, rhrd. 14 (1881) 2540.
H.-D. Scharf, H.-J. Knops, H.-G. Fitzky. Chem. Ber. 109 (1976) 1163, and
references cited therein.
M. S. Rasch, R. E. Miegel, J. E. Castle, J. Am. Chem. Soc. 81 (1959) 2678.
A. A. Bothner-By, S . M. Castellano (LAOCN3, A Program for Cumpuler
Simulurion of Complex N M R Spectra) in D. F. de Tar (Ed.): Computer
Programs fur Chemistry, Vul. I , New York 1968; MS-DOS version for
IBM Personal Computer: M. Clark, J. S . Thrasher, The University of
Alabama. Tuscaloosa, USA.
G. M. Sheldrick: SHELXS-86, A Program fur Crystal Structure Solution,
Gottingen 1986.
G. M. Sheldrick: SHELX-76. A Programjor Crysral Structure Determina/ion, Gottingen 1976.
[22] N. Walker, D. Stuart, Aria Crysralfugr.Seer. A39 (1983) 158
Borole Dianions: Metalation of
l-(Dialkylamino)-2,5-dihydro-1H-borolesand the
Structure of Li,(C4H4BNEt,) TMEDA **
By Gerhard E. Herberich,* Martin Hostaiek, R a y Laven,
and Roland Boese
Borole dianions (dihydroborolediides) are,"] as boracarbocyclic 6x-electron systems, isoelectronic with the cyclopentadienide ion (Scheme 1). We report here on the synthesis of some dilithium 1-(dialky1amino)dihydroborolediides and on the structure of one of their TMEDA adducts.
I
R
Scheme 1
[*I Prof. Dr. G. E. Herberich, Dr. M. Hostalek, Dr. R. Laven
Institut fur Anorganische Chemie der Technischen Hochschule
Professor-Pirlet-Strasse 1, D-5100 Aachen (FRG)
Dr. R. Boese
Institut fur Anorganische Chemie der Universitat-Gesamthochschule
Universititsstrasse 3-5, D-4300 Essen 1 (FRG)
[**I Derivatives of Borole, Part 15. This work was supported by the Deutsche
Forschungsgemeinschaft and the Fonds der Chemischen 1ndustrie.Part 14: G. E. Herberich, I. Hausmann, B. Hessner, M. Negele. J.
Organomer. Chem. 362 (1989) 259.
Angrw Chon. lnt. Ed. EngI. 29 (1990) Nu. 3
C
As a rule 1 -(Dialkylamino)-2,5-dihydro-lH-boroles 1 121
are quaternized by organolithium compounds L i R to borates 2.[*]Borate formation can be suppressed only by steric
hindrance at the boron atom and at the basic center of LiR':
l c reacts with LitBu to give the lithiation product ~ c . [ ' ~ I
2
1
a, R
=
Me; b, R = Et; c, R
=
3
iPr
Quaternization usually also occurs with lithium amides:
from 1 a/LiNMe, , 1 b/LiNEt, and from 1 a/LiNiPr, or
1 c/LiNMe, the corresponding bis(dialky1amido)borates
4a, b, d are formed, recognizable in the NMR experiment by
4a,
4b,
4c,
4d,
R = R =Me
R = R = Et
R = R = i Pr
R = Me, R = rPr
a shift of the "B signal from 6 E 51 12] to 6 zz 5.[j1 The oily
borate 4a was converted with tetramethylethylenediamine
(TMEDA) into a crystalline adduct 5.[,] At 60°C, borate
formation is reversible; metalation (25 h) of 1 a, b leads
to formation of the dihydroborolediides 3a,b with
6("B) = 25-27.13] In the case of 1 c/LiNiPr, the formation
of the borate 4c is blocked because of double steric hindrance, and at 60 "C 1 c isomerizes very slowly (7 d)I3l to the
known 1-(diisopropylamino)-4,5-dihydro-lH-borole.[']
With the sterically demanding lithium 2,2,6,6-tetramethylpiperidide (LiTMP), borate formation does not take place.
Here, the metalation of 1 a, b to 3a, b already occurs at room
temperature, and the troublesome problems of ether cleavage do not arise. In contrast, l c does not react with LiTMP
at 20°C.
Li,(C,H,BNR,)
. TMEDA
6a, R = Me
6b, R = Et
6c. R = iPr
The lithium derivates 3a-c are powdery solids which form
well crystallized derivatives 6a-c with TMEDA. The determination of the structure of a dihydroborolediide was possible for the first time with the diethylamino compound 6
(Fig. 1).[', 61
6b is a centrosymmetric dirner containing a phane-like
(C,H,BNEt, Li), ring and two external Li(TMEDA)
groups. Both Li atoms of a dihydroborolediide unit are pentahapto bound, and the higher coordinated Lil atom of the
Li(TMEDA) group is expectedly weaker than the Li2 atom
of the Li-NEt, group. The n-coordination of the Li atom
and the formation of a dimer with the help of N-donor atoms
of the metalated ring are known structural patterns in the
case of organolithium corn pound^.^'^
The C,B ring is planar (maximum deviation 0.5 pm for the
B atom). The bond pattern in the ring is that of a delocalized
6x-electron system and impressively reflects the occupation
of the borole LUMO (B-C1, B-C4 and C2-C3 shortened,
VCH Verlagsgesellschajt m6H. 0-6940 Weinherm, 1990
0S?0-0833/90/0303-0317 S 02 SO10
317
volume and crystallization at - 78 "C furnished 1.9 g (97 YO)of clustered crystals of 6a. M.p. >250°C, extremely sensitive towards air and moisture [12].NMR data: [3b, 131.
6b: synthesis as in the case of 6a yielded colorless rectangular crystals of 6b
(94%). M.p. 166 "C, decomp. 210°C (black coloration). extremely sensitive
towards air and moisture [12].-NMR data: [3b, 131.
6c: synthesis from 3c [l b] as in the case of 6a afforded colorless rectangular
crystals of 6c (97%). M.p. 193 T , no decomposition up to 250°C, extremely
sensitive towards air and moisture [12].-NMR data: [3 b, 131.
Received: October 23, 1989 [Z 3602 IE]
German version: Angen. Chem. 102 (1990) 330
Fig. 1. Structure of 6 in the crystal. Selected bond lengths [pm]: Lil-Cl
227241, Lil-C2 218.4(4), Lil-C3 217.1(4), Lil-c4 226.9131, Lil-B 234.1(3),
Lil-CJ-ring 186.9, LIT-C1 220.2(4), Li2'-C2 212.3(3), LiT-C3 213.2(4), Li2'C4 219.5(4), LIT-B 227.5(4), LiZ'-C,B-ring 179.5, Lil-Nl 215.0(4), Lil-N2
216.9(3), LiZ-N202.8(3);in theC,B-ring: B-CI 152.2(3),C1-C2 143.4(3),C2-C3
139.9(3), C3-C4 144.0(3), C4-B 152.0(3); B-N 151.513).
C1-C2 and C3-C4 lengthened). The n-interaction with the
exocyclic amino group is also greatly weakened: the B-N
bond (151.5 pm) is about 10 pm longer than that typically
found in (dialky1amino)boranes ( 1 41 - 142 pm ['I), and the
amino group is no longer planar (sum of angles at the N
atom 344.7' vs. 328.5" in the case of the regular tetrahedron).
Dihydroborolediides are interesting synthetic building
blocks, as has already been demonstrated in the case of the
diisopropylamino compound 3c.''] However, in the numerous transition metal complexes of 3c, substitution at the B
atom has thus far proven impossible.rgb1We shall shortly
show elsewhere that this limitation does not arise in the case
of complexes of 3a, b:13b,l o ] borole complexes with quite
different substituents at the B atom can be prepared via the
1-(dimethylamino)- and 1-(diethy1amino)borole complexes
by substitution reactions.
Experimental
3a: a solution of LiTMP Ill] (18.0 g, 122 mmol) in T HF (60 mL) was treated
at -78°C with 6.4g (59 mmol) of l a [2] and the mixture stirred for 12h at
20 "C. Concentration of the solution, addition of200 mL of pentane and double
crystallization at - 78 "C furnished colorless needles of 3a . T HE which on
drying in vacuo
bar) yielded 5.0 g (70%) of powdery 3a. M.p. 2250°C.
extremely sensitive towards air and moisture [12]. 'H NMR (80 MHz,
[DJTHF, int. TMS): 6 = 5.35 (m; H-3,4). 4.03 (m; H-2,5), N = 3 J 2 , 3+
,J2..,= 7.4 Hz, 2.27 (s; NMe,); "B NMR (32.08 MHz, [DJTHF, ext.
BF, . Et,O): 6 = 27 (halfwidth 280 Hz); I3C NMR (67.88 MHz, 213 K,
[D,]THF, int. TMS): 6 = 98.9 (d, J = 151 Hz; C3,4), 82.8 (d, J = 140 Hz;
C2,5), 44.5 (4, J = 129 Hz; NMe,).
3b: synthesis as in the case of 3a afforded a colorless powder of 3b (71 O h ) . M.p.
126"C, no decomposition up to 250°C extremely sensitive towards air and
water [12].--'H NMR (80 MHz, [DJTHF, int. TMS): 6 = 5.37 (m; H-3,4),
3.95 (m; H-2,5), N = 3J2,3+ 4J2,4= 7.3 Hz, 2.70 (q, J = 7 1 Hz; 2 CH,), 0.96
(t, J = 7.1 Hz; 2 Me); I i B NMR (32.08 MHz, [DJTHF, ext. BF, . Et,O):
6 = 25 (halfwidth, 400 Hz).
4a: LiNMe, (1.0 g, 20 mmol) was treated at 0° C with 2.1 g (19.3 mmol) of 1 a
[2] and the mixture stirred for 3 h at 20°C. Removal of the solvent in vacuo
(lo-' bar) furnished 4a as a highly viscous oil (97%), which could not be
brought to crystallization from, e.g., Et,O/pentane at -70 "C; soluble in THF,
insoluble in pentane.-NMR data: [3b]; see also 5 [13].
5: a solution of 4a (1.5 g, 9.4 mmol) in T HF (20 mL) was treated with 1.2 g
(10 mmol) of TMEDA. Concentration of the solution, layering with pentane,
and cooling to - 78 "C furnished 2.4 g (93 %) of white crystals of 5. M.p. 53 "C,
decomp. llO"C, sensitive towards air and moisture [12]. 'H NMR (SO MHz,
[DJTHF, int. TMS): 6 = 5.55 (m, H-3,4), 0.92 (s br; H-25). 2.33 (s. 2 NCH,),
2.18 (s; 2 + 2 NMe,): "BNMR (32.08 Mhz, [DJTHF, ext. BF, . Et,O):
6 = 5.0 (halfwidth, 49 Hz); "C NMR (67.88 MHz, 300 K, [DJTHF, int.
TMS): 6 = 134.0 (d, J = 153 Hz; C3,4), 26.3 (t. J = 132 Hz; C2,5), 44.5 (4,
J = 133 Hz; 2NMe,); TMEDA: 58.3 (t, J = 129Hz; ZNCH,), 46.1 (4.
J = 134 Hz, 2 NMe,).
6a: a solution of 3a (1.0 g, 8.3 mmol) in THF (30 mL) was treated with 1.2 g
(10 mmol) of TMEDA. Evaporation of the reaction solution to a half of its
318
0 VCH
Verlagsgesekhaft mbH, 0-6940 Weinhernz, 1990
[I] a) K,[C,BPh,]: G. E. Herberich, B. Buller, B. Hessner, W. Oschmann, J:
Organomet. Chem. 195 (1980) 253; J. J. Eisch, J. E. Galle, S. Kozima, J: Am.
Chem. SOC.108 (1986) 379; b) 3c: G. E. Herberich, H. Ohst, Z Naturforsch 838 (1983) 1388; c) K,[C,BEt,Me,] in THF: B. Wrackmeyer,
Organometallirs 3 (1984) 1.
121 G. E. Herberich, W. Boveleth, B. Hessner, M. Hostalek, D. P. J. Koffer, H.
Ohst, D. Sohnen, Chem Ber. 119 (1986) 420.
131 a ) R. Laven, Diplomarheit. Technische Hochschule Aachen 1987; b) Dissertation, Technische Hochschule Aachen 1990.
[4] Such amidoborates are rare; cf. R. Koster in Houben- Weyl-Miiller; Methoden der Organischen Chemre, Bd. f 3 , Tei/3b, Thieme, Stuttgart 1983,
pp. 854, 860-862.
[5] The same type of structure was found X-ray crystallographically in the
case of 6c; the crystals however, were disordered.
[6] Nicolet R3m/V, Mo,, radiation, measurement temperature 125 K. 4b:
P2,/n (No. 14). a = 1014.4(2), b = 1142.6(2), c = 1517.0(3)pm, fl =
103.91(2)"; V = 1.7522(6) nm'; Z = 412; e,,,.o = 0.967gcm-,; 2271 independent reflections with Fo t 4u(F); non-hydrogen atoms refined anisotropically, H atoms placed at calculated positions and their isotropic
temperature factors refined groupwise: 220 parameters, extinction correc= u 2 ( F o )+ 0.00179 4.Further detion, R = 0.55, R, = 0.076 with I+-'
tails of the crystal structure investigation are available on request from the
Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlichtechnische Information mbH, D-7514 Eggenstein-Leopoldshafen 2
(FRG), on quoting the depository number CSD-320068, the names of the
authors, and the journal citation.
[7] W N. Setzer, P. von R. Schleyer, Adv. Organomet. Chem. 24 (1984) 353;
a-lithio-2,6-dimethyIpyridine-TMEDA
dimer: P. von R. Schleyer, R.
Hacker, H. Dietrich, W. Mahdi, J. Chem. Soc. Chem. Commun. 1985,622.
181 P. Paetzold. Adv. inorg. Chem. 31 (1987) 123.
191 a) G. E. Herberich, H. Ohst, H. Mayer, Angew. Chem. 96 (1984) 975;
Angen. Chem. Int. Ed. Engl. 23 (1984) 969; G. E. Herberich, H. Ohst,
Chem. Ber. 118 (1985) 4303; G. E. Herberich, B. Hessner, H. Ohst, I.
Raap, J. Organomet. Chem. 348 (1988) 305; b) H. Ohst, Dissertation, Technische Hochschule Aachen 1984.
[lo] G. E. Herberich, M. Hostalek, unpublished.
[ l l ] M. Fieser, L. F. Fieser: Reagentsfor Organic Synthesis. Vol. 4, Wiley Interscience, New York 1974.
[12] Correct C, H analyses.
[13] The NMR spectra of 5 and 6a-c show no significant differences from
those of the TMEDA-free compounds apart from the additional signals of
the TMEDA.
Synthesis and Structure of the Novel p,-Carbido
Complex [(TPP)Fe = C = Re(CO),Re(CO),] **
By Wolfgang Beck,* Wolfgang Knauer, and Christian Rob1
Dedicated to Professor Giiniher Wilke on the occasion ofhis
60th birthday
Of the organometallic compounds with multiple bonds
between substituent-free main group elements and transition
[*I Prof. Dr. W. Beck, DipLChem. W. Knauer, Dr. habd. C. Rob1 ['I
Institut f i r Anorganische Chemie der Universitat
Meiserstr. 1, D-8000 Munchen (FRG)
['I X-ray structure analysis.
[**I Hydrocarbon-Bridged Complexes, Part 16. This work was supported by
the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen
Industrie. We thank Professor Dr. W Herrmann and Dr. E. Herdtwerk,
Technische Universitlt Munchen, for valuable discussions.-Part 15: 1181.
0570-0833/90/0303-03f8S 02.50j0
Angew. Chem. hi.Ed. Engl. 29 (1990) No. 3
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dihydro, structure, dialkylamino, tmeda, borole, li2, dianion, bnet2, metalation, boroles
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