Reactions of group 13 and 14 hydrides and group 1, 2, 13 and 14 organyl compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

FULL PAPER

Reactions of Group 13 and 14 Hydrides and Group 1, 2, 13 and 14 Organyl

Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

Ulrike Braun,^[a]Barbara Böck,^[a]Heinrich Nöth,*^[a]Ingo Schwab,^[a]Manfred Schwartz,^[a]

Siegfried Weber,^[a]and Ulrich Wietelmann^[a]

Dedicated to Professor Dr. Dr. h. c. mult. Ernst Otto Fischer on the occasion of his 85th birthday

Keywords: BN triple bonds / Insertion reactions / (N-Metal-tert-butylamino)(2,2,6,6-tetramethylpiperidino)boranes /

Multinuclear NMR / X-ray structures

(tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane (1) is

a highly reactive species. Its BϵN triple bond inserts into the

B−H bond of boranes, R₂BH, generating diborylamines of the

type tmp−BH−NtBu−BR₂(tmp = 2,2,6,6-tetramethylpiperid-

provide access to N-lithiodiaminoboranes of the type

tmp−BR−NtBu−Li. The stability of these compounds depends

on the substituent R. The least stable compound was the

B−tBu derivative followed by the B-methyl compound. How-

ino; R = H, Cl, Br, or organyl). Thexylborane reacts analog- ever, in the presence of TMEDA tmp−BMe−NtBu−Li is suffi-

ously, but only one of its two B−H bonds is used for the hydro-

boration of 1. However, dihaloboranes HB(Hal)₂−SMe₂(Hal =

Cl, Br) give B-haloboration products tmp−B(Hal)−NtBu−

BH(Hal), while reactions with H₂B(Hal)−SMe₂produce a

ciently stable to allow reactions, e.g. with B-chlorocatechol-

borane, to produce tmp−BMe−NtBu−BO₂C₆H₄. The most

stable lithium compound so far is tmp−BPh−NtBu−Li−OEt₂,

whose structure has been determined by X-ray crystallo-

mixture of two isomers by competing hydroboration and graphy. MgBu₂behaves like LiR and both of its Mg−C bonds

haloboration reactions. Tmp−BH−NtBu−AlH₂was obtained

from 1 and AlH₃−NMe₃. It is a dimer in the solid state with

pentacoordinate Al atoms and AlH₂Al bridges. Hydrosilyl-

ation of 1 was achieved with Me₂SiHCl, SiHCl₃or Ph₂SiH₂

can be used for the insertion reaction. The same is also true

of ZnMe₂. In contrast, at ambient temperature, only one of

the E−C bonds of triorganylalanes, triorganylgallanes and

InPh₃is used for the insertion reaction. In the solid state, most

to give the N-silyl-substituted diaminoboranes tmp-BH- of the new compounds show a weak to strong coordinate

NtBu−SiX_3−nR_n. Me₃SnH and Bu₃SnH behave similarly,

giving the corresponding N-stannylated diaminoboranes.

However, when Ph₃SnH was treated with 1, the stannylbor-

bond between the electrophilic centre (Li, Mg, Zn, Cd, B, Al,

Ga and In) and the nitrogen atom of the tmp group which

generates a four-membered ring.

ane tmp−B(SnPh₃)−NHtBu was formed showing an umpo- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,

lung of the hydrostannylation. Organyllithium compounds

Germany, 2004)

Introduction

reactions, the (amino)(imino)boranes add to carbonylmetal

fragments at the imino nitrogen atom of 1. They also add

protic acids HX or an EϪX bond of sufficiently strong

Lewis acids EX_nacross the BϵN triple bond.^[1,2]Here we

Iminoboranes, RNϭBRЈ, featuring a BϵN triple bond

are highly reactive chemical species due to their unsaturated

character. Their reactivity exceeds that of the corresponding

isolobal alkynes, a consequence of the higher polarity of

the BϵN bond compared with the less polar CϵC bond of

alkynes. The chemistry of iminoboranes has been reviewed

in two comprehensive articles.^[1,2]Iminoboranes have a high

tendency to dimerize to 1,3-diaza-2,3-diboretidines or trim-

erize to borazine derivatives.^[3,4]In the case of the (tert-bu-

tylimino)(2,2,6,6-tetramethylpiperidino)borane (tmpϪBϭ

NϪtBu, 1) the rate of dimerization is retarded for steric and

electronic reasons.^[4]Besides this and related cycloaddition

[a]

Department of Chemistry, University of Munich,

Butenandtstr. 5Ϫ13, 81377 Munich, Germany

E-mail: H.Noeth@lrz.uni-muenchen.de

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DOI: 10.1002/ejic.200300820

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Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

FULL PAPER

report a systematic study of the behaviour of 1 towards hy-

On the other hand, no hydroboration of 1 was observed

drides of group 13 and 14 as well as organyl derivatives of when employing the aminoboranes H₃BϪNEt₃or

the group 1, 2, 13 and 14 elements. Several hydroboration H₃BϪNHiPr₂at ambient temperature. However, when a

reactions of iminoboranes are already known,^[1,2,5]but solution of 1 and H₃BϪNHiPr₂was kept at reflux in hex-

these and (amino)(imino)boranes offer even more interest- ane, hydrogen gas was formed besides the diborylamine 6

ing scopes.^[6,7]

as shown in Equation (4). Hydroboration of 1 can also be

Usually, acidic polar hydrogen compounds HX [X ϭ hal- achieved with catecholborane, dicyclohexylborane, di-

ogen, OR, SR, NHR, NR₂, Co(CO)₄] react with 1 by pro- isoamylborane or 9-borabicyclo[3.3.1]nonane (9-BBN) as

tonation of the tert-butylimino nitrogen atom according to shown in Equations (5) and (6).

Equation (1). In the case of bulky X groups, for instance

Co(CO)₄,^[8]diaminoborinium salts are formed as shown in

Equation (2). This indicates that the first step in reaction

(1) is the protonation of the imino nitrogen atom. On the

other hand, when hydrides of electropositive elements,

ER_rnϪnH_n, are allowed to react with 1, then the hydrogen

atom of an EϪH bond attacks at the boron atom.^[2]This

finally results in the formation of N-substituted diamino-

boranes tmpϪBHϪNtBuϪER_mϪnH_nϪ1as shown in Equa-

tion (3). Reaction (3) starts with an electrophilic attack at

the N atom of the NCMe₃group by the Lewis acidic centre

of the element hydride ER_mϪnH_n, followed by a hydride

transfer to the boron atom. This kind of reaction will not

occur if the central E atom is too weak a Lewis acid.

In this work we report on the behaviour of various hy-

drides of boron, aluminium, silicon and tin as well as of

organyl compounds of lithium, magnesium, zinc, cadmium,

boron, aluminium, gallium and indium.

Because the BϵN triple bond of 1 also inserts into the

BϪC bond of triorganylboranes (vide infra), there might be

competition between the insertion of the BϪC bond and

the BϪH bond if both are present in the molecule. The

results with the diorganylboranes indicate convincingly that

the BϪH bond is more reactive than the BϪC bond, al-

though thermodynamically there should be no strong dif-

ference between the two since the number of BϪC and

BϪH bonds does not change. Kinetic investigations into

the hydroboration of alkynes have shown that the rate of

hydroboration depends on the equilibrium between the di-

meric borane and the monomeric borane.^[9,10]In spite of

the high steric requirements of the diorganylboranes used

in this study, all three compounds reacted chemoselectively.

However, the rates of the reactions were quite different. 9-

BBN reacted fastest and the reaction was complete within

2 h. Disiamylborane required 24 h and dicyclohexylborane

needed 96 h. Amongst these, the dicylohexylborane is cer-

tainly the least bulky. Nevertheless, it showed the lowest

rate. This is because the concentration of its monomeric

unit is very low compared with those of the other species.^[9]

One factor that governs the monomer/dimer equilibrium is

the strength of the BHB bridge bond as demonstrated by

Results

Reactions with Hydrides of Boron and Aluminium

We have already recently reported on the reaction of

BH₃ϪTHF with 1.^[5]When diborane is used as the source

of BH₃in the presence of hexane as a solvent, four com-

pounds, 2Ϫ5, besides the dimer of 1, can be detected. After

warming the reaction mixture from Ϫ196 °C to ambient

temperature, ¹¹B NMR signals were found at δ ϭ 28.7 and

Ϫ4.4 (for 2), 37.2 (for 3), Ϫ20.8 (for 4), and Ϫ26.2 ppm

(for 5). However, when BH₃ϪTHF was used, the product

distribution depended both on the concentration and the

temperature of the solutions. At Ϫ60 °C, dilute solutions

favoured the formation of 2. Yields up to 82% can be

achieved.

An almost quantitative conversion of 1 to 2 can be the corresponding BHB bridge frequencies in the IR spec-

achieved, however, by employing H₃BϪSMe₂as the hydro- tra. These frequencies are 1590 cm^Ϫ1for dicyclohexylbor-

borating reagent. In this case, it is important to add a hex- ane,^[11]1551 cm^Ϫ1for disiamylborane^[12]and 1560 cm^Ϫ1for

ane solution of 1 slowly at ambient temperature to a solu- 9-BBN.^[13]In contrast to these diorganylboranes, the sym-

tion of H₃BϪSMe₂in hexane. Under these conditions the metric dithexyldiborane shows a BHB band at 1565 cm^Ϫ1

dimerization of 1 is prevented due to the presence of a local which is very close to that of the dimeric disiamylborane.^[14]

excess of the borane reagent.

However, 8 d are required for a quantitative conversion of

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1 into 11. In contrast to the hydroboration of organic sub- electronic structure of H₂NϪBϭNϪMe is best described

strates with thexylborane,^[14Ϫ16]only one of its two BϪH by the two formulae A and B.

hydrogen atoms is used for the hydroboration of 1.

In contrast, the haloboranes H_3ϪnB(Hal)_nin the form of

their Me₂S adducts react with 1 by hydroboration and/or

haloboration. The dihaloboranes HBCl₂and HBBr₂show

The adduct C, which is considered to be the first step in

the hydro/haloboration of H₂NϪBϭNϪMe, is more stable

by 110.68 kJ/mol compared with the reagents. The adduct

shows an allene-type configuration with a torsion angle

HϪNϪNϪC of Ϫ95.7°. The BϪN bond lengths for the

H₂NϪB and BϪNMe(BH₂Cl) groups were calculated as

high positive charges at the boron atoms, e.g. ϩ0.976 in

HBCl₂(see Table 1) which is almost the same as for BCl₃

but less than in BH₂Cl. Bond dissociation energies may also

play a role and should favour the hydroboration route.^[17]

Both HBCl₂ϪSMe₂and HBBr₂ϪSMe₂exclusively give,

however, the haloboration products 12 and 13 [Equation

(7)]. This can be readily demonstrated by the absence of a

doublet in the ¹¹B NMR spectrum for the tricoordinate B

atom but the presence of a doublet for the tetracoordinate

boron atom. This also confirms that compounds 12 and 13

have cyclic structures.

˚

1.357 and 1.309 A while the BϪN bond to the monochloro-

˚

borane unit is 1.606 A. This type of structure has been de-

duced from NMR spectroscopic data for 1ϪECl₃(E ϭ Al,

Ga)^[18]or 1ϪM(CO)₅(M ϭ Cr, W)^[19]and determined by

X-ray crystallography for tmpϭBϭNtBu(ECl₃) [E ϭ Ga,

and In with 1.345(2) and 1.316(2) A, respectively].^[20]These

˚

data are in agreement with BϭN double bonding between

the dicoordinate B atom and the tricoordinate N atoms

(see Figure 1).

The adduct C is, however, less stable than the chlorobor-

ation/hydroboration compounds D and E. The hydrobor-

ation product E is more stable by 154.46 kJ/mol than C,

while the chloroboration product

D is more stable

by178.76 kJ/mol. As expected, the energy difference be-

tween D and E of 24.21 kJ/mol is not large. In each case,

the ‘‘open chain’’ structures are energetically favoured over

the ring structures F and G. The energy difference between

D and F is 65.47 kJ/mol in favour of D, while E is 65.62 kJ/

mol more stable than the ring compound G. Thus, chlorob-

oration to D is the thermodynamically more favourable re-

action. This is in contrast to the observed preferred hydro-

boration of 1 with BH₂Cl. Thus, the model system does not

mirror the experimental system.

Table 1. Calculated charge densities for the series of chlorobor-

anes BH_3ϪnCl_n

The calculated BϪN bond lengths in E are in agreement

with BϭN double bonding. The shortest BϪN bond (1.395

BH₃

0.495

H₂BCl

HBCl₂

BCl₃

0.9995

Ϫ0.3332

˚

A) was calculated for an H₂NϪB bond while those to the

˚

BH₂group are longest at 1.417 A. However, the ‘‘central’’

q_B

q_H

q_Cl

0.724

Ϫ0.209

Ϫ0.307

0.976

Ϫ0.149

Ϫ0.414

˚

Ϫ0.165

Ϫ

BϪN bond is also short at 1.449 A. This indicates a bond-

ing situation also found in 1,3-butadienes. In the case of D

and E, the cis conformations were found to be energy min-

ima. As can be seen from the BϪN bond lengths of the ring

structure F (see Table 2), there is only one N bond with

On the other hand, reactions of H₂BClϪSMe₂and double bond character. The H₂N···BH₂bond is rather long

˚

H₂BBrϪSMe₂with 1 lead to a mixture of the hydrobor- at 1.701 A and the N and B atoms now exhibit tetracoordi-

ation products 15 and 17 with the haloboration products 14 nation. Although compound F shows three BϪN single

and 16. The product ratio of 14/15 was 33:66 while it was bonds and one BϪN π-bond, one BϪN bond in particular

50:50 for 16/17. Therefore, there is a statistical preference is quite weak and this is certainly the reason why the chain

for the hydroboration product 15 but not for 17.

compound D with three BϪN π-bonds is more stable. On

In order to obtain an insight into the formation of com- the other hand, although the chloroboration chain com-

pounds 14 and 15, we performed calculations at the B3LYP/ pound D is favoured over the hydroboration product E, the

6-311g and B3LYP/8-311ϩg(2d,f) levels for the model sys- ring isomer G is definitely more stable than the ring F. One

tem ClBH₂/H₂NϪBϭNϪMe. The results are summarised of the reasons for this is that the BϪN bond of the group

in Table 2 and shown in Figure 1. The two BϪN bonds of H₂NϪBHCl is much shorter than in F which leads to its

the (amino)(imino)borane are in agreement with a higher stabilisation. However, as shown experimentally for com-

bond order for the imino nitrogen atom, but also the BϪN pound 14 and 15, only the ring structures were experimen-

bond of the amino group NH₂reveals π-bonding. Thus, the tally observed and not the open-chain compounds as the

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Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

FULL PAPER

Table 2. Model compounds optimised at the B3LYP level of theory; all structures are without imaginary frequencies, i.e. they are real

minima; relative energies refer to E(BH₂Cl) ϩ E(iminoborane) ϭ 0. 1 Hartree ϭ 627.5095 kcal/mol ϭ 2627.2568 kJ/mol

B3LYP/6-311g

ϪE [kJ/mol] zpe [kJ/mol]

B3LYP/b3lyp/6-311ϩg(2df,p)

˚

ϪE [a.u.]

BϪN [A]

ϪE [a.u.]

ϪE [kJ/mol]

zpe [kJ/mol]

BϪN [A]

BH₂Cl

Iminoborane

Ϫ486.28

Ϫ175.51

55.36

19.00

Ϫ

Ϫ486.31

Ϫ175.57

0

55.37

18.56

1.24723

1.39743

1.30918

1.35696

1.60588

1.39564

1.41705

1.44942

1.39874

1.40058

1.46438

1.35622

1.53900

1.57649

1.70103

1.37194

1.53374

1.57333

1.65177

Adduct1

Adduct2

iso-Adduct2

Ring

Ϫ110.6829

Ϫ265.1378

Ϫ289.3429

Ϫ199.6628

26.10

26.50

26.70

Ϫ89.1037

Ϫ253.5101

Ϫ275.8459

Ϫ192.7342

25.64

26.23

26.24

26.49

1.67613

1.64624

iso-Ring

Ϫ223.7185

26.76

Ϫ204.2356

26.52

For this reason we also performed calculations on

tmpϪBPhϪNtBuϪBH₂whose ring structure was deter-

mined by X-ray crystallography.^[21]Indeed, optimization of

the open-chain structure leads to the ring as the most stable

species (Figure 2). The calculated BϪN bond lengths com-

pare favourably with the experimental values [experimental:

PhBϪN 1.594(3), PhBϪNtBu 1.367(3), tBuNϪBH₂

˚

1.555(3), H₂BϪN(tmp) 1.665(3) A, calcd. 1.618, 1.377,

˚

1.561, 1.691 A]. Clearly, a sufficiently basic N atom of the

amino group is needed to favour the ring structure over the

open-chain isomer.

Figure 2. Optimised structure for tmpϪBPhϪNtBuϪBH₂at the

B3LYP/6-311G level of theory

Figure 1. Optimised structures in the BH₂Cl/H₂NϪBϭNϪMe sys-

tem

Compound 1 forms adducts of type C with AlCl₃, AlBr₃,

[18,20]

calculations suggest and this may be due to the fact that GaCl₃and InCl₃

and no insertion reactions have so

the amino nitrogen atom of the tmp unit is more basic than far been observed for these trihalide adducts in contrast

the NH₂group of the model system.

with halosilanes.^[22]It was, therefore, of interest to study the

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H. Nöth et al.

FULL PAPER

behaviour of AlH₃. This hydride was employed as well as diborylamines of the type (R₂N)₂BϪNMeϪBMe₂

AlH₃ϪNMe₃[see Equation (10)].

(δ¹¹B ϭ 44Ϫ46 ppm) for the Me₂B group.^[25]Thus, the ob-

served chemical shifts for 8Ϫ10, which show a better shield-

ing than for any of these aminoboranes, indicate not only

that BϪN π-bonding is present for the BH group but also

that there is a weak interaction of the R₂B group with the

tmp nitrogen atom. This is in agreement with a bonding

description provided by the formulae HϪK.

The reaction was followed in hexane solution by ¹¹B

NMR spectroscopy which showed that two products were

formed. Two new ¹¹B NMR signals appeared at δ ϭ 33 and

27 ppm in a ratio of 1:4. In the proton coupled ¹¹B NMR

spectrum, the signal at δ ϭ 27 ppm was a doublet showing

that this boron atom carries one hydrogen atom as expected

for a hydroalumination product. Two ²⁷Al NMR signals at

δ ϭ 115 and 80 ppm in an intensity ratio of 1:4 support the

formation of two products. While the low-field signal points

to the presence of a tetracoordinate Al atom, the other rep-

resents a pentacoordinate Al centre. The intensities of the

¹¹B and ²⁷Al signals change with time. The two high-field

signals gain intensity and the low-field signals decrease cor-

respondingly. Moreover, the IR spectrum contains a strong

band at 1806 cm^Ϫ1which is typical for an antisymmetric

NBN vibration. These latter data are in agreement with the

formation of compound 18.

Attempts to separate the two compounds by fractional

crystallisation from toluene were unsuccessful. The solid

obtained showed the same NMR signals as the original re-

action mixture. However, well-formed single crystals of di-

meric 19 (vide infra) could be selected from the solid mate-

rial which separated from a hexane solution.

Diisobutylalane reacted chemoselectively with 1 by hy-

droalumination to the cyclic compound 20. No transfer of

the organyl group was observed. Thus, this reaction corre-

sponds to the hydroalumination of CϪC multiple bonds.^[23]

The contribution of K cannot be significant because there

are only single ¹H and ¹³C resonance signals for the methyl

groups at positions 6/7 of the tmp unit in compounds 9 and

10 which indicates free rotation about the BϪN bond of

the tmp group. However, for the disiamylborane 8, there are

two signals for these hydrogen atoms and four ¹³C reson-

ances. This can be rationalised by the presence of a non-

planar NBNB skeleton or by a slow interconversion be-

tween a cyclic and a noncyclic species. In contrast to these

diborylamines, those bearing hydrogen and halogen atoms

at the boron atoms are of a cyclic nature as evidenced by

two ¹¹B NMR signals as well as two ¹H and ¹³C resonances

for the tmp methyl groups. Those of the tricoordinate boron

atoms can be found between δ ϭ 20.0 and 28.8 ppm,

whereas those of the tetracoordinate boron atoms are in the

1

range of δ ϭ 2.8 to Ϫ5.9 ppm. There are six H NMR sig-

nals for the NMe₂groups of tmp in the mixture of the

monohalogen derivatives 14Ϫ17. One may expect that com-

pounds 14 and 16 should give rise to two signals for the

methyl groups of the tmp ligand and four for compounds

15 and 17. For the cyclic diborylamines one can expect four

signals for these methyl groups provided that the ring is not

planar. This is the case for the cyclic diborylamine

Cl₂BϪNtBuϪBClϪtmp.^[26]The C-1/5 carbon atoms of the

tmp unit in the dichloro derivative 12 are more deshielded

than in the monochloro isomers 14 and 15, an effect of the

stronger Lewis acidic character of the Cl₂B group compared

with BHCl. Unfortunately, the corresponding ¹³C NMR

spectroscopic data for the bromo compounds are not avail-

able. Conversely, the parent cyclic diborylamine 2 shows

only two signals for the methyl groups at positions 6 and 7

Nevertheless, compound 20 could not be obtained in a pure

[24]

form. The reaction of [(tBuO)₂AlH]₂

produced a mix-

ture of three compounds according to the ¹¹B NMR spec-

trum. We were unable to separate these compounds.

NMR and IR Spectra

1

both in the H and ¹³C NMR spectra.^[5]

Table 3 summarises the NMR spectroscopic data of the

Compounds 19 and 20 give two ¹H and ¹³C NMR signals

hydroboration/haloboration products of the (amino)- for the methyl groups of the tmp substituent in agreement

(imino)borane 1. For the diborylamines of the type with its cyclic structure. However, the proton resonance for

tmpϪBHϪNtBuϪBX₂, one would expect two ¹¹B NMR 19 is not well resolved and appears as a broad signal. While

signals. This is, however, not the case for 8, 9, 10 and 11. the ¹¹B NMR signal for 19 at δ ϭ 26.8 ppm is a doublet in

Only one broad signal was observed which showed a barely the proton-coupled spectrum [¹J(¹¹B¹H) ϭ 130 Hz] no

resolved doublet structure, indicating the presence of a BH AlϪH coupling was observed for the broad ²⁷Al signal at

group. In the proton-decoupled spectra the doublet van- δ ϭ 80 ppm (h_1/2ϭ 9670 Hz) or for that in 18 [δ²⁷Al ϭ 32.6

ished but the signal was still broad. Chemical shifts which (h_1/2ϭ 5170 Hz]. A strong band at 2468 cm^Ϫ1in the IR

can be compared with those of 8 to 11 occur in (amino)(or- spectrum is typical for a terminal ¹¹BH group of a tricoord-

ganyl)boranes R₂NϪB(H)ϪR (δ¹¹B ϭ 41Ϫ43 ppm), mono- inate boron atom. Only a broad and unresolved band

meric aminoboranes R₂NϪBH₂(δ¹¹B ϭ 37Ϫ39 ppm) as centred at 1830 cm^Ϫ1was observed for the AlH_nvibrations.

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Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

Table 3. Selected NMR spectroscopic data of compounds tmpϪBXϪNCMe₃ϪBYYЈ; chemical shifts in ppm; coupling constants in Hz

FULL PAPER

X

Y

H

YЈ

δ¹¹

B

δ¹H

6/7-H

δ¹³

C

C-3 C-6/7

2-H/4 3-H

CMe₃C-1/5

C-2/4

C-10 CMe₃

2

8

9

10

11

H

28.8 (d),^[a]Ϫ4.4 (t)^[b]

56.6

1.44 54.1

1.51 55.9

1.49 55.9

1.36 56.4

1.47 55.1

1.50 55.1

37.5

36.8

37.6

37.2

37.4

37.7

17.2 25.8, 30.1

15.7 30.7, 31.2, 34.3, 35.0 574 33.0

15.8 32.9

15.9 32.2

16.2 33.8, 34.6

16.7 30.1, 30.3

49.6 30.3

C₅H₁₁C₅H₁₁35.5 (d)^[c]

C₆H₁₃C₆H₁₃36.1^[d]

1.59Ϫ1.80 (m) 1.47, 1.50

1.60Ϫ1.88 (m) 1.42

53.4 34.1

53.6 33.9

55.0 33.1

54.9 33.6

51.1 32.9

51.6 30.7

9-BBN

Thex

H

35.3 (d)^[e]

35.9 (d)^[f]

25.1, Ϫ5.9 (t)^[g]

30.6 (d),^[h]3.8 (d)^[i]

25.1, 3.5 (d)^[k]

(br. m)

1.38

1.32

H

14 Cl

15

0.93Ϫ1.28 (m) 1.29, 1.31, 1.51

0.93Ϫ1.28 (m) 1.32, 1.37, 1.55

0.98Ϫ1.41 (m) 1.23, 1.31,

H

Cl

36.7, 40.6 16.1 30.7, 30.8

12 Cl Cl

1.37 59.8, 60.2 37.1

16.6 25.3, 26.7

30.5, 31.7

16 Br

17

H

Br

H

30.8, 2.4 (t)^{[k] [l]}

32.3,^[m]1.0 (d)^[n]

0.98Ϫ1.41 (m) 1.24, 1.26

0.8Ϫ1.15 (m) 1.28, 1.29

1.35, 1.36

1.59

1.40

38.7

H

13 Br Br

H

22.6, 0.8 (d)^[q]

0.8Ϫ1.15 (m) 1.20, 1.24, 1.63, 1.78 1.40

^{[a] 1}J(¹H¹¹B) ϭ 1.56. ^{[b] 1}J(¹H¹¹B) ϭ 111. ^{[c] 1}J(¹H¹¹B) ϭ 112. ^{[d] 1}J(¹H¹¹B) ϭ 119. ^{[e] 1}J(¹H¹¹B) ϭ 82. ^{[f] 1}J(¹H¹¹B) ϭ 108. ^{[g] 1}J(¹H¹¹B) ϭ

[h]

[i]

[k]

[l]

[m]

[n]

[q]

125.

¹J(¹H¹¹B) ϭ 142.

¹J(¹H¹¹B) ϭ 155.

¹J(¹H¹¹B) ϭ 148.

¹J(¹H¹¹B) ϭ 75.

¹J(¹H¹¹B) ϭ 105.

¹J(¹H¹¹B) ϭ 50.

¹J(¹H¹¹B) ϭ 105.

Crystal Structure of 19

The cyclic (tmp)borylaminoalane 19 crystallises in the tri-

¯

clinic space group P1 with Z ϭ 4. Therefore, there are two

independent monomeric molecules in the unit cell. As

shown in Figure 3, the monomers are connected to dimeric

molecules via AlϪHϪAl bridges. The dimeric molecules

possess crystallographic inversion centres making each Al

˚

atom pentacoordinate. The Al1ϪN1 bond is 0.242 A longer

than the Al1ϪN2 bond to the tricoordinate nitrogen atom

N2. Also the B1ϪN1 bond is considerably longer [1.546(5)

˚

A] than the B1ϪN2 bond [1.369(5) A] which is typical for

BϪN π-bonding in monoaminoboranes. The hydrogen

bonds between the two Al atoms are asymmetric as shown

by the Al(1)ϪH1 and Al(1A)ϪH1 bond lengths of 1.65 and

Figure 3. ORTEP representation of the molecular structure of 19;

˚

selected bond lengths [A]: Al1ϪN1 2.115(3), Al1ϪN2 1.873(1),

1.46 A, respectively, while the terminal AlϪH bond has a

length of 1.48 A. The four-membered N1ϪB1ϪN2ϪAl1

Al1···B1 2.445(4), Al···Al1A 2.813(1), B1ϪN1 1.546(5), B1ϪN1

1.369(5), N1ϪC1 1.534(5), N1ϪC5 1.582(4), N2ϪC10 1.483(5),

Al1ϪH1 1.65, Al1ϪH1A 1.46, Al1ϪH2 1.48, B1ϪH1B 1.18; selec-

ted bond angles [°]: N1ϪAl1ϪN2 72.6(1), N1ϪB1ϪN2 108.5(3),

Al1ϪN1ϪB1 82.2(2), B1ϪN2ϪAl1 96.7(2), Al1ϪN1ϪC5 116.2(2),

Al1ϪN1ϪC1 117.2(1), Al1ϪN2ϪC10 135.6(2), H1ϪAl1ϪH1A

121(1), H1ϪAl1ϪH1C 111, Al1ϪH1ϪAl1A 130, N1ϪAl1ϪH1A

103, N1ϪAl1ϪH1 157, H1BϪB1ϪN2 130, H1BϪB1ϪN1 121

˚

ring is almost planar, the largest deviation from the mean

plane is 0.012(3) A. The geometry around Al1 is strongly

˚

distorted tetragonal-pyramidal. This is of course due to the

sharp bond angles N1ϪAl1ϪN2 of 72.6(1)° and

B1ϪN1ϪAl1 of 82.2(1)°. The bond angle N1ϪAl1ϪH1 to

the apical atoms is 156.7°. As expected, the tmp ring adopts

a chair conformation.

Moreover, when 1 was treated with Me₂SiHCl or SiHCl₃

the corresponding hydrosilylation products 22 and 23 were

formed and isolated as viscous oils in good yields.

Reactions with Hydrides of Silicon, Germanium and Tin

Within the series of hydrides of the heavier group 14 ele-

ments, the bond polarity of the EϪH bond changes con-

siderably. Moreover, the hydrides are only weak Lewis acids.

Therefore, one may surmise that these hydrides will either

not react with 1 or do so only very sluggishly and the hy-

drogen atom will either move to the boron atom or the ni-

trogen atom depending on the polarity of the EϪH bond.

The latter can, of course, be influenced by substituents.

No reaction was observed between Me₃SiH or Ph₃SiH

and 1. However, Ph₂SiH₂did hydrosilylate 1 according to

Equation (11) to yield tmpϪBHϪNtBuϪSiPh₂H (21).

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

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3617

H. Nöth et al.

FULL PAPER

Me₃GeH and Ph₃GeH did not react with 1 at ambient figuration and whose C1ϪN1ϪC5 plane includes a twist

temperature. At elevated temperature only the dimerization angle with the N1ϪB1ϪN2 plane of 85.2°. The sum of the

of 1 to its corresponding 1,3,2,4-diazadiboretidine oc- bond angles at N1 is 354.2° which shows that the N1 atom

curred.^[4]However, Me₃SnH and Bu₃SnH hydrostannylated is almost sp²-hybridised. There is a strong steric interaction

1 as shown in Equation (14) while Ph₃SnH reacted accord- between one of the phenyl groups with the tert-butyl group

ing to Equation (15).

as seen by a B1ϪN2ϪC10 bond angle of 137.2(2)°. The

torsion angle for the atoms Sn1ϪB1ϪN2ϪC10 is 13.5°,

and the tmp substituent (C1ϪN1ϪC5) stands almost verti-

cal (91.7°) to the N1ϪB1ϪSn1 plane.

Reactions of Main Group Elements with Organyl

Compounds MR_n(n

؍

1؊3)

Reactions with Organyllithium Compounds

Some reactions of organylmetal compounds MR_nwith 1

have so far only been described for M ϭ Li and Mg in

a review article.^[3]In principle, organyllithium compounds

should add to 1 according to Equation (16) but the stability

of the resultant N-lithiodiaminoboranes depends on the na-

ture of R.

NMR Spectra

In the ¹¹B NMR spectrum of 26 [δ¹¹B ϭ 44.6 ppm (br.,

h_1/2ϭ 700 Hz)], no ¹¹B¹¹⁹Sn coupling could be observed.

This is not unusual because of the rapid relaxation due to

the quadrupole moment of the ¹¹B nucleus. Also, no ¹¹⁹Sn

resonance was found for the same reason. However, a broad

¹H NMR signal at δ ϭ 5.13 ppm indicates the presence of

an NH group. Moreover, the IR spectrum of 26 contains a

strong band at 3383 cm^Ϫ1due to the NH vibration.^[27]In

1

addition, the H and ¹³C NMR spectra show three sets of

signals for the phenyl groups. Clearly, the vicinity of the

bulky tmp substituent induces hindered rotation about the

SnϪC bonds. Furthermore, there is only one broad ¹H

NMR signal for the methyl group at the tmp substituent

and there was no sharpening of the signal at Ϫ60 °C. There

are, however, two ¹³C resonances for the methyl groups

showing that rotation about the BϪN bond is hindered.

Most likely, the tmp group stands perpendicular to the

N1ϪB1ϪSn1ϪN2 plane. The final proof of the structure

of 26 came from an X-ray diffraction study.

Table 4 shows that the boron nuclei of the two stannyl-

For instance, tert-butyllithium reacts according to Equa-

tion (16) but the product 27 is unstable and decomposes

into Li(tmp) and the 1,3,2,4-diazadiboretidine 28 [Equation

(17)]. In contrast, n-butyllithium leads to the stable N-

lithiodiaminoborane 29. Methyllithium yields compound 30

which, like 27, decomposes. However, when the reaction

(19) is performed in the presence of tetramethylethylenedi-

amine then 30 can be treated with B-chlorocatecholborane

to produce the cyclic diborylamine 31. No reaction

occurred between fluorenyllithium and 1, but phenyllithium

reacted smoothly in diethyl ether to give compound 32

which could be isolated as single crystals from a hexane/

diethyl ether solution.

ation products of 1 are better shielded than they are in the

1

hydrosilylation products. Moreover, the H and ¹³C reson-

ances for the tmp methyl groups are at higher field than

those of the silyl compounds 21 and 22. Compounds 21 to

1

24 all show two H and ¹³C resonances for these methyl

groups indicating hindered rotation. Therefore, one can as-

sume that all these compounds most likely have cyclic struc-

tures.

X-ray Structure Analysis of 26

Crystals of 26 are orthorhombic. The space group is

P2₁2₁2₁with Z ϭ 4. Figure 4 depicts the molecular struc-

ture of this molecule. It supports the conclusions deduced

from the spectroscopic data.

X-ray Structural Analyses of 32 and 31

˚

The BϪSn bond length in 26 of 2.295(2) A corresponds

to

a

single bond as found, for example, in

Figure 5 shows the molecular structure of 32. It features

[28]

˚

Me₃Sn(Me₂N)BϪB(NMe₂)SnMe₃[2.276(2) A]. The two a four-membered LiN₂B ring with a tricoordinate Li atom.

B1ϪN bonds differ by 0.087(3) A, the longer bond involves The Li1ϪN2 bond is 0.21 A shorter than the coordinate

the BϪN bond to the tmp group which shows a crown con- Li1ϪN1 bond. Atom N2 has a planar geometry which al-

˚

3618

 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

Table 4. Selected NMR spectroscopic data of compounds 19Ϫ25; chemical shifts δ in ppm; additional data can be found in the Exp. Sect.

FULL PAPER

δ¹¹B

δE

δ¹H

6/7-H

δ¹³C

C-6/7

2-H/4 3-H

CMe₃

C-1/5

C-2/4

C-3

C-10

CMe₃

19

20

21

22

23

24

25

26

26.8(d)^[a]

33.5 (d)^[c]

37.7(d)^[d]

34.6^[e]

80^[b]

109.5

Ϫ21.9

1.49Ϫ1.58 m

1.35 1.53

1.22 1.36

1.23 br.

1.46 br

1.37 1.40

1.35 1.37

1.17 1.28

1.18 1.28

1.26

1.06

1.29

1.35

1.38

1.34

1.13

52.8

55.5

54.5

55.6

53.3

52.6

52.9

38.4

37.4

37.2

36.7

37.9

40.4

39.7

17.1

17.0

15.9

15.4

18.5

18.6

18.7

22.7 31.8

26.9, 29.2

33.5 br

32.7 34.8

32.1 35.7

26.9 36.1

27.3 35.5

29.1, 33.4

49.3

50.5

54.7

56.7

54.9

55.4

55.2

51.0

33.5

33.8

32.9

31.6

32.4

34.9

34.0

32.6

1.5 m, vbr

1.3Ϫ1.7 m

1.2Ϫ1.6 m

1.1Ϫ1.5 n

1.1Ϫ1.5 m

1.40 m br.

35.9^[f]

39.4^[g]

39.2

44.6

Ϫ

[a]

[b]

[c]

[d]

[e]

[f]

[g]

¹J(¹¹B¹H) ϭ 52.

Line width 9670 Hz.

¹J(¹¹B¹H) ϭ 111.

¹J(¹¹B¹H) ϭ 114.

¹J(¹¹B¹H) ϭ 126.

¹J(¹¹B¹H) ϭ 111.

Figure 5. Molecular structure of 32, ORTEP diagram; selected

˚

Figure 4. The molecular structure of (tert-butylamino)(tetramethyl-

bond lengths [A]: Li1ϪN1 2.085(6), Li1ϪN2 1.884(5), Li1ϪO1

˚

piperidino)(triphenylstannyl)borane (26); selected bond lengths [A]: 1.929(5), N1ϪB1 1.564(4), N2ϪB1 1.361(4), N2ϪC10 1.467(4),

B1ϪSn1 2.295(2), B1ϪN1 1.476(3), B1ϪN2 1.389(3), N1ϪC1

1.496(2), N1ϪC5 1.492(2), N2ϪC10 1.485(2), Sn1ϪC14 2.166(2),

N1ϪC1 1.495(4), N1ϪC5 1.485(4), B1ϪC14 1.617(4); selected

bond angles [°]: N1ϪLi1ϪN2 75.70(2), Li1ϪN1ϪB1 78.9(2),

Sn1ϪC20 2.166(2), Sn1ϪC26 2.166(2); selected bond angles [°]: N1ϪB1ϪN2 112.9(2), B1ϪN2ϪLi1 91.6(2), N1ϪB1ϪC14

N1ϪB1ϪN2 119.4(2), N1ϪB1ϪSn1 116.4(1), N2ϪB1Sn1 140.0(2), 126.2(3), N2ϪB1ϪC14 120.9(3), N1ϪLi1ϪO1 136.2(3),

B1ϪN1ϪC1 117.2(1), B1ϪN1ϪC5 116.7(1), C1ϪN1ϪC5 120.3(2),

B1ϪN2 C10 137.2(2), H2ϪN2ϪB1 109(1), H2ϪN2ϪC10 112(1),

N2ϪLi1ϪO1 142.5(3), C1ϪN1ϪC5 116.2(2)

C14ϪSn1ϪC20

104.44(7),

C14ϪSn1ϪC26

99.79(7),

C20ϪSn1ϪC26 102.74(8)

˚

to B2 are 1.753(3) A (N1) and 1.495(3) A (N2), respectively.

The latter is typical for a single bond between an sp³-hy-

bridised boron atom and an sp²-hybridised N atom. The

long B2ϪN1 distance corresponds to a weak bond which

is in agreement with the NMR spectra which show only one

signal for the tmp methyl groups indicating rotation about

its BϪN bond in solution. Although one might have ex-

pected the two BϪO bonds to be equal in length, this is not

lows good BϪN π-bonding. The phenyl group stands al-

most perpendicular to the N1ϪB1ϪN2 plane (τ ϭ 89.5°).

This prevents BϪC π-bonding. The four-membered ring

has a flat butterfly structure as shown by an interplanar

angle

τ

ϭ

9.1° for the planes B1ϪN2ϪLi1 and

B1ϪN1ϪLi1. As usual, the tmp ring has a chair confor-

mation. Its N1 atom adopts a distorted tetrahedral ge-

ometry with bond angles ranging from 78.9(2) to 118.0(2)°.

Although the ring structure of 32 is certain in the solid

state, it is very likely that this structure is not retained in

solution since only a single signal was observed for the

˚

the case and they differ by 0.04 A. Their lengths are similar

to those found for the bis(catecholato)borate anion.^[29]The

planes N1ϪC1ϪC5 and B2ϪO1ϪO2 stand almost perpen-

dicular to the B1ϪN1ϪB2ϪN2 ring plane by 92.5 and

89.8°, respectively.

1

methyl groups at the tmp substituent, both in the H and

Reactions with Diorganylmagnesium, -zinc, -cadmium and

-mercury Compounds

¹³C NMR spectra.

An ORTEP plot of the molecular structure of the cyclic

diborylamine 31 is shown in Figure 6. It features a planar

In order to test the possibility of a double insertion of 1

˚

four-membered B₂N₂ring. The B1ϪN1 bond is 0.262 A into metalϪcarbon bonds of dialkylmetal compounds ER₂

˚

longer than the B1ϪN2 bond [1.378(3) A]. The BϪN bonds (E ϭ Mg, Zn, Cd, Hg), we studied the reaction of 1 with

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

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3619

H. Nöth et al.

FULL PAPER

Figure 6. Molecular structure of tmpϪBMeϪNtBuϪBcat (31);

˚

selected bond lengths [A]: B1ϪN1 1.756(4), B1ϪN2 1.377(4),

B1ϪC14 1.578(5), N1ϪB2 1.561(4), B2ϪN2 1.494(4), B2ϪO1

1.503(6), B2ϪO2 1.423(6), N1ϪC1 1.559(6), N1ϪC5 1.534(6).

O1ϪC15 1.347(5), O2ϪC20 1.395(5); selected bond angles [°]:

B1ϪN1ϪB2 79.8(2), N1ϪB2ϪN2 86.0(2), B2ϪN2ϪB1 95.9(2),

N1ϪB1ϪN2 98.3(2), B1ϪN2ϪC10 134.6(3), B2ϪN1ϪC10

129.5(2),

C14ϪB1ϪN1

129.4(3),

C1ϪN1ϪC5

114.7(3),

O1ϪB2ϪO2 105.9(2), O1ϪB2ϪN1 112.7(3), O2ϪB2ϪN1 115.5(4)

NMR Spectra

An overview of relevant NMR spectroscopic data of the

lithium, magnesium, zinc and cadmium compounds is given

in Table 5. The magnesium compound 33 exhibits only sin-

dibutylmagnesium. Reactions (20) and (21) proceeded rap-

idly at Ϫ78 °C. Only a single ¹¹B NMR signal was found

at δ¹¹B ϭ 37.6 ppm. This value is typical for metallated

diaminoboranes. Compound 33 was obtained as a viscous

oil and attempts at crystallisation were unsuccessful. Be-

cause the NMR spectroscopic data for 33 and 34 are rather

similar to those of the lithium compound 30, we assume

that the magnesium atom is coordinated to the tmp nitro-

gen atom. Dibutylmagnesium reacts with 1 not only in a

1:1 stoichiometry but also in a 1:2 ratio to produce 34. This

product is also a viscous oil with δ¹¹B ϭ 39.0 ppm.

1

gle H and ¹³C NMR signals for the methyl groups at the

piperidino ring. This suggests a weak interaction of the Mg

atom with the tmp nitrogen atom allowing rotation of the

tmp group in solution. A similar situation is, therefore, ex-

pected for 34 which shows a broad low-field proton NMR

signal for the C-6/7 group but two ¹³C NMR signals. This

can be explained by a hindered rotation about the BϪN

bond of the BNCMe₃group where the tBu group attached

to the boron atom can be oriented either cis or trans to the

tert-butyl group. This suggestion is supported by the strong

deshielding of the protons of the CMe₃group in 34. The

¹¹B NMR signals of the two Mg compounds are rather

similar, and the shielding of the boron nuclei are similar to

those of the Li and Zn compounds.

1

The H NMR spectrum of 35 reveals two sharp singlets

for the BMe and ZnMe groups in a 1:1 ratio. Also, two ¹³

C

Dialkylzinc compounds are less reactive than dialkylmag- NMR signals were observed for these groups. These are

nesium compounds. Nevertheless, 1 reacted with dimeth- sharp for ZnMe (δ¹³C ϭ 11.3 ppm) and broad for BMe

ylzinc in toluene to produce a solid 1:1 insertion product (δ¹³C ϭ 1.0 ppm). A single resonance represents the methyl

35, δ¹¹B ϭ 39.4 ppm, as shown in Equation (22). The com- groups at tmp and two signals in a 2:1 ratio were found for

pound was obtained as single crystals. A reaction in a 1:2 the CH₂groups of the piperidino ring. Thus, in solution,

ratio to give 36 was also successful.

the structure of compound 35 may either be monomeric or

As a representative of organylcadmium compounds we dimeric. However, in the case of the dimer (35B) one would

studied the reaction of diphenylcadmium with 1 in toluene. expect a low-field shift of the protons of the CMe₃group,

Reaction (24) proceeded smoothly to give compound 37. due to the tetracoordination of the respective nitrogen

In contrast, diphenylmercury did not react with 1 either at atom. Because monomeric organylzinc amides are scarce,

ambient temperature or in refluxing toluene.

the alternative 35A is not very likely. Another possibility

From the solutions of 37, a few well-shaped crystals sepa- might be the dimeric structure 35C which we regard as un-

rated within several days. These, however, proved not to be likely because two sets of NMe₂group are to be expected.

compound 37 but rather CdPh₂. As far as we know, the However, the molecular structure of 35 has been shown to

structure of this compound has not yet been determined. be a cyclic N-(methylzinc)diaminoborane in the solid state.

Therefore, some data for this linear compound are listed in For this reason we suggest that the structure of 36 is also

the references.^[30]37 is isostructural with HgPh₂.^[31]

spirocyclic in solution as found for 35 in the solid state.

3620

 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

Table 5. Selected NMR spectroscopic data of compounds 30 and 32Ϫ37; additional data can be found in the Exp. Sect.

FULL PAPER

δ¹¹B

δ¹H

δ¹³C

C-10

2,4-H

3-H

6,7-H

CMe₃

C-1,5

C-2,4

C-3

C-11Ϫ13

C-6,7

30

32

33

34

35

36

37

39.1

34.0

37.6

39.0

39.5

39.1

35.4

1.41 (t)

1.54 (t)

0.95

0.72 (Ϫ)

1.38 (m)

1.15 (Ϫ)

1.32 (t)

1.66 (m)

1.62 (m)

1.68 (m)

1.59 (br.)

1.66 (m)

1.64 (br. m)

1.54 (m)

1.24 (br.)

1.30

1.26

1.23

1.26

1.13, 1.24

1.06, 1.38

1.13

1.02

1.18

0.87

1.13

1.26

1.08

51.05

52.67

51.3

53.8

50.9

51.2

53.2

40.83

37.89

39.9

35.7

40.8

41.0

43.5

18.14

19.14

18.0

17.8

18.1

18.4

17.8

8.49

49.91

48.8

52.0

53.2

53.4

50.6

32.26

3.86

32.7

32.0

32.1

35.6

31.9

36.64

32.3

31.0, 32.5

31.8

32.4, 38.6

25.3, 38.6

The chemical shift δ¹¹B ϭ 35.4 ppm for 37 is compatible

with the suggested PhBN₂unit as found in PhB(NMe₂)₂

(δ ϭ32.4 ppm) or PhB(NEt₂)₂(δ ϭ34.1 ppm).^[25]As for 34,

1

only one H NMR signal but two ¹³C resonances were ob-

served for the methyl groups at tmp in the ¹H and ¹³C

NMR spectra. The presence of the Cd atom follows from

the satellites observed on the methyl carbon resonance

3

which indicates a J(^111/113Cd¹³C) coupling.

Molecular Structure of 35

The zinc compound 35 crystallises in the monoclinic

space group P2₁/c. Figure 7 shows the ORTEP plot. In the

solid state, the methyl[N-(methylzinc)-tert-butylamino](te-

tramethylpiperidino)borane is present as a four-membered

almost planar ring. Its shape, however, is a strongly dis-

torted trapezoid due to four different endocyclic bond 1.944(3), N1ϪC1 1.514(3), N1ϪC5 1.514(3), B1ϪN1 1.555(3),

lengths. Endocyclic bond angles range from 70.43(8)°

Figure 7. Molecular structure of 35 in the solid state; selected bond

˚

lengths [A]: Zn1ϪN1 2.222(2), Zn1ϪN2 1.908(2), Zn1ϪC15

B1ϪN2 1.380(4), B1ϪC14 1.597(4), N2- C10 1.481(3); selected

bond angles [°]: Zn1ϪN1ϪB1 81.59(2), Zn1ϪN1ϪC1 110.9(2),

(N1ϪZn1ϪN2) to 98.7(2)° (B1ϪN2ϪZn1). The in-

terplanar angle, τ, between the planes N1ϪZn1ϪN2 and

N1ϪB1ϪN2 is 2.9°. Notable is the tricoordinate zinc atom

(sum of the bond angles ϭ 360°). The B1ϪN2 bond is quite

Zn1ϪN1ϪC5 110.2(2), N1ϪB1ϪN2 109.2(2), N1ϪB1ϪC14

122.8(2), N2ϪZn1ϪN1 70.43(8); angles between planes [°]:

Zn1N1nB1/Zn1N2B1 2.9, C1N1C5/Zn1N2B1N2 90.0

˚

short at 1.350(4) A, implying the presence of a BϪN π-

observed in reactions with 1 because the (amino)(imino)-

borane is only a moderate base. Indeed, no evidence for a

stable 1:1 coordination compound with triorganylboranes

was observed by NMR spectroscopy. However, organobor-

ation of 1 occurs easily, but the rate depends strongly on

the steric requirements of the organyl group. This is shown

by the data for reaction (25).

bond. As in many of the other structures presented here,

˚

the B1ϪN1 bond is long [1.555(3) A], typical for a single

˚

bond. Analogously, the Zn1ϪN1 bond [2.222(2) A] is much

˚

longer than the Zn1ϪN2 bond (1.908 A). The tmp group

adopts a chair conformation.

As far as we are aware, the structure of compound 35 is

unique since alkylzinc amides RZnNR₂are usually dimeric,

containing a four-membered Zn₂N₂ring.^[31,32]The X-ray

structure of (MeZnNPh₂)₂^[33]shows ZnϪN bond lengths of

˚

2.080 and 2.066 A to the tetracoordinate nitrogen atoms.

These are much shorter than in compound 35 but longer

than the Zn1ϪN2 bond to the tricoordinate N atom. Di-

mers of the type (RZnNR₂)₂can be broken up with donors

such as pyridine, but no adducts of the type RZnNR₂(py)

have yet been characterised in contrast to RZnNR₂(py)₂, in

which the zinc atom is tetracoordinate.^[33]

To rationalise these results we assume that there is a pre-

equilibrium 1 ϩ BR₃^Ǟ_ǟ1·BR₃. The position of this equilib-

rium lies more on the side of the individual components

Reactions with Triorganylboranes, -alanes, -gallanes, and

-indanes

The triorganyl compounds of the group 13 elements are the more bulky the R group becomes. Thus, the lower the

medium to strong Lewis acids, the acidity being determined concentration of the adduct, the slower the reaction rate. In

principally by the steric requirements of the organyl group. the case of B-methyl-9-borabicyclo[3.3.1]nonane, it is the

It was, therefore, expected that no 1:1 adducts would be methyl group which moves to the boron atom. Most of

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

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3621

H. Nöth et al.

FULL PAPER

these new asymmetrically substituted diborylamines hand, the rather broad ²⁷Al NMR signal at δ ϭ 150 ppm

(38Ϫ42) are liquids. for 44 points to a noncyclic structure with hindered rotation

Although the triorganyl compounds of the heavier group about the BϪN bond of the tmp group. This conclusion for

13 element are all dimeric, they react rapidly with 1 accord- 43 as well as for 46 is supported by the X-ray structures

ing to Equation (26). Most of the resultant compounds are of tmpϪBPhϪNtBuϪEMe₂(E ϭ Al, Ga) which will be

viscous liquids. Some are solids, however, but single crystals discussed shortly.^[21]

of these could not be obtained.

Discussion

The BϵN triple bond of iminoboranes is highly reactive

and this has been further demonstrated by results described

here for the (amino)(imino)borane 1. The reaction with di-

borane is not selective because four different compounds

were observed in addition to the hydroboration product 2.

The by-products result from BϪN bond cleavages. How-

ever, 2 can be formed in high yield by employing

H₃BϪSMe₂as the borane source. On the other hand, only

NMR Spectra

hydroboration of 1 occurs with diorganylboranes and thex-

The NMR spectroscopic data of compounds 38Ϫ41 and ylborane (employed as its dimer). Hence, this reaction is

43Ϫ48 are summarised in Table 6 (ignoring the data for the faster than the organoboration of 1 which can be achieved

substituents at element E which are found in the Exp. Sect.). by using triorganoboranes. This can be rationalised by the

The dialkyl[N-(tetramethylpiperidinoboryl)-tert-butylami- higher negative charge at the hydrogen atom compared with

no]boranes 38Ϫ41 exhibit two ¹¹B NMR signals. In case of the organyl group, as well as of the ability of the hydridic

39, only a single signal was observed. This is not totally hydrogen atom to form hydrogen bonds between two elec-

surprising since resonances of CBN₂and C₂BN groups can tropositive atoms. The competition between hydroboration

be close together [Ph₂BNR₂: δ ϭ 40Ϫ43 ppm; PhB(NR)₂: and haloboration is chemoselective for the former in the

δ ϭ 33Ϫ36 ppm; (Ph₂B)₂NH: δ ϭ 41 ppm].^[25]In general, case of the dihaloboranes HB(Hal)₂ϪSMe₂, while in case

for the two groups, those of the C₂BN type are less well of monohaloboranes both reactions compete with each

shielded than those for CBN₂. In general, boron atoms of other. In this case, the hydroboration should be statistically

diborylamines are less well shielded than boron atoms of more favourable. This is indeed observed for H₂BClϪSMe₂

aminoboranes. In all cases, two resonances were observed but not for H₂BBrϪSMe₂. In the latter case the observed

for the C-6/7 atoms revealing hindered rotation about the 1:1 product ratio of the two isomers shows that bromobor-

tmp group. No systematic influence on the δ¹¹B shifts by ation is favoured. If the determining factor were the partial

the group 13 element atoms in compounds 39Ϫ48 could be negative charges at the hydrogen and halogen atoms, then

1

observed. Because all show two H and ¹³C signals for the the haloboration should win the competition as observed

C-6/7 methyl groups, it follows that these compounds most for HB(Hal)₂. From this point of view it was most surpris-

likely have ring structures with EϪN1 bonds. This is sup- ing to find that HSiCl₃reacts with 1 exclusively by hydrosi-

ported by a ²⁷Al NMR signal at δ ϭ 105 ppm for 43 which lylation, although statistically the chlorosilylation of 1

is consistent with a tetracoordinate Al atom. On the other should be favoured and this is indeed observed when em-

Table 6. Selected NMR spectroscopic data of compounds 38Ϫ48; chemical shifts δ in ppm; additional data can be found in the Exp. Sect.

δ¹¹B

δ¹¹B/²⁷Al

δ¹H

δ¹³C

C-6/7

2,4-H

3-H

CMe₂

CMe₃

C-1/5

C-2/4

C-3

C-10

C-11Ϫ13

38

39

40

41

43

44

45

46

47

48

49

40.7

43.1

40.9

40.6

38.5

37.9

42.1

36.3

36.9

35.5

37.6

45.7

43.1

46.1

49.4

105^[a]

150^[b]

Ϫ

1.53 (br.)

1.55 (br. m)

1.6 (br. m)

1.63Ϫ1.89

1.62 (m)

1.83 (m)

1.40Ϫ1.8 (m)

1.45Ϫ1.80 (m)

1.37, 1.44

1.49

1.43

1.41

1.37

1.9

56.4

56.8

56.9

53.3

57.1

55.0

57.5

54.8

54.6

54.0

56.4

38.3

41.3

38.9

28.2

36.8

37.0

36.4

36.9

36.4

36.5

15.2

17.4

15.5

32.3, 33.1

33.0, 37.0

27.2, 33.5

53.1

56.4

53.3

32.7

33.7

33.3

1.49

1.43

1.25

1.28

1.15

1.19

1.26

1.30

1.48, 1.61

1.50, 1.71

1.32, 1.24

1.27, 1.37

1.64

16.2

16.9

14.7

17.0

18.0

17.8

17.6

30.1, 32.1

30.7, 32.4

31.3, 33.2

30.5, 32.1

31.3, 32.4

33.0, 33.5

32.1, 33.0

50.6

51.9

50.7

50.8

51.6

51.3

32.2

33.6

32.8

33.6

33.4

34.7

1.52 (t)

1.34 (t)

1.78 (m)

1.77 (m)

(br.)

1.62

[a]

[b]

Line width 780 Hz. Line width 2600 Hz.

3622

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Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

FULL PAPER

ploying diorganyldichorosilanes, trichloro(organyl)silanes

Experimental Section

or silicon tetrahalides.^[8,22]The silanes must be sufficiently

Lewis acidic. Thus, Me₃SiH and Ph₃SiH do not react with

1 in contrast to Me₂SiHCl and Ph₂SiH₂, although both are

not strong Lewis acids but obviously of sufficient strength

to induce the hydrosilylation of 1. On the other hand, the

hydrides Ph₃EH (E ϭ Si, Ge) did not react with 1 in con-

trast to Me₃SnH, Bu₃SnH and Ph₃SnH. This indicates that

steric factors also influence the hydrometallation of 1. How-

ever, it was most surprising that with Ph₃SnH an umpolung

of the insertion occurs. The imino nitrogen atom of 1 is

protonated with formation of a BϪSn bond.

General: All experiments were performed under anhydrous con-

ditions using Schlenk or vacuum-line techniques. Solvents were

dried by conventional methods. Commercial chemicals were puri-

fied either by distillation, crystallisation or were used as supplied

(solutions of LiR compounds). Several compounds were already

available in our laboratory. The following compounds were pre-

pared by literature methods: 1,^[4]AlMe₃ϪOEt₂,^[40]Ph₃InϪ1,4-diox-

ane,^[41]

Ph₃Al,^[42]

thexylborane,^[12]

disiamylborane,^[43,44]

HBCl₂ϪSMe₂and H₂BClϪSMe₂,^[45]HBBr₂ϪSMe₂and

[46]

H₂BBrϪSMe_2,

9-BBN.^[47]NMR: Bruker AC 200 (⁷Li, ¹¹B,

¹¹⁹Sn), Jeol GS270 (¹H, ⁷Li, ¹¹B, ¹³C, ¹⁴N, ¹¹⁹Sn), Jeol EX400 (¹H,

¹³C) instruments. If not otherwise stated all NMR spectra were

recorded in C₆D₆. References: SiMe₄(int.), BF₃ϪOEt₂(ext.), 1 

aqueous LiCl (ext.), C₆D₆(int.), aqueous 1  NaNO₃(¹⁴N), SnMe₄

(ext.). IR: Nicolet FT-IR spectrometer (liquids as capillary films,

solids as nujol mulls). MS: Atlas CH7 instrument, 70 eV; reported

data: mass, relative intensity, assignment. X-ray: Siemens P4 dif-

fractometer equipped either with a scintillation counter or a CCD

detector. Low-temperature device LT2, Mo-K_αradiation, graphite

monochromator.

The organylmetal compounds LiR, MgR₂, ZnR₂, CdR₂,

BR₃, AlR₃, GaR₃and InPh₃all react with 1 by organomet-

allation. This is a new route to compounds of the type

tmpϪBRϪNtBuϪER_nϪ1. Paetzold et al. have studied the

reactions of LiR compounds with the iminoboranes XϪBϭ

NϪCMe₃(X ϭ Me, Et, Bu). These react in a 1:2 ratio and

provided N-lithioazaborazoniaborate compounds.^[34]How-

ever, with iminoboranes XϪBϵNϪCMe₃[X ϭ CMe₃,

N(SiMe₃)CMe₃] N-lithioaminoboranes LiN(CMe₃)ϪBXR

were obtained of which (TMEDA)LiN(CMe₃)ϪB(CMe₃)₂

was crystallographically characterised.^[34]Usually, N-li-

thioaminoboranes are prepared by deprotonation of amino-

boranes R₂BϪNHRЈ, RB(NHRЈ)₂or B(NHR)₃.^[35Ϫ40]De-

protonation of the diborylamine mes₂BϪNHϪBmes₂with

LiR in diethyl ether leads to ionic [(Et₂O)₃Li][N(Bmes₂)₂]

with a linear BNB unit of an allenic type and short BϪN

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]-

borane (2): A solution of H₃BϪSMe₂(0.39 mL, 7.0  solution in

hexane, 2.8 mmol) was added to a solution of 1 (2.9 mL of a 0.96

 solution, 2.8 mmol) in hexane. The reaction was slightly exother-

mic. After 24 h of stirring, all volatile components were removed

at ambient temperature in vacuo. 2 remained as a colourless oil.

¹H (¹¹B-decoupled) NMR: δ ϭ 3.91 (br., 2 H, BH₂), 4.77 (br., 1 H,

BH) ppm. C₁₃H₃₀B₂N₂(236.0): calcd. C 66.16, H 17.94, N 11.87;

found C 64.76, H 17.25, N 11.67.

˚

bonds [1.343(5), 1.348(5) A] due to the dicoordinate N

atom,^[36]while deprotonation of mes₂BϪNH₂gives dimeric

[(Et₂O)LiNHBmes₂]₂.^[37]In both cases the Li atoms are

tricoordinate. In the latter case, the nitrogen atoms are

tetracoordinate. Consequently, the BϪN bond of the di-

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]diisopropyl-

aminoborane (6): To a solution of freshly distilled diisopropylamine

(0.42 mL, 3.0 mmol) in hexane (20 mL) was added at 0 °C a solu-

tion of BH₃ϪTHF in hexane (1.0 , 3.0 mL). After warming to

ambient temperature, all volatile components were removed in va-

cuo leaving behind 0.44 g of H₃BϪNH(iPr)₂{δ¹¹B ϭ Ϫ20.58

˚

meric molecule is longer [1.386(4) A] than in mes₂BNH₂.

Association of N-lithioaminoboranes can be prevented by

using multidentate bases as ligands as has been demon-

strated for 9-N-lithio(trimethylstannylamino)borabicyclo-

[3.3.1]nonaneϪpentamethylethylenetriamine.^[39]The mono-

meric N-lithiodiaminoborane 32 is unique because in the

solid state the intramolecular coordinative LiϪN bond

stabilises the tricoordination of the Li atom and the bulki-

ness of the groups at the two nitrogen atoms hinders associ-

ation. The B2ϪN2 bond of 32 is at the shorter end for

1

[quat., J(¹H¹¹B) ϭ 96 Hz] ppm}. A solution of 1 in hexane (0.96

, 3.10 mL, 3.0 mmol) was then added at Ϫ78 °C. No reaction

occurred at room temperature. On heating to reflux overnight, the

formation of 6 was noted by its ¹¹B NMR signal at δ ϭ 50.6 ppm.

The compound was isolated as a solid after removal of all volatile

components in vacuo. Yield 0.82 g of 6 (98%). The ¹H NMR spec-

trum was not very informative as the signals were strongly overlap-

ping.

˚

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]dicyclohexyl-

borane (8): A solution of 1 (7.9 mL, 0.462 , 3.6 mmol) in hexane

was added with stirring to tetracyclohexyldiborane (0.65 g,

1.8 mmol). The diborane derivative dissolved slowly. About 2 h

later, a precipitate formed. According to ¹¹B NMR spectroscopy

the reaction was complete after 4 d. After removal of the solvent

in vacuo, a colourless powder remained which proved to be pure 8.

BϪN bonds [1.361(4) A] between tricoordinate B and N

atoms indicating a high degree of π-bonding. However, the

˚

Li1ϪN1 bond is weak and is 0.2 A longer than the Li1ϪN2

bond. This is a general observation for all the N-metallated

diaminoboranes reported here (19, 32 and 35) and many

others of a similar type.^[21]In solution, however, the coordi-

nate Li1ϪN1 bond (also MgϪN, BϪN, AlϪN, GaϪN and

1

Yield 1.4 g of 8 (98%), m.p. 122Ϫ124 °C. H NMR: δ ϭ 1.78 (br.,

1

InϪN bonds) is opened as shown by only one H or ¹³C

22 H, C₆H₁₁), 2.15 (br., 1 H, BH) ppm. ¹³C NMR: δ ϭ 24.1 (br.,

BC), 27.7 (p-C of C₆H₁₁), 28.7 (m-C), 28.9 (o-C) ppm. MS (70 eV):

NMR signal for the methyl groups attached to the piperid-

ino ring. For those where two or more signals were ob-

served, one can assume that the ring structure with a coor-

dinate N1ϪE bond is retained in solution as shown, for

instance, for compounds 12Ϫ17. In particular, the lithium

compound 32 proved to be a versatile reagent and we will

report on its chemistry in a forthcoming paper.^[21]

m/z (%) ϭ 400 (75) [M^ϩ], 385 (15) [M^ϩϪ Me], 317 (100) [M^ϩ

Ϫ

C₆H₁₁] and others. C₂₅H₅₀B₂N₂(400.31): calcd. C 75.01, H 12.59,

N 7.00; found C 74.54, H 11.25, N 6.77.

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]diisoamyl-

borane (9): A solution of 1 (8.65 mL, 0.462 , 4.0 mmol) in hexane

was added with stirring to a hexane solution of freshly prepared

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3623

H. Nöth et al.

FULL PAPER

dimeric disiamylborane (4.0 mmol). ¹¹B NMR spectroscopic analy-

¹¹B NMR: δ ϭ 1.0 [d, ¹J(¹¹B¹H) ϭ 50 Hz], 32.3 [d, ¹J(¹¹B¹H) ϭ

sis showed that the hydroboration of 1 was complete after 24 h.

105 Hz] ppm. The mixture of isomers was not characterised by el-

Removal of volatile material in vacuo left an oily residue which emental analysis.

turned out to be pure 9. Yield 1.47 g (97%). ¹H NMR: δ ϭ 3.78

{(tert-Butyl)[chloro(2,2,6,6-tetramethylpiperidino)boryl]amino}-

(br., 1 H, BH), 1.36, 1.35 [each 3 H, B(CHMe)], 1.01, 1.08 (each 6

H, CHMe₂) ppm. ¹³C NMR: δ ϭ 16.6 (br., BC), 23.0 (CHMe₂),

22.7 (BCHMe), 55.7 (CHMe₂) ppm. MS (70 eV): m/z (%) ϭ 376

(28) [M^ϩ], 361 (14) [M^ϩϪ Me], 319 (40) [M^ϩϪ C₄H₉], 305 (100)

[M^ϩϪ C₅H₁₁], 235 (100) [305 Ϫ C₅H₁₀]^ϩ, 222 (24) [235 Ϫ CH₂]^ϩ

and fragments of lower mass. C₂₃H₅₀B₂N₂(376.29): calcd. C 73.42,

H 13.39, N 7.44; found C 74.25, H 13.66, N 7.80.

chloroborane (12): To a stirred solution of HBCl₂ϪSMe₂(1.50 mL,

1.30 , 1.9 mmol) was added dropwise a hexane solution of 1

(7.28 mL, 0.267 , 1.9 mmol). After 48 h, the reaction was quanti-

tative. Removal of the volatile material left behind a colourless oil.

Yield 0.55 g of 12 (93%). IR: ν˜ ϭ 2480 (νBH), 1480, 1450 (νBN₂),

660 (νBCl) cm^Ϫ1. C₁₃H₂₈B₂Cl₂N₂(304.9): calcd. C 51.21, H 9.26,

N 9.89; found C 51.11, H 9.39, N 9.34.

9-[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]-9-borabi-

Bromo{[bromo(2,2,6,6-tetramethylpiperidino)boryl](tert-butyl)-

cyclo[3.3.1]nonane (10):

A solution of dimeric 9-borabicy-

amino}borane (13): In analogy to 12

a hexane solution of

clo[3.3.1]nonane (0.30 g, 1.4 mmol) in pentane (30 mL) was cooled

to Ϫ78 °C. A solution of 1 (12.3 mL, 0.277 , 2.8 mmol) in pentane

was then slowly added. After stirring for 2 h at ambient tempera-

ture, the reaction was complete. A light yellow oil remained after

removal of the pentane in vacuo (50 Torr). After addition of hexane

(1 mL) and cooling of the solution to Ϫ50 °C, a colourless powder

HBBr₂ϪSMe₂(19 mL, 0.23 , 4.4 mmol) was allowed to react with

1 (7.33 mL, 0.23 , 4.4 mmol). The reaction was slightly exother-

mic. After heating for several minutes to reflux, all volatile materi-

als were removed in vacuo. 13 was obtained as a colourless viscous

oil. Yield 1.69 g of 13 (97%). C₁₃H₂₈B₂Br₂N₂(313.89): calcd. C

49.70, H 8.92, N 8.92; found C 48.98, H 8.97, N 8.76.

1

of 10 precipitated. Yield 0.91 g (95%), m.p. 65Ϫ67 °C. H NMR:

δ ϭ 1.05 (2 H, CH), 1.90 (br., 12 H, 6 CH₂) ppm. ¹³C NMR: δ ϭ

12.1 (br., BMe), 23.5 (C_a), 26.5 (C_d), 33.0 (C_c) 33.2 (C_b) ppm. ¹⁴N

NMR: δ ϭ Ϫ231 ppm. MS (70 eV): m/z (%) ϭ 344 (95) [M^ϩ], 329

(90) [M^ϩϪ Me], 288 (15) [M^ϩϪ C₄H₈], 261 (93) [M^ϩϪ C₆H₉],

and fragments of lower mass. C₂₁H₄₂B₂N₂(344.20): calcd. C 73.28,

H 12.30, N 8.14; found C 75.43, H 12.75, N 7.83.

Dimeric [(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]alane

(19): A solution of 1 in hexane (18.7 mL, 0.186 , 3.5 mmol) was

diluted further with hexane (15 mL), cooled to Ϫ78 °C, and a solu-

tion of AlH₃ϪNMe₃(0.31 g, 3.5 mmol in 25 mL of diethyl ether)

was added dropwise with stirring. After warming the mixture to

ambient temperature, the ¹¹B NMR spectrum showed a broad sig-

nal at δ ϭ 34.7 ppm and doublet at δ ϭ 27.1 ppm. The volume of

the solution was then reduced by about 50%. After 1 d at Ϫ20

°C, crystals had separated. The majority of the crystals were well-

developed prisms which proved to be 19. The compound is very

moisture-sensitive. Selected IR bands: ν˜ ϭ 2515, 2468 (ν^10/11BH),

1831 (νAlH), 1460 (νBN₂) cm^Ϫ1. C₂₅H₆₀Al₂B₂N₄(504.37): calcd.

C 61.92, H 11.99, N 11.11; found C 57.05, H 11.78, N 9.45.

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino](1,1,2-tri-

methylpropyl)borane (11): To freshly prepared sym-dithexyldibor-

ane(6) (2.5 mmol) was added, with stirring, a solution of 1

(10.8 mL, 0.462 , 5.0 mmol) in hexane. After stirring for 8 d. the

reaction was complete as shown by ¹¹B NMR spectroscopy. After

removal of the hexane in vacuo, a colourless, mobile liquid was left.

Yield 1.19 g of 11 (98%). The compound decomposed on attempted

distillation at 130 °C/10^Ϫ2Torr with formation of 2,3-dimethyl-2-

butene (trapped at Ϫ196 °C and identified by NMR spectroscopy).

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]-

diisobutylalane (20): To a stirred solution of 1 (3.0 mL, 0.96 ,

2.9 mmol) in hexane was added a hexane solution of iBu₂AlH

(2.9 mL, 1.0  diluted with 10 mL of hexane). After 24 h, the hex-

ane was removed in vacuo leaving behind 20 as a colourless air-

and moisture-sensitive liquid (1.05 g, 99%). ¹H NMR: δ ϭ 0.46 [d,

3

¹H NMR: δ ϭ 0.91 [d, J(¹H¹H) ϭ 6.6 Hz, 6 H, CHMe₂], 0.94 (6

H, CMe₂) ppm. ¹³C NMR: δ ϭ 18.6 (CH₂), 22.5 (CMe₂), 29.0,

(br., CB), 37.3 (CHMe₂) ppm. MS (70 eV): m/z (%) ϭ 236 (32) [M^ϩ

Ϫ C₆H₁₂], 180 (9) [236 Ϫ C₄H₈]^ϩ, no M^·ϩ. C₁₉H₄₂B₂N₂(320.18):

calcd. C 71.28, H 13.23, N 8.75; found C 72.14, H 13.11, N 9.21.

3

³J(¹H¹H) ϭ 6.3 Hz, 4 H, AlCH₂], 1.22 [d, J(¹H¹H) ϭ 6.3 Hz, 12

H, CH(CH₃)₂], 2.20 [m, 2 H, CH(CH₃)₂] ppm. ¹³C NMR: δ ϭ 28.8,

29.2 [CH(CH₃)₂], 32.7 ppm; CH(CH₃)₂, AlC not observed. ²⁷Al

NMR: δ ϭ 109.5 (h_1/2ϭ 1960 Hz) ppm. IR: ν˜ ϭ 2460 cm^Ϫ1(νBH).

C₂₁H₄₆AlBN₂(364.41): calcd. C 69.22, H 12.72, N 7.69; found C

68.21, H 12.08, N 8.12.

{(tert-Butyl)[chloro(2,2,6,6-tetramethylpiperidino)boryl]amino}-

borane (14) and [(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)am-

ino]chloroborane (15): To an emulsion of BH₂ClϪSMe₂in hexane

(2.7 mmol in 1.60 mL) was added dropwise a hexane solution of 1

(10.3 mL, 0.267 , 2.7 mmol). After stirring for 5 h, a clear solution

resulted. All volatile materials were removed in vacuo leaving be-

hind a colourless viscous oil. In C₆D₆, this solution showed the

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]diphenyl-

silane (21): To a solution of Ph₂SiH₂(0.415 g, 2.25 mmol) in tolu-

ene (10 mL) was added a solution of 1 (4.6 mL, 0.5 ) in hexane

diluted with toluene (10 mL). The mixture was stirred for 2 weeks.

After this time, the ¹¹B NMR signal of 1 could no longer be de-

tected. Removal of the solvents left behind a colourless oil. At-

tempts at crystallisation were unsuccessful. Because the NMR spec-

troscopic data showed no impurities, no further purification at-

tempts were deemed necessary. ¹H NMR: δ ϭ 0.57 (SiMe₂),

7.10Ϫ9.0 (m, Ph) ppm. ¹³C NMR: δ ϭ 129.01, 129.53, 130.17,

136.17, 17.71 (Ph) ppm. ²⁹Si NMR: δ ϭ Ϫ21.87 [¹J(¹H²⁹Si) ϭ

21 Hz] ppm. Selected IR bands: ν˜ ϭ 2490, 2395 (νBH), 2120 (νSiH)

cm^Ϫ1. C₂₅H₃₉BN₂Si (406.2): calcd. C 73.96, H 9.68, N 6.89; found

C 72.63, H 9.77, N 7.08.

1

presence of two isomers. 14: ¹¹B NMR: δ ϭ Ϫ5.9 [t, J(¹¹B¹H) ϭ

125 Hz], 25.1 ppm (ratio 1:1). 15: ¹¹B NMR:

δ ϭ 3.8 [d,

¹J(¹¹B¹H) ϭ 125 Hz], 30.6 [d, ¹J(¹¹B¹H) ϭ 142 Hz] ppm (ratio 1:1).

In addition a signal for (tmpBϪNCMe₃)₂(δ¹¹B ϭ 34.6 ppm) was

observed. The mixture could not be separated by fractional distil-

lation.

{[Bromo(2,2,6,6-tetramethylpiperidino)boryl](tert-butyl)amino}-

borane (16) and Bromo[(tert-butyl)(2,2,6,6-tetramethylpiperidinobor-

yl)amino]borane (17): In analogy to 15 the components

H₂BBrϪSMe₂(1.50 mL, 1.5 , 2.2 mmol) and 1 (4.87 mL, 0.462

, 2.2 mmol) were allowed to react in hexane. After 24 h, neither

of the two starting materials could be detected by ¹¹B NMR spec-

troscopy. Four new signals were present, both as pairs in a 1:1 ratio.

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinobory)amino]trichlorosilane

16: ¹¹B NMR: δ ϭ 2.4 [t, ¹J(¹¹B¹H) ϭ 75 Hz], 30.8 (s) ppm. 17: (22): To a toluene solution of 1 (0.67 g, 3.0 mmol in 4.6 mL) was

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Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

FULL PAPER

added at 0 °C a solution of SiHCl₃(0.4 mL, 0.54 g, 4.0 mmol) in 33.3 ppm. The brownish solid that remained after evaporation of

toluene (6 mL). After stirring for 30 min, all volatile material was the solvents in vacuo was crystallised from toluene at Ϫ78 °C. Yield

removed in vacuo. Distillation afforded 0.66 g of 22 (62%), b.p. 1.55 g of 32 (61%), m.p. 162 °C. ¹³C NMR: δ ϭ 125.14, 126.44,

110Ϫ115 °C/0.005 Torr, m.p. 40 °C. ¹⁴N NMR: δ ϭ Ϫ235, 134.13 (Ph) ppm; BC not found. ⁷Li NMR (hexane): δ ϭ

Ϫ298 ppm. IR: ν˜ ϭ 2492, 2460 st (νBH) cm^Ϫ1. C₁₃H₂₈BCl₃N₂Si 2.3 (h_1/2ϭ 9.7 Hz) ppm. C₂₃H₄₂BLiN₂O (380.34): calcd. C 72.63,

(357.64): calcd. C 43.66, H 7.89, N 7.83; found C 43.06, H 8.04,

N 7.93.

H 11.13, N 7.37; found C 64.75, H 10.04, N 7.41.

Lithium (tert-Butyl)[methyl(2,2,6,6-tetramethylpiperidino)boryl]-

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]chloro- amide؊Tetramethylethylenediamine (30-TMEDA): To a solution of

dimethylsilane (23): Me₂SiHCl (300 mg, 3.2 mmol) was cooled to

Ϫ78 °C. A solution of 1 (0.71 g, 3.2 mmol) in toluene (4.9 mL)

was then added. The solution was then allowed to warm to room

temperature with stirring. All volatile materials were removed in

vacuo and the remaining liquid distilled at 70 °C/10^-3Torr. Yield

1 (13.6 mL, 0.22 , 3.0 mmol) in hexane at Ϫ78 °C was added

tetramethylethylenediamine (0.45 mL, 3.0 mmol). A solution of

LiMe in diethyl ether was then added (1.88 mL, 1.6 , diluted with

25 mL of diethyl ether). After the addition, the solution became a

bluish colour but at room temperature the solution was colourless.

Some solid had formed which was removed by filtration. Dissolved

in C₆D₆, this solid proved to be tmpϪBMeϪNCMe₃Li. Two ¹¹B

NMR signals were observed for the filtrate at δ ϭ 35.3 (90%) and

1

0.96 g of 23 (95%), m.p. 25Ϫ26 °C. H NMR: δ ϭ 0.57 (SiMe₂),

5.3 (BH, at Ϫ54 °C) ppm. ¹³C NMR: δ ϭ 8.75 (SiC) ppm. ¹⁴N

NMR: δ ϭ Ϫ248, Ϫ307 ppm. IR: ν˜ ϭ 2460 (sh), 2420 m (νBH)

cm^Ϫ1. C₁₅H₃₄BClN₂Si (316.80): calcd. C 56.87, H 10.82, N 8.84; 39.6 ppm (10%). The signal at δ ϭ 39.6 ppm increased in intensity

found C 54.07, H 10.79, N 9.28. The same result was achieved in

the presence of a small amount of hydroquinone as a catalyst.

with time.

(tert-Butyl)[methyl(2,2,6,6-tetramethylpiperidinoboryl)amino]-

catecholborane (31): A solution of 30ϪTMEDA (3.0 mmol, 16 mL)

was allowed to quickly reach room temperature. A solution of B-

[(tert-Butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]trimethyl-

stannane (24): To a solution of 1 (0.44 g, 2.0 mmol) in hexane

(14 mL) was added Me₃SnH (1 mL). After heating the mixture to chlorocatecholborane (0.6 g, 3.0 mmol) in diethyl ether (15 mL)

50 °C, the reaction was complete (¹¹B NMR). All volatile materials

were removed in vacuo. The residue, a colourless oil, proved to be

sufficiently pure. However, on distillation only 1 could be isolated,

b.p. 100Ϫ130 °C/0.1 Torr. Yield (before distillation) 0.40 g of 24

(93%). ¹H NMR: δ ϭ 0.4 [²J(¹H¹¹⁹Sn ϭ 55.1 Hz), SnMe₃] ppm.

¹³C NMR: δ ϭ 2.11 [¹J(¹³C¹¹⁹Sn) ϭ 388 Hz, SnMe₃] ppm. IR: ν˜ ϭ

was then added with stirring. A white precipitated rapidly formed.

The suspension was stirred for 3 h and the solid was then removed

by filtration and the filtrate reduced in volume to about 20 mL in

vacuo and kept at Ϫ20 °C. Crystals of 31 separated within 2 d.

Yield 0.75 g (73%), m.p. 158 °C. ¹H NMR: δ ϭ 0.78 (s, BMe),

6.69Ϫ1.76 (m, 5 H) ppm. ¹³C NMR: δ ϭ 110.0, 119.27, 150.55

2413, 2385 m (νBH) cm^Ϫ1. C₁₆H₃₇BN₂Sn (386.99): calcd. C 49.66, (C_arom) ppm. C₂₀H₃₄BN₂O₂(356.11): calcd. C 67.45, H 9.62, N

H 9.64, N 7.24; found C 49.43, H 9.31, N 7.21. 7.87; found C 67.42, H 9.51, N 7.83.

Tributyl[(tert-butyl)(2,2,6,6-tetramethylpiperidinoboryl)amino]- Reaction of 1 with Butyllithium: BuLi (7.46 mL of a 0.670  hexane

stannane (25): A solution containing 1 (0.89 g, 4.0 mmol) and solution, 5 mmol) was stirred and cooled to Ϫ78 °C followed by

Bu₃SnH (1.32 mL, 5.0 mmol) in toluene (10 mL) was heated to 60 addition of a hexane solution of 1 (3.2 mL, 1.57 ). After warming

°C for 2 h. The ¹¹B NMR spectrum showed the absence of 1 and

to room temperature, a yellow solution formed. Evaporation of the

a new signal at δ ϭ 39.6 ppm. Volatile materials were removed from solvent in vacuo gave a yellow solid, m.p. 74Ϫ75 °C. It showed a

the solution in vacuo (0.001 Torr). The remaining colourless oil was

distilled. The fraction of b.p. 120Ϫ135 °C/0.001 Torr consisted of

¹¹B NMR signal at δ ϭ 33.6 ppm (about 70%) and two other sig-

1

nals in toluene solution. The H and ¹³C NMR spectra indicated

90% 25 and 10% Bu₃SnH according to NMR spectroscopic data. that the product was not pure. Attempts at purification by subli-

¹H NMR (only main component): δ ϭ 0.8Ϫ1.5 (m, Bu) ppm. ¹³C

NMR: 360 Hz, C_α], 29.09

18.75 [¹J(¹³C¹¹⁹Sn)

[²J(¹³C¹¹⁹Sn) ϭ 16 Hz, C_β], 27.79 [³J(¹³C¹¹⁹Sn) ϭ 76 Hz, C_γ], 13.79

(C_δ) ppm. IR: ν˜ ϭ 2415 sh, 2388 m (νBH) cm^Ϫ1

mation or crystallisation were unsuccessful.

δ

ϭ

Reaction of 1 with tert-Butyllithium. Formation of 1,2,3,4-tert-Butyl-

1,3,2,4-diazadiboretidine (28): To a stirred solution of 1 (7.46 mL,

0.670 ) in hexane at Ϫ78 °C was added a hexane solution of

LiCMe₃(3.13 mL, 1.60 , 5 mmol). The mixture was then allowed

to warm to room temperature with stirring to give a yellow solu-

tion. After removal of all volatile components in vacuo, a yellow

solid remained which on sublimation at 40 °C/0.001 Torr yielded

.

(tert-Butyl)[(2,2,6,6-tetramethylpiperidino)(triphenylstannyl)boryl]-

amine (26): Ph₃SnH (0.53 g, 1.5 mmol) was dissolved in toluene

(50 mL). A solution of 1 in hexane (5.6 mL, 0.27 , 1.5 mmol) was

then added with stirring. After stirring for 1 d, a single ¹¹B NMR

resonance at δ ϭ 44.6 ppm was observed. A solid residue was left

1

colourless crystals of the diazadiboretidine 28, m.p. 58Ϫ60 °C. H

after removing all volatile components in vacuo. The solid was NMR: δ ϭ 1.23 (s, BCMe₃), 1.32 (NCMe₃) ppm (ratio 1:1). ¹³C

crystallised from hexane (40 mL) at Ϫ80 °C. Yield 0.44 g of 26

NMR: δ ϭ 30.5 (BCMe₃), 33.8 (NCMe₃), 49.5 (NCMe₃) ppm; BC

(75%), m.p. 106 °C. ¹H NMR: δ ϭ 7.19 (m, 9 H, o-Ph and p- not detected. ¹¹B NMR: δ ϭ 41.1 ppm.

Ph), 7.81(m, 6 H, m-Ph) ppm. ¹³C NMR: δ ϭ 128.1, 128., 138.2,

Butylmagnesium (tert-Butyl)[butyl(2,2,6,6-tetramethylpiperidino)-

144.6 ppm. ¹¹⁹Sn NMR signal not detectable. C₃₁H₄₃BN₂Sn

(573.17): calcd. C 64.90, H 7.50, N 4.98; found C 64.74, H 7.41,

N 4.62.

boryl]amide (33): A hexane solution of 1 (17.5 mL, 0.114 ,

2.0 mmol) was further diluted with hexane (20 mL). To the stirred

solution at Ϫ78 °C was added a hexane solution of MgBu₂

(2.0 mL, 1 ). At room temperature the solution showed only one

¹¹B NMR signal at δ ϭ 37.5 ppm indicating a quantitative reaction.

Removal of the volatile materials gave an oily, non-volatile, moist-

Lithium

(tert-Butyl)(2,2,6,6-tetramethylpiperidinophenylboryl)-

amide؊Diethyl Ether (32): A hexane solution of 1 (0.89 , 5.59 mL,

5.0 mmol) was cooled to Ϫ78 °C. A solution of PhLi in cyclohex-

ane/diethyl ether (2.0 , 2.8 mL, 5.0 mmol) was then added drop- ure-sensitive residue. Attempted crystallisation from pentane at low

wise with stirring. After the clear solution had reached room tem-

perature, a light yellow precipitate appeared which redissolved on

continued stirring. The solution showed a ¹¹B NMR signal at δ ϭ

temperature afforded no crystals. Attempted distillation in vacuo

led to decomposition. ¹H NMR: δ ϭ 0.95, 1.04, 1.11, 1.91, 1.27,

1.38, 1.51, 1.59 (Bu groups) ppm. ¹³C NMR: δ ϭ 14.3, 19.2, 27.0,

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

3625

H. Nöth et al.

27.8, 32.7, 38.6 (Bu) ppm. C₂₁H₄₅BMgN₂(360.72): calcd. C 69.98, 107Ϫ110 °C. ¹H NMR: δ ϭ 7.25Ϫ8.04 ppm (m, 15 H, Ph). ¹³C

FULL PAPER

H 12.50, 7.76; found C 63.65, H 11.90, N 7.30.

NMR: δ ϭ 149.6 (br., BC), 125.9, 126.8, 127.4 130.8, 135.9, 138.8

(Ph), 149.6 (BC) ppm. MS (70 eV): m/z (%) ϭ 464 (5) [M^ϩ], 449

(15) [M^ϩϪ Me], 387 (35) [M^ϩϪ Ph], 299 (25) [M^ϩϪ BPh₂], 222

(47) [1^ϩ]. C₃₁H₄₂B₂N₂(464.2): calcd. C 80.19, H 9.12, N 6.03;

found C 78.02, H 9.05, N 5.80.

Magnesium

Bis{(tert-butyl)[butyl(2,2,6,6-tetramethylpiperidino)-

boryl]amide} (34): Prepared in analogy to 33 from 1 (0.114  solu-

tion, 22.0 mL, 2.4 mmol) and MgBu₂(1.25 mL, 1 , 1.25 mmol).

Colourless oil, yield 0.7 g (95%). ¹¹B NMR: δ ϭ 39.0 ppm. ¹H

NMR: δ ϭ 0.72Ϫ1.59 ppm (br. m, 2/4-H, 3-H, Bu). ¹³C NMR:

δ ϭ 14.0, 27.5, 29.5, 31.8, 38.1 ppm (main signals). C₂₄H₇₂B₂MgN₄

(582.90): calcd. C 70.06, H 12.45, N 9.61; found C 67.61, H 12.02,

N 8.74.

Dibutyl{(tert-butyl)[butyl(2,2,6,6-tetramethylpiperidino)boryl]-

amino}borane (40): To a hexane solution of 1 (8.80 mL, 0.283 ,

2.5 mmol) at room temperature was added BBu₃(0.40 g, 2.5 mmol)

with a syringe. After stirring for 2 d, the reaction was complete.

Volatile materials were then removed in vacuo. The remaining

colourless oil of 40 solidified at Ϫ78 °C. Yield 0.95 g (94%). ¹H

NMR: δ ϭ 0.87Ϫ1.24 (several m, Bu) ppm. ¹³C NMR: δ ϭ 14.4

(Me of Bu), 20.1 (br., BC), 24.0 (br., N₂BC), 26.6, 27.0, 27., 30.2,

34.2 (BCH₂CH₂CH₂Me) ppm. C₂₅H₅₄B₂N₂(404.34): calcd. C

74.26, H 13.46, N 6.93; found C 72.97, H 13.03, N 6.77.

Methylzinc (tert-Butyl)[methyl(2,2,6,6-tetramethylpiperidino)boryl]-

amide (35): To a stirred solution of 1 (0.27 , 7.4 mL, 2.0 mmol),

diluted with hexane (20 mL) at Ϫ78 °C, was added a solution of

ZnMe₂(0.09 , 2.9 mL, 2.0 mmol), dissolved in toluene (10 mL).

After the solution had attained ambient temperature, the volume

of the solution was reduced to about 20 mL. At Ϫ78 °C, crystals

appeared within a week. These were highly sensitive towards moist-

ure. Recrystallisation at Ϫ40 °C from hexane yielded single crystals.

9-{(tert-Butyl)[methyl(2,2,6,6-tetramethylpiperidino)boryl]-

amino}-9-borabicyclo[3.3.1]nonane (41): A solution of 1 (2.5 mmol

in 8.9 mL of hexane) at Ϫ78 °C was added to 9-methyl-9-borabicy-

clo[3.3.1]nonane (0.34 g, 2.5 mmol). Within 4 d, a clear solution

had formed. Most of the solvent was then removed in vacuo and

the solid material isolated by filtration. Yield 0.8 g of 41 (93%),

m.p. 82 °C. The product was pure as shown by the NMR spectro-

1

The yield was not determined. H NMR: δ ϭ Ϫ0.09 (ZnMe), 0.62

(BMe) ppm. ¹³C NMR: δ ϭ Ϫ11.3 (ZnMe), 1.0 (br., BMe) ppm.

C₁₅H₃₃BN₂Zn (317.61): calcd. C 56.67, H 10.39, N 8.52; found C

52.44, H 9.75, N 8.49.

1

scopic data. H NMR: δ ϭ 1.95 (br., 12 H) ppm. ¹³C NMR: δ ϭ

Zinc

Bis{(tert-butyl)[methyl(2,2,6,6-tetramethylpiperidino)boryl]-

amide} (36): Prepared in analogy to 35 from 1 (2.5 mmol) in hexane

(40 mL) and ZnMe₂(1.8 mL, 0.69 , 1.25 mmol), dissolved in tolu-

ene (10 mL).36 is a sticky oil from which no crystals could be ob-

tained. Yield 0.64 g (96%). ¹¹B NMR: δϭ 39.1 ppm. ¹H NMR: δ ϭ

δ ϭ 1.32 (br., BMe) ppm.

C₂₈H₆₀B₂N₄Zn (539.81): calcd. C 62.40, H 11.13, N 10.04; found

C 62.95, H 11.41, N 10.12.

22.9 (C-α), 23.1 (C-β), 32.5 (C-γ) ppm.

{(tert-Butyl)[methyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

dimethylalane (43): A hexane solution of (AlMe₃)₂(0.95 mL, 2.19

, 1.05 mmol) at Ϫ78 °C was added to a stirred solution of 1 in

hexane (3.5 mL, 0.586 , 2.1 mmol). At room temperature, the

mixture was stirred for 24 h. The hexane was then removed. The

remaining oil could not be distilled without decomposition. Yield

0.58 g of 43 (96%). Due to the high sensitivity of the oil towards

moisture and air only an approximate elemental analysis was ob-

tained, while the ¹H NMR spectrum showed the correct intensities

for the CMe₃, AlMe₂and BMe groups. The same compound was

obtained by using AlMe₃·OEt₂instead of Al₂Me₆. Elemental

analysis was performed without sufficient protection against the

0.62 (BMe) ppm. ¹³C NMR:

Phenylcadmium (tert-Butyl)[phenyl(2,2,6,6-tetramethylpiperidino)-

boryl]amide (37): A solution of 1 (3.2 mmol) in hexane (49 mL) was

cooled to Ϫ78 °C. A solution of CdPh₂(0.16 g, 3.2 mmol) in

CHCl₃(30 mL) was then added with stirring. At room temperature,

all volatile materials were removed in vacuo and the oily residue

treated with small quantities of toluene. From the resultant solu-

tion appeared some well-shaped crystals which proved to be CdPh₂.

Concentration of the solution yielded 37 as a microcrystalline pow-

1

atmosphere. H NMR: δ ϭ Ϫ0.11 (AlMe₂), 0.78 (BMe) ppm. ¹³C

NMR: δ ϭ 7.0 (AlMe₂), 18.9 (br., BMe) ppm. ²⁷Al NMR: δ ϭ

105.9 (h_1/2ϭ 780 Hz) ppm. C₁₆H₃₀AlBN₂(294.27): calcd. C 63.11,

H 15.53, N 9.53; found C 51.82, H 9.04, N 7.93 (ratio C/H/N ϭ

15:31:2).

1

der. Yield 1.19 g of 37 (76%), m.p. 160 °C (dec.). H NMR: δ ϭ

7.13, 7.21, 7.27, 7.53, 7.50, 7.71 (m, Ph) ppm. ¹³C NMR: δ ϭ 126.0,

126.8, 128.3, 132.9, 139.5 (Ph) ppm. C₂₅H₃₇BCdN₂(488.36): calcd.

C 61.43, H 7.63, N 5.73; found C 59.00, H 7.60, N 5.52.

{(tert-Butyl)[ethyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

diethylalane (44): Prepared in analogy to 43. AlEt₃(0.38 g,

0.33 mmol) in hexane (3.3 mL), 10.9 mL of a hexane solution of 1

(0.306 mmol). Mobile, air- and moisture-sensitive liquid. Yield

{(tert-Butyl)[methyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

dimethylborane (38): A solution of 1 in hexane (11.0 mL, 0.362 ,)

was frozen at Ϫ196 °C and BMe₃(4.1 mmol) condensed onto it.

The mixture was allowed to slowly thaw. After 4 h of stirring, all

volatile material was evaporated in vacuo at 50 Torr. A colourless

1

3

1.11 g of 44 (98%). H NMR: δ ϭ 0.40 [q, J(¹H¹H) ϭ 7.3 Hz, 4

H, AlCH₂], 0.81Ϫ1.19 (m, 5 H, BEt), 1.42 [t, J(¹H¹H) ϭ 7.3 Hz,

3

1

6 H, AlCH₂CH₃] ppm. ¹³C NMR: δ ϭ 7.9 (br., AlCH₂), 10.7

(AlCH₂CH₃), 11.5 (BCH₂CH₃), 14.2 (br., BCH₂) ppm. MS (70 eV):

m/z (%) ϭ 336 (2) [M^ϩ] and others. C₁₉H₄₂AlBN₂(336.35): calcd.

C 67.85, H 12.59, N 8.33; found C 62.97, H 11.84, N 7.69.

oil remained. Yield 1.07 g of 38 (97%), m.p. 18Ϫ20 °C. H NMR:

δ ϭ 0.58 (6 H, BMe₂), 0.82 (3 H, BMe) ppm. ¹³C NMR: δ ϭ 12.1

(br., BMe, BMe₂) ppm. ¹⁴N NMR: δ ϭ Ϫ230.6 (h_1/2ϭ 500 Hz)

ppm. MS (70 eV): m/z (%) ϭ 263 (1) [M^ϩϪ Me], 222 (100)

[tmpBNCMe₃^ϩ]. C₁₆H₃₆B₂N₂(278.10): calcd. C 69.10, H 13.05, N

10.07; found C 69.02, H 12.85, N 10.32.

{(tert-Butyl)[phenyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

diphenylalane (45): Obtained in analogy to 43. To AlPh₃(0.26 g,

1.0 mmol, 5 mL hexane) was added a solution of 1 in hexane

(4.0 mL, 0.252 , 1.0 mmol). The mixture was stirred for 4 d and

{(tert-Butyl)[phenyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

diphenylborane (39): To a suspension of BPh₃(1.00 g, 4.1 mmol) in

hexane (20 mL) was added a solution of 1 in hexane (14.7 mL, the solid isolated by filtration (0.38 g). From the solution another

0.283 , 4.1 mmol). After stirring for 16 h, the ¹¹B NMR spectrum

showed the absence of 1. When the solvent was removed in vacuo

a precipitate appeared which was isolated by filtration. A second

crop of 0.08 g was obtained by partially removing the hexane.

Yield: 0.46 g of 45 (95%), m.p. 168Ϫ170 °C (dec.). ¹H NMR

(CDCl₃):δ ϭ 7.22Ϫ8.11 (m, 15 H, Ph) ppm. ¹³C NMR (CDCl₃):

crop was obtained from the filtrate. Yield 1.65 g of 39 (86%), m.p. δ ϭ 126.8, 126.9, 127.1, 128.7, 134.1, 17.6, 139.2 (Ph) ppm.

3626  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjic.org

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

Reactions of Organyl Compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

FULL PAPER

C₃₁H₄₂AlBN₂(480.49): calcd. C 77.49, H 8.81, N 5.83; found C

75.87, H 8.88, N 5.33.

all volatile components were removed in vacuo and the solid 48

crystallised from a minimum amount of hexane. Yield 1.12 g (89%),

m.p. 133Ϫ135 °C. ¹H NMR (CDCl₃): δ ϭ 7.37Ϫ8.07 (m, Ph) ppm.

¹³C NMR (CDCl₃): δ ϭ 126.5 (p-C), 126.9, 127.3 (p-, m-, o-C of

BPh); 127.9, 134.0, 138.6 (p-, m-, o-Ph of InPh₂), 144.0 (br., i-C of

BPh), 156.5 (br., i-C of InPh₂) ppm. MS (70 eV): m/z (%) ϭ 568

(2) [M^·ϩ], 491 (5) [M^ϩϪ Ph], and many others. C₃₁H₄₂BInN₂

(568.32): calcd. C 65.52, H 7.45, N 4.93; found C 53.37, H 7.30,

N 4.93.

{(tert-Butyl)[methyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

dimethylgallane (46): At Ϫ78 °C a solution of 1 (10.9 mL, 0.306

, 3.3 mmol) was slowly added to GaMe₃(0.38 g, 3.3 mmol) with

stirring. The mixture was stirred at ambient temperature for 5 d.

Removal of the hexane left a colourless, highly air-sensitive mobile

1

oil which proved to be pure 46 by NMR spectroscopy. H NMR

(CDCl₃): δ ϭ Ϫ0.12 (6 H, GaMe₂), 0.58 (3 H, BMe) ppm. ¹³C

NMR (CDCl₃): δϭ 3.3 (br., GaMe₂), 14.2 (br., BMe) ppm. IR: ν˜ ϭ

1370 (δ_asGaMe₂), 1210 (δ_symGaMe₂) cm^Ϫ1. MS (70 eV): m/z (%) ϭ

336 (1) [M^ϩ], 321 (100) [M^ϩϪ Me]. C₁₆H₃₆BGaN₂(337.01): calcd.

C 57.02, H 10.74, N 8.31; found C 61.52, H 10.96, N 7.87.

X-ray Structural Determinations: Single crystals were placed in per-

fluoro ether oil under a blanket of nitrogen in the case of very

sensitive crystals at Ϫ40 °C and a suitable crystal was selected. It

was mounted on the tip of a glass fibre which was placed on the

goniometer head while cooling with a stream of nitrogen, generally

held at Ϫ80 °C. After alignment, data were collected on five sets

of 15 frames each, which were used to determine the unit cell (Pro-

gram SMART).^[48]Data collection was then started (in case of data

collection with a CCD device, data on 1200 frames were collected).

After data reduction (Program SAINT),^[48]the cell parameters were

determined with a larger set of data. No absorption correction was

applied except in the case of compound 24. All structures were

solved by direct methods (SHELX97).^[49]Non-hydrogen atoms

were refined anisotropically. In most cases, the hydrogen atoms

were placed in calculated positions using the riding-model ap-

proach. However, NH, BH and AlH hydrogen positions were taken

from the difference Fourier maps and refined isotropically. Relevant

data can be found in Table 7. CCDC-221516 to -221520 contain

the supplementary crystallographic data for this paper. These data

{(tert-Butyl)[ethyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

diethylgallane (47): Obtained from GaEt₃(0.34 g, 2.2 mmol) and 1

(7.2 mL, 0.306 , 2.2 mmol); 24 h of stirring at ambient tempera-

ture. Colourless, mobile liquid, very moisture-sensitive. Due to the

high sensitivity of the compound only an unsatisfactory C,H analy-

sis was obtained. ¹³C NMR (CDCl₃): δ ϭ 10.8 (BCH₂CH₃), 11.4,

11.5 (GaEt), 14.0 (br., BCH₂CH₃) ppm. MS (70 eV, ¹¹B, ⁶⁹Ga):

m/z (%) ϭ 349 (7) [M^ϩϪ Et], 239 (5) [tmpGaEt^ϩ], 126 (100) [tmp^ϩ

Ϫ Me]. C₁₉H₄₂BGaN₂(379.09): calcd. C 60.20, H 11.17, N 7.39;

found C 59.07, H 7.45, N 7.03.

{(tert-Butyl)[phenyl(2,2,6,6-tetramethylpiperidino)boryl]amino}-

diphenylindane (48): TriphenylindiumϪ1,4-dioxane (0.95 g,

2.2 mmol) in hexane (15 mL) was treated for 15 min with a hexane

solution of 1 (7.2 mL, 0.306 , 2.2 mmol). After 24 h of stirring,

Table 7. Crystallographic data and information regarding the data collection and structure solutions for compounds 19, 26, 31, 32 and 35

19

26

32

31

35

Empirical formula

Formula mass

Crystal size [mm]

Crystal system

Space group

C₂₆H₅₉N₄Al₂B₂

503.35

C₃₁H₄₃B₂BSn

573.17

C₂₃H₄₂N₂OBLi

380.34

0.21 ϫ 0.10 ϫ 0.30

monoclinic

P2₁/n

9.772(8)

13.187(8)

19.02(1)

90

96.40(2)

90

2436(3)

4

1.037

0.061

840

C₂₀H₃₄N₂O₂B₂

356.11

C₁₅H₃₃N₂BZn

317.61

0.15 ϫ 0.15 ϫ 0.1

monoclinic

P2₁/n

9.5172(2)

17.1486(1)

10.8449(1)

90

91.459(1)

90

1769.39(4)

4

1.192

1.379

688

0.1 ϫ 0.2 ϫ 0.25

triclinic

0.20 ϫ 0.30 ϫ 0.30

orthorhombic

P2₁2₁2₁

9.6974(1)

16.0246(1)

18.9810(2)

90

0.5 ϫ 0.5 ϫ 0.6

orthorhombic

P2₁2₁2₁

19.799(1)

11.4759(1)

9.044(1)

90

¯

P1

˚

a [A]

10.499(4)

11 016(4)

14.822(8)

89.82(2)

71.75(2)

80.28(1)

1603(1)

2

˚

b [A]

˚

c [A]

α [°]

β [°]

γ [°]

90

˚

V [A]

2949.59(6)

4

1.291

0.0887

1192

2052.87(2)

4

1.152

0.072

776

Z

ρ (calcd.) [Mg/m³]

µ [mm^Ϫ1

F(000)

]

0.111

558

Index range

Ϫ12 Յ h Յ 12

Ϫ12 Յ k Յ 12

Ϫ16 Յ l Յ16

49.42

Ϫ12 Յ h Յ12

Ϫ20 Յ k Յ 20

Ϫ22 Յ l Յ 24

58.22

Ϫ12 Յ h Յ 7

Ϫ14 Յ k Յ 16

Ϫ24 Յ l Յ 17

57.94

Ϫ22 Յ h Յ 22

Ϫ13 Յ k Յ 13

Ϫ9 Յ l Յ 10

48.80

Ϫ12 Յ h Յ 11

Ϫ20 Յ k Յ 19

Ϫ13 Յ l Յ 13

58.72

2θ [°]

T [K]

183(2)

Reflections (collected)

Reflections (unique)

Reflections (observed) (4σ)

R (int.)

7885

4152

3482

0.0366

17229

6204

5962

0.0201

6400

4141

2646

0.0548

9728

3181

2973

0.0370

10100

3540

2969

0.0281

Variables

345

324

262

243

181

Weighting scheme x/y

GOOF

Final R (4σ)

Final wR2

0.0376/2.4969

1.170

0.0713

0.1497

0.492

0.0166/0.4828

1.056

0.0193

0.0413

0.220

0.0308/1.7488

1.221

0.0807

0.1422

0.166

0.0325/1.5867

1.157

0.0615

0.1264

0.234

0.03550/1.4932

1.137

0.0414

0.0879

0.466

3

˚

Largest residual peak [e/A ]

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

www.eurjic.org

 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

3627

H. Nöth et al.

FULL PAPER

can be obtained free of charge at www.ccdc.cam.ac.uk/conts/

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3628

 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org

Eur. J. Inorg. Chem. 2004, 3612Ϫ3628

Article Doi

Reactions of group 13 and 14 hydrides and group 1, 2, 13 and 14 organyl compounds with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane

DOI: 10.1002/ejic.200300820

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