Synthesis and structures of new borylferrocenes, and structures of, 2-chalcogeno-bis(aminoboryl)[3]ferrocenophanes and 1,1′-tris(di- methylaminoboryl))][3]ferrocenophane [1, 2]

ARTICLE

DOI: 10.1002/zaac.201000167

Synthesis and Structures of New Borylferrocenes, and Structures of

2-Chalcogeno-bis(aminoboryl)[3]ferrocenophanes and 1,1'-Tris(di-

methylaminoboryl))][3]ferrocenophane [1, 2]

Andrea Appel^[a]and Heinrich Nöth*^[a]

In Memory of Professor Herbert Schumann

Keywords: 1,1'-(Bromodiorganylaminoboryl)ferrocenes; 1,1'-Bis[bis(diorganylamino)boryl]ferrocenes;

1,1'-Tris(dimethylaminoboryl)[3]-ferrocenophane; 1,1'-[2-Chalcogeno-bis(1,3-diorganylaminoboryl)[3]ferrocenophanes;

NMR spectroscopy; X-ray diffraction

Abstract. The reaction of Br₂BCpFeCp with (Me₃Si)₂S affords the The Br(R₂N)B and the (R₂N)₂B groups are increasingly twisted against

hexacyclic tris(ferrocenyl)trithia-triborine (CpFeCp-BS)₃, whereas the their Cp planes. In case of 1,1'-[Br(iPr₂N)BCp]₂Fe the CB(Br)N planes

tris(ferrocenyl)boroxine is obtained from CpFeCpB(NMe₂)₂and H₂O are twisted against the respective Cp planes by 38.7 and 112.5°, which

via the isolated intermediate [CpFeCpBO)₃·HNMe₂. In this compound brings the bromine atoms closer to the iron atom. This twisting is

there are two ferrocenyl units in trans-orientation and a third one is enhanced by an increase of the steric demands by the amino groups

bonded to an O₂BNHMe₂unit with formation of a tetracoordinated and is largest for (iPr₂NtBuHNBCp)₂Fe. The structures of two 1,1'-

boron atom (We use the symbol Cp here not only for the C₅H₅unit chalcogeno-bis(diorganylaminoboryl)[3]ferrocenophanes X[(R₂N)-

but also for C₅H₄or C₅H₃units). The structures of several bromo(dial- BCp]₂Fe (X = O. S; R = Me, iPr) are reported as well as the new 1,1'-

kylamino)borylferrocenes and the 1,1'-bis[bromo(dialkylamino)- tris(dimethylaminoboryl)[3]ferrocenophane.

boryl]ferrocenes were determined. They show no Fe–B interaction.

atom. This can be explained by B(sp²)–M(d_{x –y}, d_z) interac-

tions. Meanwhile it is well known that this bending depends

strongly on the Lewis acidity of the boryl BX₂substituent [19,

21].

2

Introduction

Since the detection of ferrocene [3–5] its chemistry has been

extensively investigated [6, 7]. Due to its stability and its ver-

satility it has become an important reagent in many areas of

chemistry including material chemistry [8], catalysts [9] and

polymer chemistry [10]. Planar-chiral ferrocenes, in general

1,2- and 1,3-disubstituted ferrocenes, are used in stereoselect-

ive syntheses, for instance for the synthesis of precursor mole-

cules en route to (+)biotine [11] or to the herbizide (S)-metola-

chlor [12].

In this paper we describe the synthesis of a number of new

boryl-substituted ferrocenes having weak Lewis acidic BX₂or

BXY substituents (OR, NR₂) as well as some boron substituted

ferrocophanes like the novel 1,1'-Fe(CpBNMe₂)₂BNMe₂.

Meanwhile, a large number of monoborylated and 1,1'-dibor-

ylated ferrocenes are known as well as tri- and tetraborylated

ferrocenes [13–21]. Siebert et al. [13], Wrackmeyer et al. [14.

18] and we [2, 20] have shown that the reaction of ferrocene,

ruthenocence and osmocene with BBr_3,depending on the stoi-

chiometry, produces the dibromoboryl metallocenes

(Br₂BCp)MCp, (Br₂BCp)₂M, (Br₂BCp)M[Cp(BBr₂)₂] and

[(Br₂B)₂Cp)₂]₂M (M = Fe, Ru Os). All of these compounds

show BBr₂groups that are bent in the direction towards the M

Results

Ferrocenyltrichalcogenotriboranes

The first tri(ferrocenyl)trichalcogenotriborane, [CpFeCp-

BSe]₂was obtained by the reaction of CpFe(CpBBr₂) with

(Me₃Si)₂Se in the presence of NEt₃and CH₂Cl₂[22]. Its crystal

structure shows an almost planar B₃Se₃ring with Se–B–Se

bond angles close to 128.7 and B–Se–B bond angles of 111.3°.

We obtained the missing link between [CpFeCpBSe]₃and

[CpFeCpBO)₃(2) the trithiatriborane [CpFeCp-BS]₃(1) by the

reaction of Br₂BCpFeCp and (Me₃Si)₂S in boiling hexane as

shown in Equation (1). However, we obtained no crystals suit-

able for an X-ray determination of its molecular structure.

* Prof. Dr. H. Nöth

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

[a] Department of Chemistry and Biochemistry

University of Munich

Butenandtstr. 5–13

81377 München, Germany

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wileyonlinelibrary.com

Z. Anorg. Allg. Chem. 2010, 636, 2329–2342

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A. Appel, H. Nöth

ARTICLE

e.g. the C₅planes of C1 to C5 and C11 to C15 are oriented by

61.6° against each other, whereas the angle for the planes C1

to C5 against the plane of C21 to C25 is larger with 73.4° and

the angle between the planes C11 to C15 and C21 to C25 adopt

a twist angle of 64.4°.

The known tris(ferrocenyl)boroxine [CpFeCpBO]₃, (2) was

prepared from CpFeCp-BCl₂by hydrolysis to give the boronic

acids CpFeCp-B(OH)₂which readily dehydrates to produce the

six-membered boroxine 2 [23], whose crystal structure showed

an almost planar ring system [24]. The ferrocene units stand

all on one side of the ring.

We tried to prepare 2 from CpFe(CpBBr₂) and (Me₃Si)₂O as

shown in Equation (2). The cleavage of the Si–O bond proved

to be very slow even under reflux condition. On the other hand,

the hydrolysis of CpFe(CpBBr₂) with water or aqueous ethanol

produced at room temperature only a green solid precipitate,

which may consist of a ferrocenium salt. However, the hydrol-

ysis of CpFeCpB(NMe₂)₂with water in THF at low tempera-

ture (starting at –60 °C) was successful. As shown in

Scheme 1, the first isolable product is the dark red 1:1 dimeth-

ylamine adduct 3 of tris(ferrocenyl)boroxine 2. Several crystal-

lisation steps were necessary to obtain the Me₂NH free com-

pound 2 as an orange microcrystalline powder. The molecular

structure of 3 could be determined by X-ray crystallography.

It crystallises in the orthorhombic space group Pna2 with one

molecule of [CpFeCpBO]₃·HNMe₂and one molecule of ben-

zene in the asymmetric unit. Its structure is depicted in Fig-

ure 1 and its packing in the unit cell in Figure 2. The non

planar six-membered boroxine ring of 3 consists of two trico-

ordinated boron atoms and one tetracoordinated boron atom

and three dicoordinated oxygen atoms. The B2–C bond of the

tetracoordinated boron atom is slightly but significantly longer

than the other two B–C bonds. Also, the B2–N1 bond is, as

expected, longer than the B2–O bonds (for more data see Fig-

ure 1). The FeCp₂units are differently oriented to one another,

Figure 1. The molecular structure of [CpFeCp-BO]₃NHMe₂(3). Ther-

mal ellipsoids are shown on a 25 % probability scale. Selected bond

lengths are given in Å and bond angles in deg. B1–O1 1.396(9), B1–

O2 1.324(9), B2–O2 1.450(9), B2–O3 1.461(9), B3–O3 1.345(9), B3–

O1 1.381(9), B1–C1 1.56(1), B2–C11 1.58(1), B3–C21 1.56(1), B2–

N1 1.653(9), Fe1–C10 2.018(8), Fe1–C1 2.082(8), Fe2–C21 2.046(7),

Fe3–C11 2.077(6), B1–C1 1.52(1), B2–C11 1.528(9), B3–C21 1.53(1),

C–C 1.37(1) – 1.455(9). O1–B1–O2 123.3(7), O2–B2–O3 114.0(6),

O3–B3–O1 122.5(6), B1–O1–B3 117.7(6), B2–O3–B3 119.7(6), B1–

O2–B2 120.4(6). Twist angles: C1–C5/O1B1O2 103.1; C11–C15/

O3BO2 46.1, C21–C25/ O1B3O3 24.4.

.

Figure 2. Packing of [CpFeCp-BO]₃NHMe₂C₆H₆. View down the b axis.

The B1O1B3 plane forms an angle of 20.9° with the

O2B2O3 plane. Two of the FeCp₂units (at B1 and B3) are

fixed at the B₃O₃ring in opposite directions. This arrangement

reduces steric strain. Therefore, the two boroxine derivatives 2

and 3 are sterically different.

The ¹¹B chemical shifts of 1, 2, and 3 correspond with other

triorganyltrithiaboranes and triorganylboroxines [27]. The ¹¹B

Scheme 1.

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Z. Anorg. Allg. Chem. 2010, 2329–2342

Synthesis and Structures of New Borylferrocenes

resonance of 1 was observed at 57.5 ppm, which falls in the F₃B·OEt₂in diethyl ether suspension led to a solution of

area of other cyclic RB(SR')₂systems (δ¹¹B range from 61 to bis(benzodioxaboryl)ferrocene 9 as shown in Equation (6). It

58 ppm). Only one ¹¹B NMR signal was observed for 2 at crystallises as thin orange platelets in 99 % yield, δ¹¹B =

31.6 ppm (range for boroxines (RBO)₃= 29 to 34 ppm) [25]. 35.7 ppm. The boron atom of 9 is significantly deshielded

¹³C NMR signals were observed at 70.0 ppm for the unsubsti- compared to 8 (δ¹¹B = 29.7 ppm).

tuted Cp rings, and those at 73.3 and 74.4 ppm are associated

Compound 9 is the thermodynamic trap of the reaction of

with the substituted Cp rings whose boron bonded carbon atom [(Me₂N)₂BCp]₂Fe (7) with catechol because the 1:1 reaction

could not be localised. The dimethylamine adduct 3 showed yielded a mixture of 8 and 9, respectively. And 9 resulted also

only a broad ¹¹B NMR signal at 24.6 ppm

besides some byproducts by treatment of [Br(Me₂N)Cp]₂Fe

with dilithium catecholate in a 1:1 ratio instead of generating

a catecholato bridge between the two boron atoms of

[Br(Me₂N)Cp]₂Fe by elimination of LiBr.

1,1'-Bis(organyloxoboryl) Ferrocenes

Siebert et al. [13] and Wrackmeyer et al. [14, 18] early dem-

onstrated that the dihalogenoborylferrocenes, particularly the

dibromoborylferrocenes are excellent precursors for the syn-

thesis of other borylferrocenes. For instance, the reaction of

1,1'-(Br₂BCp)₂Fe with SnMe₄generates either 1,1'-

(BrMeBCp)₂Fe or 1,1'-(Me₂BCp)₂Fe depending on stoichiom-

etry and reaction conditions. Reactions with AsF₃or AsCl₃

gives access to (F₂BCp)₂Fe or (Cl₂BCp)₂Fe whereas the reac-

tion with secondary amines yields either [Br(R₂N)BCp]₂Fe or

[(R₂N)₂BCp]₂Fe, depending on stoichiometry. Reactions be-

tween (Br₂BCp)₂Fe and Et₂O leads to ether cleavage and for-

mation of ethyloxoborylferrocenes [18]. However, we could

not isolate [(EtO)₂BCp]₂Fe as previously reported [18]. But we

were able to isolate [Br(EtO)BCp]₂Fe in 67.8 % yield as

shown in Equation (3). This compound shows an ¹¹B NMR

signal at 38.9 ppm.

When the reaction of (Br₂BCp)₂Fe with Et₂O was carried out

at –30 °C or at room temperature, a mixture of bromo-

(ethoxo)borylferrocenes Br_n(EtO)_4–nB₂Cp₂Fe could be ob-

served in the ¹¹B NMR spectrum. However, [(EtO)₂BCp]₂Fe

(6) resulted at –30 °C as shown in Equation (4) by the solvoly-

sis of [(Me₂N)₂BCp]₂Fe with anhydrous ethanol. The orange-

red crystals were isolated in 65 % yield, δ¹¹B = 29.7 ppm. At

room temperature, a green precipitate formed from the two

components, and in the filtrate an ¹¹B NMR signal at 18.0 ppm

shows the presence of B(OEt)₃. The solid, most likely is a

ferrocinium salt, but it was not characterised.

Organylaminoborylferrocenes

The aminolysis of bis(dibromoboryl)ferrocene was first stud-

ied by Siebert et al. [13]. Its bromine atoms can be succes-

sively replaced by R₂N groups. Wrackmeyer et al. used the

reaction of (iPr₂N)₂BCl with 1,1'-dilithiumferrocene to prepare

1,1'-[(iPr₂N)₂BCp]Fe [18]. We used often reactions of trimeth-

ylsilyl diorganylamines with (Br₂BCp)₂Fe for preparing 1,1'-

(bromodiorganyl-aminoboryl) ferrocenes as shown in

Scheme 2 because Me₃SiBr can be readily removed from the

reaction mixture in vacuo.

Scheme 2.

Reactions in analogy to Equation (4) provide an easy access

to other organyloxoborylferrocenes. For instance, catechol re-

acts with 5 to produce bis(benzodioxaboryl)ferrocene, which

was isolated as its bis(dimethylamine) adduct 8 (see Equation

(5)). This compound crystallises in lemon yellow platelets, m.

However, for introducing bulky amino groups such as the

p, 280 °C. Treatment of this solid with two equivalents of 2,2,6,6-tetramethylpiperidino group (tmp) we could isolate the

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A. Appel, H. Nöth

ARTICLE

corresponding bis(bromoaminoboryl)ferrocene (14) only when 168 Hz). For 17 the chemicals shifts are 79.01, 81.80 and

Litmp was reacted with (Br₂BCp)₂Fe. On the other hand, we 68.96, ppm for C-2,5, C-3,4 and C1, respectively. This de-

were surprised that 1,1'-bis(diisopropylamino-tert-butylamino- shielding of the ring carbon atoms particularly for 17 can be

boryl)ferrocene (15) could be prepared from 1,1'- bis[bromo- attributed to the strong twisting of the BN₂atom group which

bis(isopropylamino)boryl]-ferrocene and tert-butylamine in the results also in longer B–C bonds [1.599, 1.594(6) Å] than

presence of triethylamine inspite of the fact that this combina- found for 16 [1.569(4) Å]. On the other hand the B–N bond

tion of amino groups is sterically quite demanding as shown lengths are on the shorter side for 16 [1.410, 1.405(3) Å] com-

in Eq.(7).

pared to 17 [1.445 to 1.437(6) Å]. They correspond with those

There is no steric hindrance to synthesise 1,1'-bis(N,N'-di- of the analogous 2,3-dihydro-1H-1,3,2-diazaborylferrocenes

methyl-1,3,2-diazaborolidyl)-ferrocene (16). This compound [26].

was first described by Herberhold et al. [27]. It was prepared

from 1,3-dimethyl-2-chloro-1,3,2-diazaborolane and 1,1'-di-

lithiumferrocene. We obtained single crystals of 16 by ami-

nolysis of (Br₂BCp)₂Fe with MeHN-CH₂CH₂NHMe in the

presence of NEt₃[Equation (8)] as well as the corresponding

1,1'-bis(N,N'-di-tert-butylboryl-1,3,2-diazaborolidyl)ferrocene

(17)and determined its crystal structures. These compounds are

of interest as well as [(isoPr₂N)tert-BuNHBCp]₂Fe (15) for

studying the influence of bulky groups on the conformation of

these compounds.

The boron nuclei of the tetrakis(bromodialkylaminobo-

ryl)ferrocenes 18 and 19, prepared according to Equation (9),

are shielded with δ¹¹B = 37.3 and 36.5 ppm. This fits well

with other bromo(amino)organylamines [25]. The structures of

these compounds could be determined (see below). They are

of interest because one can expect that two bromoaminoboryl

groups bonded to a Cp ring will lead to steric crowding.

The shielding of the boron nuclei of compounds 10–17 cor-

respond with noncyclcic and cyclic bromo(dialkylamino)aryl-

boranes and bis(diorganylamino)arylboranes [25]. Amongst

the bromo(dialkylamino)borylferrocenes, compound 10

(δ¹¹B = 35.4 ppm) shows the best shielded boron nucleus,

whereas the boron atoms of the tmp derivative 14 (δ¹¹B =

42.9 ppm) is less shielded due to its significantly twisted tetra-

methylpiperidino group. Hindered rotation about the B–N bond

is observed for compounds 10 and 11.

Borylferrocenophanes

The analogous N,N'-di-tert-butyl-2,3-dehydro-1H-1,3,2 diaz-

Borylgroup containing ferrocenophanes were first described

aborolidinyl ferrocene compounds [26] are closely related to by Herberhold et al. [27]. They reported i. a. the synthesis of

compounds 16 and 17 [26], but the ¹¹B chemical shifts for the X(Me₂NBCp)₂Fe (X = S, Se, Te) and of Se(iPr₂NBCp)₂Fe by

dehydro derivative show much better shielding of the boron the reaction of [Cl(R₂N)BCp]₂Fe with Li₂X (X = S, Se, Te).

atoms both for the monosubstituted ferrocene and 1,1'-disubsti- They determined the molecular structure of Se(iPr₂NBCp)₂Fe.

tuted derivative (both with δ¹¹B = 25.3 ppm). It is interesting We prepared the ferrocenophanes 20–23 (see Equation (10))

to note that the C2,5 atoms of 16 are about 2.9 ppm deshielded analogously and we could grow well shaped single crystals of

compared with the atoms C3,4, but for 17 the two resonances 20 and 23 for the determination of their molecular structures.

are 10 ppm apart. This is due to the observation that the two

We also prepared 1,1'-bis(dimethylaminoboryl)[3]ferroceno-

Cp rings are tilted against the CBN2 plane by 30.8 and 32.1 phane [2] and determined its structure. But we need not discuss

ppm in 16 but in 17 by of 43.9 and 75.9°, respectively. This it here as its synthesis and structure has already been ade-

affects also the ¹³C chemical shift of the C1 atoms.

quately described by Herberhold et al. [28] and Braunschweig

In most cases the boron bonded carbon atoms are not ob- et al. [29]. Braunschweig and Manners et al. [30] also prepared

served in the ¹³C NMR spectra due to the large quadrupole and determined the structure of several aminoboryl[1] bridged

moment of the boron atoms. But in case of 16 and 17 we could ferrocenophanes, R₂NB(Cp)₂Fe [30]. We extended the bridging

observe the ¹³C NMR signal for C1 after applying a large num- boron atoms to three by preparing tris(dimethylaminobo-

ber of pulses within 11 hours or collecting the data at –70 °C. ryl)[3]ferrocenophane (24) according to Equation (11) by re-

¹³C NMR signals for C-2,5 and C-3,4 are 73.98 and 71.06 ppm acting (LiCp)₂Fe [31] with the triborane derivative

for 16 and its signal for C1 was found at 66.94 ppm (h_1/2

=

Cl(Me₂N)B–BNMe₂–B(NMe₂)Cl [32]. Compound 24 crystal-

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Z. Anorg. Allg. Chem. 2010, 2329–2342

Synthesis and Structures of New Borylferrocenes

lises in orange-red platelets. So it is now possible to compare

the influence of mono-, di- and triboryl substituents on the

structure of boryl[η]ferrocenophanes.

X-ray Structural Studies

We

determined

the

crystal

structure

of

3,

CpFe{CpBBr(NiPr₂)}, 11, 12, 15, 16, 17, 18, 19, 20, 23 and

24 which are shown in Figure 1, Figure 2, Figure 3, Figure 4,

Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10,

Figure 11, Figure 12, and Figure 13. Table 1 gives an over-

view of selected bonding parameters for the structures of the

aminoborylferrocenes presented in this paper.

The bromo(diisopropylamino)borylferrocene (see Figure 3)

crystallises in the monoclinic space group P2₁/n. There are two

independent molecules in the unit cell. Its Cp rings adopt an

almost eclipsed position (12°) and the two Cp planes are tilted

against each other by only 1.3°. The Fe–C distance to the boryl

group carrying C1 atom is 2.063(4) Å. All other Fe–C bonds

are significantly shorter, the shortest is the Fe1–C10 distance

with 2.025(5) Å. There is no B···Fe interaction as demon-

Figure 3. Molecular structure of CpFe{(CpBBr(NiPr₂)}. Thermal el-

lipsoids are shown on a 25 % probability scale. Selected bond lengths

in Å and bond angles in deg. B1–Br1 1.994(5), B1–N1 1.374(6), B1–

C1 1.554(6), Fe1–C1 2.063(4), Fe1–C2 2.032(4), Fe1–C3 2.042(5),

Fe1–C4 2.047(5), Fe1–C5 2.043(4), Fe1–C6 2.032(5), Fe1–C7

2.039(5), Fe1–C8 2.044(9), Fe1–C9 2.033(4), Fe1–C10 2.025(5),

Fe1···B1 3.235(6), C1–C2 1.436(6), C2–C3 1.407(7), C3–C4 1.402(8),

C4–C5 1.435(7), C5–C1 1.433(6), C6–C7 1.369(9), C7–C8 1.372(8),

C8–C9 1.382(8), C9–C10 1.406(8), C10–C6 1.445(9). – C1–C2–C3

108.9(4), C2–C3–C4 109.9(4), C3–C4–C5 107.6, C4–C5–C1 108.4(4),

C5–C1–C2 106.4), C1–B1–N1 128.0(4), C1–B1–Br1 112.2(3), Br1–

B1–N1 119.7(3). –Twist angle C1–C5/C6–C10 1.8°, deviation from

ecliptic conformation 14°.

strated by an increase of the Fe···B distance from 2.855 structure is depicted in Figure 4. The iron atom lies on a two-

(2.742 Å) in CpFeCpBBr₂[18] to 3.235 Å in fold axis. Its Cp groups are tilted against each other by 2.7°,

CpFe{CpBBr(NiPr₂)}.

and their carbon atoms are present in an almost perfect

The C–C bonds are of different lengths, the longest ones eclipsed position. Its B1–C1 bonds are 2.56(1) Å. Amongst

are C1–C2 and C1–C5 [1.436(6) and 1.433(6) Å] whereas the the Fe–C bonds the Fe–C1 bond is the longest [2.066(8) Å]

shortest is the C3–C4 bond opposite to atom C1 with compared to the short Fe–C5 bond of 2.027(8) Å, thus the iron

1.402(8) Å. As expected, the tricoordinate boron atom has a atom is not located above the centre of the Cp rings. Also, the

planar environment with a B1–C1 bond length of 1.554(6) Å. B–N bonds [1.39(1) Å] are typical for mono(amino)boranes.

The B1–N1 bond length is 1.374(6) Å, typical for a planar The BBrN plane is bent with respect to the C1C2C5 plane by

environment about the nitrogen atom and the presence of B– 23.6°, and this brings the boron and bromine atoms closer to

N π-bonding. The BBrN plane is twisted against its Cp plane the iron atom (3.229 and 4.0665 Å, respectively).

by 22°.

The orange-brown needles of 1,1'-bis(bromopiperidinobo-

Crystals of 1,1'-bis(bromodimethylaminoboryl)ferrocene ryl)ferrocene, 12, crystallise in the monoclinic space groups

(11) are orthorhombic, space group Pbcn, Z = 4. Its molecular C2/c with Z = 4. Figure 5 presents its molecular structure for

Table 1. Selected bonding parameters of the molecular structures of monoboryl and bis(boryl) ferrocenes. Bond lengths and distances d are

presented in Å, angles between planes in degree.

d(B–C) /Å

d(B···Fe) /Å

d(B–N) /Å

C1–C5/C6–C10 /° C1–C5/BNX /° d(Fe···Br) /Å

(BriPr₂NB)CpFeCp

1.554(6)

1.56(1)

3.235

3.229

3.218

3.258

3.441

3.288

3.499

3.596

1.374(6)

1.38(1)

1.8

37.7

3.849

4.065

4.112

4.075

(BrMe₂NBCp)₂Fe (11)

(BriPr₂NBCp)₂Fe (10)

(BrPipBCp)₂Fe (12)

2.7

23.8

1.57(2)

1.36(2)

10.8/12.0

3.5

11.7

3.7

12.6

38.6

1.56(2)

1.36(2)

22.4

(iPr₂NtBuNHBCp)₂Fe (15)

(Me₂N₂C₂H₂B₂Cp)₂Fe (16)

(tBu₂N₂C₂H₂B₂Cp)₂Fe (17)

1.595(4)

1.569(4)

1.604(5)

1.593(8)

1.461, 1.394

1.405(4)

1.437(7)

1.430(6)

47.9

30.8, 32.1

43.9

76.9

[(Me₂NBrB)₂Cp]₂Fe (18)

[(iPr₂NBrB)₂Cp]₂Fe (19)

1.55(1), 1.57(1) 3.197, 3.232

1.37(1), 1.38(1) 2.7

24.0, 25.6

142,1

147.2

145.9

142.5

4.044, 4.045

3.886,

1.578

1.527

1.552

1.553

3.274

3.222

3.228

3.315

1.345

1.420

1.369

1.375

3.4

3.892

3.896

3.955

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Figure 6. Molecular structure of [iPr₂N(tBuNH)BCp]₂Fe (15). Only

one of the two independent molecules in the unit cell is shown. Ther-

mal ellipsoids are presented on a 25 % probability scale. Selected bond

lengths are given in Å and bond angles in deg. B1–C1 1.61(1), B1–

N1 1.476(8), B1–N2 1.40(1), C1–C2 1.46(1), C2–C3 1.44(1), C3–C4

1.43(2), C4–C5 1.40(1), C5–C1 1.39(2), Fe1–C1 2.109(6), Fe1–C2

2.112(8), Fe1–C3 2.082(8), Fe1–C4 2.039(9), Fe1–C5 2.032(7). N1–

B1–N2 120.2(6), N1–B1–C1 115.1(7), C1–B1–N2 124.7(5), B1–C1–

C5 126.0(7), B1–C1–C2 126.4(7), C2–C1–C5 105.7(8). Torsion an-

gles: C2C1B1N1 126.0°, C5C1B1N1 –43.0°. Tilt angle: C1–C5/C1A–

C5A 11.7°, C21–C25/C21A–C25A 1.7°.

Figure 4. Molecular structure of [Br(Me₂N)BCp]₂Fe (11). Thermal el-

lipsoids are shown on a 25 % probability scale. Selected bond lengths

are given in Å and bond angles in deg. B1–C1 1.56(1), B1–N1 1.38(1),

B1–Br1 1.968(9), N1–C6 1.47(1), N1–C7 1.45(1), C1–C2 1.44(1), C2–

C3 1.34(1), C3–C4 1.43(1), C4–C5 1.40(1), C5–C1 1.43(1), Fe1–C1

2.066(8), Fe1–C2 2.044(8), Fe1–C3 2.051(9), Fe1–C4 2.051(9), Fe1–

C5 2.027(8). N1–B1–Br1 117.9(7), N1–B1–C1 126.5(8), C1–B1–Br1

115.6(6), C6–N1–C7 110.9(7), C6–N1–B1 123.3(7), C7–N1–B1

125.7(8); Twist angles: C1–C5/B1N1Br1 23.8°, B1C1C2C5/C1–C5

0.5°, B1C1Fe1/B1AC1AFe1 16.5°, C6N1C7/C1B1Br1. Tilt angle Cp/

Cp': 2.7°.

Figure 7. Molecular structure of 1,1'-bis(dimethyldiazaborolidinyl)fer-

rocene (16). Selected bond lengths in Å and bond angles in deg. B1–

C1 1.569(4), B1–N1 1.410(3), B1–N2 1.405(3), C1–C2 1.432(4), C1–

C5 1.424(3), C2–C3 1.413(3), C4–C5 1.420(4), C3–C4 1.404(4), N1–

C8 1.428(3), N2–C9 1.435(3), Fe1–C1 2.076(2), Fe1–C2 2.055(2),

Fe1–C3 2.040(2), Fe1–C4 2.033(2), Fe1–C5 2.040(2), Fe1···B 3.288;

C1–B1–N1 124.9(2), C1–B1–N2 126.9(2), N1–B1–N2 108.1(2), B1–

C1–C2 127.3(2), B1–C1–C5 126.5(2), C1–C2–C3 109.0(2), C1–C5–

C4 108.6(2), C2–C3–C4 107.9(3), C5–C4–C3 108.3(2). Twist angles:

C1 to C5/B1N1N2 149.0, Fe1–C1–B1/Fe1C(1A)B(1A) 15.5, C1–C5/

C1A–C5A 4.8°. Tilt angle; 3.7.

Figure 5. Molecular structure of [Br(pip)BCp]₂Fe (12). Only one ori-

entation of the piperidine rings is shown. Thermal ellipsoids are pre-

sented on a 25 % probability scale. Selected bond lengths are given in

Å and bond angles in deg. B1–C1 1.56(2), B1–N1 1.36(2), B1–Br1

1.96(1), C1–C2 1.44(1), C2–C3 1.40(1), C3–C4 1.30(1), C4–C5

1.43(1), C6–C7 1.36(2), C7–C8 1.51(2), C8–C9 1.51(2). C9–C10

1.39(2), Fe1–C1 2.066(9), Fe1–C2 2.040(9), Fe1–C3 2.05(1), Fe1–C4

2.054(9), Fe1–C5 2.040(9), C1–C2 1.44(1), C2–C3 1.40(1), C3–C4

1.40(1), C4–C5 1.43(1), C6–C7 1.36(2), C7–C8 1.51(2), C8–C9

1.51(2), C9–C10 1.39(2); N1–B1–Br1 117.1(8), C1–B1–Br1 114.9(7),

N1–B1–C1 128.0(9), C2–C1–C5 105.4(8), C1–C2–C3 108.1(0), C2–

C3–C4 110.6(9), C3–C4–C5 106.6(9), C4–C5–C1 109.3(8). Tilt angle:

3.5°. Twist angle: C1 – C5/B1Br1N1 21.8,.

one of the two site disordered piperidino group. The iron atom

is sitting on a C₂axis. The BBrN planes are twisted against

the C₅plane by 21.6° whereas the two Cp rings are tilted

against each other by 3.3°. The bond C3–C4 is the shortest C–

C bond [1.40(1) Å], the longest ones are those to atoms C1

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Synthesis and Structures of New Borylferrocenes

Figure 8. Molecular structure of 1,1'-bis(di-tbutyldiazaborolidinyl)fer-

rocene (17). Thermal ellipsoids are shown on a 25 % probability scale.

Selected bond lengths in Å and bond angles in deg. B1–C1 1.599(5),

B1–N1 1.445(6), C1–N2 1.435(6), B2–C6 1.594(6), B2–N3 1.437(5),

B2–N4 1.432(6), C1–C2 1.423(6), C2– C3 1.412(5), C3–C4 1.412(7),

C4–C5 1.418(6), C1–C5 1.433(5), C6–C7 1.438(6), C7–C8 1.320(6),

C8–C9 1.412(7), C9–C10 1.416(6), C6–C10 1.423(6), Fe1–C1

2.136(3), Fe1–C2 2.041(3), Fe1–C3 2.042(4), Fe1–C4 2.042(4), Fe1–

C5 2.075(4), Fe1– C6 2.156(4), Fe1–C7 2.055(4), Fe1–C8 2.028(4),

Fe1–C9 2.032(4), Fe1–C10 2.076(4). C1–B1–N1 120.8(3), C1–B1–

N2 131.8(4), C6–B2–N3 120.4(3), C6–B2–N4 131.3(4), N1–B1–N2

107.3(3), N2–B2–N4 108.2(3), B1–C1–C2 121.8(2), C1–C2–C3

110.8(2), C2–C3–C4 106.8(4), C3–C4–C5 108.3(3), C4–C5–C1

109.2(4), B2–C6–C7 122.3(3), C6–C7–C8 109.4(4), C7–C8–C9

1107(6)(4), C8–C9–C10 107.7(4), C9–C10–C6 110.1(4). Tilt angle:

12.6, Twist angles; C1–C5/B1N1N2 131,8, C6 to C19/B2N3N4 103.3,

B1 N1N2/B 2N3N4 88,8.

Figure 10. Molecular structure of 1,1',3,3'-tetrakis(bromodiisopropyl-

aminoboryl)ferrocene (19). Only one of the two independent molecules

in the unit cell is shown. Thermal ellipsoids are presented on a 25 %

probability scale. Selected bond lengths are given in Å and bond angles

in deg. B1–Br1 2.00(2), B1–N1.33(2), B1–C1 1.59(2), B2–Br2

1.99(2), B2–N2 1.41(2), B2–C3 1.53(2), B3–Br3 1.98(2), B3–N3

1.37(2), B3–C10 1.56(2), B4–Br4 1.99(2), B4–N4 1.38(2), B4–C8

1.55(2), Fe1–C1 2.09(1), Fe1–C2 2.05(1), Fe1–C3 2.098(2), Fe1–C4

2.06(1), Fe1–C5 2.04(1), Fe1–C6 2.01(1), Fe1–C7 2.03(1), Fe1–C8

2.09(1), Fe1C9 2.05(1), Fe1–C10 2.07(1). C1–B1–Br1 112.4(13), C1–

B1–N1 125.9(16), N1–B1–Br1 112.4(13), C3–B2–Br2 113.0(10), C3–

B2–N2 128.4(13), N2–B2– Br2 118.6(119); C10–B3–Br3 113.8(10),

C10–B3–N3 126.5(12), Br3–B3–N3 119.6(11), C8–B4–Br4 120.0(11),

C8–B4–N4 127.5(14), Br4–B4–N4 120.0(11), Fe1–C1–B1 126.1(11),

Fe1–C3–B2 126.4(10), Fe1–C10–B3 125.5(10), Fe1–C8–B4

130.4(11). Tilt angle C1–C5/C6–C10 3.4. Twist angle: C1–C5/

B1N1Br1 142.1, C1–C5/B2N2Br2 147.2, C6–C19/B3N3Br3 145.8,

C6–C10/B4N4Br4 142.5.

of the piperidino group compared to the dimethylamino group.

The B–N bond length of 1.36(1) Å is typical for B–N π-bond-

ing, the N1C6C10 plane is bent against the B1N1Br1 plane by

12°.

Compound 15 is monoclinic, space group C2/c. There are

two independent molecules in the asymmetric unit. Only one

molecule is shown in Figure 6. The iron atoms are located on

a C₂axis. Its B–C bonds are comparatively long [1.61(1) for

B1–C1 and 1.56(1) Å for B2–C2]. Astonishingly, the two B–

N bonds at the boron atoms are quite different: 1.45(1) and

1.48(1) Å to the tert-butylamino groups at B1 and B2. 1.39(1)

and 1.40(1) were found for the BN bonds to the isopropylam-

ino group. The tilt angle for C1–C5/C1A–C5A (10.2°) is much

larger compared with the angle of only 1.7° for C21–C26/

C21A–C26A. Both features are also typical for the derivatives

16 and 17.

Figure 9. Molecular structure of 1,1',3,3'-tetrakis(bromodimethylami-

noboryl)ferrocene (18). Only one of the two independent molecules in

the unit cell is shown. Thermal ellipsoids are presented on a 25 %

probability scale. Selected bond lengths are given in Å and bond angles

in deg. B1–Br1 1.982(9), B1–N1 1.37(1), B1–C1 1.55(1), B2–Br2

1.978(9), B2–N2 1.38(1), B2–C4 1.57(1), Fe–C1 2.062(8), Fe–C2

2,035(9), Fe–C3 2.054(7), Fe–C4 2.071(7), Fe–C5 2.026(7). C1–B1–

N1 127,7(8), C1–B1–Br1 115.3(6), N1–B1–Br1 117.0(6), C4–B2–N2

125.3(9), C4–B2–Br2 115.7(6), N2–B2–Br2 119.0(7), B1–C1–Fe

123.8(6), B1–C1–C2 126.7(7), B1–C1–C5 128.6(7), B2–C4–Fe

124.4(6), B2–C4–C3 128.3(7), B2–C4–C5 126.7(7). Tilt angle: 2.7°.

Twist angle: C1–C5/B1Br1N 24.5. C1–C5/B2N2Br2 25.6.

The 1,1'-bis(dimethyldiazaborolidinyl)ferrocene (16) crystal-

and C5. This stands in contrast to compound 11 where the C3– lises in the orthorhombic space group P2₁2₁2. The asymmetric

C4 bond is longer than the adjacent C2–C3 and C4–C5 bonds. unit contains only half a molecule. Its iron atom resides on a

This difference may be caused by the larger steric requirement twofold axis. The Cp rings are almost eclipsed and they form

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Figure 11. Molecular structure of 2-oxo-1,3-[bis(dimethylaminobo-

ryl][3]-ferrocenophane (20). Thermal ellipsoids are drawn on a 25 %

probability scale. Bond lengths in Å, bond angles in deg. B1–O1

1.384(4), B2–O1 1.386(4), B1–N1 1.397(4), B2–N2 1.394(4), B1–C1

1.580(4), B2–C6 1.580(4), C1–C2 1.4534(4), C2–C3 1.419(4), C3–C4

1.416(5), C4–C5 1.426(4), C5–C1 1.433(4), C6–C7 1.432(4), C7–C8

1.422(4), C8–C9 1.401(5), C9–C10 1.436(4), C10 –C6 1.434(4), Fe1–

C1 2.028(3), Fe1–C2 2.022(3), Fe1–C3 2.044(3), Fe1–C4 2.065(3),

Fe1–C5 2.047(3), Fe1–C6 2,021(3), Fe1–C7 2.041(3), Fe1–C8

2.066(3), Fe1–C9 2.056(3), Fe1–C10 2.014(3). B1–O1–B2 131.8(2),

C1–B1–N1 121.7(3), C1–B1–O1 121.2(2), N1–B1–O1 117.2(3),C6–

B2–N2 122.2(3), C6–B2–O1 120.7(2), N2–B2–O1 117.1(2), B1–C1–

C2 128.3(3), C1–C2–C3 109.3(3), C2–C3–C4 108.2(3), C3–C4–C5

107.4(3), C4–C5–C1 109.4(3), C6–C7–C8 109.5(3), C7–C8–C9

108.0(3), C8–C9–C10 108.1(3), C9–C10–C6 108.7(2). Tilt angle C1–

C5/C6–C10 9.0.

Figure 13. Molecular structure of 1,2,3-(tris(dimethylaminoboryl)[3]-

ferrocenophane (24). Thermal ellipsoids are drawn on a 25 % probabil-

ity scale. Bond lengths in Å, bond angles in deg. B1–B2 1.708(3), B2–

B3 1.709(3), C1–B1 1.577(3), B1–N1 1.395(3), C6–B3 1.581(3), B3–

N3 1.398(3), C1–C2 1.432(3), C2–C3 1.426(2), C3–C4 1.414(3), C4–

C5 1.427(3), C5–C1 1.443(2), C6–C7 1.431(3), C7–C8 1.423(3), C8–

C9 1.419(4), C9–C10 1.425(3), C10–C6 1.443(3); Fe1–C1 2.076(1),

Fe1–C2 2.033(1), Fe1–C3 2.041(2), Fe1–C4 2.467(2), Fe1–C5

1,053(2), Fe1–C6 2.071(2), Fe1–C7 2.036(2), Fe1–C8 2.040(2), Fe1–

C9 2.504(2), Fe1–C10 2.052(2). B1–B2–B3 111.8(1), C1–B1–N1

120.5(2), C1–B1–B2 113.3.(2), B1–B2–B3 111.8(2), B1–B2–N2

124.4(2), C6–B3–B2 114.2(2), C6–B3–N3 119.9(2), B3–B2–N2

122.8(2).B1–C1–C2 124.2(2), C1–C2–C3 109.7(2), C2–C3–C4

107.7(2), C3–C4–C5 107.9(2), C4–C5–C1 109.3(3). Tilt angle: 1.9°.

a twist angle with the BN1N2 plane of 31.6°. Its B–C bonds

are longer than in bromodialkylaminoborylferrocenes. Another

feature is that the B–N bonds are on the longer side with

1.410(3) and 1.405(3) Å. This is typical for bis(amino)-borane

systems. The B1 atom is slightly moved above the C1–C5

plane by 0.042 Å. These features are also observed for com-

pound 17 which crystallises in the triclinic system, space group

¯

P1. The tilting of the Cp ring planes is comparatively large

with 13.2° (see Figure 7 and Figure 8). The steric effect of the

tBu group is, therefore, rather drastic which becomes evident

also by the torsion of its BN₂planes against the Cp planes

by 43.9°and 76.9°. The BN₂C₂rings are bent upwards and

downwards, respectively. Atom B1 is 0.332 Å above the C1–

C5 plane, whereas atom B2 is 0.530 Å below the C6–C10

plane.

Steric effects are significant in the 1,1',3,3'-tetrakis(bromodi-

organylaminoboryl)ferrocenes 18 and 19. Compound 18 crys-

tallises monoclinically in space group P2₁/n with Z = 2 (see

Figure 9). That there are only two molecules of 18 in the unit

cell is due to the fact that the iron atom is located on an inver-

sion centre. This has also the consequence that the carbon at-

oms of the Cp rings are present in a staggered conformation.

The Cp rings are oriented almost parallel to one another, and

the BNBr planes include a twist angle with their respective Cp

planes of 24.0 and 25.6°. This strong twisting brings the bro-

Figure 12. Molecular structure of 2-thio-1,3-[bis(diisopro-

pylaminoboryl][3₂]ferrocenophane (23). Thermal ellipsoids are drawn

on a 25 % probability scale. Bond lengths in Å, bond angles in deg.

B1–S1 1.863(9), B2–S1 1.877(8), B1–N1 1.41(1), B2–N2 1.10(1), B1–

C1 1.58(1), B2–C6 1.56(1), N1–C11 1.502(9), N1–C14 1.484(8), N2–

C17 1.498(8), N2–C20 1.495(9), C1–C2 1.422(9), C2–C3 1.42(1), C3–

C4 1.39(1), C4–C5 1.42(1), C5–C1 1.42(1), C6–C7 1.42(1), C7–C8

1.42(1), C8–C9 1.42(1), C9–C10 1.41(1), C10–C6 1.44(1). B1–S1–B2

112.4(4), C1–B1–N1 120.5(7), C1–B1–S1 121.2(8), S1–B1–N1

118.1(5), C6–B2–S1 118.5(5), C6–B2–N2 123.6(6), S1–B2–N2

117.8(8), B1–C1–C2 129.8(7), C1–C2–C3 109.6(7), C2–C3–C4

107.7(7), C3–C4–C5 107.9(7), C4–C5–C1 109.6(7). Tilt angle: C1–

C5/C6–C10 9.0.

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Synthesis and Structures of New Borylferrocenes

mine atoms closer to the iron atom (see Table 1). The torsion B3 (84.5°). Almost coplanar are the atoms C1–N1–B1–B2 as

angles C2–C1–B1–Br1 of –154.2° and C3–C4–B2–Br2 of shown by a torsion angle of 175.6° and for C16–N3–B3–B2

153.1° show that the boron atoms are bent slightly underneath with 178.6°. The Fe–C bond lengths span a range from 2.02

the Cp planes by 0.065Å. The boron and nitrogen atoms reside to 2.64 Å, the shortest bonds are to atoms C2 and C7 (both

in a planar environment and the B–N bond lengths with values 2.020 Å). The Fe1–B distance to atom B1 is 3.174 Å, to atom

of 1.37(1) and 1.38(1) Å are in agreement with B–N π-bonding. B3 3.155 Å and to atom B2 3.401 Å. The B–B bond lengths

The molecular structure of 19 (Figure 10) is similar to 18. are 1.708(3) for B1–B2 and 1.709(3) for B2–B3. They are typ-

The two Cp rings are bent against each other by 3.5°. But the ical for electron precise triboranes [30]. The substituents at the

BNBr planes include now a larger twist angle with its Cp ring boron and nitrogen atoms are present in a planar environment.

of 38.7° (B1N1Br1) and 145.9° (B2N2Br2). This generates an The N1–B1–B2 bond angle is quite open with 125.84(1)°, the

angle of 112.5° between the B1N1Br1 and B2N2 Br2 planes. N1–B1–C1 bond angle corresponds with 120.5(2)° to a trigo-

The C₂N1 plane forms an angle with the C1B1Br1 plane of nal planar environment, whereas the C1–B1–B2 angle is rather

11.3°, the other three C₂N units are bent against the respective acute with 113.3(2)°. Additional data are listed in Figure 13.

CBBr planes by 9.4, 6.8 and 4.5°.

Compound 20, the oxadiborylferrocenophane crystallises

Discussion and Conclusion

monoclinically, space group P2₁with Z = 2 (see Figure 11).

The tilting of its two Cp rings is 9.8°, and the B1–O1–B2 unit

is not perpendicularly oriented to the two Cp rings as shown

by the angle C1–C5/N1–B1–O1 of 57.2° and C 6–C10/N2–/

B2–O1 of 55.7°. The torsion angle B1–C1–C6–B2 is 27.3°

whereas the torsion angles of C1–B1–O1–B2, C11–N1–B1–O1

and C13–N2–B2–O1 are 17.7, –173.1 and 2.6°. Fe1–C distan-

ces are short for Fe1–C1 (2.028 Å) and Fe1–C6 (2.021 Å), but

the Fe1–C10 bond is even shorter with 2.014 Å. Both Fe1–B

distances are 3.077 Å. Actually, the O1 atom is not much more

apart from the iron atom with 3.371 Å. It should be noted that

the B–O bond lengths are 1.384(4) (O1) and 1.386(4) (O2) Å,

and the B1–O1–B2 bond angle is 131.8(2)°. This indicates that

the B–O bond may have some weak π-bond character.

Amongst the interesting species of borylated ferrocenes are

those where the FeCp₂molecule is attached to a six-membered

B₃X₃ring (X = Se, S, O). The tris(ferrocenyl)selenaborane ring

[CpFeCpBSe]₃(1) was the first of this kind whose structure

had been determined by X-ray crystallography. The ring sys-

tem is planar, and its Cp rings are present in an eclipsed config-

uration [14]. Unfortunately, we could not get single crystals of

the corresponding triferrocenylthiaboroxine 1. However,

Wagner et al. [24] solved the structure of triferrocenylboroxine

2, which has an almost planar B₃O₃ring with B–O bond

lengths of 1.379 to 1.389 Å. Its B–O–B bond angles are

slightly larger than 120° and the O–B–O bond angles conse-

quently a bit smaller than 120° (119.4–119.7°). The Cp₂Fe

units are placed only one side of the B₃O₃ring, and the Cp

groups of the Cp₂Fe units are present in the eclipsed configura-

tion. In contrast, the adduct (CpFeCp)BO)₃·HNMe₂(3) a pre-

cursor of 2, shows a half chair conformation with two tricoor-

dinate boron atoms and one tetracoordinated boron atom. This

arrangement induces a staggered conformation for the Cp ring

at the tetracoordinated boron atom and an eclipsed conforma-

tion for the FeCp₂group at the tricoordinated ring boron atom.

The B–C bond lengths of 3 are comparatively long [1.56(1)

and 1.57(1) Å], in contrast to 2, where the three B–C bond

lengths are shorter (1.524, 1.532 and 1.532 Å) [24]. The B–C

bond length difference in 3 between the tricoordinate boron

atoms and the Cp rings is 0.02 Å compared with the longer

B–C bond to the tetracoordinated B2 atom [1.58(1) Å]. This

rather small difference indicates that B–C π-bonding can be

neglected. The B–C bond lengths can be compared with those

of (PhBO)₃(1.544, 1.544 and 1.549 Å) [29], which are slightly

shorter than in 2 but close to those of (EtBO)₃(1.563 to

1.568 Å) [30].

The orange thiadiborylferrocenophane 23 crystallises also

monoclinically but in space group P2₁/n with Z = 4 (see Fig-

ure 12). The two Cp rings are tilted by 7.5°, and the bending

of the planes C1–C5 against the N1–B1–S1 plane is 61.5° and

of C6–C10 against N2–B2–S1 is 42.4°. The planes N1B1C1

and N2B2C6 enclose an angle of 39.0°. The torsion angle B1–

C1–C6–B2 was determined as 35.2°. Other torsion angles are

C1–B1–C6–B2 = 35.2°, S1–B1–N1–C1 = 171.8°, B2–S1–B1–

C1 = 4.6°, and B1–S1–B2–C6 = 37.4°. The Fe1–B1 and Fe1–

B2 distances are 3.174 and 3.141 Å, and the Fe1 distance to

S1 is 3.759 Å. Amongst the Fe–C bond lengths those to atoms

C2 and C7 (2.03 and 2.02 Å) are shorter than to the boron

bonded atoms C1 and C6 (both 2.036 Å). The B1–C1 and B2–

C6 bond lengths are 1.58(1) and 1.56(1) Å. The Fe1···B1 dis-

tance is 3.17 and the Fe1···B2 distance is 3.14 Å. These are

shorter than for the other dialkylaminoborylferrocenes. It

should be noted that the B1–S1–B2 bond angle of 112.5° is

quite open for a dicoordinated sulfur atom.

The tris(dimethylaminoboryl)[3]ferrocenophane 24 crystal-

lises monoclinically, space group P2₁/n, with Z = 4. The “long”

triboryl group has the effect that the tilt angle between the two

Cp rings in now only 1.9°. These rings are present in an

eclipsed conformation as shown by a torsion angle B1C1C6B3

of only 1.6°. The N1B1B2 plane is twisted against the Cp1–5

ring by 54.3° and the N3B3B2 plane against the Cp6–10 ring

by 121.8°. An almost perpendicular arrangement is observed

In compounds 16 and 17 the Cp rings adopt eclipsed posi-

tions as well as in 11, 12, 18 and 19 due to the C₂symmetry of

the molecules. As the steric requirement of the amino groups

increase we can notice a lengthening of the B–C bonds. The

longest one was observed for compounds 15 and 17. As far as

we are aware these are the longest B–C bonds of borylferroce-

nes. The diazaborolidinyl rings of 16 are twisted by 30.8 and

for the three Me₂NB planes as shown by torsion angles for 32.1° against its Cp rings, whereas the BN₂units of 17 are

N3–B3–N2–N2 (–84.5°), N1–B1–B2–N2 (88.0°), N2–B2–N3– even stronger twisted with 43.0° (Cp1) and 76.9° (Cp6) in the

Z. Anorg. Allg. Chem. 2010, 2329–2342

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2337

A. Appel, H. Nöth

ARTICLE

sium/benzophenone). Amines were either distilled before use or re-

crystallised from an anhydrous solvent. Borylated ferrocene starting

materials were prepared by literature procedures [13–21]. NMR: Jeol

L 60 (¹H), Jeol GSX 270 (¹H), Jeol EX 400 (¹³C, ¹¹B) with SiMe₄or

BF₃OEt_2’as standards. IR: Nicolet 520-FT-IR spectrometer, usually in

nujol/hostaflon oil; X-ray: Siemens R3m/V or P4 diffractometer, Mo-

K_αradiation, graphite mono-chromator, scintillation counter or area

detector. In most cases the melting of the compounds was accompanied

by decomposition.

opposite direction, i.e. there is an angle of 86.6° between the

two diazaborolidinyl rings. The boron atoms of 16 are located

slightly above the Cp rings as has also been observed for the

dehydrodiazaborolidylferrocene [26] but the boron atoms of 17

are significantly located above and below their Cp rings. This

is due to the stronger disturbance of symmetry by the di-tert-

butyldiazaborolidinyl group of compound 17. This is mirrored

by the Fe–C distances. Their average length is 2.068 Å, which

are longer than in ferrocene itself (2.052 Å), Their structures

can be compared with the unsaturated mono- and bis(bis(tert-

butyl-dehydrodiaza-borolidyl)ferrocenes [26]. Their Cp rings

are twisted by 9.8° for the monosubsituted ferrocene

CpFeCpB(N₂C₄tBu₂H₂), and by 12.9° for the disubstituted de-

rivative Fe(CpBN₂C₂tBu₂H₂)₂in contrast to the almost co-

planar Cp rings in 18 and 19. However, the strongest twisting

of the Cp planes against each other is observed for bis(diiso-

propyl-tert-butyl-boryl)ferrocene, 15. These results clearly

show that the conformation of the boryl-substituted ferrocenes

is strongly influenced by steric effects.

The first 2,1,3-chalcogeno-bis(dimethylaminoboryl)[3]ferro-

cenophanes, X(Me₂NBCp)₂Fe (X = O, S, Se, Te) were reported

by Herberhold et al. in 1995 [27]. They determined only the

structure of Se(iPr₂NBCp)₂Fe. We now add the structure of

two more species, O(Me₂NBCp)₂Fe and S(iPr₂NBCp)Fe.

Three features are of interest: the dependence of the angle be-

tween the Cp ring depending on the size of the chalcogen

atom, the bending angle between a Cp ring and the B(NR₂)X

group and finally the angle B–X–B. In case of the oxo com-

pound 20, the Cp rings are tilted by 8.2°, in case of the sulfur

compound by 7.5°, and in case of the selenium compound by

2.4°. The angle between the Cp rings and the B(NR₂)X groups

are 57.3° for 20, 58.9° for Cp1–5/B1NMe₂(S) for 23. The B–

O–B bond angle is 131.8°, the B–S–B bond angle 112. 4° and

the B–Se–B angle 110.2°. There is, therefore, a considerable

widening of the B–X–B bond angle for all these compounds

particularly compared with the respective dialkylderivatives

R₂BX.

2,4,6-Triferrocenyl-1,3,5,2,4,6-trithiatriborine (1): A solution of

(Me₃Si)₂S (1.0 mL, 5.98 mmol) in hexane (10 mL) was slowly added

to an ice cooled solution of dibromoborylferrocene (2.13 g,

5.98 mmol) in hexane (30 mL). Even after keeping the mixture at re-

flux for 3 h, the compounds had not reacted quantitatively. In spite of

this, all volatile products were removed in vacuo. The residue was

afterwards treated with hot benzene (50 mL) leaving 310 mg of an

undissolved solid. The residue of the filtrate, after removing the ben-

zene, was afterwards crystallised form pentane at –30 °C to produce

1.67 g (41 %) of red-brown microcrystalline crystals of 1, m.p. 158–

160 °C. C₃₀H₂₇B₃S₃Fe₃(683.73): calcd. C 52.7, H 3.99; found C 51.0,

H 3.58 %. NMR in CDCl₃: ¹H: δ = 4.14 (s, 15 H, Cp), 4.72 (t,

³J(H,H) = 1.46 Hz, 6 H, Cp-subst.), 4.83, (t, ³J(¹H¹H) = 1.47 Hz, 6 H,

Cp subst.). ¹³C: δ = 70.2 (Cp unsubst.), 74.0 (Cp subst.), 74.7 (Cp

subst,), CB not obsv. ¹¹B (C₆D₆): δ = 57.5 (br). IR: ν = 3091 m, 2924

st, 1434 vst, 1376 st, 1244 vst, 1003 vst, 819 vst, 763 st, 677 vst, 495

st, 479 st, 441 m cm^–1.

Tris(ferrocenyl)boroxine-Dimethylamine (3) and Tris(ferrocenyl)-

boroxine (2): To a THF solution (10 mL) of (Me₂N)₂BCpFeCp

(690 mg, 2.40 mmol) was added a 0.5 m solution of water in THF

(5 mL) at –60 °C. The mixture was stirred until it has reached ambient

temperature. Under these conditions dimethylamine developed readily.

After stirring the solution for 12 h a broad ¹¹B NMR signal at 24.

6 ppm for 3 with a shoulder at lower field was observed. Compound

2 was isolated from part of the THF solution which was kept at reflux

for 1 week. This resulted in a shift of the ¹¹B NMR signal to 31 ppm

besides a weak signal at δ = 25 ppm. Afterwards, all volatiles were

removed in vacuo. Crystallisation of the solid residue from toluene

(30 mL) gave as a first fraction tiny crystals of orange coloured 3

whose structure was determined by X-ray crystallography. Three fur-

ther crystallisations yielded crystals of 2. Yield: 1.27 g (67 %), m.p.

236–238 °C. C₃₀H₂₇O₃B₃Fe (633.55): calcd. C 56.7, H 4.29; found C

56.5, H 5.04 %. NMR of 2 (C₆D₆): ¹H: δ = 4.12 (s, 15 H, unsub.

The structure of the triborylferrocenophane allows a compari-

son with the monoboryl- and diboryl-ferrocenophanes. The

most intriguing molecules are those of the monoboryl species.

Tilt angles of 31.2 to 32.4° were observed for Me₂NB(Cp)₂Fe,

(Me₃Si)₂NB(Cp)₂Fe_,tBu(Me₃Si)NB(Cp)₂Fe, iPr₂NB(Cp)₂Fe

[31]. In case of 1,2-bis(dimethylaminodiboryl)-[2]ferroceno-

phane [32] the tilt angle is only 11.1°, and this angle is even

further reduced to 2.6° in 24. Moreover, in case of compound

24 the B–B–B bonds angle is 111.8° which is smaller than for

most triborane derivatives, and the N–B–B–N torsion angles of

88.0° and –84.5° show, that they are similar to those of

(Me₂N)₂B–BNMe₂–B(NMe₂)₂[33]. There is no doubt, that all

3

Cp), 4.38 (pseudotrip., J(H,H) = 1.47 and 1.95 Hz resp., 6 H), 4.81

3

(pseudotrip., J(H,H) = 1.46 and 1.96 Hz, 6 H). ¹³C: δ = 70.0, 73.1,

74.4, CB (not obs.). ¹¹B: δ = 31.6, (br). IR: ν = 3228 w, 3088 w. 2927

m, 1462 st, 1311 vst, 1106 st, 1024 m, 823 st, 729 st, 650 m, 427 vst,

482 st cm^–1.

1,1'-Bis(brom-ethoxyboryl)ferrocene (4): [13c]: At –70 °C, a solu-

tion of (Br₂BCp)₂Fe (4.35 g, 4.28 mmol) in CH₂Cl₂(50 mL) was

added to a solution of diethyl ether (640 mg, 8.56 mmol) in CH₂Cl₂

(10 mL). The solution was allowed to attain room temperature within

4 h. Afterwards, all volatile materials were removed in vacuo. The

these borylferrophanes offer a wide field for interesting re- residue was dissolved in pentane (15 mL). At –78 °C a red-brown

precipitate formed (2.65 g, 62 %). This material transformed into an

oil at room temperature from which crystals of 4 separated on standing

for two weeks, m.p. 140–145 °C. C₁₄H₁₈O₂BBr₂Fe (355.57): calcd. C

search.

1

36.9, H 3.98, found C 36.7, H 4.26 %. NMR (in C₆D₆): H: δ = 1.07

Experimental Section

(t, ³J(H,H) = 7.32 Hz, 6 H, Me), 4.07 (q, ³J(H,H) = 7.32 Hz, 4 H,

3

All reactions were performed in an atmosphere of nitrogen or argon CH₂), 4.32 (pseudotrip., J(H,H), = 1.47, 1.97 Hz, 4 H, Cp). ¹³C: δ =

using the Schlenk techniques. Solvents were made anhydrous before 16.8 (Me), 65.7 (CH₂), 74.8 (C-3,4), 76.1 (C-5), CB not found. ¹¹B:

use by the usual methods (drying with CaH₂, P₂O₅, LiAlH₄, or potas- δ = 38.9. IR: ν = 3099 w, 2982 st, 2931 m, 1484 vst, 1755 vst, 1379

2338

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Z. Anorg. Allg. Chem. 2010, 2329–2342

Synthesis and Structures of New Borylferrocenes

vst, 1229 vst, sh, 1220 st, 1098 m, 936 m, 772 st, 653 m, 479 st cm^–1. 1490 vst, 1265 vst, 1210 vst, sh, 1110 m, 927 m, 767 st, 653 m. 464

C₁₄H₁₈O₂BBr₂Fe (355.57): calcd. C 36.9, H 3.98, found C 36.7, H m cm^–1.

4.26.

1,1'-Bis(bromodiphenylaminoboryl)ferrocene (13): Prepared in

1,1'-Bis(diethoxyboryl)ferrocene (6): [13c]: [(Me₂N)₂BCp]₂Fe, 5 analogy to 12 from (Br₂BCp)₂Fe (2.58 g, 4.67 mmol) and Me₃SiNPh₂

(2.72 g, 7.12 mmol), was dissolved in hexane (15 mL) and a solution (2.24 g, 9.32 mmol) in hexane (20 mL). Red crystals. Yield of 13:

of ethanol (1.68 mL, 28.5 mmol) diluted with hexane (5 mL) was 62 %; m.p. 80–85 °C. C₃₄H₂₈N₂Br₂B₂Fe (702.03): calcd. C 58.17, H

added dropwise at –60 °C whilst stirring. At –30 °C compound 6 sepa- 4.02, N 3.99; found C 56.95, H 3.92, N 3.82 %. NMR (C₆D₆): ¹H:

rated as an orange red crystalline powder. Yield: 1.79 g (65 %), m.p. δ = 4.10 (br., 4 H, H-2,5), 4.32 (br., 4 H, H-3,4), 6.94 (m, 12 H, Ph,

140 °C. C₁₈H₂₈O₄B₂Fe (385.89), calcd. 56.0, H 7.31; found C 55.0, H H-2,4,6), 7.03 (m, 8 H, Ph, H-3,5). ¹³C: δ = 74.4, (C-3,4), 77.4 (C-

6.82 %. NMR (in C₆D₆) H¹: δ = 1.27 (t, ³J(H,H) = 6.84 Hz, 12 H, 2,5), CB(not found), 126.2 (Ph, C-4) 128.2, 129.0 (Ph, C-2,6, C-3,5),

3

Me), 4.07 (q, J(H,H) = 6.84 Hz, 8 H, CH₂), 4.30 (t, J(H,H) = 1.47, 148.5 (Ph, C-1). ¹¹B: δ = 39.9. IR: ν = 3062 w, 1587 m, 1443 st, 1387

1.95 Hz, 4 H, Cp), 4.36 (t, J(H,H) = 1.47, 1.95 Hz, 4 H, Cp). ¹³C: st, 1245 st, sh, 1061 m, 945 m, 838 m, 774 m, 696 st, 502 m, 484 m

3

δ = 17.6 (Me), 59.4 (CH₂), 72.1 (C-3,4), 74.7 (C-2,5), CB (not detect.). cm^–1.

¹¹B: δ = 29.7.

1,1'-Bis(bromo-tetramethylpiperidino-boryl)ferrocene (14): A so-

1,1'-Bis(catecholatoboryl)ferrocene (9): To

a

solution of lution of (Br₂BCp)₂Fe (4.02 g, 7.61 mmol) in hexane (30 mL) was

[(Me₂N)₂BCp]₂Fe (890 mg, 2.41 mmol) in CH₂Cl₂(40 mL) was cooled to –78 °C. Afterwards, a solution prepared from tmpH

dropped a solution of 1,2-dihydroxybenzene (530 mg, 4.82 mmol) in (2.59 mL, 2.15 g, 15.2 mmol) and LitBu (9.97 mL, 1.56 m) was

CH₂Cl₂(20 mL). A yellow precipitate formed quickly which proved slowly added. After stirring for 3 d, the solvent was removed in vacuo.

to be 8 (1.02 g, 68 %), m.p. 280 °C (dec.). To a stirred suspension of The residue on crystallisation from pentane (20 mL) yielded 3.76 g

this adduct (280 mg, 0.55 mmol) in diethyl ether (15 mL) was added (77 %) of orange microcrystals of 14; m.p. 151 °C. NMR (C₆D₆): ¹H:

BF₃OEt₂(160 mg, 1.1 mmol). This resulted in a slow change of the δ = 1.44–1.46 (m, 12 H, H-2,3,4), 1.51 (s, 24 H, Me), 4.57 (t, ³J(H,H) =

.

3

yellow colour to orange whilst the precipitate went into solution. After 1.96 Hz, 4 H, H-2,5), 4.66 (t, J(H,H) = 1.96 Hz, 4H, H-3,4). ¹³C: δ =

removal of all volatiles the residue was crystallised from diethyl ether 15.1 (C3), 33.2 (C6,7,8,9), 36.5 (C2,4), 56.5 (C1,5), 74.9 (C3,4), 77.3

at –30 °C. Yield of 9: 230 mg (99 %), m.p. 181 °C, orange crystals. (C2,5), CB not obs. ¹¹B: δ = 42.9. IR: ν = 3004 w, 2943 st, 1439 st,

C₂₂H₁₆O₄B₂Fe (424.85), (9): calcd. C 62.62, H 3.80; found C 62.2, H sh, 1385 vst, 1244 m, 1049 st, 966 st, 827 m, 650 m, 505 m, 466 m

1

3

3.84 %. NMR (in C₆D₆): H: δ = 4.15 (t, J(H,H) = 1.46, 1.96 Hz, 4 cm^–1.

3

H, Cp), 3.66 (t, J(H,H)) 1.46, 1.96 Hz, 4 H, Cp), 6.78 (m, 6 H, H-

3,3',6,6'), 6.96 (m, 4 H, H-4,4',5,5'). ¹³C: δ = 73.8 (C-3,4), 74.9 (C-

2,5), CB (no found), 112.5 (C-3,3',6,6'), 122.6 (C-4,4',5,5'), 149.0 (C-

1,1',2,2'). ¹¹B: δ = 35.7. IR: ν = 3038 w, 1512 m, 1501 st, 1489 st,

1479 vst, 1387 st, 1322 st, 1312 st, 1238 st, 1132 m, 1115 st, 899 m,

811 m, 744 vst, 689 m, 499 m, 427 m cm^–1.

1,1'Bis(diisopropylamino-tert-butylamino)borylferrocene, (15): A

solution of 1,1'-bis(bromo-diisopropylaminoboryl)ferrocene (1.04 g,

1.84 mmol) in hexane (15 mL) was cooled to –15 °C. Afterwards, a

mixture of tert-butylamine (0.19 mL, 1.84 mmol) and triethylamine

(0.51 mL, 3.68 mmol) in hexane (10 mL), was added slowly whilst

stirring. Stirring was continued at room temperature for 21 h. The

1,1'-Bis(bromodiisopropylaminoboryl)ferrocene (10): [18, 27]: To insoluble [Et₃NH]Br was removed by filtration and the hexane from

an ice cold stirred solution of (Br₂BCp)₂Fe (3.78 g, 7.20 mmol) in the filtrate in vacuo. The remaining solid was afterwards crystallised

hexane (60 mL) was slowly added a solution of diisopropylamine from hexane (30 mL) at –30 °C to give orange-red crystals of 15.

(4.06 mL, 28.9 mmol). A suspension formed. At room temperature the Yield: 420 mg, 42 %, m.p. 155 °C. C₃₀H₅₆N₄B₂Fe (550.27): calcd. C

solid [iPr₂NH₂]Br was removed by filtration. (3.06 g, 16.8 mmol) and 65.48, H 10.26, N 10.18; found C 64.60, H 9.54, N 9.73 %. IR: ν =

the solution reduced to 20 mL in vacuo. After cooling to –30 °C 2.77g 3105 w, 3083 w, 2966 vst, 1487 st, 1386 m, 1277 vst, 1233 st, 1224

(68 %) of orange brown crystals of 10 separated, m.p. 151–152 °C.

m, 821 m, 617 m, 510 w cm^–1.

1,1'-Bis(bromodimethylamino)borylferrocene (11): A solution of 1,1'-Bis[1,3-dimethyl-1,3,2-diazaborolidinyl)ferrocene (16): [14c]:

1,1-bis(dibromoboryl)-ferrocene (3.25 g, 9.14 mmol) in hexane To a solution of Fe(CpBBr₂)₂(1.11g, 2.10 mmol) in benzene (40 mL)

(25 mL) was cooled to –50 °C. Whilst stirring, a solution of was added whilst stirring a solution of N,N'-dimethylethylene-diamine

Me₂NSiMe₃(2. 88 mL, 2.13 g, 18.2 mmol), in hexane (50 mL) was (0.45 mL, 4.2 mmol) and triethylamine (1.17 mL, 8.4 mmol) in ben-

added. After the mixture had attained room temperature another por- zene (15 mL) at 0 °C. Stirring was continued until the suspension at-

tion of pure Me₂NSiMe₃(0.50 mL) was added. Afterwards, after 1 h, tained room temperature. Afterwards, the precipitate (1.45 g,

all volatiles were removed in vacuo. Crystallisation of the residue from 7.97 mmol) of [Et₃NH]Br was removed by filtration, followed by re-

hexane at –78 °C produced 1.78 g (98 %) of red crystals of 11, m.p. moval of the solvent from the filtrate in vacuo. The red crystalline

46 °C. δ¹¹B (C₆D₆) = 33.4 ppm. For further data see [27].

residue was recrystallised by adding hexane (25 mL) at –30 °C, Yield:

650 mg, 71 %, m.p. 83 °C. C₁₈H₂₈N₄B₂Fe (378.06), calcd. C 57.19, H

7.47, N 14.83; found C 56.32, H 7.23, N 14.77 %. IR: ν = 3104 m,

3083 m, 2857 vst, 1501 vst, 1402 vst, 1288 st, 1214 s, 821 st. sh, 670

m, 502 st, 478 m cm^–1.

1,1'-Bis(bromopiperidinoboryl)ferrocene (12): Prepared according

to 11 from Me₃Si(NC₅H₁₀) (1.54 g, 9.78 mmol) and (Br₂BCp)₂Fe

(2.70g, 4.89 mmol) in hexane (29 mL). Red crystals of 12, yield:

80 %. m.p. 76–78 °C C₂₀H₂₈N₂B₂Br₂Fe (533.81): calcd. C 46.50, H

5.78, N 5.25; found: C 46.32, H 5.64, N 5.12 %.. NMR (in CDCl₃) 1,1'-Bis(1,3-di-tert-butyl-1,3,2-diazaborolidinyl)ferrocene (17): In

¹H: δ = 1.57 (m, 8 H, CH₂, H-2,4), 1.68 (m, 4 H, CH₂, H-3), 3.50 (t, analogy to 16,

a solution of N,N'-di-tert-butylethylenediamine

3

³J(H,H) = 5.3 Hz, 4 H, CH₂), 3.60 (t, J(H,H) = 5.3 Hz, 4 H, CH₂), (1.88 mL, 10.7 mmol) and triethylamine (2.98 mL, 21.5 mmol) in

3

4.38 (pseudotr., J(H,H) = 1.46, 1,96 Hz, 4 H, H-2,5), 4.41 (pseudotr. hexane was slowly added to a stirred solution of (Br₂BCp)₂Fe (2.81 g,

3

5, J(H,H) = 1.46, 1.96 Hz). ¹³C: δ = 25.4 (pip C3), 28.0, 28.3 (pip, 5.35 mmol) in hexane (40 mL) at 5 °C. The suspension that formed

C2, C4), 50.9, 52.5 (pip. C1, C5), 73.6 (C-3,4), 77.3 (C-2,5), CB (not was stirred for 1 h. Afterwards, the precipitate of [Et₃NH]Br (3.92 g,

found). ¹¹B: δ = 36.1 (br). IR: ν = 2995 w, 2932 m, 2852 st, 1496 vst, 21.5 mmol) was removed by filtration and 50 % of the solvent of the

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2339

A. Appel, H. Nöth

ARTICLE

filtrate was evaporated in vacuo. From the remaining solution sepa- dissolved in hexane (30 mL). After filtration the filtrate was kept at –

rated at –30 °C red crystals of 17, m.p. 148 °C. Yield: 2.28 g, 78 %. 30 °C. 320 mg of orange crystals (yield: 25 %), separated within a

C₃₀H₅₂N₄B₂Fe (546.24): calcd. C 65.92, H 9.59, N 10.26; found: C few days. m.p. 200 °C(dec.). C₃₆H₆₂N₄B₄Br₄Fe (945.6): calcd. C 43.2,

1

65.97, H 9.51, N 10.02 %. IR: ν = 3094 w, 3081 w, 2967 st, 1473 m, H 6.61, N 5.93; found C 43.2, H 7.07, N 5.21 %. NMR (C₆D₆): H:

1394 vst, 1265 vst, br, 1232 vst, br., 821 m, 672 w, 497 m, 470 w δ = 0.92 (d, ³J(H,H) = 6.84 Hz, 12 H, Me), 1.04 (d, ³J(H,H) = 6.84 Hz,

cm^–1.

12 H, Me), 1.57 (d, ³J(H,H) = 6.84 Hz, 12 H, Me), 1.60 (d, ³J(H,H) =

6.84 Hz, 12 H, Me), 3.31 (sept., br., 4 H, CH), 4.53 (sept. (³J(H,H) =

4

1,3,1',3'-Tetrakis(bromodimethylaminoboryl)ferrocene (18): A so-

lution of 1,1',3,3'-tetra(dibromoboryl)ferrocene [20] (8.98 g,

10.4 mmol) in hexane (75 mL) was cooled to – 50 °C. Whilst stirring

a solution of Me₃SiNMe₂(86.59 mL, 4.88 g, 41.6 mmol) in hexane

(25 mL) was added slowly. After the addition the mixture was allowed

to attain ambient temperatue. All volatile material (hexane and

Me₃SiBr) was evaporated in vacuo. The residue was afterwards dis-

6.84 Hz, 4 H, CH), 5.02 (d, J(H,H) = 1.46 Hz, 4 H, H4,5), 5.04 (t.,

br. 2 H, H2). ¹³C: δ = 21.5 (Me), 22.0 (Me), 23.9 (Me), 24.1 (Me),

47.7 (CH), 52.6 (CH), 81.7 (C-4,5), 86.1 ppm (C2), CB (not obs.).

¹¹B: δ = 36.5 ppm. IR (nujol, hostaflon): ν = 3027 w, 2970 st, sh, 2931

m, 1470 vst, 1367 st, 1330 vst, 1188 m, 1137 st, 1092 st, 1005 st, 778

m, 756 m, 503 w cm^–1.

solved in hexane (ca. 50 mL), the turbid solution filtered and the fil- 1,1'-(Bis(dimethylaminoboryl)-2-oxo[3]-ferrocenophane (20): To a

trate kept at –30 °C. Within 4 days red crystals had separated which solution of (BrMe₂NBCp)₂Fe (780 mg, 1.08 mmol) in THF (20 mL)

were isolated by filtration and dried in vacuo. Yield of 18: 5.06 g, was added Li₂O (65 mg, 2.16 mmol). The suspension was stirred over-

1

67.5 %, m.p. 160–162 °C. NMR (C₆D₆): H: δ = 2.68 (s, 12 H, Me), night. Afterwards, the solvent was removed in vacuo and the residue

3

2.85 (s, 12 H, Me), 4.92 (d. J(H,H) = 0.98 Hz, 4 H, H4,5), 4.99 (t, treated with hexane (50 mL). After 630 mg insoluble LiBr were sepa-

³J(H,H) = 1.46 Hz, 2 H, H2). ¹³C: δ = 41.2 (Me), 43.1 (Me), 82.5 rated by filtration 270 mg of an orange powder was recovered by evap-

(C4,5), 86.6 ppm (C2), CB (not obs.). ¹¹B: δ = 37.3 (br). IR (nujol, oration of the solvent. The residue was crystallised from hot hexane/

hostaflon): ν = 2954 st, 2932 st, 2872 st, 1518 st, 1461 st, 1255 m, dichloroethane (1:1). Yield: 100 mg (21 %) of 20., m.p. 198–200 °C.

875 m. 847 m, 651 st, 538 m, 492 m cm^–1.

C₁₈H₃₀N₄O₂B₄Fe, calcd. C 49.9, H 6.97, N 12.9; found C 50.6, H 7.70,

N 13.0 %. NMR (C₆D₆): ¹H: δ = 2.80 (br., 24 H, Me), 4.38 (d,

⁴J(H,H) = 0.98 Hz, 4 H, H3,4), 4.50 (t. ⁴J(H,H) = 0.98 Hz, 2 H, H2,5);

δ¹³C = 36.3 (Me), 39.1 (Me), 83.0 (C3,4), 85.4 (C2,5) C1 (not obs.).

¹¹B: δ = 31.1, br.

1,3,1',3'-Tetrakis(bromodiisopropylaminoboryl)ferrocene (19): To

a stirred solution of 1,1',3,3'- [(Br₂B)₂Cp]₂Fe (1.16 g, 1.34 mmol) in

benzene (50 mL) was added at 0 °C a solution containing iPr₂NH

(0.75 mL, 5.36 mmol) and Et₃N (0.74 mL, 5.36 mmol) in benzene

(20 mL). After stirring for 2 h, the insoluble material was removed by 1,1'-(Bis(diisopropylaminoboryl)-2-oxo[3]-ferrocenophane (21): To

filtration and benzene evaporated from the filtrate. The residue was a solution of 1,1'-bis(diisopropylamino-bromoboryl)ferrocene (1.15 g,

Table 2. Crystallographic data and data related to data collection and structures solution for compounds 9–12 and 15–17.

Compound

3·C₆H₆

9

10

11

12

15

16

17

Formula

M_r

Crystal size / 0.6 × 0.5 × 0.5

mm

C₃₈H₄₀NO₃B₃Fe₃C₁₆H₂₃NBBrFe C₂₂H₃₆N₂B₂Br₂Fe C₁₄H₂₀N₂BBr₂Fe C₂₀H₂₈N₂B₂Br₂Fe C₃₀H₅₄B₂N₄Fe C₁₈H₂₈N₄B₂Fe C₃₀H₅₂N₄B₂Fe

758.69

375.92

565.82

453.61

0.36 × 0.2 × 0.2

533.73

0.30 × 30 × 0.2

548.24

377.91

546.23

0.5 × 0.3 × 0.3 0.6 × 0.6 × 0.4

0.3 × 0.35 × 0.6 0.65 × 0.3 × 0.280.4 × 0.32 × 0.18

Crystal system orthorhombic

monoclinic

P2₁/n

6.003(1)

19.702(5)

13.936(6)

90

91.41(3)

90

1647.7(9)

4

triclinic

P1

orthorhomic

Pbcn

13.889(2)

9.868(2)

12.275(2)

90

1682.4(5)

4

1.791

monoclinic

C2/c

19.824(7)

10.329(3)

11.585(4)

90

114.97(3)

90

2150(1)

4

monoclinic

C2

23.133(8)

8.987(23)

18.858(7)

90

123.89(1)

90

3254.4(9)

4

orthorhombic

P2₁2₁2

11.717(3)

8,093(2)

9.8892(2)

90

938.0(4)

2

1.338

triclinic

P1

¯

Space group

a /Å

b /Å

Pna2₁

15.992(4)

19.515(2)

11.061(2)

90

7.90(1)

11.69(1)

14.03(2)

83.00(9)

89.3(1)

83.3(1)

1278(3)

2

10.76(1)

12.09(1)

13.45(1)

109.44(1)

91.22(2)

112.46(1)

1503(3)

2

c /Å

α /deg

β /deg

γ /deg

V /Å³

Z

3452(1)

4

D_calcd./g·cm^–31.460

1.515

3.329

1.471

3.728

1.649

4.425

1.119

0.487

1.207

0.527

μ(Mo-K_α) /mm^–11.283

5.639

0.812

F(000)

2568

273

3.3–50.0

–19 ≤ h ≤ 1

–1 ≤ k ≤ 23

–13 ≤ l ≤ 8

768

193

3.56–48.06

–6 ≤ h ≤ 6

–5 ≤ k ≤ 22

–15 ≤ l ≤ 3

2640

576

273

2.44–46.1

–8 ≤ h ≤ 8

–12 ≤ k ≤ 12

0< ≤ <1 ≤

3706

896

203

5.06–47.98

–11 ≤ h ≤ 2

0 ≤ k ≤ 14

–1 ≤ l ≤ 15

1864

1072

193

4.54–50.06

–23 ≤ h<0

–12 ≤ k ≤ 0

–12 ≤ l ≤ 12

1911

1192

273

3.72–48.00

1 ≤ h ≤ 26

–10 ≤ k ≤ 10

–21 ≤ l ≤ 18

5347

400

293

5.38–50.00

–13 ≤ h ≤ 13

–1 ≤ k ≤ 9

–1 ≤ l ≤ 11

2384

592

293

3.26–50.00

0 ≤ h ≤ 12

–13 ≤ k ≤ 12

–15 ≤ l ≤ 15

5372

Temp /K

2θ range

Index range

Refl. measured 5501

Refl. unique

R_int

Param. refined 433

5081

0.0478

2542

0.055

181

3541

0.2543

270

1286

0.0299

98

1853

0.0776

131

4251

0.0496

345

1658

0.0148

116

4271

0.0681

345

R1 (4σF)

0.0438

1.066

0.0556

1.038

0.553/–0.496

0.1114

0.2888

0.217/–0.117

0.0414

0.854

0.480/–0.391

0.0675

0.1357

0.896/–0.642

0.1011

1.053

0.066/–0–482

0.0270

1.061

0.321/–0.216

0.0712

1.029

0.75/–0.43

GOF (F²)

Δρ(max/min) / 0.388/–0.429

e·Å^–3

2340

www.zaac.wiley-vch.de

Z. Anorg. Allg. Chem. 2010, 2329–2342

Synthesis and Structures of New Borylferrocenes

1.22 mmol) in THF (40 mL), was added Li₂O powder (73 mg,

2.44 mmol). After stirring the suspension for 23 h the solvent was

evaporated from the filtrate whose residue was dissolved in hexane

(40 mL). The insoluble part (420 mg, 4.84 mmol LiBr, 99 %) was sep-

arated by filtration. 50 % of the hexane was afterwards evaporated in

vacuo, and the remaining solution cooled to –30 °C. 21 separated as a

microcristalline yellow-orange powder, m.p. 150 –155 °C which con-

tained about 5 % impurities. C₃₄H₆₂N₄O₂B₄Fe (657.98): calcd. C

62.10, H 9.50, N 8.51; found; C 61.3, H 9.03, N 7.93 %. NMR (C₆D₆):

X-ray Structure Determinations

Samples were covered with perfluoroether oil and a crystal selected

at –30 °C under a blanket of nitrogen. The selected crystal was after-

wards transferred on the tip of a glass fibre, which was attached to a

small copper tube. The tube was mounted on the head of the diffrac-

tometer (Siemens P4 equipped with scintillation counter or an area

detector) which was in most cases cooled by a cold stream of nitrogen

(–80 °C). Data collection was performed with graphite monochro-

mated Mo-K_αradiation. The unit cell dimensions were calculated by

using the reflections collected on 5 sets of 10 frames each at different

θ and ω angles, or from the positions of the reflections on a set of up

to 10 exposures on photographic plates. Data were collected with the

area detector by using the hemisphere mode or with the scintillation

counter in the ω/2θ mode. The programs SAINT and SMART were

used for data reduction [35], and the structures solved by using the

SHELXTL or SHELX93 data programmes [36]. A survey of the crys-

tallographic data and data referring to data collection and structure

solution is presented in Table 2 and Table 3. Further data referring to

the structure solution can be obtained from the Cambridge Crystallo-

graphic Data Center via www.ccde.cam.ac.uk/data_–re_–request by citing

the CCDC numbers 772990–773001. The piperidino compound 12

showed a disordered piperidine ring with two six membered ring chair

conformation. Their positions were refined with a site occupation fac-

tor of 0.5. Compound (tBuNH/iPr₂NBCp₂)Fe proved to be twinned

and refinement took care of this. Absorption correction was performed

for most data sets of the bromoboryl ferrocences.

3

¹H: δ = 1.03 (d, J(H,H) Hz, Me), 1.21 (d, J(H,H) = 6.83 Hz, 12 H,

Me), 1.47 (d, ³J(H,H) = 6.84 Hz, 12 H, Me), 1.55 (d, ³J(H,H) =

3

6.83 Hz, 12 H, Me), 3.30 (sept., J(H,H) = 6.83 Hz, 4 H, CH), 3.29

3

(sept, J(H,H) = 6.84 Hz, 4 H, CH), 4.58 (br., 4 H, H4,5), 4.65 (br., 2

H, 2 H). ¹³C: δ = 22.9 (Me), 23.1 (Me), 24.3 (Me), 25.2 (Me), 44.4

(CH), 49.4 (CH), 82.6 (C-4,5), 84.8 (C-2), CB (not obs.). ¹¹B: δ =

29.4, br.

1,1'-Bis(dimethylaminoboryl)-2-thia[3]-ferrocenophane (22): 1,1'-

(BrMe₂NBCp)₂Fe (1.21 g, 1.68 mmol)) was dissolved in THF

(15 mL). Whilst stirring a suspension of Li₂S (154 mg, 3.56 mmol) in

THF (10 mL) was added. Stirring was continued for 12 h. This resulted

in an orange colored suspension. The slightly yellow solid (1.0 g) was

afterwards removed by filtration. After the hexane was evaporated in

1

vacuo 0.23 g (31 %) of 22 were left as an orange powder whose H

NMR spectrum showed that it consisted of 85 % of 22 and 15 % of

impurities. Crystallisation from hexane improved the purity, but no

analytically pure 22 was obtained. C₁₈H₃₀N₄B₄N₄S₂Fe (465.67); calcd.

C 46.40, H 6.49, N 12.0; found C 45.3, H 6.43,.N 11.20 %. NMR

1

(C₆D₆): H: δ = 2.66 (s, 12 H, Me), 2.96 (s, 12 H, Me), 4.47 (br., 4 H,

H4,5), 4.50 (br., 2 H, H2); ¹³C: δ = 41.1(Me), 41.4 (Me), 79.7 (C4,5),

84.2 (C-2), CB (not obs.); ¹¹B: δ = 40.2 (br). IR (nujol/hostaflon): ν =

3006 w, 2927 vst, 1506 vst, 1391 vst, 1210 st, 1106 st, 971 m, 892 m,

799 w, 531 m, 455 w cm^–1.

Table 3. Crystallographic data and data related to data collection and

structures solution for compounds 20, 23 and 24.

Compound

20

23

24

Chem. formula

Form wght.

Crystal size /mm

Crystal system

Space group

a /Å

C₁₄H₂₀N₂OB₂Fe C₂₂H₃₆N₂B₂FeNS C₁₆H₂₆B₃FeN₃

1,1'-Bis(diisopropylaminoboryl-2-thia[3]-ferrocenophane (23): To

a solution of (BriPr₂NBCp)₂Fe (1.61 g, 1.7 mmol) in CH₂Cl₂(40 mL

was added Li₂S (160 mg, 3.48 mmol) and 15-crown-5 (1.35 mL,

6.8 mmol). After stirring for 2 h the ¹¹B NMR signal has shifted from

36.5 to 40.1 ppm. After removing the solvent in vacuo the residue

was treated with hexane (70 mL). Insoluble material was removed by

filtration and the filtrate reduced in volume by appr. 50 %. The result-

ing solution was afterwards kept at –30 °C for crystallisation. Yield:

850 mg of yellow orange needles, m.p. 249 °C (dec.).

C₃₄H₆₂N₄N₄B₄S₂Fe (690.10: calcd. C 59.2, H 9.06, N 8.12; found C

58.2, H 8.93, N 8.08) % . NMR (C₆D₆): ¹H: δ = 0.95 (d, ³J(H,H))

309.79

438.06

348.68

0.3 × 0.3 × 0.3

monoclinic

P2₁/n

0.2 × 0.3 × 0.3 0.3 × 0.25 × 0.1

monoclinic

P2₁

monoclinic

P2₁/n

9.561(2)

7.522(1)

10.299(2)

90

5.961(1)

11.949(5)

32.00(1)

90

8.758(2)

13.120(3)

15.899(5)

90

b /Å

c /Å

α /°

β /°

94.49(2)

90

92.7(2)

90

90.98(1)

90

γ /°

V /Å³

738.4(2)

2

1.393

1.015

2277(1)

4

1.278

0.764

1826.6(8)

4

Z

D(calc) /Mg·m^–3

μ /mm^–1

F(000)

1.268

3

6.84 Hz, 12 H, Me), 0.96 (d, J(H,H)) 6.84 Hz, 12 H, Me), 1.69 (d,

3

³J(H,H) = 6.84 Hz, 12 H, Me), 1.72 (d, J(H,H)) 6.84 Hz, 12 H, Me),

0.825

3.36 (sept., ³J(H,H) = 6.84 Hz, 4 H, CH), 3.48 (sept. ³J(H,H)) 6.84 Hz,

4 H, CH), 4.54 (br. 2 H, H2), 4.62 (br., 4 H, H4,5). ¹³C: δ = 22.2 (Me),

22.3 (Me), 24.4 (Me), 24.6 (Me), 46.3 (CH), 52.6 (CH), 80.7 (C-4,5),

85.1 (C2), CB (not obs.). ¹¹B: δ = 40.2 (br); IR (Nujol, hostaflon): ν =

3091 w, 3067 w, 2967 st, 2864 m, 1472 st, 1459 st, 1365 st, 1314 vst,

1299 vst, 1193 st, 1187 st, 1098 st,sh, 1013 st, 961 m, 874 m, 859 m,

800 st, 533 st, 532 m, 505 m cm^–1.

324

036

736

Index range

–11 ≤ h ≤ 11

–8 ≤ k ≤ 8

–12 ≤ l ≤ 12

54.74

0 ≤ h ≤ 6

–1 ≤ k ≤ 13

–36 ≤ l ≤ 36

48.04

–9 ≤ h ≤ 10

–13 ≤ k ≤ 13

–20 ≤ l ≤ 20

55.50

2θ /°

Temp /K

222

208

163(1)

Refl. collected

Refl. unique

4258

2606

4308

6829

3524

3333

Refl. observed (4σ) 2484

3522

2996

R (int.)

0.0445

185

0.081

0.0486

312

1,1'-(Tris(dimethylaminoboryl[3]-ferrocenophane (24): In analogy

to the preparation of 19 a solution of 1,3-dichloro-1,2,3-tris(dimethyl-

amino)triborane [33] (4.5 mmol) in Et₂O (10 mL) was added to a THF

solution of 1,1-dilithiumferrocene [34] (4.5 mmol). After stirring over-

night the solid was removed from the red-orange solution. Afterwards,

the solvents were evaporated. Crystallisation of the residue from hex-

ane at –30 °C yielded 3.5 mmol of 24. Only its crystal structure was

determined.

No. variables

361

Wght. scheme¹x/y 0.0381/0.0798

0.0778/0.00

0.976

0.0174/1.2762

1.065

GOOF

1.073

0.0309

0.0758

Final R(4σ)

Final wR2

0.0643

0.130

0.0302

0.0716

0.310

Larg. res. peak /e·Å³0.406

0.507/–0.376

* w^–1= s²F_o²+ (xP)²+ yP; P = (F_o²+ 2F_c²)/3

Z. Anorg. Allg. Chem. 2010, 2329–2342

www.zaac.wiley-vch.de

2341

A. Appel, H. Nöth

ARTICLE

P. Jutzi, N. Lenze, B. Neumann, W. Schoeller, H.-G. Stammler,

Chem. Eur. J. 2006, 12, 5471–5480.

Acknowledgement

We are indebted to Fonds der Chemischen Industrie as well as Chemet-

all AG for financial support, Mrs. D. Ewald for the recording of mass

spectra and Mr. P. Maier for the NMR spectra.

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Article Doi

Synthesis and structures of new borylferrocenes, and structures of, 2-chalcogeno-bis(aminoboryl)[3]ferrocenophanes and 1,1′-tris(di- methylaminoboryl))][3]ferrocenophane [1, 2]

DOI: 10.1002/zaac.201000167

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