First ferrocenylstibines and their molecular structures

Article abstract of DOI:10.1016/j.inoche.2005.09.029

Stibines Ph₂SbFc containing the pendant arm [2-(Me ₂NCHR)] [where R = H(1) or Me(2)] on ferrocenyl ring were synthesized, and reaction of (1) with CH₃I was carried out to obtain the monoammonium salt {[2-(Me₃N

Full text of DOI:10.1016/j.inoche.2005.09.029

Inorganic Chemistry Communications 9 (2006) 82–85
www.elsevier.com/locate/inoche
First ferrocenylstibines and their molecular structures
a,
a
b
a
a
Pankaj Sharma *, Jose G. Lopez , Carmen Ortega , Noe Rosas , Armando Cabrera ,
a
a
a
Cecilio Alvarez , Alfredo Toscano , Elizabeth Reyes
a
Instituto de Quı´mica, UNAM, Circuito Exterior, Me´xico D.F. 04510, Mexico
Departmento de Quı´mica Organica, Facultad de Quı´mica, UNAM, Circuito Exterior, Me´xico D.F. 04510, Mexico
b
Received 8 August 2005; accepted 29 September 2005
Available online 15 November 2005
Abstract
Stibines Ph2SbFc containing the pendant arm [2-(Me2NCHR)] [where R = H(1) or Me(2)] on ferrocenyl ring were synthesized, and
reaction of (1) with CH3I was carried out to obtain the monoammonium salt {[2-(Me3N+CH2)Fc]} SbPh2[I]À. All new stibines have been
characterized by various physicochemical techniques. The structures of all these 1,2-disubstituted ferrocenylstibines were determined by
X-ray diffraction analyses. This is the first report on the stibines containing disubstituted ferrocenyl group and it is worth mentioning that
even monosubstituted ferrocenylstibines are virtually unknown. Heterobimetallic stibine (1) does not show intramolecular Sb–N inter-
actions while the stibine (2) is stabilized by intramolecular Sb–N interactions.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ferrocene; Stibines; Hypervalent; Heterobimetallic; X-ray structure
1,2-Disubstituted ferrocenylphosphines are important
catalytic precursors for many different types of reaction,
e.g., hydrogenation, carbonylation and hydrosilylation
[1–3]. To best of our knowledge, few examples associated
with ferrocene bonded directly to a bismuth atom have
appeared in organobismuth chemistry [4–6], but still ferro-
cene bonded antimony is unknown. In 1984, a report
appeared mentioning the Rf value of one ferrocenylstibine,
while its synthesis and characterization data have not been
mentioned in the report [7].
Ligands with the potential for supplemental Lewis base
interactions are finding increasing utility. A noteworthy
development, in this regard, is the isolation of higher coor-
dinate main group compounds in which the customary
coordination number is expanded by virtue of an intermo-
lecular dative interaction. This interaction, which is catego-
rized as hypervalent bonding, is of interest because of the
effect it may have on the structure, chemical properties
and biological activities [8–12]. Recently, our group has
reported some new stibines containing CH(R)NMe2 (where
R = H, Me) pendant arm at the ortho position showing
these interactions [13].
Considering the vast number of ferrocene ligands and
the unique stereoelectronic properties of the ferrocene
framework and in view of the nonexistence of ferrocene
bonded antimony in the literature and our interest in
stibine ligands [13–17], some novel diphenylstibines con-
taining ferrocenyl group having pendant arm [2-
(Me2NCHR)] on ferrocenyl ring were synthesized and their
structures were determined.
The yellowish orange colored crystalline stibines 1[18]
and 2 [19] were prepared via a salt elimination reaction
of 2-lithiated (N,N-dimethylamino) methylferrocene or
(N,N-dimethylamino) ethylferrocene, respectively , with
Ph2SbCl in ether at À20 ꢁC , while the orange compound
3[20] was prepared by salt formation reaction of amine
with CH3I. It is to be noted that phosphorus analogue of
(1) reacts with one equivalent of MeI and give an unstable
N-methylated product while with an excess of MeI yields
the respective P,N-dimethylated salt [21,22], which in dif-
ferent to the case of antimony where with one or more
*
Corresponding author. Tel.: +525 55 6224556; fax: +525 55 6162217.
E-mail address: pankajsh@servidor.unam.mx (P. Sharma).
1387-7003/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2005.09.029

P. Sharma et al. / Inorganic Chemistry Communications 9 (2006) 82–85
83
equivalent of MeI, a very stable N-methylated product was
obtained.
The molecular structures of (1), (2) and (3) have been
confirmed by X-ray crystallography [23] as shown in Figs.
1–3. All these compounds are monomeric in nature and no
significant intermolecular interactions were observed. The
ammonium salt (3) crystallizes with one molecule of etha-
nol as solvent of crystallization. Further, crystallographic
structure of 3 does not show significant cation–anion inter-
actions. It is to be mentioned here that X-ray structure of
N-alkylated salt of disubstituted ferrocene is only the sec-
ond reported in the literature as molecular structure of only
All the compounds are soluble in CH2Cl2 and CHCl3.
These stibines are stable and melt without decomposition.
These compounds were analyzed by FAB+ mass spectrom-
etry. For compounds 1 and 2 molecular ion peaks were
observed along with fragments corresponding to the suc-
cessive loss of organic entities attached to antimony atom.
In the FAB+ mass spectra of compound 3, dimerization
of two stibine cations was observed but the X-ray structure
of 3 shows its monomeric nature. In the far IR spectra of
these compounds, Sb–C vibrations have been observed.
In all of the compounds the assignment of individual
protonic signals in the 1H NMR spectra was based on
JHH coupling constant values and was confirmed by COSY
and HETCOR. The chemical shifts due to the proton adja-
cent to the antimony atom in C5H3 ring of (2) appeared at
upfield region (3.79 and 3.84 ppm, respectively) compared
with those due to the other two protons in the ring. This
may be due to the ring current of the aryl groups attached
to antimony. A similar observations was made in homolo-
gous ferrocenylbismuth compounds [5,6]. All proton sig-
nals of the ammonium compound 3 appear downfield of
those of compound 1.
rac-benzyldimethyl
{2-(diphenylphosphinoferrocenyl)
methyl} ammonium bromide is known [24]. Intramolecular
interactions between the Sb atom and N atom of amine
side chain is present in stibine 2.
The average Sb–C(ferrocenyl) bond length found in these
˚
ferrocenylstibines is 2.123 A, which is slightly shorter than
that found in other known tertiary stibines. The shortest
Sb–C(ferrocenyl) bondlength is ascribable to the effect of
bidentate and electron donating. This may be due to the
pp–dp bonding to a greater extent and thus shortening of
Sb–C bond ferrocenyl group in all the compounds.
Stibine (1) and its ammonium salt (3) are pyramidal.
The average C–Sb–C angle is 97.42ꢁ and 95.62ꢁ, respec-
tively , which is slightly higher than found in PH3Sb or tris
˚
˚
Fig. 1. Molecular structure of diphenyl(N,N-dimethylaminomethylferrocenyl)stibine; Sb(1)–C(2) = 2.122(3) A, Sb(1)–C(18) = 2.141(3) A, Sb(1)–
˚
C(12) = 2.147(3) A, C(2)–Sb(1)–C(18) = 95.17(11)ꢁ, C(2)–Sb(1)–C(12) = 97.58(11)ꢁ, C(12)–Sb(1)–C(18) = 95.17(12)ꢁ.

84
P. Sharma et al. / Inorganic Chemistry Communications 9 (2006) 82–85
˚
their Van der waals radii (3.74 A) [25]. These distances
are slightly longer than the covalent bond length of
˚
2.11 A [25]. This result indicates hypervalent bond forma-
tion between antimony and nitrogen. The geometry about
antimony atom is distorted pseudotrigonal bipyramid
where the two carbon atoms bound to antimony atom
(1Ph and 1Fc) occupy the equatorial plane. The apical
positions are occupied by nitrogen atom and carbon atom
of phenyl group with an C–Sb–N angle 158.7ꢁ. The lone
pair of electrons can be considered to occupy the equatorial
˚
position. The C21–Sb bond [2.162(2) A] trans to the nitro-
gen atom is slightly longer than the other Sb–C bonds,
˚
2.142(2) A. A similar structure and lengthening of one of
the Sb–C bond length were reported earlier in similar com-
pounds Tol2Sb[2-(Me2NCH2)C6H4] and Tol2 Sb{1-[8-
(Me2NCH2)C10H6]} [7]. This tendency, also observed in
these stibines, is considered to be the hypervalent effect
on the central antimony. The two phenyl groups in stibine
1 and 2 are at an angle of 68.1ꢁ and 68.9ꢁ, respectively, to
each other.
In conclusion, the paper presents the first well-charac-
terized ferrocenylstibines and their crystal structures.
The existence of strong interactions between antimony
and nitrogen, transcending the octet theory, and classified
as the hypervalent bonding, was shown not only in tri
aryl stibines but also in ferrocenylstibines. This hyperva-
lent Sb–N bonding was demonstrated by single crystal
X-ray analysis. The synthesis of other triferrocenylstibines
and their platinum and palladium complexes are in
progress.
Fig. 2. Molecular structure of diphenyl(N,N-dimethylaminoethylferroce-
nyl)stibine; Sb(1)–C(6) = 2.124(2) A, Sb(1)–C(15) = 2.142(2) A, Sb(1)–
˚
˚
˚
˚
C(21) = 2.162(2) A,
Sb(1)–N(1) = 3.042(2) A,
C(6)–Sb(1)–C(15) =
96.76(9)ꢁ, C(6)–Sb(1)–C(21) = 94.97(9)ꢁ, C(15)–Sb(1)–C(21) = 96.12(9)ꢁ,
C(6)–Sb(1)–N(1) = 66.32(7)ꢁ.
(2-thienyl)stibine. In stibine 2, a distance between nitrogen
atom of NMe2 group and the central antimony atom is
˚
3.041(2) A, which is much shorter (80%) than the sum of
˚
˚
Fig. 3. Molecular structure of diphenyl[(N,N-trimethylammoniomethylferrocenyl)iodide]stibine Sb(1)–C(2) = 2.123(4) A, Sb(1)–C(15) = 2.141(4) A,
˚
Sb(1)–C(21) = 2.160(4) A, C(2)–Sb(1)–C(15) = 96.17(15)ꢁ, C(2)–Sb(1)–C(21) = 94.78(14)ꢁ, C(15)–Sb(1)–C(21) = 95.93(16)ꢁ.

P. Sharma et al. / Inorganic Chemistry Communications 9 (2006) 82–85
85
74.0 (C–Sb, C5H3), 91.12 (C, C5H3), 127.91 (C, Ph), 128.28 (C, Ph),
135.93 (C, Ph), 136.81 (C–Sb).
Acknowledgment
[19] Compound 2 was synthesized as compound 1, Fc(Me)NLi was used
in place of FcNLi. Yield 55%; m.p.: 60–61 ꢁC; IR (m cmÀ1): 453 (Sb–
C), 3060 (C–H aromatic) FAB+ (m/z): 531(100%) [M]+, 502(6%)
[M À Me2]+, 487 (62%) [M À NMe2]+, 454 (28%) [M À Ph]+ 410
Authors are thankful to DGAPA UNAM for financing
the project IN 210905.
(16%) [M À Ph À NMe2]+, 275(14%) [SbPh2]+
,
257(13%)
References
[FcCHMeNMe2]+
;
1H NMR (CDCl3, d ppm) 1.15 (d, 3H, CH3),
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1.73 (s, 6H, NMe2), 3.84 (q, 1H, CH), 4.00 (s, 5H, C5H5), 4.12 (t, 1H,
C5H3), 4.20 (m, 1H, C5H3), 4.30 (m, 1H, C5H3), 7.23–7.58 (m, 10H,
Ph); 13C NMR (CDCl3, ppm) : 7.50 (Me), 38.66 (NMe2), 59.30 (CH),
68.89 (C, C5H5), 68.99 (CH, C5H3), 69.31 (CH, C5H3), 72.06 (CH,
C5H3), 74.68 (C–Sb, C5H3), 96.04 (C, C5H3), 127.84 (C, Ph), 128.09
(C, Ph), 128.17 (C, Ph), 136.57 ( C–Sb).
[20] In a schlenk tube, to a solution of stibine 1 (1.9 mmol) in CH2Cl2
(20 ml), was added CH3I (8.03 mmol) with continuous stirring. The
reaction was stirred for 24 h and the solution was concentrated under
vacuum to obtain a orange product which was isolated by filtration.
The compound was recrystallized from ethanol. Yield: 93%; m.p.:
120 ꢁC; IR (m cmÀ1): 462 (Sb–C), 3058 (C–H aromatic); FAB+ m/z :
1064(6%) [2M]+, 946(16%) [2M À 2NMe3]+, 532(95%) [M]+, 473
(36%) [M À NMe3]+, 454 (21%) [M À Ph]+, 397 (29%)
[M À Ph À NMe2]+, 275 (31%) [SbPh2]+ ; 242(12%) [FcCH2NMe2]+;
1H NMR (CDCl3, d ppm) 3.12 (s, 9H, NMe3), 4.05(d2 JHH, 12.5 Hz,
1H, CH2), 4.30 (d2 JHH, 12.4 Hz, 1H, CH2), 4.58 (m, 1H, C5H3), 4.20
(s, 5H, C5H5), 5.05 (t, 1H, C5H3), 5.53 (m, 1H, C5H3), 7.29–7.56 (m,
10H, Ph); 13C NMR (CDCl3, ppm) 52.87 (NMe3), 68.08 (CH2), 70.40
(C, C5H5), 74.29 (CH, C5H3), 76.02 (CH, C5H3), 76.98 (CH, C5H3),
78.28 (C–Sb C5H3), 93.28 (C, C5H3) 128.92 (C, Ph), 129.35 (C, Ph),
135.79 (C,Ph), 136.57 (C–Sb).
[13] P. Sharma, D.A. Castillo, N. Rosas, A. Cabrera, E. Gomez, A.
Toscano, F. Lara, S. Hernandez, G. Espinosa, J. Organomet. Chem.
689 (2004) 2583.
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Cabrera, J. Mol. Catal. 170 (2001) 271.
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R.M. Gomez, S. Hernandez, Z. Anorg. Allg. Chem. 626 (2000) 2330.
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L. Velasco, J. Perez, R. Guiterrez, J. Organomet. Chem. 690 (2005)
3286.
[22] B.W. Rockett, G. Marr, J. Organomet. Chem. 416 (1991) 327.
[23] Crystal data. Compound 1: crystal dimensions 0.368 · 0.178 ·
0.034 mm3, empirical formula = C25H26FeNSb, Fw = 518.07, triclinic,
ꢀ
space group P1, a = 7.7115(4), b = 10.3465(5), c = 14.6537(7),
3
˚
a = 70.184(1), b = 82.810(1), c = 83.632(1),V = 1088.35(9) A , Z = 2,
[17] J. Vela, P. Sharma, A. Cabrera, C. Alvarez, N. Rosas, S. Hernandez,
A. Toscano, J. Organomet. Chem. 634 (2001) 5.
Dc = 1.581 mg/m3, l = 1.917, F(000) = 520, independent reflec-
tions = 7761, R[I>2r(I)] = 0.0456. D/r = 1.123/À0.379 e AÀ3, GOF =
˚
[18] In a Schlenk tube a solution of Ph2SbCl (1.0 mmol) in anhydrous
THF (10 ml) was added dropwise under a nitrogen atmosphere to 2-
FcNLi (1.1 mmol) which was synthesized in situ according to
reported method [26] at À20 ꢁC with continuous stirring. The mixture
was further stirred for 24 h at room temperature (r.t.) and then
reaction was quenched with ice. After extraction with dichlorometh-
ane (3 · 10 ml) and drying over sodium sulfate, solvent was removed
under vacuum. Slow concentration from chloroform solution gives
the orange crystalline compound. Yield: 60%; m.p.: 90–91 ꢁC; IR
(m cmÀ1): 458 (Sb–C), 3057 (C–H aromatic) FAB+ m/z 517 (95%)
[M]+, 473(36%) [M À NMe2]+, 440 (17%) [M À Ph]+, 397 (29%)
[M À Ph À NMe2]+, 275(9%) [SbPh2]+, 242(18%) [FcCH2NMe2]+; 1H
NMR (CDCl3, d ppm) 1.91 (s, 6H, NMe2), 3.03 (d2 JHH, 12.7 Hz, 1H,
CH2), 3.66 (d2 JHH, 12.9 Hz, 1H, CH2), 3.79 (m, 1H, C5H3), 3.98 (s,
5H, C5H5), 4.20 (t, 1H, C5H3), 4.31 (m, 1H, C5H3), 7.19–7.59 (m,
10H, Ph); 13C NMR (CDCl3, ppm) 44.78 (NMe2), 59.91 (CH2), 69.28
(C, C5H5), 69.97 (CH, C5H3), 71.96 (CH, C5H3), 72.48 (CH, C5H3),
0.999. CCDC No. = 280195; Compound 2: crystal dimensions
0.346 · 0.322 · 0.142 mm3,
empirical
formula = C26H28FeNSb,
ꢀ
Fw = 532.09, triclinic, space group P1, a = 8.0351(4), b = 10.8605(6),
c = 13.7936(8), a = 74.648(1), b = 89.276(1), c = 81.366(1) V =
3
1147.0(1) A , Z = 2, Dc = 1.541 mg/m3, l = 1.917, F(000) = 536,
˚
independent reflections = 8168, R[I>2r(I)] = 0.0445, D/r = 1.000/
À0.507 e AÀ3, GOF = 0.990. CCDC No. = 280196; Compound 3:
˚
crystal dimensions 0.214 · 0.192 · 0.078 mm3, empirical formula =
C
28H35FeINOSb, Fw = 706.07, monoclinic, space group P21/n, a =
15.3782(8), b = 13.2581(7),c = 15.7316(8), a = 90, b = 118.975(1),
3
c = 90, V = 2806.0(3) A , Z = 4, Dc = 1.671 mg/m3, l = 2.600,
˚
F(000) = 1392, independent reflections = 10163, R[I>2r(I)] = 0.0456.
D/r = 1.612/À0.733 e AÀ3, GOF = 1.009, CCDC No. = 280197.
˚
[24] P. Stepnicka, I. Cisarova, Organometallics 22 (2003) 1728.
[25] J. Emsley, The Elements, third ed., Clarendon, Oxford, 1998.
[26] D. Marquarding, H. Klusacek, G. Gokel, P. Hoffmann, I. Ugi, J. Am.
Chem. Soc. 92 (1970) 5389.