Heterocyclic systems containing antimony (III) -VIII . Hypervalency by intramolecular 1,5-chelation Sb · · · N in rings RSb [ (CH2) 3] 2NR′ (NR′ = NMe, NBz, NBui) and comparison to analogous compounds of AsIII, BiIII, GeIV and SnIV

Article abstract of DOI:10.1016/S0277-5387(98)00024-2

Eleven antimony compounds RSb [ (CH₂) ₃] ₂ NR′ and eight germanium compounds R₂Ge [ (CH₂) ₃] ₂ NR′ (some combinations of R = Cl, I, NCS, OSiPh₃, Ph, and NR′ = NMe, NBz, NBuⁱ) have been synthesized by diGrignard reactions and subsequent treatment with AgSCN, Ph₃SiONa or PhLi. The compounds were compared to 14 Sn, 1 As, 5 Sb and 4 Bi analogues taken from the literature. Evidence is provided for 1,5-chelation Sb · · · N via crystal structure determinations (5+1 (lit) Sb compounds) , ¹³C- and ²⁹Si-NMR chemical shifts, ¹²;Sb and ¹²;I Moessbauer data (11 and 3 Sb compounds, respectively) , cyclic voltammetry (9 Sb compounds) and semi-empirical MO calculations on the Extended Hueckel level (8 present compounds and 4 models) . The ligand sequence (Cl < I < NCS) holds for an increasing approach N · · · Sb. The effect of electronegativity and the effect of n- or π → σ* charge transfer into the LUMO at Sb are counteractive. The intramolecular donor strength increases in the following order : NBuⁱ < NBz < NMe. Simultaneously a decrease of the absolute value of the ¹²;Sb quadrupole coupling constant from Moessbauer spectroscopy occurs. The postulation of a control of the Sb · · · N chelation by frontier orbital interactions is supported by the CV results in CH₂Cl₂ at a AuHg electrode. It is proved by scan rate dependence that the observed reversible reductionoxidation process is diffusion controlled, and by coulometry that the reduction takes place by transfer of one electron.

Full text of DOI:10.1016/S0277-5387(98)00024-2

Polyhedron Vol[ 06\ No[ 05\ pp[ 1544Ð1557\ 0887
Þ 0887 Elsevier Science Ltd
Pergamon
All rights reserved[ Printed in Great Britain
9166Ð4276:87 ,08[99¦9[99
\
PII ] S9166Ð4276"87#99913Ð1
Heterocyclic systems containing antimony
"III#!VIII ð0Ł[ Hypervalency by intramolecular
0\4!chelation Sb = = = N in rings RSbð"CH1#2Ł1NR?
"NR? ꢀ NMe\ NBz\ NBui# and comparison to
analogous compounds of AsIII\ BiIII\ GeIV and
SnIV
Elmar Brau\a Andrea Zickgraf\a Martin Drager\aꢀ Enrico Mocellin\bꢀ
Ã
Ã
Masaki Maeda\c Masashi Takahashi\c Masuo Takedacꢀ and Carlo Meallid
a Institut fur Anorganische Chemie und Analytische Chemie der Johannes Gutenberg!Universitat\
Ã
Ã
D!44988 Mainz\ Germany
b School of Biological and Chemical Sciences\ Faculty of Science and Technology\ Deakin University\
Geelong Victoria 2106\ Australia
c Department of Chemistry\ Faculty of Science\ Toho University\ Funabashi\ Chiba 163\ Japan
d Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione\ C[N[R[\
I!49021 Firenze\ Italia
"Received ] 06 November 0886 ^ accepted 5 January 0887#
Abstract*Eleven antimony compounds RSbð"CH1#2Ł1 NR? and eight germanium compounds R1Geð"CH1#2Ł1
NR? "some combinations of R ꢁ Cl\ I\ NCS\ OSiPh2\ Ph\ and NR? ꢁ NMe\ NBz\ NBui# have been synthesized
by diGrignard reactions and subsequent treatment with AgSCN\ Ph2SiONa or PhLi[ The compounds were
compared to 03 Sn\ 0 As\ 4 Sb and 3 Bi analogues taken from the literature[ Evidence is provided for 0\4!
chelation Sb = = = N via crystal structure determinations "4¦0 "lit# Sb compounds#\ 02C! and 18Si!NMR chemical
shifts\ 010Sb and 016I Mossbauer data "00 and 2 Sb compounds\ respectively#\ cyclic voltammetry "8 Sb
Ã
compounds# and semi!empirical MO calculations on the Extended Huckel level "7 present compounds and
Ã
3 models#[ The ligand sequence "Cl ³ I ³ NCS# holds for an increasing approach N = = = Sb[ The e}ect of
electronegativity and the e}ect of n! or p : sꢀ charge transfer into the LUMO at Sb are counteractive[ The
intramolecular donor strength increases in the following order ] NBui ³ NBz ³ NMe[ Simultaneously a
decrease of the absolute value of the 010Sb quadrupole coupling constant from MoÃssbauer spectroscopy occurs[
The postulation of a control of the Sb = = = N chelation by frontier orbital interactions is supported by the CV
results in CH1Cl1 at a Au:Hg electrode[ It is proved by scan rate dependence that the observed reversible
reduction:oxidation process is di}usion controlled\ and by coulometry that the reduction takes place by
transfer of one electron[ Þ 0887 Elsevier Science Ltd[ All rights reserved
Keywords] antimony ^ hypervalency ^ frontier orbitals ^ MoÃssbauer spectroscopy ^ cyclic voltammetry ^ coul!
ometry ^ NMR[
———————————————————————————————————————————————
Recently we have created a novel view about the bond! systematic experimental investigations in some series
ing scheme of the long!known phenomenon of hyp! of heterocycles which contained a potential intra!
ervalency at tin"IV# ð1Ł[ This view arose from molecular donor and the axial:equatorial ligands Cl\
Br\ I and Me ð1Ł[ The sequences of interaction
ꢀ Authors to whom correspondence should be addressed[
"donor# = = = Sn showed that\ with regard to the ligands
1544

1545
E[ Brau et al[
Ã
Scheme 0[ Short notation for a compound] number"door:ligands#^ e[g[ 0 "NMe:Cl1# for the _rst compound[
NMe
NBz NBui
NMe
NBz
NBui
NMe NMe
NBz
Clc
NBui
Clc
NMe NBz
d
e
e
c
Cl1
ClPh
"OSiPh2#1
Cl1
Cl1
Cl1
Cl1
Cl1
Cl1
Clc
Brc
I
Clc
Ic
Clc
Ic
ClPh
ClPhe
ClPhe
ClPhe
e
e
e
"OSiPh2#1
"OSiPh2#1
"OSiPh2#1
I
I
e
e
e
Ph1
Ph1
Ph1
NCS
NCS
NCS
"OSiPh2#Phe "OSiPh2#Phe
OSiPh2 OSiPh2 OSiPh2
Ph Ph
aIn addition data for 0 "O:Cl1# and 0 "S:Cl1# are given[
bIn addition data for 3 "S:Cl# are given[
cSee Ref[ ð5aŁ[
dSee Ref[ ð4Ł[
eSee Ref[ ð5bŁ[
at Sn\ their electronegativity and a n : sꢀ charge Molecular structures
transfer into the LUMO at SnIV are counteractive[
The geometric impetus for this view came from the
Five structure determinations have been carried out
method of structure correlation of Burgi and Dunitz in this paper ^ the data for the compound 3 "NMe:Cl#
Ã
ð2aŁ and from papers of van Koten ð2bŁ\ whereas the were taken from Ref[ ð5aŁ[ Bond distances at antimony
theoretical portions build on papers of Musher ð2cŁ and axial and equatorial bond angles are given in
and of Noyori ð2dŁ[
Table 0[ The cores of all six molecular structures are
In this work our ideas shall be extended to anti! similar[ Figures 0 and 1 show exemplarily plots of the
mony"III# as a central atom\ and the question of the compounds 3 "NMe:NCS# and 3 "NBui:I#[
in~uence of the lone pair of electrons in a c!trigonal
In order to get an idea about the goodness of the
bipyramidal geometry arises ð3Ł[ We synthesized a c!trigonal bipyramidal geometry around antimony\
series of compounds 3 with SbIII and\ in addition\ the angle di}erences have been included in Table 0[ Dis!
compounds 0 with GeIV as a central atom "Scheme 0# tances between atoms of di}erent kinds were trans!
ð4Ð6Ł[ Structural\ spectroscopic and electrochemical formed into Pauling bond orders BO ð7Ł in order to
data and semi!empirical MO calculations for these obtain comparability[ All six structures have similar
compounds will be compared to the analogous data conformations\ and no short intermolecular contacts
of the rings 1\ 2 and 4\ which contain SnIV ð5bŁ\ AsIII disturb the distances given in Table 0[
ð5aŁ and BiIII ð5aŁ as central atoms "Scheme 0#[
Spectroscopic data
RESULTS
Table 1 contains the 02C NMR chemical shifts of
Synthetic aspects
the a!CH1 groups in equatorial position at Ge\ Sn
ð5bŁ\ As ð5aŁ\ Sb\ or Bi ð5aŁ for all compounds of
The Cl1\ ClPh\ Cl and I substituted heterocycles 0 Scheme 0[ In addition\ the 18Si NMR chemical shifts
and 3 were obtained by reaction of the diGrignard of the OSiPh2 groups are given[ A full set of the 02C
reagent R?Nð"CH1#2MgClŁ1 with GeCl3 ð1dŁ\ PhGeCl2\ NMR chemical shifts of the compounds 0 and 3 has
SbCl2 or SbI2[ To obtain the NCS substituted com! been deposited with the Editor as supplementary
pounds\ R?Nð"CH1#2Ł1SbI was reacted with AgSCN in material[
CH1Cl1[ The heterocycles substituted with "OSiPh2#
Table 2 contains the 010Sb and 016I MoÃssbauer par!
or Ph have been obtained from those with Cl1 or Cl ameters of the compounds 3[ Figure 2 gives exemp!
substitution by reaction with Ph2SiONa in toluene or larily the 010Sb Mossbauer spectra of the compounds
Ã
with PhLi in n!hexane[
3 "NMe:Cl\Br\I#[ The asymmetric shape of the

Heterocyclic systems containing antimony "III#!VIII
1546
Table 0[ Distances d and Pauling bond orders BOa\ axial and equatorial bond angles u"ax# and u"eq#b and di}erence of the
angles Duc for the heterocycles 3d "e[s[d[s in parentheses#
Sb = = = N
d"_#
Sb0R"ax#
u"ax#
">#
u"eq#
">#
Du
">#
Compound
BO
d"_#
BO
3 "NMe:Cl#e
3 "NMe:I#
1[268"3#
1[238"3#
1[213"03# 9[42"1#
1[394"4#
1[280"6#
1[319"4#
9[335"5#
9[383"8#
1[530"0#
1[884"0#
1[14"1#
1[505"1#
1[871"0#
1[883"0#
9[346"1#
9[312"1#
9[57"6#
9[385"3#
9[330"1#
9[313"0#
77[7"0#\89[3"0#
75[9"0#\89[5"1#
74[6"5#\74[6"5#
78[2"1#\82[4"1#
76[7"2#\80[2"1#
77[2"1#\78[5"1#
099[2"1# 09[6
090[7"1# 02[4
091[9"7# 05[2
3 "NMe:NCS#f
3 "NBz:Cl#
3 "NBz:I#
9[301"7#
9[32"0#
9[282"8#
87[3"1#
88[0"3#
6[9
8[5
3 "NBui:I#
090[1"2# 01[2
aSee Ref[ ð7Ł[
b1 angles u"ax#] R"ax#0Sb0CH1^ 0 angle u"eq#] CH10Sb0CH1[
cDu ꢁ u"eq#−"Su"ax##:1^ Du ꢁ 9> for a perfect c!tetrahedron^ Du ꢁ 29> for a perfect c!trigonal bipyramid^ cf the related
Su as a parameter for the goodness of a trigonal bipyramid ð1a\bŁ[
dDistance d"Sb0C# ꢁ 1[03−1[12 _^ conformations of the eight!membered rings] 4×boat!chair\ 0×chair!chair "com!
pound 3 "NMe:NCS##^ no intermolecular distances shorter than 3[4 _[
eSee Ref[ ð5aŁ[
fA disorder in the eight!membered ring and at the nitrogen atom of NCS "see Experimental# results in large e[s[d[s[
Fig[ 1[ Ortep plot of the compound 3 "NBui:I#^ thermal
ellipsoids are at the 39) probability level[ Hydrogen atoms
are omitted for better clarity[
Extended Huckel calculations
Ã
Fig[ 0[ Ortep plot of the compound 3 "NMe:NCS#^ thermal
ellipsoids are at the 39) probability level[ Partial disorder
at C"1# and at N"1# "see Experimental#[ Hydrogen atoms are
omitted for better clarity[ The perfect Cs plane is outlined[
To support the bonding scheme of hypervalency
which had been introduced in Ref[ ð1Ł\ semi!empirical
MO calculations on the Extended Huckel level have
Ã
been performed for the six compounds 3 whose
geometry is known from the crystal structure analyses
ð02a\03Ł[ Figure 3 shows in graphical form the ener!
getical sequence of the MO|s for the compound 3
"NMe:Cl# and the distribution of three _lled and one
absorption peaks shows that the sign of the qua! empty orbital over the atoms of the molecule[ Table
drupole coupling constant "e1qQ# is obviously nega! 3 summarizes some typical results and contains also
tive ð01bŁ[
results for the compounds 0 "NBui:Cl1# and 1 "NBui:

1547
E[ Brau et al[
Ã
Table 1[ 02C NMR chemical shifts of the a!CH1 group at Ge\ Sn\ As\ Sb or Bi and 18Si NMR
chemical shifts of the 0OSiPh2 ligand "ambient temperature\ CDCl2 solution#
Compound
d"02C# "ppm#
Compound
d"02C# "ppm#
0 "NMe:Cl1#
17[1
17[9
11[3
00[0
00[9
03[9
20[8
23[6
11[2
11[1
11[9
03[4
03[9
02[7
05[8
05[8
05[5
7[6
1 "NBz:"OSiPh2#Ph#e
2 "NMe:Cl#
3 "NMe:Cl#
3 "NBz:Cl#
00[5
23[5
14[8
15[9
15[0
14[3
12[5
11[3
12[2
12[9
12[7
13[5
14[9
13[3
13[1
03[7
03[7
15[6
35[5
36[1
39[8
28[5
0 "NBz:Cl1#
0 "NBui:Cl1#
0 "NMe:ClPh#
0 "NBz:ClPh#
0 "NMe:"OSiPh2#1#
0 "O:Cl1#
0 "S:Cl1#
1 "NMe:Cl1#
3 "NBui:Cl#
3 "NMe:Br#
3 "NMe:I#
3 "NBz:I#
3 "NBui:I#
1 "NBz:Cl1#
3 "NMe:NCS#a
3 "NBz:NCS#a
3 "NBui:NCS#a
3 "NMe:OSiPh2#
3 "NBz:OSiPh2#
3 "NBui:OSiPh2#
3 "NBz:Ph#
1 "NBui:Cl1#
1 "NMe:ClPh#
1 "NBz:ClPh#
1 "NBui:ClPh#
1 "NMe:"OSiPh2#1#
1 "NBz:"OSiPh2#1#
1 "NBui:"OSiPh2#1#
1 "NMe:Ph1#
1 "NBz:Ph1#
3 "NBui:Ph#
3 "S:Cl#
4 "NMe:Cl#
4 "NBz:Cl#
7[2
7[0
01[0
1 "NBui:Ph1#
1 "NMe:"OSiPh2#Ph#e
4 "NMe:I#
4 "NBz:I#f
Compound
d"18Si#b"ppm#
Compound
d"18Si#b"ppm#
0 "NMe:"OSiPh2#1#
1 "NMe:"OSiPh2#1#
−10[68c
1 "O:"OSiPh2#1#
−10[79d
−15[13
−14[87
−13[39
−12[67
−13[10
ax −13[50
eq −08[55
ax −13[18
eq −08[40
ax −13[48
eq −08[31
1 "NMe:"OSiPh2#Ph#e
1 "NBz:"OSiPh2#Ph#e
3 "NMe:"OSiPh2#
3 "NBz:"OSiPh2#
3 "NBui:"OSiPh2#
1 "NBz:"OSiPh2#1#
1 "NBui:"OSiPh2#1#
ad"02C# for NCS] 3 "NMe:NCS# 023[6\ 3 "NBz:NCS# 022[0\ 3 "NBui:NCS# 025[7 ppm[
bd"18Si# for the compound O"SiPh2#1 −07[34 ppm[ cOne sharp signal[ dOne broad signal[ eSee
Ref[ ð09Ł[ fSee Ref[ ð00Ł[
Cl1# ð5cŁ with Ge and Sn as central atoms ð02a\03Ł[ electron transfer from the reference electrode into the
In addition\ Table 3 gives the results for the four LUMO# were found[ The results are summarized in
hypothetical molecules Cl1Ge:SnBun and ClAs:
Table 4\ and two examples of the cyclic vol!
tammograms obtained are shown in Fig[ 4[
1
SbBun1\ for which a perfect tetrahedral:c!tetrahedral
With regard to the initial anodic sweep direction\
all nine investigated Sb compounds show an oxidative
peak Eox between ¦9[44 and ¦0[14 V[ The peaks
are generally small and broad[ After inversion of the
applied potential at ¦0[4 V\ a decomposition of the
compounds occurs in most cases[ Only for 3 "NBz:I#
"Fig[ 4a# and for 3 "NBui:I# a quasi!reversible
reduction peak Ered was found[
With regard to the initial cathodic sweep direction\
three of the investigated Sb compounds "3 "NBui:Cl#\
3 "NBz:I# "borderline case\ see footnote d of Table 4#
and 3 "NMe:OSiPh2## decompose immediately under
the in~uence of the reductive potential[ The six other
investigated compounds result in reversible cyclic vol!
geometry had been optimized by means of a force!
_eld calculation prior to the Extended Huckel calcu!
Ã
lation ð02b\03Ł[
Cyclic voltammetry in CH1Cl1 solution
To get an experimental support of the calculated
2
HOMO "lone pair s# and LUMO "2!center sꢀ# of
Fig[ 3\ cyclic voltammetric experiments with nine from
the sixteen available Sb compounds 3 have been per!
formed ð04Ł[ After considerable optimization the pro!
per conditions for reproducible results in both initial
sweep directions "oxidative electron transfer from the
HOMO into the reference electrode and reductive tammograms with Ered−Eox between 9[09 and 9[03

Heterocyclic systems containing antimony "III#!VIII
1548
Table 2[ 010Sb and 016I Mossbauer data "isomer shifts da "mm s−0#\ quadrupole
Ã
coupling constants e1qQ "mm s−0#\ asymmetry parameters h\ and half widths G
"mm s−0#\ and for 016I outer electron con_gurations "electrons# and charges Z"I#
"electrons# from a Townes!Dailey treatmentb
010Sb
Compound
da
e1qQ
h
G
3 "NMe:Cl#
3 "NBz:Cl#
3 "NBui:Cl#c
3 "NMe:Br#
3 "NMe:I#
−1[64
−1[39
−1[16
−1[34
−1[27
−1[38
−1[34
−1[13
−1[20
−1[11
−1[74
−17[1
−17[3
−20[9
−17[5
−15[8
−16[7
−18[8
−29[6
−20[0
−20[5
−16[5
9[54
9[55
9[14
9[46
9[63
9[55
9[36
9[55
9[46
9[47
9[53
1[48
1[42
1[35
1[40
1[50
1[54
1[74
1[34
1[30
1[22
1[48
3 "NBz:I#
3 "NBui:I#
3 "NMe:NCS#
3 "NBz:NCS#
3 "NBui:NCS#
3 "S:Cl#
016Id
Compound
da
e1qQe
−01[0
−01[7
−01[4
G
Z"I#
3 "NMe:I#
4s:4px:4py:4pz
3 "NBz:I#
−9[02
−9[96
−9[02
1[75
−9[65
−9[61
−9[64
1[99:1[99:1[99:0[65
1[53
0[87:1[99:1[99:0[63
1[48
4s:4px:4py:4pz
3 "NBui:I#
4s:4px:4py:4pz
1[99:1[99:1[99:0[64
aRelative to InSb and KI\ both at 19K[ bSee Ref[ ð01aŁ[ cPoor _t of the spectrum^
the spectrum for a synthetically di}erent batch was not better[ dh _xed to 9[9[
e0 mm s−0 corresponds to 35[35 MHz[
V "Fig[ 4b#[ The voltammograms are comparable to
those of the used standard ferrocene " Ered
DISCUSSION
−
Eox ꢁ 9[02 V#[ The solution di}usion control of the Investi`ation in the solid
process was established by measuring the peak cur!
rents for both reduction "ic# and oxidation "ia# for 3
The X!ray data of Table 0 demonstrate the order
"NMe:I# and 3 "NMe:NCS# and plotting ic and ia "0# for the intramolecular nucleophilic attack of the
against the square root of the scan rate over three donor R?N at the s!Lewis acidic Sb on a path to a
decades of speed "09Ð0999 mV s−0# and using fer! four!electron three!center interaction R?N = = = Sb0
rocene as a standard ð04aŁ[
R"ax#[
d"R?N ===SbCl# × d"R?N = = = SbI#
× d"R?N = = = SbNCS# "0#
Bulk electrolysis in CH1Cl1 solution
Geometrically\ a continuous change from a c!tetra!
To ascertain the number of electrons involved in hedral three!coordination to a c!trigonal!bipyramidal
the reversible redox process\ controlled potential elec! four!coordination occurs[ The order "0# is not gov!
trolysis "coulometry# ð05bŁ was performed for the erned by the electronegativity of the ligands R "in~u!
compound 3 "NMe:I#[ The results are given in Table ence of the HOMO#[ An enhanced n : sꢀ or p : sꢀ
5[ After extensive optimization of the experimental charge transfer from R"ax# into the LUMO of the p!
conditions "applied potential\ cooling# it was con! acidic Sb promotes the path ð1Ł[ With regard to the
cluded de_nitely that the process is a one!electron! HOMOs\ the negative sign of the 010Sb coupling con!
transfer[
stant e1qQ "Table 2# suggests a larger population of

1559
E[ Brau et al[
Ã
Fig[ 2[ 010Sb Mossbauer spectra of the three compounds 3 "NMe:Cl\Br\I# at 19 K[
Ã
Fig[ 3[ Sequence of the Mo|s for compound 3 "NMe:Cl# and CACAO!graphs ð02a\03Ł[

Heterocyclic systems containing antimony "III#!VIII
1550
Table 3[ LUMO and HOMO energies of 0\ 1\ and 3 "geometry of the crystal structure determinations#a and
for the compounds Cl1MBun1 "M ꢁ Ge\ Sn# and ClMBun1 "M ꢁ As\ Sb# "tetrahedral:c!tetrahedral geometry#b
HOMOs "eV#
isolated
HOMOs "eV#
at lower energy
Compound
LUMO "eV#
0 "NBui:Cl1#c
1 "NBui:Cl1#c
3 "NMe:Cl#
3 "NMe:I#
3 "NMe:NCS#
3 "NBz:Cl#
3 "NBz:I#
−9[745
−9[744
−1[348
−3[497
−1[228d
−3[328d
−3[486d
−3[758
9[429
−01[992
−01[009
−00[417
−00[433
−00[445
−00[278
−00[364
−00[450
−01[959
−01[989
−00[465
−00[325
−01[258
³−02[0
³−02[9
³−02[4
³−02[2
³−02[1
³−02[9
³−01[5
³−02[1
−01[150
−01[475
−01[266
−01[122
−01[184
−01[108
−01[116
−02[971
−01[471
−01[509
−01[583
−01[456
−01[463
−01[853
−01[678
−01[737
3 "NBui:I#
Cl1GeBun1
Cl1SnBun1
9[451
−9[180
−0[269
ClAsBun1
ClSbBun1
a See Ref[ ð02 a\ 03Ł[ b See Ref[ ð02b\ 03Ł[ c See Ref[ ð5cŁ[ d Coe.cients at Sb ^ additional LUMOs at NCS
"−5[49 and −5[43 eV ] pꢀ "NCS## and at benzyl "−7[96 and −7[19\ −7[03 and −7[03 eV ] pꢀ "phenyl##[
Table 4[ Cyclic voltammetric peak potentials Eox and Ered\ DE and current ratios ia:ic vs[ a Ag:AgCl
reference electrodea in CH1Cl1 solution for the compounds 3 "2Ð7 mg:4 ml CH1Cl1# and for ferrocene as a
controlling standard
Compound
Eox "V#
Ered "V#
Eox "V#
DE "V#
ia:ic
initial oxidative sweep directionb
ferrocene
9[39
9[47
9[44
9[16
9[25
9[25
9[02
9[11
9[08
9[81
0[08
9[72
3 "NBz:I#
3 "NBui:I#
initial reductive sweep directionc
3 "NMe:Cl#
−0[10
−0[02
"−0[10
−0[00
−0[06
−0[98
−0[03
−0[00
−0[92
−0[99
−9[87
−0[94
−9[84
−0[99
9[09
9[09
9[10
9[02
9[01
9[03
9[03
9[78
9[87
0[07#
0[03
9[77
9[87
0[95
3 "NMe:I#
3 "NBz:I#d
3 "NBui:I#
3 "NMe:NCS#
3 "NBz:NCS#
3 "NBui:NCS#
a Counter electrode Pt ^ scan rate 099 mV s−0 ^ evaluation of the voltammograms according to Ref[ ð05aŁ[
b Working electrode Pt ^ sweep range 9[9 to ¦0[4 to −0[4 to 9[9 V[
c Working electrode Au:Hg ^ sweep range −9[1 to −0[6 "or −1[9# to −9[1 V[
d Scan rate 299 mV s−0\ at lower scan rates immediate decomposition ^ result not fully reproducible[
the antimony 4p electrons in the equatorial plane "5 ultaneous increase in the electron density of the axial
electrons# compared to those in the axial direction three!center interaction R?N = = = Sb0R"ax#[
" ³ 3 electrons#[
In Fig[ 5 the bond orders of the ligands at antimony
BO"Sb0R"ax## are plotted versus BO"Sb = = = N# for
the _ve halide substituted cases[ The familiar struc!
tural trans in~uence "shorter N = = = Sb and longer
Sb0R"ax## is valid for pairs of identical donor groups
"NBz and NMe#[ It inverts or becomes zero at an
interchange of the donor groups "NBui into NBz\
NBz into NMe ^ compounds 3 "NBui:I# : 3 "NBz:I# ]
d"Sb = = = N# 1[319 "4# : 1[280 "6# _ and d"Sb!I# 1[883
With regard to the donor group R?N\ Table 0 dem!
onstrates the order "1# of increasing interaction\ i[e[
increasing s!donor strength[
d"BuiN = = = SbI# × d"BzN = = = SbI# × d"MeN = = = SbI#
"1#
The absolute value e1qQ of 010Sb "Table 2# decreases
for all three investigated ligands\ Cl\ I and NCS\ ident! "0# : 1[871 "0# _ ^ for similar results in three series of
ically to order "1#[ This decrease suggests a sim! tin compounds and in one series of silicon compounds

1551
E[ Brau et al[
Ã
Fig[ 4[ Cyclic voltammograms of the compound 3 "NBz:I# a# "oxidative sweep direction\ Pt electrode# and 3 "NMe:I# b#
"reductive sweep direction\ Au:Hg electrode#[
Table 5[ Controlled potential electrolysis of 3 "NMe:I# "29Ð39 mg:59
ml CH1Cl1# at −09>C
Reductive
No[ of
electrons
Reductive
No[ of
electrons
potentiala "mV#
potentiala "mV#
−0159
−0169
−0179
−0189
−0219
9[33
9[76
9[61
9[62
0[99
−0239
−0269
−0499
−0699
b
b
b\c
b\c
a Ag:AgCl reference electrode di}erent from that used in Table 4 ]
CV peaks "scan rate 099 mV s−0# for ferrocene Eox:Ered ¦257:¦089
mV\ for 3"NMe:I# Ered:Eox −0298:−0011 mV[
b Decomposition into colorless\ insoluble Sb"III# material ^ without
cooling\ elementary antimony precipitates[
c Amalgamation of the precipitated elementary antimony with the
mercury pool cathode[
see Ref[ ð1dŁ#[ This behaviour supports the assump! d"Sb0I# 1[884"0# − d"Sb0I# 1[883"0#
tion of a charge ~ow from the ligands into the LUMO
× d"Sb0I# 1[871"0#_ "3#
at Sb[
With regard to the charges on 016I "Townes!Dailey
treatment ð01aŁ in Table 2#\ the order "2# mirrors the
structural _nding "3#[ Compounds with a longer Sb!I
distance own a more negative charge on the iodine
atom\ i[e[ the Sb!I bond seems to be more ionic[
HOMO and LUMO by cyclic voltammetry and coul!
ometry
The oxidation of the compounds 3 at a positive
potential is followed in most cases by decomposition[
The two cases of quasi!reversible oxidation:reduction
=Z"I#="MeN = = = SbI# − =Z"I#="BuiN = = = SbI#
× =Z"I#="BzN = = = SbI# "2# suggest that no full oxidation of Sb"III# to Sb"V#

Heterocyclic systems containing antimony "III#!VIII
1552
Fig[ 5[ Related trans bond orders of the four!electron three!center interaction N = = = Sb!Hal[
occurs[ The signals are broad ^ for a two!electron pro! the ligand Ph induces a distinct up!_eld shift[ The
cess narrow signals should be expected ð04bŁ[
special kind of donor group NR? has no in~uence on
The reversibility of the redox potentials Ered and d"02C#[
Eox in the reductive mode\ the proof of a di}usion
For the three Sb0NCS compounds d"02C# is
controlled molecular process in solution and the proof slightly deshielded " ꢁ 024 ppm# in comparison to
of a one!electron reduction for 3 "NMe:I# support Me0NCS " ꢁ 017[4 ppm ð07Ł#[ This deshielding is in
experimentally the likelihood of a charge ~ow from accordance with the assumed charge!giving power of
the ligands into the LUMO mostly associated with the isothiocyanate ligand into the LUMO at Sb[ On
the central Sb atom[ The similarity of all CVs and the other hand\ the bonding isomerism Sb0NCS
their peak voltage positions indicate that for all these "compound 3 "NMe:NCS#\ is con_rmed also for the
Sb compounds a transfer of one electron into an equi! two other compounds "d"02C"Et0SCN# 001 ppm
valent molecular orbital eventuates[ Because of the ð07Ł#[
extended time frame of the bulk electrolysis compared
to the cyclic voltammetry in the former\ restricted
experimental conditions are involved while in the lat!
18Si NMR chemical shifts in CDCl2 solution
ter no such decomposition occurred due to the brevity
of the experiment[
In view of the qualitative nature of the kinetically
The values of d"18Si# for the "0OSiPh2# ligand in
the compounds 0\ 1\ 3 and in the tetrahedral analogue
Ph2SiOSiPh2 are sterically determined ] −07[4\ −08[4
controlled method cyclic voltammetry ð06Ł\ and with
and −"13 to 15# ppm for the ligand in tetrahedral\
regard to the approximations of the Extended HuÃckel
equatorial and axial trigonal bipyramidal position\
method\ no direct numerical comparison of the poten!
respectively[ In two cases\ the "0OSiPh2# ligands
tials of Table 4 "units V# to the calculated LUMO
exchange at room temperature on the NMR time
energies of Table 3 "units eV# can be made[
scale[ With regard to axial "0OSiPh2# bound to Sn
or Sb\ no di}erence in d"18Si# exists[
02C NMR chemical shifts in CDCl2 solution
Figure 6 summarizes the chemical shifts of the a!
EXPERIMENTAL
methylene groups in the rings of Scheme 0[ The overall
sequences of the 02C deshielding "CH1Ge − CH1Sn General considerations
and CH1Bi × CH1As × CH1Sb# suggest sequences of
electronegativity
"EN"Ge# − EN"Sn#
of
the
and
central
atoms
The starting ligands R?Nð"CH1#2ClŁ1 and the related
EN"Bi# × EN"As# × diGrignard reagents were prepared as described pre!
EN"Sb##\ respectively "for a detailed discussion of this viously ð5aŁ[ Grignard iniators were CCl3 for the chlor!
aspect see Ref[ ð5aŁ#[ For each element individually\ ine substituted compounds and I1 for the iodine

1553
E[ Brau et al[
Ã
Fig[ 6[ Sequence of d"02C# for the equatorial a!methylene groups in the rings 0 to 4 in CDCl2 solution[
substituted ones[ The reagent AgSCN was pre! ing crude product was recrystallized from ethanol to
cipitated from an aqueous solution of KSCN with obtain a colorless solid[ Table 6 summarizes the yields
AgNO2\ washed with cold acetone and dried in vacuo[ and the analytical data for the 08 synthesized com!
The reagent Ph2SiONa was obtained by reaction of pounds[ For some of the Ge compounds 0 the ana!
Ph2SiOH with sodium in toluene[ Melting points were lytical data are not satisfying[ All these compounds 0
determined in glass capillaries in a Ko~er block[ were obtained in low yields and the separation from
Elemental analyses were carried out by the Micro! oligomeric by!products was di.cult[ Repeated chro!
analytical Laboratory of the Institut fuÃr Organische matographic puri_cations resulted in no better ana!
Chemie\ Universitat Mainz[ NMR spectra were rec! lytical data[ Nevertheless\ the identities of the
Ã
orded on
a
Bruker WP!79:DS spectrometer compounds are not in doubt[ The compound 0 "O:Cl1#
"02C:19[04\ 18Si:04[81 MHz ^ solvent CDCl2 ^ ambient was not obtained in a pure state at all[
temperature ^ external standard SiMe3#[ Mass spectra
were recorded using a Finnigan 7129 spectrometer[
Mossbauer spectroscopy
Ã
Preparations of 0 and 3
010Sb MoÃssbauer spectra were measured with an
The syntheses of the Cl substituted compounds were Austin Science S!599 Mossbauer spectrometer using
Ã
carried out as described previously ð5aŁ[ Detailed pro! a Ca010mSnO2 source "05 MBq# and a pure germanium
cedures follow for the compounds 3 "NMe:I# and 3 detector ð08aŁ[ 016I Mossbauer spectra were recorded
Ã
"NBz:NSC#[ Under the exclusion of light and air and in the same way as described previously by using a
under vigorous stirring\ 9[97 mol of the diGrignard Mg2016mTeO5 source instead of a Zn016mTe source
reagent MeNð"CH1#2MgClŁ1 in 049 ml THF and 9[97 ð08bŁ[ The MoÃssbauer source "0[5 GBq# was prepared
mol SbI2 as a solid were added simultaneously into by a high ~ux neutron irradiation of Mg2015TeO5 "082
0[4 l toluene "three!necked 1 l ~ask# over a period of mg# at a reactor core of JRR!2M of the Japan Atomic
0[4 h[ Stirring was continued at room temperature for Energy Research Institute[ Both the corresponding
13 h[ The dark!reddish reaction mixture was _ltered sources and the samples ð"04 mg Sb#:cm1 or "29 mg
twice to remove MgI1[ The solvent was removed under I#:cm1 were kept at 19 K in a cryostat incorporating
vacuum and moderate temperature\ and the crude a closed!cycle refrigerator ð08cŁ[ The Doppler velocity
product was recrystallized from ethanol[ A colorless was measured with an Austin Science LC!8 laser inter!
solid was obtained[ A suspension of 9[994 mol of ferometer and calibrated by measuring the 46Fe
freshly prepared and dried AgSCN and 9[994 mol 3 Mossbauer spectrum of an iron foil at 19 K using a
Ã
"NBz:I# were stirred in 049 ml CH1Cl1 for 13 h at 46Co"Rh# source[ The spectra were _tted to twelve!
room temperature[ The reaction mixture was _ltered line quadrupole!split lines by using a transmission
o} and the solvent removed under vacuum[ The result! integral method ð08dŁ[

Heterocyclic systems containing antimony "III#!VIII
1554
Table 6[ Preparation and analytical data for 0a and 3a
Method
yield ")#
Formula
Mr
mp ">C#
Anal[ found "calcd#
Compound
M:eb ")#
)C
)H
)N
)Hal
0 "NMe:Cl1#
0 "NBz:Cl1#
diGrignard
04
diGrignard
09
diGrignard
2
diGrignard
01
diGrignard
03
diGrignard
01
Ph2SiONa
13
diGrignard
20
diGrignard
24
diGrignard
12
Ph2SiONa
45
Ph2SiONa
48
Ph2SiONa
17
AgSCN
71
AgSCN
64
AgSCN
38
PhLi
64
C6H04Cl1NGe
145[61
C02H08Cl1NGe
221[71
C09H10Cl1NGe
187[68
C5H01Cl1SGe
148[63
C02H19ClNGe
187[26
C08H14ClNGe
264[37
C32H34NOSi1Ge
608[66
C6H04INSb
250[75
C02H08INSb
326[85
C09H10INSb
392[83
C14H29NOSiSb
409[24
C20H23NOSiSb
475[34
C17H25NOSiSb
441[33
C7H04N1SSb
182[92
C03H08N1SSb
258[02
C00H10N1SSb
224[00
009
22[11
"21[61#
36[24
"35[76#
28[91
"39[02#
15[23
"16[61#
49[73
"41[17#
47[83
"59[61#
69[81
"60[57#
12[39
"12[12#
24[80
"24[54#
18[79
"18[62#
45[52
"47[73#
52[87
"52[38#
59[31
"59[77#
21[64
"21[68#
34[21
"34[44#
27[89
"28[32#
47[59
4[83
"4[73#
4[75
"4[60#
5[73
"6[91#
3[22
"3[51#
5[43
"5[69#
5[41
"5[55#
5[29
"5[14#
3[27
"3[07#
3[29
"3[26#
4[32
"4[31#
5[12
"4[81#
4[85
"4[73#
5[26
"5[46#
4[08
"4[05#
4[01
"4[08#
5[54
"5[21#
5[11
4[33
"4[34#
3[11
"3[10#
3[52
*
"16[55#
*
"10[22#
*
"12[64#
*
"16[23#
*
"00[89#
*
146c "099#
077
220 "7#
003
188 "6#
023
159 "2#
094
0 "NBui:Cl1#
0 "S:Cl1#
"3[57#
0 "NMe:ClPh#
0 "NBz:ClPh#
0 "NMe:OSiPh2#1#
3 "NMe:I#
3[22
"3[58#
2[52
"2[61#
0[53
"0[83#
2[74
"2[76#
2[05
"2[19#
2[31
"2[36#
1[70
"1[63#
1[16
"1[28#
1[32
"1[43#
8[41
"8[45#
6[38
"6[48#
7[99
"7[25#
2[41
188 "7#
070
230d "2#
038
"8[34#
352e "13#
196
22[23i
"24[96#
17[00i
123f "099#
113
3 "NBz:I#
209f "099#
027
"17[87#
3 "NBui:I#
20[91j
393 "9[4#
081
"20[31#
3 "NMe:OSiPh2#
3 "NBz:OSiPh2#
3 "NBui:OSiPh2#
3 "NMe:NCS#
3 "NBz:NCS#
3 "NBui:NCS#
3 "NBz:Ph#
498 "84#
86
4[99h
"3[68#
474` "099#
090
442` "099#
199
181 "1#
043
257` "1#
87
225` "1#
027
C08H13NSb
277[05
C05H15NSb
238[09
277 "099#
oil
238 "099#
"47[68#
43[56
"44[94#
"5[12#
5[82
"5[45#
"2[50#
3[03
"3[90#
3 "NBui:Ph#
PhLi
36
a Compound 0"O:Cl1# could not be obtained in a pure state ^ for the compounds 3"NMe:Cl\ NBz:Cl\ NBui:Cl\ NMe:Br
and S:Cl# see Ref[ ð5aŁ[ b EI mass spectra ] M¦[ c FI mass specrum[ d M¦0"Cl#[ e M¦0"OSiPh2#[ f M¦0"I#[ ` FD mass
i
j
spectrum[ h Si by X!ray ~uorescence analysis[ Contaminated by some Cl from the Grignard reagent[ Traces of Cl\ see X!
ray crystallography[
Electrochemistry
pad which was exclusively used for these electrodes
and then again washed with water\ acetone and _nally
The CV measurements of Table 4 were performed with dry CH1Cl1\ and the Hg amalgamating procedure
with a BAS CV 16 Voltammograph coupled with a was repeated[ Auxiliary electrodes were of 0 mm diam!
Houston Instruments Series 1999 Omnigraph X!Y eter Pt wire[ Reference electrodes were Ag:AgCl _lled
recorder[ The scan rate dependence and the coul! with CH1Cl1 "saturated LiCl# and were separated from
ometry were done with a BAS 099 B:W elec! the test solution by a fritted salt bridge containing
trochemical analyser coupled to a PC[
CH1Cl1 and the electrolyte[ Measurements were made
Conventional disk gold electrodes "1[4 mm diam! in a conventional three electrode cell\ from quiescent
eter# were amalgamated by dipping in triple distilled solutions blanketed with N1\ which were previously
mercury until a good coating of mercury completely sparged with dry high purity N1[
covered the gold surface\ and used immediately[ To
The bulk electrolysis was performed in a cylindrical
renew the Au surface\ the electrode was dipped in glass cell equipped with a separate fritted anode com!
nitric acid and washed with water\ polished on a cloth partment "Pt basket anode# and a magnetically stirred

1555
E[ Brau et al[
Ã
Table 7[ Summary of crystal data\ intensity data collection "Mo radiation\ ambient temperature# and re_nement for the
compounds 3
3"NMe:I#
3"NMe:NCS#
3"NBz:Cl#
3"NBz:I#
3"NBui:I#
Crystal system
Space group
a "_#
b "_#
c "_#
monoclinic
P10:n "no 03#
6[472 "1#
09[644 "1#
02[435 "2#
82[95 "2#
orthorhombic
Pnam "no 51#
00[138 "1#
02[091 "2#
6[677 "1#
monoclinic
C1:c "no 04#
13[026 "4#
8[819 "1#
00[580 "1#
87[77 "2#
monoclinic
C1:c "no 04#
14[974 "4#
09[070 "1#
00[448 "1#
87[65 "2#
triclinic
PÞ0 "no 1#
6[486 "1#
7[939 "1#
00[839 "1#
64[41 "2#\
73[95 "2#\
67[26 "2#
580 "0#
1
b ">#
V "_2#
Z
0092 "0#
3
0037 "0#
3
1655 "0#
7
1807 "0#
7
F "999#
Dcalcd
561
1[068
1[071
9[4612
2410
465
0265
0553
273
0[832
0[760
9[6924
0[585
0[575
9[4999
0838
0[553
0[510
9[3428
2007
0[883
0[879
9[5277
2679
Dexptl "g cm−2
#
sin Umax:l "_−0
re~ ] meas
#
3186
indep "int R#
no[ of variables "ratio r~ns:var#
R
2023 "9[906#
82 "14[1#
9[9214
0689
55 "03[6#
9[9791
1327 "9[929#
036 "00[8#
9[9204
2388 "9[914#
036 "04[8#
9[9366
3904 "9[906#
019 "13[2#
9[9469
mercury pool cathode[ The solution was continually molecule#[ Re_nements in the space group Pna10
sparged with N1 during the coulometric measurement[ resulted in a severely distorted molecule and in many
The electrolysis was stopped if no further current correlations[ The crystal of 3 "NBui:I# contained
decrease occurred "04 to 4) of the initial current\ traces of Cl from the Grignard reagent "residual 3[9
about 0 h#[
The CH1Cl1 "anal[ gr[ BDH# was passed through ine content in Table
e−:_2\ Dcalcd:Dexptl 0[83:0[76 g cm−2\ the analytical iod!
is low# which crys!
6
activity 0 alumina which had been previously pre! tallographically could not be re_ned[ Details of crystal
heated to 599>C[ The supporting electrolyte\ data and structure determinations\ ORTEP views\
Bun NPF5\ was stored over P1O4 for 37 h prior to tables of positional and thermal parameters\ bond
3
usage and solutions of this in CH1Cl1 "9[0 M# were lengths\ bond angles and torsion angles have been
made up just prior to the measurements[ Ferrocene deposited with the Editor as supplementary material[
"Riedel!de Haen# was used as a standard[
Ã
CONCLUSIONS
X!ray crystallo`raphy
All experimental data "structure determinations\
Colorless single crystals were obtained from ethanol
"3"NMe:I\ NMe:NCS\ NBui:I\ NBz:Cl## or from
ethanol:toluene 0 ] 0 "3"NBz:I##[ A summary of the
crystal data\ of the intensity data collections and of
the re_nements is given in Table 7[ The densities were
determined by ~otation in aqueous polytungstate
solution[ The quality of the crystals was examined by
Laue exposures[ Integrated intensities were measured
by means of v:1u scans on an Enraf!Nonius CAD3
di}ractometer[ The structures were solved by Pat!
terson syntheses and completed by Fourier syntheses
"program package SHELXTL#[ The re_nements
resulted in good convergences and in even dis!
tributions of the variances[ Hydrogen atoms were cal!
culated and re_ned as riding on their carbon atoms[
Two atoms of the compound 3 "NMe:NCS# are sev!
erely disordered "N"1# and the ring atom C"1## ^ all
attempts to resolve this disorder failed[ The space
Mossbauer spectroscopy\ electrochemistry\ NMR
Ã
spectroscopy# and the Extended Huckel calculations
Ã
are in a rough agreement with the assumed bonding
scheme of hypervalency ] four!electron three!center
interaction and its main control by a partial charge
transfer from the ligands into the three!center LUMO[
In view of the fact that the Extended Huckel method
Ã
is a very _rst approximation\ a state of the art ab initio
calculation is needed for a fully consistent interpret!
ation of the experimental _ndings[ Such calculations
are in preparation[
Acknowled`ements*We gratefully acknowledge Prof[ Alan
Bond\ Monash University\ Melbourne\ Australia\ for his
supporting electrochemical discussions[ We are grateful for
_nancial assistance from the Deutsche Forschungsge!
meinschaft\ Bonn\ Germany\ from the Fonds der Chem!
ischen Industrie\ Frankfurt:Main\ Germany\ and by Grants!
group is unambiguously Pnam "no[ 51 ] Cs symmetric in!Aid for Scienti_c Research "No[ 95342942# from the Min!

Heterocyclic systems containing antimony "III#!VIII
1556
istry of Education\ Science and Culture of the Japanese
Government[
0884\ 03\ 636 ^"c# M ꢁ Pb ] Drager\ M[ and
Ã
Kleiner\ N[\ An`ew[ Chem[\ 0879\ 81\ 849 ^ An`ew[
Chem[ Int[ Ed[ En`l[\ 0879\ 08\ 812 ^ "d# M ꢁ As ]
Cea!Olivares\ R[\ Estrada\ M[ R[\ Espinosa!Perez\
G[\ Haiduc\ I[\ Garcia\ P[ G[ Y[\ Lopez!Cardoso\
M[\ Lopez!Vaca\ M[ and Cotero!Villegas\ A[!M[\
Main Group Chem[\ 0884\ 0\ 048 ^ "e# M ꢁ Sb ]
Cea!Olivares\ R[\ Munoz!Hernandez\ M[!A[\
Hernandez!Ortega\ S[ and Silvestru\ C[\ Inor`[
Chim[ Acta\ 0884\ 125\ 20 ^ "f# M ꢁ Bi ] Agocs\
L[\ Burford\ N[\ Cameron\ T[ S[\ Curtis\ J[ M[\
Richardson\ J[ F[\ Robertson\K[ N[ and Yhard\
G[ B[\ J[ Am[ Chem[ Soc[\ 0885\ 007\ 2114[
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An`ew[ Chem[\ 0885\ 097\ 428 ^ An`ew[ Chem[ Int[
Ed[ En`l[\ 0885\ 24\ 366[
4[ The compound 1 "NMe:Cl1# of Scheme 0 has been
synthesized as the _rst compound of this class ]
Jurkschat\ K[ and Tzschach\ A[\ J[ Or`anomet[
Chem[\ 0873\ 161\ C02[ For further analogues and
homologues see ] "a# M ꢁ Sn ] Jurkschat\ K[\
03[ Extended Huckel parameters H "eV#:exponent ]
Ã
ii
Schilling\ J[\ Mugge\ C[\ Tzschach\ A[\ Meunier!
Ã
Piret\ J[\ van Meerssche\ M[\ Gielen\ M[ and
Willem\ R[\ Or`anometallics\ 0877\ 6\ 27 ^ "b#
M ꢁ Si ] Jurkschat\ K[\ Mugge\ C[\ Schmidt\ J[
Ã
and Tzschach\ A[\ J[ Or`anomet[ Chem[\ 0874\
176\ C0 ^ "c# M ꢁ P ] Wilbrandt\ D[\ Jurkschat\ K[
and Meunier!Piret\ J[\ Phosphorus\ Sulfur\ Silicon\
0880\ 50\ 150 ^ cf also ] Toto\ S[ D[\ Arbuckle\ B[
W[\ Bharadwaj\ P[ K[\ Takahashi Doi\ J[ and
Musker\ W[ K[\ Phosphorus\ Sulfur\ Silicon\ 0880\
45\ 16[
C"1s −10[39:0[514\ 1p −00[39:0[514# ^ H"0s
−02[59:0[299# ^ As "3s −05[11:1[12\ 3p
−01[05:0[78# ^ Cl "2s −15[29:1[072\ 2p
−03[19:0[622# ^ Ge "3s −05[99:1[059\ 3p
−8[99:0[749# ^
−02[39:0[849# ^
N
S
"1s −15[99:0[849\ 1p
"2s −19[9:1[011\ 2p
−02[2:0[716# ^ Sb "4s −07[79:1[212\ 4p
−00[69:0[888# ^ Sn "4s −05[05:1[019\ 4p
−7[21:0[719#[ Compilation by ] Alvarez\ S[\ Table
of Parameters for Extended Huckel Calculations\
Ã
Barcelona\ 0874[
5[ "a# Five of the Sb compounds 3 and the _ve As
and Bi compounds 2 and 4 of Scheme 0 have been
04[ "a# For a recent concise introduction to cyclic
voltammetry see ] Brett\ C[ M[ A[ and Oliveira
Brett\ A[ M[\ Electrochemistry\ Ch[ 8\ Oxford
University Press\ Oxford\ New York\ Tokyo\
0882 ^ "b# much cyclic voltammetric work has
been done on transition metals ] Noel\ M[ and
Vasu\ K[ I[\ Cyclic voltammetry and the frontiers
of electrochemistry\ Aspect Publ[\ London\ 0889 ^
"c# for cyclic voltammetry on organic antimony
compounds see ] Dessy\ R[ E[\ Chivers\ T[ and
Kitching\ W[\ J[ Am[ Chem[ Soc[\ 0855\ 77\ 356[
05[ "a# Kissinger\ P[ T[ and Heineman\ W[ R[\ eds[\
Laboratory Techniques in Electroanalytical Chem!
istry\ Marcel Dekker Inc[\ New York\ Basel\ 0873\
p[ 77 ^ "b# Bard\ A[ J[ and Faulkner\ L[ R[\ Elec!
trochemical Methods\ Ch[ 09\ Wiley + Sons\ New
York\ 0879[
described in a previous paper ] Brau\ E[\ Falke\
Ã
R[\ Ellner\ A[\ Beuter\ M[\ Kolb\ U[ and Drager\
Ã
M[\ Polyhedron\ 0883\ 02\ 254 ^ "b# the data for
the fourteen Sn compounds 1 were taken from
Ref[ ð1dŁ ^ "c# the crystal structure data for the
compounds 0 "NBui:Cl1# and 1 "NBui:Cl1# were
taken from Ref[ ð1dŁ[
6[ Much work has also been done previously on the
analogous
compound
series
R1M:RM!
ðSCH1CH1Ł1X[ "a# M ꢁ Ge ] Drager\ M[\ Z[
Ã
Anor`[ All`[ Chem[\ 0865\ 312\ 42 ^ "b# M ꢁ Sn
ð1a\bŁ ] Tzschach\ A[ and Jurkschat\ K[\ Com!
ments Inor`[ Chem[\ 0872\ 2\ 24 ^ Jung\ O[!S[\
Jeong\ J[ H[ and Sohn\ Y[ S[\ Or`anometallics\
0880\ 09\ 650 ^ Cea!Olivares\ R[\ Loleli\ V[\ Her!
nandez!Ortega\ S[ and Haiduc\ I[\ Polyhedron\

1557
E[ Brau et al[
Ã
06[ Kissinger\ P[ T[ and Heineman\ W[ R[\ J[ Chem[
Educ[\ 0872\ 59\ 692[
awa\ H[\ Takahashi\ M[\ Takeda\ M[\ Takano\
T[ and Ito\ Y[\ Radioisotopes\ 0889\ 28\ 101 ^ "c#
Takano\ T[\ Ito\ Y[ and Takeda\ M[\ Radio!
isotopes\ 0879\ 18\ 18 ^ "d# Shenoy\ G[ K[\ Friedt\
07[ Kalinowski\ H[!O[\ Berger[ S[ and Braun\ S[\ 02C!
NMR!Spektroskopie\ Thieme Verlag\ Stuttgart\
New York\ 0873\ p[ 117[
J[ M[\ Maletta\ H[ and Ruby\ S[ L[ In Mossbauer
Ã
08[ "a# Takeda\ M[\ Radioisotopes\ 0874\ 23\ 517 ^
Takeda\ M[\ Takahashi\ M[\ Ohyama\ R[ and
Nakai\ I[\ Hyper_ne Int[\ 0875\ 17\ 630 ^ "b# Ikez!
Effect Methodolo`y\ Vol[ 8\ ed[ I[ J[ Gruverman\
C[ W[ Seidel and D[ K[ Dieterly\ Plenum Press\
New York\ 0863\ p[ 166[