H[ Aneetha et al[:Polyhedron 07 "0888# 188Ð296
290
spectrophotometer[ Fast atom bombardment "FAB#
mass spectra were recorded on JEOL SX 091:DA!5999
mass spectrometer:data system using Xenon "5 KV\
09 mA# as the FAB gas and m!nitrobenzyl alcohol was
used as matrix[ Cyclic voltammograms were recorded
on Cypress systems model CS!0989:CS!0976 computer
controlled electroanalytical system[ All the experiments
were performed under dry nitrogen in acetonitrile and
dichloromethane solvents[ 0×09−2 mol dm−2 solutions
were used with 9[0 mol dm−2 NBu3ClO3 as supporting
electrolyte\ a glassy carbon working electrode\ Ag!AgCl
electrode as reference and platinum wire as auxiliary elec!
trode[ FerroceneÐferrocenium couple was used as the
redox standard[
Ph!terpy complexes "0# and "2# and a dinuclear structure
for diterpy complexes "1# and "3#[
The FAB!mass spectra of the mononuclear complexes\
"0# and "2# exhibit peaks corresponding to ðCpꢀML0ClŁ
and the dinuclear complexes\ "1# and "3# to
ð"CpꢀMCl#1L1"BF3#Ł[ In addition\ fragments due to
ðCpꢀML0Ł\ ðML0Ł and ðCpꢀMŁ for mononuclear com!
plexes and ð"CpꢀM#1L1ClŁ\ ð"CpꢀM#1L1Ł\ ðML1Ł and
ðCpꢀMŁ for dinuclear complexes are observed[ Based on
these data\ the complexes\ "0# and "2# are assigned mono!
nuclear structure where the metal ion is coordinated by
Cpꢀ\ chloride and the ligand in a bidentate fashion[ The
complexes\ "1# and "3# are assigned a dinuclear structure
where the ligand diterpy acts as a bridge coordinating
two metal ions at two ends in a bidentate bonding mode[
Each metal ion is also coordinated by Cpꢀ and chloride[
The proposed structures of the complexes are given in
Fig[ 1[
1[0[ X!ray
crystal
structure
determination
of
ðCpꢀRhL0ClŁBF3 "0#
A
crystal of dimensions 9[11×9[39×9[39 mm\
2[0[ Crystal structure of ðCpꢀRhL0ClŁBF3 "0#
obtained by di}usion of ether into methanol solution was
sealed in a glass capillary[ Preliminary examination and
intensity data collection were carried out with an EnrafÐ
Nonius CAD!3 automatic di}ractometer using graphite
To con_rm the proposed structures of the complexes\
the crystal structure of complex ðCpꢀRhL0ClŁBF3 "0# was
solved[
Ä
monochromated Mo Ka radiation "lꢁ9[60962 A#[ Inten!
¹
The complex crystallises in triclinic P0 space group
sity data were collected using the u!1u scan mode for
1u¾34> and then corrected for absorption and decay[
The structure was solved by MULTAN ð12Ł in triclinic
with two molecules per unit cell[ The crystallographic
parameters are given in Table 0[ The ORTEP drawing of
the molecule "0# along with the atom!numbering scheme
is shown in Fig[ 2[ The asymmetric unit consists of a
rhodium atom displaying the three!legged {piano stool|
geometry[ It is coordinated to one h4!"C4Me4# group\ one
chloride and two nitrogens of Ph!terpy in a bidentate
bonding mode\ as postulated from experimental data[
The pentamethylcyclopentadienyl ligand is sym!
metrically bound to the metal ion[ All the Cpꢀ atoms fall
in a fairly good plane\ the root mean square deviation of
¹
space group P0 and was re_ned with full!matrix least!
squares on F with wꢁ0[9:ðs1"Fo#¦9[9990Fo1Ł[ In the _nal
cycles all the non!hydrogen atoms were re_ned aniso!
tropically and the hydrogen atoms were _xed at idealized
Ä
positions "dCÐHꢁ0[99 A# calculated during anisotropic
convergence stage[ Scattering factors for neutral atoms
and anomalous scattering coe.cients for non!hydrogen
atoms were taken from ref ð13Ł[ All calculations were
carried out with a Micro VAX 2599 computer using NRC
VAX program package ð14Ł[ There were 4907 unique
re~ections of which 3366 with I×1s "I# were used for
the structure solution[ Re_nement converged at a _nal
Rꢁ2[2) and Rwꢁ2[5) "260 variable parameters#[
ꢀ
Ä
the Cp from a least!squares plane being 9[904 A[ The
distance between Rh and the least!squares plane of the
ꢀ
Ä
Ä
Cp ring is 0[672 A[ The RhÐCl bond length is 1[287"0# A[
These bond distances are close to the RhÐCpꢀ\ 0[671 and
RhÐCl\ 1[275 bond lengths in ðCpꢀRh"phen#ClŁ¦ complex
ð15Ł[
The RhÐN distances are unequal with RhÐN"0#\
Ä
Ä
1[975"2# A and RhÐN"1#\ 1[086"2# A[ This has been
observed in other complexes involving bidentate terpy
ð01Ł[ The presence of uncoordinated pyridine ring gives
rise to steric interactions\ resulting in signi_cantly longer
RhÐN"1# bond compared to the RhÐN"0#[
2[ Results and discussion
Reactions of ðCpꢀRh"m!Cl#ClŁ1 with L0 "Ph!terpy# and
L1 "diterpy# in methanol in presence of NaBF3 gave
orange red microcrystalline products "0# and "1#[ Simi!
larly reaction of these ligands with ðCpꢀIr"m!Cl#ClŁ1 gave
complexes "2# and "3#[ The IR spectra of the complexes
exhibit sharp bands with medium intensities in the range
0599Ð0399 cm−0 originating from the polypyridyl
ligands[ In addition\ complexes gave a broad band at
0949 cm−0 due to BF3 anion[ The C\ H\ N analytical data
agree with a mononuclear formula ðCpꢀML0ClŁBF3 for
The metallacyclic moiety containing Rh\ N"0#\ C"4#\
C"5# and N"1# shows considerable deviation from plan!
arity "the root mean square deviation of these atoms from
Ä
a least!square plane is 9[29 A#[ The structure is stabilized
by hydrogen bonding between chloride and H"07# of the
uncoordinated pyridine ring\ the distance between them
Ä
being 1[45 A which is less than the sum of their respective
Van der Waals radii[Table 1
Aneetha
