Preparation and spectral study of mixed-ligand nickel (II) chelates containing N- or N,N′-methylated ethylenediamines and tropolonate or hinokitiolate ligands

Article abstract of DOI:10.1016/S0277-5387(98)00071-0

Eleven mixed-ligand chelates of Ni (II) containing a molecule of N,N-di-, N,N,N′-tri-, or N,N,N′,N′-tetramethylethylenediamine, and a tropolonate (trop) or hinokitiolate (hino) ligand, were prepared, and their electronic spectra in solid state and in various organic solvents were studied. Most systems studied were green, containing octahedral chelate species [Ni (trophino) (diamine) (H₂OSolvent) ₂] ⁺ or [Ni (NO₃) (trophino) (diamine) ] , but some were red, containing square planar [Ni (trophino) (diamine) ] ⁺, and an equilibrium between the octahedral and square planar species was sometimes observed in solutions. Strong spectral resemblances with the corresponding diamine-β-diketonate chelates of Ni (II) could be pointed out.

Full text of DOI:10.1016/S0277-5387(98)00071-0

Polyhedron Vol[ 06\ No[ 08\ pp[ 2136Ð2142\ 0887
Þ 0887 Elsevier Science Ltd
Pergamon
All rights reserved[ Printed in Great Britain
9166Ð4276:87 ,08[99¦9[99
\
PII ] S9166Ð4276"87#99960Ð9
Preparation and spectral study of mixed!ligand
nickel"II# chelates containing N! or N\N?!
methylated ethylenediamines and tropolonate
or hinokitiolate ligands
Y[ Ihara\aꢀ K[ Teranishi\a N[ Hirose\a and K[ Soneb
a Laboratory of Chemistry\ Faculty of Education\ Kanazawa University\ Kakumamachi\
Kanazawa 819!0081\ Japan
b Department of Chemistry\ Faculty of Science\ Josai University\ Keyakidai 0!0\ Sakado\
Saitama 249!9189\ Japan
"Received 03 October 0886 ] accepted 02 February 0887#
Abstract*Eleven mixed!ligand chelates of Ni"II# containing a molecule of N\N!di!\ N\N\N?!tri!\ or N\N\N?\N?!
tetramethylethylenediamine\ and a tropolonate "trop# or hinokitiolate "hino# ligand\ were prepared\ and their
electronic spectra in solid state and in various organic solvents were studied[ Most systems studied were green\
containing octahedral chelate species ðNi"trop:hino#"diamine#"H1O:Solvent#1Ł¦ or ðNi"NO2#"trop:hino#!
"diamine#Ł\ but some were red\ containing square planar ðNi"trop:hino#"diamine#Ł¦\ and an equilibrium
between the octahedral and square planar species was sometimes observed in solutions[ Strong spectral
resemblances with the corresponding diamine!b!diketonate chelates of Ni"II# could be pointed out[ Þ 0887
Elsevier Science Ltd[ All rights reserved
Keywords] nickel"II# chelates^ tropolonate^ hinokitiolate^ solvatochromism[
———————————————————————————————————————————————
It is known that b!diketonates "b!dike# and N! or a close resemblance was found between the chelates
N\N?!alkylated ethylenediamines "Rnen# react with obtained in this study and the corresponding diamine!
Ni"II# or Cu"II# to produce the mixed!ligand chelates\ b!diketonate chelates\ in particular with respect to
ðM"b!dike#"Rnen#ŁX "X is a univalent anion such as their solvatochromic behaviors\ which will now be
ClO−3 #\ which are soluble both in polar and non! reported in this paper[
polar solvents exhibiting pronounced solvatochromic
behaviors ð0Ð2Ł[ Such chelates may serve as visual
indicators to estimate the polarities of organic
EXPERIMENTAL
solvents\ with which their electronic spectra regularly
vary ð2Ł[
Preparation of the chelates
We have recently reported on the solvatochromic
properties of the mixed!ligand chelates of Cu"II#
All the reagents\ including the solvent molecules\
used for preparing the mixed nickel"II# chelates were
with N\N!:N\N?!di!\ N\N\N?!tri!\ or N\N\N?\N?!tetra!
commercial reagent grade chemicals and used without
methylethylenediamine and a tropolonate "trop# or
further puri_cation[ Tropolone and hinokitiol were
hinokitiolate "hino ^ 3!isopropyltropolonate# ligand
supplied by Tokyo Chem[ Ind[ Co[
"i# ðNi"trop#"tetmen#"H1O#1ŁClO3 "a# ] Nickel"II#
perchlorate hexahydrate "1 mmol\ 9[62 g# was dis!
solved in a small amount of water\ and an ethanolic
solution "4 cm2# containing equimolar amounts of
N\N\N?\N?!tetramethylethylenediamine "tetmen\ 9[12
ð3Ł[ In continuation of the study\ we tried to prepare
similar chelates of Ni"II# and investigate their spectral
behaviors[ As was the case with the Cu"II# chelates\
ꢀ Author to whom correspondence should be addressed[
g# and tropolone "trop\ 9[14 g# was added to it with
2136

2137
Y[ Ihara et al[
"viii# ðNi"hino#"tetmen#"H1O#1ŁClO3 "h# ] Hino!
stirring[ After sodium carbonate "0 mmol\ 9[00 g# was
added to neutralize the solution\ it was gently heated kitiol "hino\ 0[4 mmol\ 9[14 g# and tetmen "0[4 mmol\
for 0 h and _ltered[ The _ltrate was kept in a refriger! 9[06 g# were added to a methanolic solution "09 cm2#
ator for several days\ and the green crystals pre! of nickel"II# perchlorate hexahydrate "0[4 mmol\ 9[44
cipitated were recrystallized from nitromethane[ g#\ successively[ The resulting suspension became a
Yield ] 9[45 g\ 54)[
deep green solution by adding sodium carbonate "9[7
"ii# ðNi"trop#"tetmen#ŁB"C5H4#3"b# ] An excess mmol\ 9[97 g# with gentle heating[ The solution was
amount of sodium tetraphenylborate "0[4 mmol\ 9[40 evaporated to dryness\ and the green powder obtained
g# was added to the suspension of a "0 mmol\ 9[32 g# was dissolved in 0\1!dichloroethane "09 cm2# and _l!
in 0\1!dichloroethane "09 cm2# with stirring and gentle tered[ The _ltrate was kept in a refrigerator for several
heating[ After the insoluble residue was removed\ the days[ The green crystals which separated out were
solution was kept in a refrigerator for several days to recrystallized from 0\1!dichloroethane[ Yield ] 9[31 g\
precipitate the red crystals[ Yield ] 9[15 g\ 32)[
"iii# ðNi"NO2#"trop#"tetmen#Ł "c# ] Nickel"II#
48)[
"ix# ðNi"hino#"tetmen#ŁB"C5H4#3 = H1O "i# ] This
nitrate hexahydrate "1 mmol\ 9[47 g# was dissolved in complex was prepared from h by the same method as
ethanol "4 cm2#\ and a chloroform solution "04 cm2# that used for b ^ 0[4 mmol of sodium tetraphenylborate
containing equimolar amounts of trop and tetmen was was added to the suspension of h "0 mmol\ 9[36 g# in
added to it with stirring[ After an aqueous solution 09 cm2 of 0\1!dichloroethane[ Yield ] 9[11 g\ 21)[
"9[4 cm2# of sodium carbonate "0 mmol# was added
"x# ðNi"NO2#"hino#"tetmen#Ł "j# ] Nickel"II# nitrate
to the solution\ it was gently heated for an hour and hexahydrate "0[4 mmol\ 9[33 g# was mixed with hino
_ltered[ The resulting solution was kept in a refriger! "0[4 mmol# and tetmen "1[2 mmol\ 9[16 g# in acetone
ator for a week to precipitate the deep green crystals[ "4 cm2#\ and the solution was gently heated to dryness[
Yield ] 9[40 g\ 60)[
The resulting solid was dissolved in 0\1!dichloro!
"iv# ðNi"trop#"trimen#"H1O#1ŁClO3 "d# ] Nickel"II# ethane "09 cm2# and then the insoluble residue was
perchlorate hexahydrate "1 mmol#\ trop "1 mmol# and _ltered o}[ After the _ltrate was evaporated to dryness
N\N\N?!trimethylethylenediamine "trimen\ 2 mmol\ again\ the green powder was extracted with three
9[20 g# were mixed successively in acetone "4 cm2#[ 09 cm2 portions of diethyl ether[ The combined ether
The resulting solution was evaporated to dryness on solution was let stand for a day at room temperature
a hot plate and the residue was suspended in diethyl to precipitate the deep green crystals which were
ether[ The green powder obtained from the suspension recrystallized from diethyl ether[ Yield ] 9[13 g\
was further treated with 0\1!dichloroethane "09 cm2#[ 39)[
After the insoluble residue was _ltered o}\ the deep
green crystals separated out immediately from the _l! el"II# nitrate hexahydrate "0[4 mmol# dissolved in
trate[ Yield ] 9[18 g\ 24)[
methanol "4 cm2#\ and a methanolic solution "4 cm2#
"xi# ðNi"hino#"NN!dmen#"H1O#1ŁNO2 "k# ] Nick!
"v# ðNi"trop#"trimen#ŁB"C5H4#3 = H1O "e# ] This containing hino "0[4 mmol# and NN!dmen "0[4 mmol\
complex was prepared from d by the same method as 9[02 g# were mixed together\ and sodium carbonate
that used for b ^ 0[4 mmol of sodium tetraphenylborate "9[7 mmol# was added to it with stirring and gentle
was added to the suspension of d "0 mmol\ 9[31 g# in heating[ The solution was concentrated on a hot plate\
09 cm2 of 0\1!dichloroethane[ Yield ] 9[04 g\ 13)[
"vi# ðNi"NO2#"trop#"trimen#Ł "f# ]
and the oily product obtained was suspended in 0\1!
Nickel"II# dichloroethane "09 cm2#[ The pale green powder iso!
nitrate hexahydrate "1 mmol# was mixed with trop "1 lated from the suspension was recrystallized from 0\1!
mmol# and trimen "2 mmol# in acetone "4 cm2#\ and dichloroethane[ Yield ] 9[40 g\ 72)[
the solution was evaporated to dryness[ The green
Attempts to prepare the mixed chelates containing
powder obtained was extracted with 0\1!dich! hino and trimen in a pure form always failed in spite
loroethane "4 cm2#\ and the insoluble residue was of many e}orts[
removed[ The resulting solution was evaporated to
dryness again[ The crude gummy product was sus!
pended in diethyl ether "19 cm2#\ and the green crys! Measurements
talline powder obtained was washed with diethyl ether
thoroughly[ Yield ] 9[40 g\ 63)[
The visible and near!UV spectra of the chelates were
"vii# ðNi"trop#"NN!dmen#"H1O#1ŁNO2 "g# ] An recorded with a JASCO V!469 spectrophotometer at
acetone solution containing the reaction mixture of room temperature "ca 19>C#[ Solvents used for the
nickel"II# nitrate hexahydrate "1 mmol#\ trop "1 spectral studies were GR or Spectro Grade products
mmol# and N\N!dimethylethylenediamine "NN!dmen\ and were stored over molecular sieves "4 _#[ The
2 mmol\ 9[15 g# was evaporated to dryness[ The green IR spectra were measured with a HORIBA FT!109
powder obtained was extracted with 0\1!dichloro! infrared spectrophotometer by the KBr disk and
ethane "09 cm2#\ and the oily residue was _ltered o}[ Nujol mull methods[ The e}ective magnetic moments
The resulting solution was concentrated slowly at were evaluated from the susceptibilities measured by
room temperature to precipitate the green crystals a Sherwood magnetic balance MSB!MKI[ Thermo!
after a few days[ Yield ] 9[26 g\ 40)[
gravimetry was carried out with a Seiko SSC:479

Study of eleven mixed!ligand chelates of Ni"II#
2138
TG:DTA!29 apparatus[ Each run was performed nitrates "g and k# show a single IR band "a weak
under a constant ~ow of nitrogen "9[1 dm2 min−0# at combination band of NO−2 # at ca 0659 cm−0\ while
a heating rate of 1>C min−0 ^ about 19 mg of sample anhydrous nitrates "c\ f and j# show two such bands
was used[
with a large separation "ca 49 cm−0#[ These data imply
that the nitrate ion in the hydrated nitrates is outside
of the coordination sphere\ while that in the anhy!
drous nitrates is a chelating nitrate ligand ð6Ł\ which
forms a 3!membered chelate ring with an anomalously
small O0Ni0O angle ð7Ł[
RESULTS AND DISCUSSION
Structures of the chelates in solid state
The presence of two water molecules in chelates a\
d\ g\ h and k\ and one water molecule in e and i was
also con_rmed thermogravimetrically[ Among the
anhydrous chelates obtained by thermal dehydration\
those from a\ d and h are red\ so that they should be
formulated as square planar ðNi"trop:hino#!
"diamine#ŁClO3!type chelates[ The anhydrous chelates
from g and k are green\ on the other hand\ and their
IR spectra show two bands around 0649 cm−0 with a
large separation "31 and 22 cm−0\ respectively#\ im!
plying that they are nitrato chelates ðNi"NO2#!
"trop:hino#"NN!dmen#Ł like c\ f and j[
Table 0 summarizes the solid!state properties and
analytical data of the eleven mixed nickel"II# chelates
obtained\ and Fig[ 0 shows the solid!phase "powder
re~ection# electronic spectra of some trop chelates[ It
can be seen that there are two types of chelates ] the
red diamagnetic ones with square planar geometry\
which show a strong dÐd band at ca 10×092 cm−0
\
and the green paramagnetic ones with octahedral
geometry\ which show two weaker bands at ca 8×092
cm−0 "Band I# and 05×092 cm−0 "Band II#\ respec!
tively ð0\2\4\5Ł[ All the tetraphenylborates belong to
the former\ while all the hydrated perchlorates\
hydrated nitrates\ and anhydrous nitrates "or nitrato
chelates ^ cf[ below# belong to the latter[
All these considerations lead to the formulations of
the obtained chelates given in Table 0[
Among the chelates containing an NO−2 ion\ the
spectrum of an anhydrous chelate is characteristically
di}erent from that of a hydrated chelate ] "0# the Band
II is notably stronger than the Band I in the former
spectrum\ while both are of comparable strength in
the latter ^ "1# the Band I in the former is much broader
than that in the latter\ and is apparently split\ indi!
cating a stronger deformation of its geometry from
octahedral symmetry[ The case of c and g is compared
in Fig[ 0[
Structures of the chelates in solutions
The chelates obtained are\ in most cases\ slightly
soluble in water\ but they are fairly soluble in most
organic solvents[ Typical data of the electronic spectra
of trop and hino chelates in various solvents are sum!
marized in Tables 1 and 2\ respectively[ It can be
seen that the red square planar species predominate
in some solutions\ but the green octahedral species "of
the hydrated!chelate type spectra ^ vide supra# pre!
dominate in most others\ and equilibrium mixtures of
the two species occur in certain cases[
In this connection\ it is also noted that hydrated
Figures 1 and 2 show the spectra of a and b in
0\1!dichloroethane "DCE#\ nitromethane "NM#\ THF
and DMSO\ respectively[ In strongly polar and coor!
dinating solvents like DMF\ DMSO\ and pyridine\
the spectra of the two chelates are nearly identical\
showing that the same octahedral species\ most prob!
ably ðNi"trop#"tetmen#"Solvent#1Ł¦\ predominate in
every case[ In weakly polar and poorly coordinating
solvents like DCE and NM\ on the other hand\ their
spectra are that of the square planar species ðNi"trop#!
"tetmen#Ł¦ "so the chelate cation in a is readily dehy!
drated in such a solvent#\ whereas the very weak
absorption in the red!to!IR region indicates that small
amounts of octahedral species coexist in equilibrium
with it[ In solvents of intermediate coordinating
power\ such as alcohols\ acetone and THF\ the solu!
tions are green\ and their spectra are similar to those in
strongly coordinating solvents ^ however\ on heating
they become yellowish to orange "thermochromism#\
and their absorption band around 10×092 cm−0 sen!
sibly increases\ forming a shoulder or hump at the
skirt of the strong band of trop which appears at the
blue end of the visible spectrum "this hump is most
Fig[ 0[ Re~ectance spectra of ðNi"trop#"tetmen#"H1O#1ŁClO3
"*#\ ðNi"trop#"tetmen#ŁB"C5H4#3 "= = =#\ ðNi"NO2#"trop#!
"tetmen#Ł "Ð Ð# and ðNi"trop#"NN!dmen#1"H1O#1ŁNO2
"* *#[
=

Table 0[ Solid!state properties and analytical data of the chelates
n
½
max:092 cm−0
n
½
NO :cm−0
Dehydrationc
Analytical datad
H")#
2
Chelate
Color
me}:B[M[
"re~[a#
"IRb#
Temp:>C
Mass loss:)d
C")#
N")#
a ðNi"trop#"tetmen#"H1O#1ŁClO3
b ðNi"trop#"tetmen#ŁB"C5H4#3
c ðNi"NO2#"trop#"tetmen#Ł
d ðNi"trop#"trimen#"H1O#1ŁClO3
e ðNi"trop#"trimen#ŁB"C5H4#3 = H1O
f ðNi"NO2#"trop#"trimen#Ł
g ðNi"trop#"NN!dmen#"H1O#1ŁNO2
h ðNi"hino#"tetmen#"H1O#1ŁClO3
i ðNi"hino#"tetmen#ŁB"C5H4#3 = H1O
j ðNi"NO2#"hino#"tetmen#Ł
green
red
deep green
green
red
green
pale green
green
red
deep green
pale green
2[95
diamag[
1[80
1[82
diamag[
2[90
1[89
2[19
diamag[
2[06
2[09
8[4 04[7
19[8
7[5 05[0
8[5 04[6
10[9
8[0 05[5
09[9 05[0
8[1 04[6
19[7
7[2 04[8
8[7 04[8
54Ð009
7[2"7[2#
9
24[80"25[08#
61[26"61[12#
32[13"32[50#
23[22"23[41#
58[30"58[72#
31[27"30[89#
24[84"25[05#
39[92"39[47#
60[09"60[03#
36[73"37[92#
39[65"30[10#
4[66"4[73#
5[63"5[61#
4[72"4[80#
4[42"4[44#
5[43"5[56#
4[58"4[46#
4[79"4[63#
5[14"5[59#
6[94"6[20#
5[66"5[79#
5[47"5[56#
5[39"5[38#
3[58"3[44#
00[76"00[63#
5[47"5[60#
0611 0669
9
59Ð044e
49Ð84
7[4"7[5#
1[5"1[8#
9
8[6"8[7#
6[1"6[5#
1[5"1[6#
9
3[78"3[41#
0605 0655
0652
00[84"01[11#
00[63"00[37#
4[86"4[81#
3[01"3[04#
09[18"09[49#
09[14"09[29#
74Ð009
34Ð89
39Ð69
0611 0669
0646
k ðNi"hino#"NN!dmen#"H1O#1ŁNO2
69Ð034
7[4"7[7#
a Wave numbers of the d!d bands in re~ectance spectrum[
b Characteristic combination band of NO−2 ^ see text[
c Thermogravimetric data[
d Calculated values are in parentheses[
e Dehydration takes place in two steps[

Study of eleven mixed!ligand chelates of Ni"II#
2140
Table 1[ Values of nmax:092 cm−0 and omax of the trop chelates in various solvents
½
Chelate Solvent
DCE
NM
MeCN
8[8"09#
Me1CO
8[3"00#
THF
MeOH
8[3"8#
EtOH
8[3"8#
DMF
DMSO
Py
a
b
19[5"087# 19[4"046#
8[0"09#
8[4"01#
8[3"09# 09[9"6#
05[7"07# 04[6"02# 04[5"00# 04[5"00# 04[3"00# 04[6"03# 04[3"01# 05[6"07#
19[6"161# 19[5"078# 09[9"01# 8[4"01# 8[9"6# 8[3"09# 8[2"00# 8[4"01# 8[3"00# 09[1"7#
04[5"00# 04[3"02# 04[6"03# 04[3"02# 05[6"10#
05[6"10# 04[6"03# 04[5"7#
19[7"60#
c
8[3"02#
05[9"16# 05[9"16#
19[7"036# 19[6"010# 09[1"02#
8[4"01#
8[5"01#
05[0"13# 05[9"15# 05[0"14# 04[7"03# 05[9"19# 04[7"05# 04[3"02# 05[6"10#
8[6"02# 8[3"01# 8[6"09# 8[5"00# 8[7"02# 8[6"00# 09[9"8#
8[3"01#
8[3"01#
8[3"09#
8[2"01#
8[5"01#
8[3"00# 09[0"7#
d
05[7"10# 05[5"03# 05[5"04# 05[9"00# 05[6"04# 05[5"07# 04[6"03# 05[6"10#
05[5"02#
e
19[7"069# 19[8"095# 09[0"02#
8[5"03#
8[3"00#
8[5"00#
8[7"01#
8[8"02#
8[5"01# 09[9"8#
05[6"12# 05[5"07# 05[6"05# 05[6"03# 05[5"12# 05[5"08# 04[8"05# 05[6"12#
05[5"05#
f
8[5"02#
05[5"17# 05[5"18#
8[4"02# 8[5"02#
05[5"16# 05[2"17#
8[5"02#
8[8"02#
05[6"13# 05[5"14# 05[5"16# 05[6"03# 05[5"06# 05[5"07# 05[5"03# 05[6"10#
8[8"02# 8[1"02# 8[3"01# 8[6"8# 8[5"01# 8[7"02# 8[4"00# 8[8"00#
05[6"12# 04[8"12# 05[5"15# 05[6"01# 05[6"19# 05[5"06# 05[5"02# 05[6"10#
8[4"02#
8[5"02#
8[6"09#
8[6"8#
8[7"02#
8[5"00# 09[9"8#
g
Table 2[ Values of nmax:092 cm−0 and omax of the hino chelates in various solvents
½
Chelate Solvent
DCE
NM
MeCN
8[8"09#
Me1CO
8[3"02#
THF
MeOH
8[3"09#
EtOH
DMF
DMSO
Py
h
i
19[6"086# 19[5"067#
19[6"104# 19[5"080#
8[0"01#
8[2"00#
8[5"01#
8[3"00# 09[0"8#
05[7"05# 04[6"04# 04[6"19# 04[5"02# 04[5"02# 04[7"05# 04[3"03# 05[8"10#
8[7"02# 8[3"01# 7[8"8# 8[1"09# 8[4"03# 8[4"01# 8[3"09# 09[9"09#
05[7"10# 04[6"03# 04[5"01# 04[8"05# 05[9"14# 04[6"06# 04[2"01# 05[7"10#
10[5"48#
j
8[3"03#
05[0"17# 05[9"18#
Insol[
8[4"02#
8[4"02#
05[0"14# 05[9"15# 05[0"16# 04[6"03# 04[8"13# 04[7"05# 04[2"03# 05[8"19#
8[8"02# 8[2"03# 8[3"02# 8[6"09# 8[5"8# 8[6"02# 8[5"00# 8[8"09#
05[6"13# 05[9"14# 05[4"15# 05[0"01# 05[0"04# 05[5"06# 04[6"02# 05[7"19#
8[3"02#
8[3"02#
8[3"09#
8[3"02#
8[4"00#
8[2"00# 09[0"8#
k
8[5"02#
05[1"17#
clearly seen in THF even at room temperature ^ cf[ lower in the case of a\ although its reliable estimate is
Fig[ 2#[ The equilibrium
hindered by the strong blue band of trop which over!
laps with its band too severely ð09Ł[
ðNi"trop#"tetmen#Ł¦¦1Solvent
Figure 3 shows the spectra of c in the same solvents
as those in Fig[ 1[ Here the predominating species is
always green and octahedral\ but there are evidently
two kinds of them[ The species formed in a strongly
coordinating solvent "e[g[ pyridine\ DMF\ DMSO\
and now alcohols# shows nearly the same spectrum as
that of a and b in the same solvent\ i[e[ ðNi"trop#!
"tetmen#"Solvent#1Ł¦[ The species formed in a less
coordinating solvent shows a di}erent spectrum\
where the omax of the Band II is notably higher than
that of the Band I\ which is very broad with a
somewhat split appearance[ This latter species is most
probably the undissociated nitrato chelate ðNi"NO2#!
"trop#"tetmen#Ł\ in view of its spectral analogy with
the solid chelates and\ here again\ with the cor!
_ ðNi"trop#"tetmen#"Solvent#1Ł¦ "0#
which is predominant in these solutions is thus shifted
to the left hand side with the rise of temperature[
All these spectral behaviors are quite similar to
those observed in the corresponding chelates with a
b!diketonate ligand\ in particular in those with an
acetylacetonate "acac# ligand ð0\2\6Ł of which trop is
a vinylog ð8Ł\ even with respect to the numerical values
of n½ of the individual case[ A closer spectral com!
max
parison of a with that of its acac analogue ðNi"a!
cac#"tetmen#"H1O#1ŁClO3 indicates however that\ in
solvents "ethanol\ butanol\ acetone and THF# where
the equilibrium "0# is established\ the relative con!
centration of the red species seems to be considerably responding b!diketonate chelates ð0\2\5\7Ł[ The pre!

2141
Y[ Ihara et al[
Fig[ 1[ Electronic spectra of ðNi"trop#"tetmen#"H1O#1ŁClO3
in DCE "*#\ NM"= = =#\ THF "Ð Ð# and DMSO "* *#[
=
Fig[ 3[ Electronic spectra of ðNi"NO2#"trop#"tetmen#Ł in
DCE "*#\ NM "= = =#\ THF "Ð Ð# and DMSO "* *#[
=
dominating equilibrium in these solutions is\ there!
fore\ that of the dissociation:solvation of nitrato
chelate\ i[e[
ðNi"NO2#"trop#"tetmen#Ł¦1Solvent
_ ðNi"trop#"tetmen#"Solvent#1Ł¦¦NO2− "1#
The spectra of the tetmen chelates of hino "h\ i and
j# are quite similar to those of the corresponding trop
chelates "a\ b and c#[ In addition\ the solvatochromic
behaviors of the trimen chelates of trop "d\ e and f#
can be understood similarly ^ even the change from
tetmen to trimen does not alter the apparent sol!
vatochromic changes of the chelates seriously\ unlike
the case of the Cu"II# chelates where the extent of
solvatochromism depends sensitively on the structures
of the diamine ligands ð3Ł[ On the other hand\ the
spectra of the hydrated nitrates with NN!dmen\ g and
k\ which are probably formed as the result of de!
creased hydrophobicity of NN!dmen\ show that they
are readily dehydrated and dissolved as ðNi"NO2#!
"trop:hino#"NN!dmen#Ł in most solvents "even in
DCE or NM\ unlike the hydrated perchlorates a\ d
and h which are merely dehydrated into ðNi"trop:
hino#"diamine#Ł¦ in them#\ and are converted into
ðNi"trop:hino#"NN!dmen#"Solvent#1Ł¦ only in strongly
coordinating solvents ð00Ł\ as in the case of c and j[
A problem which still remains unsolved is whether
the ðNi"trop:hino#"diamine#"H1O:Solvent#1Ł¦!type
Fig[ 2[ Electronic spectra of ðNi"trop#"tetmen#ŁB"C5H4#3 in
DCE "*#\ NM "= = =#\ THF "Ð Ð# and DMSO "* *#[
=

Study of eleven mixed!ligand chelates of Ni"II#
2142
Advanced Inor`anic Chemistry\ 4th edn\ Wiley\
New York\ 0877[
5[ Fukuda\ Y[ and Sone\ K[\ J[ Inor`[ Nucl[ Chem[\
0864\ 26\ 344[
6[ Lever\ A[ B[ P[\ Mantovani\ E[ and Ramaswamy\
B[ S[\ Can[ J[ Chem[\ 0860\ 38\ 0846[
7[ Fukuda\ Y[\ Fujita\ C[\ Miyamae\ H[\ Nakagawa\
H[ and Sone\ K[\ Bull[ Chem[ Soc[ Jpn[\ 0878\ 51\
634[
chelate cations are cis or trans[ Recent X!ray crystal
structural studies of the corresponding acac!diamine
chelates ð01Ð03Ł proved that they are always cis\ sug!
gesting that the trop:hino!diamine chelates are also
cis ^ there is still no direct evidence for it\ however\
and the reason why this structure is favored among
these chelates is by no means clear[ Further structural
studies are now going on along these directions[
8[ Yamada\ S[ and Tsuchida\ R[\ Bull[ Chem[ Soc[
Jpn[\ 0845\ 18\ 583[
09[ As to the relative stabilities of trop and acac
chelates\ cf[ Bryant\ B[ E[ et al[\ J[ Am[ Chem[
Soc[\ 0842\ 64\ 2673[
Acknowled`ements*This work was partially supported by
Grant!in!Aid for Scienti_c Research "C# "No[ 96539630#
from Ministry of Education\ Science\ Sports and Culture[
00[ Cf[ also Nga\ N[ T[\ Fukuda\ Y[ and Sone\ K[\
Bull[ Chem[ Soc[ Jpn[\ 0866\ 49\ 043[
01[ Yamada\ K[\ Thesis "M[Sc[#\ Ochanomizu Uni!
versity\ 0881\ and Yamada\ K[\ Hori\ K[ and
Fukuda\ Y[\ Acta Cryst[\ 0882\ C38\ 334 ] ðNi!
"acac#"tetmen#"MeOH#"H1O#ŁClO3\ ðNi"acac#!
"tetmen#"MeOH#"H1O#ŁBPh3 = ðNi1"acac#1"CO2#!
"tetmen#1Ł[
02[ Ogino\ T[\ unpublished data at Josai University\
0885 ] ðNi"acac#"tetmen#"H1O#1ŁClO3[
03[ Mafune\ K[\ Thesis "M[Sc[#\ Ochanomizu
University\ 0878 ] ð"tetmen#Ni"taet#Ni"tetmen#!
"H1O#1Ł"ClO3#1 = H1O "taet ꢁ tetraacetylethanate#[
Cf[ also Sone\ K[ and Fukuda\ Y[\ Rev[ Inor`[
Chem[\ 0880\ 00\ 012[
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