Synthesis of transition metal isocyanide complexes containing hydrogen bonding sites in peripheral locations

Article abstract of DOI:10.1016/S0020-1693(98)00352-1

The isocyanides CNC₆H₂R₂-2,6-CHO-4 (1a-b) (a: R = Me; b: R = CHMe₂), react with hydroxylamine, 2-pyridylhydrazine, and formylhydrazide to form CNC₆H₂R₂-2,6-CHNOH-4 (2a-b), CNC₆H₂R₂-2,6-CHNNH(2-C₅H ₄N)-4 (3a-b), and CNC₆H₂R₂-2,6-CHNNHCHO-4 (4b), respectively. The oxime and hydrazone derivatives 2-4 were chosen because of their potential for self-association via hydrogen bonding. Reaction of the isocyanides 1-4 (L) with FeI₂, PdI₂, and PtI₂ affords complexes of the types trans-[FeI₂(L₄)], trans-[PdI₂(L)₂], and trans-[PtI₂(L₂)]. The molecular structures of the complexes trans-[FeI₂(L₄)] (L = 1b, 2a and 2b) and trans-[PdI₂(L)₂] (L = 2b) were determined by X-ray crystallography. The oxime derivatives form extended hydrogen bonded networks.

Full text of DOI:10.1016/S0020-1693(98)00352-1

Inorganica Chimica Acta 285 (1999) 223±232
Synthesis of transition metal isocyanide complexes containing
hydrogen bonding sites in peripheral locations
Ka Yin Lau, Andreas Mayr*,1, Kung-Kai Cheung
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, Hong Kong
Received 23 September 1997; received in revised form 12 December 1997; accepted 23 January 1998
Dedicated to Professor Dr. W. Beck on the occasion of his 65th birthday.
Abstract
The isocyanides CNC6H2R2-2,6-CHO-4 (1a±b) (a: R ˆ Me; b: R ˆ CHMe2), react with hydroxylamine, 2-pyridylhydrazine, and
formylhydrazide to form CNC6H2R2-2,6-CHNOH-4 (2a±b), CNC6H2R2-2,6-CHNNH(2-C5H4N)-4 (3a±b), and CNC6H2R2-2,6-
CHNNHCHO-4 (4b), respectively. The oxime and hydrazone derivatives 2±4 were chosen because of their potential for self-association
via hydrogen bonding. Reaction of the isocyanides 1±4 (L) with FeI2, PdI2, and PtI2 affords complexes of the types trans-[FeI2(L4)], trans-
[PdI2(L)2], and trans-[PtI2(L2)]. The molecular structures of the complexes trans-[FeI2(L4)] (L ˆ 1b, 2a and 2b) and trans-[PdI2(L)2]
(L ˆ 2b) were determined by X-ray crystallography. The oxime derivatives form extended hydrogen bonded networks. # 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Isocyanides; Oximes; Hydrazones; Isocyanide metal complexes; Iron complexes; Palladium complexes; Platinum complexes
1. Introduction
the assembled structures. We have recently developed iso-
cyanide metal complexes carrying nitrogen donor groups
and have demonstrated the formation of coordination poly-
mers in combination with unsaturated metal complexes or
metal ions [37,38]. In view of their proven versatility in
molecular self-assembly processes, it appeared desirable to
include hydrogen-bonding groups in the design of the iso-
cyanide metal complex building blocks [39±60]. However,
isocyanides containing hydrogen-bonding groups are not
easily accessible, since the presence of such groups is
largely incompatible with the conditions of the major iso-
cyanide syntheses [61,62]. Thus there is a need for methods
to generate hydrogen bonding groups after the preparation of
the isocyanide functionality. It would furthermore appear
desirable to have the option to introduce the hydrogen-
bonding groups either before [63±79] or after [80±93]
coordination of the isocyanides to metal centers [94]. This
way, the possible interference of the hydrogen-bonding
groups with the formation of the isocyanide metal com-
plexes could be avoided as well. In order to satisfy these
demands, we considered the grafting of entire hydrogen-
bonding fragments onto isocyanides. The procedure
described here is based on the reactivity of formyl-substi-
tuted arylisocyanides.
Isocyanide metal complexes [1±9] are attractive as build-
ing blocks for molecular materials [10±25]. Due to their
unique bonding capabilities and slender shapes, isocyanide
ligands are capable of forming metal complexes with reg-
ular, yet open molecular structures based on all major
coordination geometries. Furthermore, because of the pre-
sence of partial metal±carbon multiple bonds, signi®cant
electronic interactions between the metal centers and unsa-
turated organic systems are possible [26±29]. By introdu-
cing suitable weak interaction sites in peripheral locations,
the isocyanide metal complexes can be induced to undergo
molecular self-assembly, whereby the geometric and elec-
tronic information stored in them can be exploited to control
the physical properties of the self-assembled molecular
materials [30±36]. The choice of the weak interaction sites
is important, since they represent the primary means to
control the relative orientations of the building blocks in
*Corresponding author. Tel.: +1-516-623-7951; fax: +1-516-632-7960;
e-mail: amayr@ccmail.sunysb.edu
1Permanent address: Department of Chemistry, State University of New
York at Stony Brook, Stony Brook, NY 11794-3400, USA.
0020-1693/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(98)00352-1

224
K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
2. Experimental
H2O: C, 73.38; H, 5.85; N, 8.56. Found: C, 74.05; H, 5.68;
N, 8.73%.
4-Amino-3,5-dimethylbenzaldehyde was prepared as
described in the literature [97]. 2,6-Diisopropylaniline, tri-
¯uoroacetic acid, 2-hydrazinopyridine, hydroxylamine,
hydrazine hydrate, FeI2, PdI2, and PtI2 were purchased from
commercial sources. 2,6-Diisopropylaniline was distilled
prior to use. The metal halides were dried under vacuum
for 1 h prior to use. THF, ether, CH2Cl2, and n-hexane were
distilled under N2 from appropriate drying agents. All other
solvents and reagents were of analytical grade and were
used as received, unless otherwise noted. Formylhydrazide
was prepared by treatment of ethylformate with hydrazine
monohydrate. The syntheses of the transition metal com-
plexes were performed under an atmosphere of N2. The
2.1.2. 4-Formyl-2,6-diisopropylphenylisocyanide (1b)
Following an established literature procedure [98], a
mixture of 2,6-diisopropylaniline (3.545 g, 20 mmol), pre-
viously distilled tri¯uoroacetic acid (30 ml) and hexa-
methylenetetramine (2.804 g, 20 mmol) is re¯uxed for 12 h
at 85±908C. Cold water (60 ml) is added, and the mixture is
made basic by addition of sodium carbonate (about 5 g).
The resulting crude 4-amino-3,5-diisopropylbenzaldehyde
is extracted with ether and puri®ed by column chromato-
graphy on silica gel using n-hexane/EtOAc (3:1) as the
eluent (Rf ˆ 0.26) and thin-layer chromatography on silica
using acetone/diethyl ether/n-hexane (1:1:4) as the eluent. A
light yellow solid is obtained. Yield: 1.46 g, 35%. 1H NMR
(CDCl3): ꢀ 9.74 (s, 1H, CHO), 7.55 (s, 2H, C6H2), 4.43 (br,
2H, NH2), 2.90 (septet, 2H, CH), 1.29 (d, 12H, CH3). 13C
NMR (CDCl3): ꢀ 191.4 (CHO), 146.8, 131.6, 127.2, 125.8
(C6H2), 27.9 (CH), 22.1 (CH3). IR (KBr, cm 1): ꢁ ˆ 3470±
3250 (m, NH2), 1707 (m), 1629 (s), 1583 (s), 1560 (s).
A mixture of acetic anhydride (6.338 g, 51.7 mmol) and
formic acid (2.858 g, 51.7 mmol) is heated with stirring for
2 h at 50±608C in a ¯ask ®tted with a drying tube. The
solution is cooled to room temperature. 4-Amino-3,5-di-
isopropylbenzaldehyde (5.31 g, 25.86 mmol) is added gra-
dually over a 10 min period using a water bath to maintain
the temperature below 398C. The mixture is allowed to cool
to 308C, and diethyl ether is added. The mixture is stirred for
24 h at room temperature. A 10% solution of aqueous
sodium carbonate (150 ml) is used to neutralize the reaction
mixture. The resulting 4-formylamino-3,5-diisopropylbenz-
aldehyde is isolated by column chromatography on silica
gel using n-hexane/EtOAc (3:2) as the eluent (Rf ˆ 0.27). A
pale yellow crystalline solid is obtained. Yield: 4.34 g, 72%,
m.p. 91±928C. 1H NMR (CDCl3), two isomers: ꢀ 10.04 (s),
10.02 (s) (1H, CHO), 8.49 (d, J ˆ 1.39 Hz), 8.07 (d,
J ˆ 11.63 Hz) (1H, NCHO), 7.74 (s), 7.73 (s) (2H,
C6H2), 7.50 (d, J ˆ 11.61 Hz), 7.02 (s) (1H, NH), 3.26
(m, 2H, CH), 1.26 (d, 12H, CH3). 13C NMR (CDCl3): ꢀ
192.2, 191.9 (CHO), 164.9, 160.3 (NHCHO), 147.5, 136.3,
136.2, 135.7, 135.4, 125.4, 125.2 (C6H2), 30.0, 28.6 (CH),
23.5, 23.4 (CH3). IR (KBr, cm 1): ꢁ ˆ 3200 (s, NH), 1697
1
NMR spectra were recorded at 300 MHz for H NMR and
75.4 MHz for 13C NMR. The elemental analyses were
performed by Butterworth Laboratories.
2.1. Syntheses
2.1.1. 4-Formyl-2,6-dimethylphenylisocyanide (1a)
A mixture of acetic anhydride (0.734 g, 7.187 mmol) and
formic acid (0.330 g, 7.187 mmol) is heated with stirring for
2 h at 50±608C in a ¯ask ®tted with a drying tube. The
solution is cooled to room temperature. 4-Amino-3,5-
dimethylbenzaldehyde (0.51 g, 3.423 mmol) is added gra-
dually over a 10 min period using a water bath to maintain
the temperature below 398C. The mixture is allowed to cool
to 308C, and diethyl ether is added to the suspension. The
mixture is stirred for 24 h at room temperature. The result-
ing 4-formylamino-3,5-dimethylbenzaldehyde is ®ltered off
and washed with ether. Toluene is used to recrystallize the
crude product to give white needle-shaped crystals. Yield:
0.375 g, 62%. 1H NMR (CDCl3), two isomers: ꢀ 9.95, 9.93
(s, 1H, CHO), 8.43, 8.20 (s, 1H, NHCHO), 7.65, 7.60 (s, 2H,
C6H2), 7.43, 7.14 (br, 1H, NHCHO), 2.33, 2.40 (s, 6H, CH3).
13C NMR (CDCl3): ꢀ 193.7 (CHO), 162.0 (NHCHO), 131.0,
130.4, 126.9 (C6H2), 18.7 (CH3). IR (KBr, cm 1): ꢁ ˆ 1700
(s), 1662 (s).
Triphosgene (1.028 g, 3.465 mmol) is ®rst dissolved in
dry CH2Cl2 and then added dropwise over a 30 min period
into a mixture containing 4-formylamino-3,5-dimethylbenz-
aldehyde (1.736 g, 9.804 mmol) and triethylamine (1.39 ml,
9.804 mmol) in CH2Cl2 (30 ml) at 788C under nitrogen.
The reaction mixture is allowed to warm up to room
temperature and is stirred for 8 h at room temperature.
The product is isolated by column chromatography on silica
gel using n-hexane/EtOAc (2:1) as the eluent (Rf ˆ 0.65). A
white solid is obtained. Yield: 0.775 g, 50%, m.p. 89±908C.
1H NMR (CDCl3): ꢀ 9.97 (s, 1H, CHO), 7.64 (s, 2H, C6H2),
2.51 (s, 6H, CH3). 13C NMR (CDCl3): ꢀ 191.1 (CHO), 171.2
(CN), 136.1, 135.6, 128.9 (C6H2), 19.0 (CH3). IR (KBr,
‡
(s), 1674 (s), 1657 (s). HRMS (M ) m/e Calc. for
C14H19NO2: MW ˆ 233.1416. Found: 233.1414.
Triphosgene (1.034 g, 3.48 mmol) is ®rst dissolved in dry
CH2Cl2 (15 ml) and is added dropwise over a 30 min period
into a mixture containing 4-formylamino-3,5-diisopropyl-
benzaldehyde (2.44 g, 10.45 mmol) and triethylamine
(1.06 g, 10.45 mmol) in CH2Cl2 (20 ml) at 788C under
nitrogen. The reaction mixture is allowed to warm up to
room temperature and is stirred for 8 h at room temperature.
The methylene chloride solution is washed several times
with 10% aqueous Na2CO3. The solvent is removed, and the
product is puri®ed by column chromatography on silica gel
using n-hexane/EtOAc (6:1) as the eluent (Rf ˆ 0.45). A
‡
cm 1): ꢁ ˆ 2115 (s, CN), 1700 (s, CHO). HRMS (M ) m/e
Calc. for C10H9NO: MW ˆ 159.0684. Found: 159.0683.
Anal. Calc. for C10H9NO (MW ˆ 159.188) with 0.25 mol

K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
225
pale yellow crystalline solid is obtained. Yield: 1.48 g, 66%,
m.p. 55±568C. 1H NMR (CDCl3): ꢀ 9.95 (s, 1H, CHO), 7.63
(s, 2H, C6H2), 3.36 (septet, 2H, CH), 1.26 (d, 12H, CH3).
13C NMR (CDCl3): ꢀ 190.4 (CHO), 171.8 (CN), 145.2,
135.2, 123.7, (C6H2), 28.9 (CH), 21.4 (CH3). IR (KBr,
the eluent (Rf ˆ 0.33). A yellow solid is obtained. Yield:
0.113 g, 53%, m.p. 199±2008C. 1H NMR (CDCl3): ꢀ 9.10 (s,
1H, NH), 8.16 (m, 1H), 7.66 (m, 2H), 7.39 (3H), 6.82 (m,
1H) (CH=N, C6H2, C5H4N), 2.45 (s, 6H, CH3). 13C NMR
(CDCl3): ꢀ 169.9 (CN), 156.5, 147.5, 138.3, 137.3, 135.3,
135.2, 125.5, 124.6, 116.1, 107.7 (C=N, C6H2, C5H4N), 19.0
(CH3). IR (KBr, cm 1): ꢁ ˆ 2114 (s, CN), 1597 (s), 1582
‡
cm 1): ꢁ ˆ 2114 (s, CN), 1698 (s, CHO). HRMS (M )
m/e Calc. for C14H17NO: MW ˆ 215.1310. Found:
215.1311. Anal. Calc. for C14H17NO (MW ˆ 215.296):
C, 78.10; H, 7.96; N, 6.51. Found: C, 78.05; H, 7.86; N,
6.69%.
‡
(s). HRMS (M ) m/e Calc. for C15H14N4: MW ˆ 250.1218.
Found: 250.1213.
2.1.6. CNC6H2-i-Pr2-2,6-[CH=NNH(C5H4N-2)]-4 (3b)
The procedure described for 3a is followed. The product
is puri®ed by column chromatography on silica gel using
n-hexane/ethyl acetate (3:2) as the eluent (Rf ˆ 0.29). A
2.1.3. CNC6H2Me2-2,6-(CH=NOH)-4 (2a)
To
a suspension of hydroxylamine hydrochloride
(0.093 g, 1.33 mmol) in pyridine (0.105 g, 1.33 mmol), a
solution of 1a (0.2 g, 1.257 mmol) in methylene chloride/
methanol (10:1, 30 ml) is added. The mixture is stirred for
24 h. The reaction mixture is washed with 10% aqueous
sodium carbonate solution (20 ml). After removal of the
solvent, a yellow solid is obtained. The solid is extracted
with hot n-hexane and any insoluble impurities are ®ltered
off. After removal of the solvent, a white powder is
1
yellow solid is obtained. Yield: 74%, m.p. 196±1988C. H
NMR (CDCl3): ꢀ 8.80 (s, 1H, NH), 6.81±8.17 (5H, C5H4N),
7.45 (s, 2H, C6H2), 7.73 (s, 1H, CH=N), 3.39 (septet, 2H,
CH), 1.33 (d, 12H, CH3). 13C NMR (CDCl3): ꢀ 169.9 (CN),
156.4, 147.6, 145.4, 138.2, 137.9, 135.7, 121.2, 116.2, 107.6
(C=N, C6H2, C5H4N), 29.9 (CH), 22.5(CH3). IR (KBr,
cm 1): ꢁ ˆ 2112 (s, CN), 1607 (s), 1583 (s). HRMS
‡
1
obtained. Yield: 0.175 g, 80%, m.p. 130±1318C. H NMR
(M ) m/e Calc. for C19H22N4: MW ˆ 306.1844. Found:
(CDCl3): ꢀ 8.06 (s, 1H, CH=N), 8.06 (br, 1H, OH), 7.32 (s,
2H, C6H2), 2.44 (s, 6H, CH3). 13C NMR (CDCl3): ꢀ 169.0
(CN), 149.1 (C=N), 135.5, 132.2, 126.2, (CH), 18.9 (CH3).
IR (KBr, cm 1): ꢁ ˆ 3390±3080 (br, OH), 2113 (s, CN).
306.1841. Anal. Calc. for C19H22N4 (MW ˆ 306.413): C,
74.48; H, 7.24; N, 18.29. Found: C, 74.67; H, 7.30; N,
18.07%.
‡
HRMS (M ) m/e Calc. for C10H10N2O: MW ˆ 174.0793.
2.1.7. CNC6H2-i-Pr2-2,6-(CH=NNHCHO)-4 (4b)
Found: 174.0792.
To a mixture of formyl hydrazide (0.07 g, 1.161 mmol) in
THF (30 ml), 1b (0.25 g, 1.161 mmol) is added. The mix-
ture is stirred for 48 h at room temperature. The solvent is
removed, and the product is puri®ed by column chromato-
graphy using ethyl acetate/n-hexane (1:1) as the eluent
(Rf ˆ 0.50). Yield: 0.215 g, 72%, m.p. 175±1778C. 1H
NMR (DMSO-d6), two isomers: ꢀ 11.92 (d), 11.61 (s)
(1H, NH), 8.73 (d), 8.24 (s) (1H, CHO), 8.13(s), 8.07 (s)
(1H, CH=N), 7.58 (s), 7.62 (s) (2H, C6H2), 2.51 (septet, 2H,
CH), 1.26 (d, 12H, CH3). 13C NMR (DMSO-d6), two
isomers: ꢀ 170.1 (CN), 165.1, 157.2 (CHO), 146.5,
144.8, 143.8, 135.0, 124.0, 122.2, 121.8 (C=N, C6H2),
29.4 (CH), 22.1 (CH3). IR (KBr, cm 1): ꢁ ˆ 2114 (s,
2.1.4. CNC6H2-i-Pr2-2,6-(CH=NOH)-4 (2b)
A mixture of 1b (0.289 g, 1.35 mmol) and hydroxyamine
hydrochloride (0.098 g, 1.41 mmol) is stirred in THF
(30 ml). Pyridine (0.12 ml, 1.41 mmol) is added. The mix-
ture is stirred at room temperature for 20 h. The solvent is
removed, and the product is isolated by column chromato-
graphy using n-hexane/EtOAc (3:1) as the eluent (Rf ˆ 0.5).
A white solid is obtained. Yield: 0.253 g, 81%, m.p. 143±
1
1448C. H NMR (CDCl3): ꢀ 8.40 (s, 1H, CH=N), 8.14 (s,
1H, OH), 7.38 (s, 2H, C6H2), 3.39 (septet, 2H, CH), 1.30 (d,
12H, CH3). 13C NMR (CDCl3): ꢀ 169.8 (CN), 149.7 (C=N),
145.7, 132.8, 122.1 (C6H2), 29.8 (CH), 22.5 (CH3). IR (KBr,
cm 1): ꢁ ˆ 3640±3100 (br, O±H), 2114 (s, CN). HRMS
‡
CN), 1699 (s, CHO), 1601 (w, C=N). HRMS (M ) m/e
Calc. for C15H19N3O: MW ˆ 257.1528. Found: 257.1526.
‡
(M ) m/e Calc. for C14H18N2O: MW ˆ 230.1419. Found:
230.1414.
2.1.8. Trans-[FeI2(CNC6H2-i-Pr2-2,6-CHO-4)4] (5b)
To a suspension of FeI2 (0.072 g, 0.232 mmol) in THF
(15 ml) under N2, 1b (0.198 g, 0.919 mmol) in THF (15 ml)
is added dropwise at room temperature. The solution turns
brownish yellow ®rst. The mixture is kept stirring overnight.
The solvent is removed under reduced pressure to afford a
green solid. Dark green sheet-like crystals are obtained from
CH2Cl2/n-hexane. Yield: 0.211 g, 79%, m.p. 257±2588C
(dec.). 1H NMR (CD2Cl2): ꢀ 10.00 (s, 4H, CHO), 7.73
(s, 8H, C6H2), 3.81 (septet, 8H, CH), 1.29 (d, 48H, CH3).
13C NMR (CD2Cl2): ꢀ 191.7 (CHO), 177.6 (CN), 147.9,
136.5, 130.3, 125.3 (C6H2), 29.9 (CH), 23.1 (CH3). IR (KBr,
cm 1): ꢁ ˆ 2116 (s, CN), 1699 (s, C=O).
2.1.5. CNC6H2Me2-2,6-[CH=NNH(C5H4N-2)]-4 (3a)
A solution of 2-hydrazinopyridine hydrochloride (0.30 g,
1.647 mmol) in water (10 ml) is treated with a solution of
sodium carbonate (0.34 g, 3.21 mmol) in water (10 ml). The
mixture is extracted with ether (three times, 20 ml each
time). The ether extracts are pooled, dried over magnesium
sulphate, and the solvent is removed. The residue is added to
a solution of 1a (0.135 g, 0.852 mmol) in THF (50 ml). The
mixture is stirred for 20 h at room temperature. The solvent
is removed, and the product is puri®ed by column chroma-
tography on silica gel using n-hexane/ethyl acetate (1:1) as

226
K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
2.1.9. Trans-[FeI2(CNC6H2Me2-2,6-(CH=NOH)-4)4] (6a)
To a suspension of iron(II) iodide (0.078 g, 0.252 mmol)
in THF under N2, 2a (0.154 g, 0.887 mmol) in THF (15 ml)
is added dropwise at room temperature. The solution turns
green. The mixture is kept stirring overnight at room tem-
perature. The solvent is removed under reduced pressure to
afford a green solid. The solid is reprecipitated from THF/n-
hexane and recrystallized from THF/n-hexane to give dark
green crystals. Yield: 0.152 g, 68%, m.p. 199±2008C (dec.).
1H NMR(CD3OD): ꢀ 8.03 (s, 4H, CH=N), 7.43(s, 8H, C6H2),
2.60(s,24H,CH3).13CNMR(CD3OD):ꢀ146.3,135.0,132.5,
126.9, 124.9 (C=N, C6H2), 16.8 (CH3). IR (KBr, cm 1):
ꢁ ˆ 3400±3300 (br, OH), 2120 (s, CN). Anal. Calc. for
C40H40N8O4I2Fe (MW ˆ 1006.469) with 2 mol THF: C,
50.10; H, 4.91; N, 9.74. Found: C, 50.67; H, 4.97; N, 10.15%.
is added dropwise at room temperature. The solution turns
green ®rst. On further stirring, a yellow precipitate forms.
The mixture is kept stirring overnight at room temperature.
The solvent is removed under reduced pressure. Hot CH2Cl2
and benzene are added to extract the complex. A yellow±
orange solid is obtained after cooling. Yield: 0.144 g, 76%,
1
m.p. 269±2718C (dec.). H NMR (CD2Cl2): ꢀ 9.99 (s, 2H,
CHO), 7.68 (s, 4H, C6H2), 2.66 (s, 12H, CH3). 13C NMR
(CD2Cl2): ꢀ 191.3 (CHO), 138.5, 129.4, 115.7 (C6H2), 19.4
(CH3). IR (KBr, cm 1): ꢁ ˆ 2197 (s, CN), 1700 (s, C=O).
2.1.13. Trans-[PdI2(CNC6H2-i-Pr2-2,6-CHO-4)2] (8b)
To a suspension of PdI2 (0.151 g, 0.418 mmol) in THF
(15 ml) under N2, 1b (0.179 g, 0.832 mmol) in THF (15 ml)
is added dropwise at room temperature. The solution turns
yellow ®rst. On further stirring, an orange solution forms.
The mixture is kept stirring overnight at room temperature.
The solvent is removed under reduced pressure to afford an
orange±yellow solid. Yellow±orange crystals are obtained
from methylene chloride/n-hexane. Yield: 0.226 g, 69%,
2.1.10. Trans-[FeI2(CNC6H2-i-Pr2-2,6-(CH=NOH)-4)4]
(6b)
To a green solution of FeI2(CNC6H2-i-Pr2-2,6-CHO-4)4,
(5b), (9.5 mg, 0.01 mmol) in THF (20 ml), hydroxylamine
hydrochloride (2.92 mg, 0.042 mmol) and a few drops of
pyridine are added at room temperature, followed by a few
drops of methanol. Initially, the solution is deep green. Upon
stirring overnight at room temperature, the reaction mixture
turns pale green. Any solid is ®ltered off. The solvent is
removed under reduced pressure to afford a green solid. The
green solid is recrystallized from THF/n-pentane to give
dark green crystals. Yield: 8 mg, 77%, m.p. 209±2118C
(dec.). In an alternative procedure, analogous to the synth-
esis of 6a, compound 6b has been prepared by reaction of
FeI2 with 2b. 1H NMR (DMSO-d6): ꢀ 10.19 (br, 4H, NOH),
8.20 (s, 4H, CH=N), 7.54 (s, 8H, C6H2), 3.66 (septet, 8H,
1
m.p. 257.5±2588C (dec.). H NMR (CD2Cl2): ꢀ 10.05 (s,
2H, CHO), 7.77 (s, 4H, C6H2), 3.63 (septet, 4H, CH), 1.39
(d, 24H, CH3). 13C NMR (CD2Cl2): ꢀ 191.6 (CHO), 148.6,
138.1, 125.4 (C6H2), 30.3 (CH), 23.0 (CH3). IR (KBr,
cm 1): ꢁ ˆ 2193 (s, CN), 1703 (s, C=O). Anal. Calc. for
C28H34N2O2I2Pd (MW ˆ 790.802): C, 42.53; H, 4.33; N,
3.54. Found: C, 42.68; H, 4.41; N, 3.68%.
2.1.14. Trans-[PdI2(CNC6H2-i-Pr2-2,6-(CH=NOH)-4)2]
(9b)
PdI2 (0.1163 g, 0.323 mmol) is suspended in THF
(15 ml). 2b (0.116 g, 0.646 mmol) in THF (15 ml) is added
dropwise at room temperature. Upon addition, the solution
turns orange. The mixture is kept stirring overnight at room
temperature. The solvent is removed under reduced pressure
to afford an orange solid. The orange product is recrystal-
lized from THF/petroleum ether (40±608C) to give orange
CH), 1.20 (d, 48H, CH3). 13C NMR (DMSO-d6): ꢀ 145.7,
1
134.0 127, 125, 121.6 (C=N, C6H2). IR (KBr, cm
)
ꢁ ˆ 3500±3300 (br, O±H), 2122 (s, CN). Anal. Calc. for
C56H72N8O4I2Fe (MW ˆ 1230.901) with 2 mol THF: C,
56.56; H, 6.38; N, 8.24. Found: C, 56.09; H, 6.49; N, 8.22%.
1
crystals. Yield: 0.152 g, 57%, m.p. 203±2048C. H NMR
2.1.11. Trans-[FeI2(CNC6H2-i-Pr2-2,6-(CH=NNHCHO)-
4)4] (7b)
(acetone-d6): ꢀ 10.76 (s, 2H, OH), 8.25 (s, 2H, CH=N), 7.67
(s, 4H, C6H2), 3.61 (septet, 4H, CH), 1.37 (d, 24H, CH3).
13C NMR (acetone-d6): ꢀ 148.5, 148.1, 137.4, 123.1 (C=N,
C6H2), 23.1 (CH3). IR (KBr, cm 1): ꢁ ˆ 2187 (s, CN). Anal.
Calc. for C28H36N4O2I2Pd (MW ˆ 820.832) with 0.25 mol
THF: C, 41.62; H, 4.81; N, 6.69. Found: C, 41.34; H, 4.50;
N, 6.66%.
To a suspension of FeI2 (0.045 g, 0.145 mmol) in THF
(15 ml) under N2, 4b (0.15 g, 0.583 mmol) in THF (15 ml)
is added dropwise at room temperature. The solution turns
green. The mixture is kept stirring overnight. The solvent is
removed under reduced pressure to afford a green solid,
which is recrystallized from THF/n-hexane. Yield: 0.14 g,
72%. 1H NMR (DMSO-d6): ꢀ 11.90 (d, 4H, CHO), 8.72 (d,
4H, NH), 8.08 (s, 4H, CH=N), 7.60 (s, 8H, C6H2), 3.66
(septet, 8H, CH), 1.21 (d, 48H, CH3). 13C NMR (DMSO-
d6): ꢀ 174.9 (CN), 165.1 (CHO), 145.8, 143.8, 134.7, 125.3,
122.0 (C=N, C6H2), 29.0 (CH), 22.4 (CH3). IR (KBr, cm 1):
ꢁ ˆ 2122 (s, CN), 1697 (s, C=O), 1614 (w, C=N).
2.1.15. Trans-[PdI2(CNC6H2-i-Pr2-2,6-(CH=NNHC5H4N-
2)-4)2] (10b)
PdI2 (0.041 g, 0.114 mmol) is suspended in THF (10 ml).
3b (0.07 g, 0.228 mmol) in THF (20 ml) is added dropwise
at room temperature. On further stirring, an orange solution
forms. The mixture is kept stirring for 3.5 h at room
temperature. The solution is ®ltered, and the solvent is
removed under reduced pressure to afford an orange solid
which is recrystallized from THF/n-hexane. Yield: 95 mg,
2.1.12. Trans-[PdI2(CNC6H2Me2-2,6-CHO-4)2] (8a)
To a suspension of PdI2 (0.10 g, 0.278 mmol) in THF
(15 ml) under N2, 1a (0.09 g, 0.566 mmol) in THF (15 ml)
1
86%, m.p. 275±2768C. H NMR (CDCl3): ꢀ 8.60 (s, 2H,

K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
227
NH), 6.82±8.17 (10H, C5H4N), 7.16 (s, 4H, C6H2), 7.51 (s,
2H, CH=N), 3.59 (septet, 4H, CH, 1.39 (d, 24H, CH3). 13
C6H2), 3.60 (septet, 4H, CH), 1.37 (d, 24H, CH3). 13C NMR
(acetone-d6): ꢀ 148.6, 148.0, 137.2, 123.1 (C=N, C6H2), 29
(CH), 23.1 (CH3). IR (KBr, cm 1): ꢁ ˆ 3300±3150 (br,
OH), 2185 (s, CN). Anal. Calc. for C28H36N4O2I2Pt
(MW ˆ 909.522) with 0.5 mol THF: C, 38.11; H, 4.26;
N, 5.93. Found: C, 38.12; H, 3.98; N, 6.09%.
C
NMR (CDCl3): ꢀ 161.9 (CN), 156.0, 147.7, 147.4, 138.3,
137.4, 129.4, 121.5, 116.5, 107.6 (C=N, C6H2, C5H4N), 29.7
(CH), 22.9 (CH3). IR (KBr, cm 1): ꢁ ˆ 2189 (s, CN), 1595
(m), 1578 (s). Anal. Calc. for C38H44N8I2Pd
(MW ˆ 973.036) with 2 mol H2O: C, 45.23; H, 4.79; N,
11.10. Found: C, 45.5; H, 4.2; N, 10.5%.
2.1.19. Trans-[PtI2(CNC6H2-i-Pr2-2,6-(CH=NNHCHO)-
4)2] (14b)
2.1.16. Trans-[PdI2(CNC6H2-i-Pr2-2,6-(CH=NNHCHO)-
4)2] (11b)
Black solid PtI2 (0.131 g, 0.291 mmol) is dried under
reduced pressure for 1 h at room temperature and suspended
in THF (10 ml). 4b (0.15 g, 0.583 mmol) in THF (20 ml) is
added dropwise at room temperature. The mixture is stirred
overnight at room temperature to afford a yellow solution. A
yellow solid is obtained after removal of solvent. The yellow
solid is recrystallized from THF/ether. Yield: 0.15 g, 71%.
1H NMR (DMSO-d6): ꢀ 11.98 (d, 2H, CHO), 8.73 (d, 2H,
NH), 8.07 (s, 2H, CH=N), 7.65 (s, 4H, C6H2), 3.43 (septet,
4H, CH), 1.29 (d, 24H, CH3). 13C NMR (DMSO-d6): ꢀ
165.3 (CHO), 146.6, 143.5, 136.8, 122.5, 122.3 (C=N,
C6H2), 29.2 (CH), 22.4 (CH3). IR (KBr, cm 1): ꢁ ˆ 2185
(s, CN), 1701 (s, C=O). Anal. Calc. for C30H38N6O2I2Pt
(MW ˆ 963.574) with 0.5 mol THF: C, 38.45; H, 4.24; N,
8.40. Found: C, 38.18; H, 4.12; N, 8.15%.
PdI2 (0.043 g, 0.120 mmol) is suspended in THF (10 ml).
4b (0.062 g, 0.241 mmol) in THF (20 ml) is added dropwise
at room temperature. On further stirring, a yellow solution is
obtained. The mixture is stirred overnight to afford an
orange solution. The solution is ®ltered and the solvent is
removed under reduced pressure and an orange solid is
obtained. Recrystallization from THF/petroleum ether (40±
608C). Yield: 80 mg, 76%. 1H NMR (DMSO-d6): ꢀ 12.00 (d,
2H), 8.75 (d, 2H) (CHO, NH), 8.10 (s, 2H, CH=N), 7.67 (s,
4H, C6H2), 3.46 (septet, 4H, CH), 1.31 (d, 24H, CH3). 13
C
NMR (DMSO-d6): ꢀ 165.2 (CHO), 146.7, 143.4, 136.9,
130.4, 122.6, 122.2 (CN, C6H2), 29.3 (CH), 22.4 (CH3). IR
(KBr, cm 1): ꢁ ˆ 2189 (s, CN), 1699 (s, C=O). Anal. Calc.
for C30H38N6O2I2Pd (MW ˆ 874.884) with 0.5 mol THF:
C, 42.38; H, 4.67; N, 9.23. Found: C, 42.38; H, 4.69; N,
9.15%.
2.2. Crystal structure determinations
Diffraction data for compounds 5b and 6a were collected
on a MAR Imaging Plate Detector System using graphite-
2.1.17. Trans-[PtI2(CNC6H2-i-Pr2-2,6-CHO-4)2] (12b)
PtI2 (0.156 g, 0.348 mmol) is suspended in THF (15 ml).
1b (0.15 g, 0.696 mmol) in THF (15 ml) is added dropwise
at room temperature. The solution turns yellowish brown
®rst. On stirring, a yellow solution forms. The mixture is
kept stirring overnight at room temperature. The solvent is
removed under reduced pressure to afford a yellow solid.
The yellow product is recrystallized from THF/n-hexane.
Yield: 0.225 g, 83%, m.p. 237±2388C. 1H NMR (CD2Cl2): ꢀ
10.04 (s, 2H, CHO), 7.77 (s, 4H, C6H2), 3.63 (septet, 4H,
CH), 1.39 (d, 24H, CH3). 13C NMR (CD2Cl2): ꢀ 191.6
(CHO), 148.6, 137.9, 125.4 (C6H2), 30.2 (CH), 23.0 (CH3).
IR (KBr, cm 1): ꢁ ˆ 2185 (s, CN), 1705 (s, C=O). Anal.
Calc. for C28H34N2O2I2Pt (MW ˆ 1059.078): C, 38.24; H,
3.89; N, 3.19. Found: C, 38.30; H, 3.94; N, 3.19%.
Ê
monochromatized Mo Ka X-ray radiation (ꢂ ˆ 0.71073 A)
from a MAR generator (sealed tube 50 kVand 50 mA), and
processed by DENZO [95]. The diffraction data for com-
pounds 6b and 9a were collected on a Rigaku AFC7R four-
circle diffractometer using graphite-monochromatized Mo
Ê
Ka X-ray radiation (ꢂ ˆ 0.71073 A) from a Rigaku RU-200
rotating-anode generator at 50 kV and 160 mA and pro-
cessed by the MSC/RIGAKU diffractometer control soft-
ware. Empirical absorption corrections from -scans were
applied to the data for compounds 6b and 9a and no
absorption correction was made on compounds 5b and
6a. All structure determinations were done using the
MSC crystal structure analysis package TeXsan [96] and
the full-matrix least-squares re®nements were on F using
re¯ections with I > 3ꢃ(I). Hydrogen atoms at calculated
positions with thermal parameters equal to 1.3 times that
of the attached C atoms were included in the calculations,
but not re®ned.
2.1.18. Trans-[PtI2(CNC6H2-i-Pr2-2,6-(CH=NOH)-4)2]
(13b)
Black solid PtI2 (0.067 g, 0.151 mmol) is dried under
reduced pressure for 1 h at room temperature and suspended
in THF (15 ml). 2b (0.07 g, 0.301 mmol) in THF (15 ml) is
added dropwise at room temperature. Upon addition, the
solution turns yellow. The mixture is kept stirring overnight
at room temperature. The solvent is removed under reduced
pressure to afford a yellow solid. The yellow product is
recrystallized from THF/petroleum ether (40±608C). Yield:
3. Results and discussion
3.1. Synthesis of the isocyanides and the isocyanide metal
complexes
1
0.063 g, 47%, m.p. 234±2358C (dec.). H NMR (acetone-
d6): ꢀ 10.80 (s, 2H, OH), 8.24 (s, 2H, CH=N), 7.66 (s, 4H,
The 4-isocyanobenzaldehydes 1a and 1b were prepared
in the established fashion from the corresponding anilines

228
K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
[97,98] by formylation and subsequent dehydration
[99,100]. As the aldehyde group is one of the most versatile
functionalities, many possibilities exist for the attachment
of hydrogen bonding groups or other intermolecular inter-
action sites. The formation of oximes, hydrazones and
related derivatives was chosen to demonstrate the new
approach. Compounds 1 react with hydroxylamine and
various hydrazine derivatives to afford the functionalized
isocyanides 2±4. The oxime, 2-pyridylhydrazone, and for-
mylhydrazone functionalities contain molecular fragments
capable of forming pairwise hydrogen bonds [30±36,
39±46].
The new isocyanides combine with FeI2, PdI2, and PtI2 to
give the complexes 5±14. The grafting procedure can also be
performed on coordinated formylisocyanoarene ligands as
demonstrated by the synthesis of complex 6b from 5b and
hydroxylamine. The IR and NMR spectroscopic parameters
of complexes 5±14 are consistent with a trans arrangement
of the iodo ligands in all complexes, i.e. square planar and
linear geometries of the tetrakis-isocyanide and bis-isocya-
nide metal cores, respectively. The formyl-substituted com-
plexes 5, 8, and 12 easily dissolve in methylene chloride or
THF, but the complexes 6±7, 9±11, and 13±14, which all
carry potential hydrogen-bonding sites, are signi®cantly less
soluble. The lower solubility of the latter complexes
strongly suggests that the metal complex units are inter-
connected by hydrogen bonds to form extended chains and
networks.
bonding, e.g. hydroxy, carboxyl, and carboxamide function-
alities, have been prepared [63±79]. Noteworthy in the
present context is also the report by Fehlhammer et al.
on the isodiazomethane complex [PdI2(CNNH2)2] [80].
This compound was isolated as the dietherate, indicating
that the amino groups form strong hydrogen bonds. The
synthetic methods used in the preparation of such isocya-
nides are typically only applicable to a narrow range of
hydrogen-bonding groups. In contrast, the grafting proce-
dure described here is free of the limitations dictated by the
reaction conditions encountered during the synthesis of the
isocyanide functionality. The attachment of entire hydro-
gen-bonding groups via transformations of the formyl
functionality can also be applied to coordinated isocyanide
ligands without affecting the metal-isocyanide core. Earlier
attempts to achieve the transformation of the ester func-
tionalities of analogous complexes of alkylisocyanobenzo-
ate ligands proved less successful [101]. Several
transformations on coordinated isocyanide and cyanide
ligands resulting in the formation of hydrogen-bonding
functionalities have been reported [94]. Of particular rele-
vance is the formation of oximes and hydrazones of coor-
dinated ꢄ-oxoalkylisocyanides described by Beck and
coworkers [88].
3.2. X-ray crystallographic studies
The molecular structures of compounds 5b, 6a, 6b, and
9a are shown in Figs. 1±4, respectively. The crystallo-
graphic data are compiled in Table 1. The crystal structure
of complex 5b reveals no speci®c intermolecular interac-
Ê
tions. The shortest contact [O(1)±C(18), 3.161(6) A] arises
from the approach of the carbonyl oxygen atom O(1)
towards C(18) of the arene ring C(16)±C(21), whereby
the carbonyl CO vector is roughly perpendicular to the
plane of the phenyl ring. There are no signi®cant p stacking
interactions between the isocyanoarene rings.
Fig. 1. Molecular structure of 5b. The thermal ellipsoids are shown at the
Ê
35% probability level. Selected bond distances (A) and angles (8). Fe(1)±
I(1) 2.6353(3), Fe(1)±C(1) 1.871(4), N(1)±C(1) 1.145(5), N(2)±C(15)
1.160(4), O(1)±C(8) 1.183(5), O(2)±C(22) 1.153(6); I(1)±Fe(1)±C(1)
89.93(10), I(1)±Fe(1)±C(15) 89.98(9), C(1)±Fe(1)±C(15) 88.2(1).
Prior to this work, a number of isocyanides and isocya-
nide metal complexes bearing groups capable of hydrogen-

K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
229
Ê
Fig. 2. (a) Molecular structure of 6a. The thermal ellipsoids are shown at the 40% probability level. Selected bond distances (A) and angles (8). Fe(1)±I(1)
2.6343(4), Fe(1)±C(1) 1.898(6), Fe(1)±C(11) 1.884(6), N(1)±C(1) 1.120(6), N(3)±C(11) 1.142(7), N(2)±C(10) 1.277(10), N(4)±C(20) 1.269(8), N(2)±O(1)
1.385(7), N(4)±O(2) 1.430(7); I(1)±Fe(1)±C(1) 89.5(2), I(1)±Fe(1)±C(11) 89.8(2), C(1)±Fe(1)±C(11) 87.1(2). (b) Short segment of a chain formed by
pairwise hydrogen-bonding of the oxime groups N(2)O(1)H (dotted lines). The isocyanide ligands not involved in these interactions are truncated to show
only the NCFeCN cores. (c) Partial segment of a layer of molecular units connected by short O(2)Á Á ÁI(1) contacts (dotted lines). The isocyanide ligands not
involved in these interactions are truncated to show only the NCFeCN cores. (d) Partial segment of a layer of complete molecular units. The O(2)Á Á ÁI(1)
contacts are indicated by dotted lines. The pairwise hydrogen-bonding contacts of the oxime groups N(2)O(1)H (indicated by double arrows) connect to the
adjacent layers above and below. (e) Partial segment of two adjacent layers. The arene groups of the isocyanide ligands are represented by single lines for
clarity. The hydrogen bonds within and between the layers are indicated by dotted lines.
The molecular units of 9b, which were designed as one-
dimensional building blocks, form the expected linear
chains by pairwise hydrogen-bonding of the oxime groups
molecular units of 6a in the solid state is furthermore
stabilized by p stacking between pairs of arene groups
(Fig. 2(d)). The shortest contacts between the offset rings
[109] [C(4)±C(17), C(5)±C(16), C(5)±C(17), and C(6)±
Ê
[O(1)±N(2), 2.824(5) A] as shown in Fig. 4(b) [102±107].
Ê
C(15)] are in the range of 3.55 to 3.64 A. The molecular
There appear to be no other signi®cant directional inter-
molecular interactions in solid 9b.
In contrast, the intermolecular interactions in solid 6a are
more complex. Only one of the two pairs of symmetry-
related mutually trans isocyanide ligands are joined at
oxime groups via pairwise hydrogen bonding [O(1)±N(2),
units of 6a are organized in layers. A section of a single
layer is shown in Fig. 2(d). The layers are interconnected by
the pairwise hydrogen bonds of the linear chains which are
running in an oblique fashion through the layers (Fig. 2(e)).
The characteristic pairwise hydrogen bonds of the oxime
groups are absent in the solid state structure of 6b. The
molecular units of 6b, if pictured as square plates, overlap
along opposite edges like the steps of a staircase (Fig. 3(b)).
The joints between adjacent oxime groups are formed by
Ê
2.72(1) A] to form extended linear chains analogous to
those found in solid 9b (Fig. 2(b)). The oxime groups of
the second pair of isocyanide ligands are in close contact
with the iodide ligands of adjacent molecular units as shown
in Fig. 2(c). The intermolecular O(2)±I(1) distance of
Ê
single OHÁ Á ÁN hydrogen bonds [O(1)±N(4), 2.790(8) A;
Ê
3.59(1) A is close to the sum of the van der Waals radii
Ê
O(3)±N(8), 2.783(7) A]. Each free OH group is hydro-
of O and I, and relatively short compared to other inter-
molecular IÁ Á ÁO contacts [108]. Even though the oxime
hydrogen atoms of 6a were not located in the X-ray
structure, this distance suggests the presence of weak
O(2)±HÁ Á ÁI(1) hydrogen bonds. The arrangement of the
gen-bonded to
Ê
a
2.654(9) A; O(4)±O(6), 2.624(8) A].
molecule of THF [O(2)±O(5),
Ê
The hydrogen-bonding capabilities of oximes are well-
documented, and hydrogen-bonded networks of polyfunc-
tional oximes have been described [102±107]. The OH

230
K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
Fig. 4. (a) Molecular structure of 9b. The thermal ellipsoids are shown at
Ê
the 50% probability level. Selected bond distances (A) and angles (8).
Pd(1)±I(1) 2.5984(4), Pd(1)±C(1) 1.970(4), N(1)±C(1) 1.142(5), N(2)±
C(8) 1.255(6), N(2)±O(1) 1.406(4); I(1)±Pd(1)±C(1) 89.1(1). (b) Short
segment of a chain of hydrogen-bonded molecular units 9b.
gen bond distances found in this study are within the
established range. In the majority of oxime structures, both
the OH group and the nitrogen atom are involved simulta-
neously, whereby the pairwise arrangement found in the
structures 6b and 9b is most common. However, as this
study con®rms, the hydrogen-bonding capability of oxime
groups is ¯exible. In each intermolecular joint of structure
6b, one OH group forms an hydrogen bond with an `exter-
nal' acceptor (THF), and one N atom is not engaged. In the
crystal structure 6a, one type of oxime group appears to
form weak OHÁ Á ÁI hydrogen bonds. In 6a, the crystal
packing is also stabilized by attractive p interactions
between the arene rings [110]. Evidently, the hydrogen
bonds of oxime groups exert a strong organizational in¯u-
ence on the packing of the crystals, but they are not of
suf®cient strength to predetermine the arrangement of the
molecular units.
4. Conclusion
A versatile method for the attachment of hydrogen-bond-
ing groups to isocyanides has been developed. The proce-
dure is useful for the design of isocyanide metal complexes
which form hydrogen-bonded networks.
Fig. 3. (a) Molecular structure of 6b. The thermal ellipsoids are shown at
Ê
the 30% probability level. Selected bond distances (A) and angles (8).
Fe(1)±I(1) 2.638(1), Fe(1)±I(2) 2.638(1), Fe(1)±C(1) 1.857(6), Fe(1)±
C(15) 1.886(8), Fe(1)±C(29) 1.887(6), Fe(1)±C(43) 1.862(8), N(1)±C(1)
1.178(7), N(3)±C(15) 1.144(9), N(5)±C(29) 1.138(7), N(7)±C(43)
1.178(9), N(2)±C(14) 1.265(9), N(4)±C(28) 1.31(1), N(6)±C(42)
1.275(8), N(8)±C(56) 1.254(8), O(1)±N(2) 1.417(7), O(2)±N(4)
1.400(8), O(3)±N(6) 1.387(7), O(4)±N(8) 1.383(7); I(1)±Fe(1)±I(2)
179.16(6), I(1)±Fe(1)±C(1) 88.8(2), I(1)±Fe(1)±C(15) 91.0(2), I(1)±
Fe(1)±C(29) 90.6(2), I(1)±Fe(1)±C(43) 90.8(2), C(1)±Fe(1)±C(15)
85.2(3), C(1)±Fe(1)±C(29) 179.2(4), C(1)±Fe(1)±C(43) 93.9(3). (b) Short
section of the staircase of molecular units of 6b. The isopropyl groups are
omitted for clarity.
5. Supplementary material
Crystallographic data have been deposited at the CCDC,
12 Union Road, Cambridge CB2 1EZ, UK and copies can be
obtained on request, free of charge, by quoting the pub-
lication citation.
Acknowledgements
group can act as an hydrogen bond donor as well as (but
rarely) an hydrogen bond acceptor. The nitrogen atom
frequently serves as an hydrogen bond acceptor. The hydro-
Support for this work by the Research Grants Council of
Hong Kong (RGC) and by the Committee on Research and

K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
231
Table 1
Crystal and data collection parameters for complexes 5b, 6a, 6b, and 9a
5b
6a
6b
9a
Formula
C56H68FeI2N4O4
1170.83
C40H40FeI2N8O4
1006.46
C56H72FeI2N8O4.2C4H8O
1375.11
monoclinic
Cc (No. 9)
20.090(4)
19.958(5)
19.552(4)
115.33(1)
7085(2)
C28H32I2N4O2Pd
816.80
Formula weight
Crystal habit
Space group
monoclinic
P21/c (No. 14)
12.423(2)
14.185(3)
16.070(3)
94.55(2)
2822.9(9)
2
monoclinic
P21/n (No. 14)
12.423(3)
12.864(2)
16.169(3)
102.98(2)
2518.0(8)
2
monoclinic
P21/n (No. 14)
10.066(3)
17.868(5)
8.943(5)
92.07(4)
1607.3(9)
2
Ê
a (A)
Ê
b (A)
Ê
c (A)
ꢅ (8)
V (A )
Ê 3
Z
4
T (K)
301
301
301
301
Crystal color
Crystal dimensions (mm)
dark green
0.20 Â 0.20 Â 0.30
1.377
dark green
0.20 Â 0.15 Â 0.30
1.327
dark green
0.20 Â 0.20 Â 0.30
1.289
orange
0.15 Â 0.10 Â 0.25
1.688
3
d(calc) (g cm
1
)
ꢆ (cm
Scan mode
)
14.06
15.67
11.34
25.28
!±2ꢇ
45
!±2ꢇ
50
2ꢇ max (8)
51.2
5463
3809
51.2
4553
3481
Unique reflections
Reflections used in least-squares
refinement (I>3ꢃ(I))
No. of variables
R
4789
2944
3728
2178
304
250
728
172
0.034a
0.045b
0.026
0.01
0.049a
0.076b
0.020
0.01
0.028a
0.032b
0.018
0.05
0.027a
0.030b
0.010
0.04
Rw
p-factor
(Á/ꢃ) max.
Goodness of fit
1.93
3.75
1.39
1.86
3
)
Ê
Áꢈ (e A
0.18/0.28
0.65/1.16
0.34/0.62
0.40/0.44
a
R ˆ Æ||Fo| |Fc||/Æ|Fo|.
b
Rw ˆ [Æw(|Fo| |Fc|)2/ÆwFo
]
2 1/2, where w ˆ Fo2/[ꢃ2(I) ‡ (pFo2)2].
[15] U. Keppeler, M. Hanack, Chem. Ber. 119 (1986) 3363.
[16] M. Hanack, S. Deger, A. Lange, Coord. Chem. Rev. 83 (1988)
115.
Conference Grants (CRCG) of The University of Hong
Kong is gratefully acknowledged. K.Y. Lau acknowledges
the receipt of a Postgraduate Studentship, administered by
The University of Hong Kong.
[17] G. Jia, R.J. Puddephatt, J.J. Vittal, N.C. Payne, Organometallics 12
(1993) 263.
[18] R. Tannenbaum, Chem. Mater. 6 (1994) 550.
[19] T. Kaharu, T. Tanaka, M. Sawada, S. Takahashi, J. Chem. Mater. 4
(1994) 859.
References
Â
[20] M. Benouazzane, S. Coco, P. Espinet, J.M. Martõn-Alvarez, J.
Chem. Mater. 5 (1995) 441.
[1] L. Malatesta, F. Bonati, Isocyanide Complexes of Transition
Metals, Wiley, New York, 1969.
[21] M.J. Irwin, L.M. Rendina, J.J. Vittal, R.J. Puddephatt, J. Chem.
Soc., Chem. Commun. 1281 (1996).
[2] P.M. Treichel, Adv. Organomet. Chem. 11 (1973) 21.
[3] S.J. Lippard, Prog. Inorg. Chem. 21 (1976) 910.
[4] Y. Yamamoto, Coord. Chem. Rev. 32 (1980) 193.
[5] E. Singleton, H.E. Oosthuizen, Adv. Organomet. Chem. 22 (1983)
209.
[22] M.J. Irwin, G. Jia, J.J. Vittal, R.J. Puddephatt, Organometallics 15
(1996) 5321.
[23] D. Fortin, M. Drouin, M. Turcotte, P.D. Harvey, J. Am. Chem. Soc.
119 (1997) 531.
[24] C.A. Daws, C.L. Exstrom, J.R. Sowa, K.R. Mann, Chem. Mater. 9
(1997) 363.
Â
[25] M.J. Irwin, L. Manojlovic-Muir, K.W. Muir, R.J. Puddephatt, D.S.
[6] F.E. Hahn, Angew. Chem. 105 (1993) 681.
[7] F.E. Hahn, Angew. Chem., Int. Ed. Engl. 32 (1993) 650.
[8] D. Lentz, Angew. Chem. 106 (1994) 1377.
[9] D. Lentz, Angew. Chem., Int. Ed. Engl. 33 (1994) 1315.
[10] A. Efraty, I. Feinstein, F. Frolow, L. Wackerle, J. Am. Chem. Soc.
102 (1980) 6341.
Yufit, J. Chem. Soc., Chem. Commun. 219 (1997).
[26] I.S. Sigal, H.B. Gray, J. Am. Chem. Soc. 103 (1981) 2220.
[27] D.S. Grubisha, J.S. Rommel, T.M. Lane, W.T. Tysoe, D.W.
Bennett, Inorg. Chem. 31 (1992) 5022.
[11] A. Efraty, I. Feinstein, L. Wackerle, F. Frolow, Angew. Chem., Int.
Ed. Engl. 19 (1980) 633.
[28] R.F. Johnston, J. Coord. Chem. 31 (1994) 57.
[29] H. Xiao, K.-K. Cheung, C.-M. Che, J. Chem. Soc., Dalton Trans.
3699 (1996).
[12] A. Efraty, I. Feinstein, F. Frolow, A. Goldman, J. Chem. Soc.,
Chem. Commun. 864 (1980).
È
[13] U. Keppeler, O. Schneider, W. Stoffler, M. Hanack, Tetrahedron
[30] J.C. MacDonald, G.M. Whitesides, Chem. Rev. 94 (1994) 2383.
[31] J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995.
[32] G.R. Desiraju (Ed.), The Crystal as a Supramolecular Entity, Wiley,
New York, 1995.
Lett. 25 (1984) 3679.
[14] I. Feinstein-Jaffe, F. Frolow, L. Wackerle, A. Goldman, A. Efraty, J.
Chem. Soc., Dalton Trans. 469 (1988).
[33] D.S. Lawrence, T. Jiang, M. Levett, Chem. Rev. 95 (1995) 2229.

232
K.Y. Lau et al. / Inorganica Chimica Acta 285 (1999) 223±232
[34] A.D. Burrows, C.-W. Chan, M.M. Chowdhry, J.E. McGrady, D.M.
Mingos, Chem. Soc. Rev. 329 (1995).
[71] W.P. Fehlhammer, K. Bartel, Angew. Chem., Int. Ed. Engl. 13
(1974) 599.
[35] D. Philp, J.F. Stoddart, Angew. Chem. 108 (1996) 1242.
[36] D. Philp, J.F. Stoddart, Angew. Chem., Int. Ed. Engl. 35 (1996)
1154.
[72] D. Samuel, B. Weinraub, D. Ginsburg, J. Org. Chem. 21 (1956) 376.
[73] J.E. Baldwin, D.R. Kelly, C.B. Ziegler, J. Chem. Soc., Chem.
Commun. (1984) 133.
[37] L.-F. Mao, A. Mayr, Inorg. Chem. 35 (1996) 3183.
[38] J. Guo, A. Mayr, Inorg. Chim. Acta 261 (1997) 141.
[39] Y.-L. Chang, M.-A. West, F.W. Fowler, J.W. Lauher, J. Am. Chem.
Soc. 115 (1993) 5991.
[74] J.P. Chupp, K.L. Leschinsky, J. Heterocyclic Chem. 17 (1980) 705.
[75] Y. Ito, K. Kobayashi, T. Saegusa, Tetrahedron Lett. (1979) 1039.
[76] R. Bossio, S. Marcaccini, R. Pepino, Liebigs Ann. Chem. 935
(1990).
[40] S.J. Geib, C. Vicent, E. Fan, A.D. Hamilton, Angew. Chem. 105
(1993) 83.
[77] K. Matsumoto, M. Suzuki, N. Yoneda, M. Miyoshi, Synthesis 249
(1977).
[41] S.J. Geib, C. Vicent, E. Fan, A.D. Hamilton, Angew. Chem., Int.
Ed. Engl. 32 (1993) 119.
[78] K. Gollnick, S. Koegler, Tetrahedron Lett. 29 (1988) 1127.
[79] K. Gollnick, S. Koegler, D. Maurer, J. Org. Chem. 57 (1992) 229.
[80] W.P. Fehlhammer, P. Buracas, K. Bartel, Angew. Chem. 89 (1977)
752.
[42] X. Wang, M. Simard, J.D. Wuest, J. Am. Chem. Soc. 116 (1994)
12119.
[43] S. Hanessian, M. Simard, S. Roelens, J. Am. Chem. Soc. 117
(1995) 7630.
[81] W.P. Fehlhammer, P. Buracas, K. Bartel, Angew. Chem., Int. Ed.
Engl. 16 (1977) 707.
[82] W.P. Fehlhammer, F. Degel, G. Beck, Chem. Ber. 120 (1987) 29.
[44] I.L. Karle, D. Ranganathan, V. Haridas, J. Am. Chem. Soc. 118
(1996) 7128.
È
[45] C.B. Aakeroy, D.P. Hughes, M. Nieuwenhuyzen, J. Am. Chem.
È È
[83] E. Bar, A. Volkl, F. Beck, W.P. Fehlhammer, A. Robert, J. Chem.
Soc., Dalton Trans. (1986) 863.
Soc. 118 (1996) 10134.
[46] F.D. Lewis, J.-S. Yang, C.L. Stern, J. Am. Chem. Soc. 118 (1996)
12029.
[84] W. Beck, W. Weigand, U. Nagel, M. Schaal, Angew. Chem. 96
(1984) 377.
[85] W. Beck, W. Weigand, U. Nagel, M. Schaal, Angew. Chem., Int.
Ed. Engl. 23 (1984) 377.
[47] S.B. Copp, S. Subramanian, M.J. Zaworotko, J. Am. Chem. Soc.
114 (1992) 8719.
[86] J. Baird, S.G. Davies, J. Organomet. Chem. 262 (1984) 215.
È
[87] E. Bar, W.P. Fehlhammer, W. Weigand, W. Beck, J. Organomet.
[48] S.B. Copp, K.T. Holman, J.O.S. Sangster, S. Subramanian, M.J.
Zaworotko, J. Chem. Soc., Dalton Trans. (1995) 2233.
È
[49] G. Schroder, B. Lippert, M. Sabat, C.J.L. Lock, R. Faggiani, B.
Chem. 347 (1988) 101.
[88] M. Schaal, W. Weigand, U. Nagel, W. Beck, Chem. Ber. 118 (1985)
2186.
Song, H. Sigel, J. Chem. Soc., Dalton Trans. (1995) 3767.
[50] P.J. Davies, N. Veldman, D.M. Grove, A.L. Spek, B.T.G. Lutz, G.
van Koten, Angew. Chem. 108 (1996) 2078.
[89] W. Weigand, U. Nagel, W. Beck, Chem. Ber. 123 (1990) 439.
[90] F.E. Hahn, M. Tamm, J. Chem. Soc., Chem. Commun. (1995) 569.
[91] F.E. Hahn, M. Tamm, T. LuÈgger, Angew. Chem. 106 (1994) 1419.
[92] F.E. Hahn, M. Tamm, T. LuÈgger, Angew. Chem., Int. Ed. Engl. 33
(1994) 1356.
[51] P.J. Davies, N. Veldman, D.M. Grove, A.L. Spek, B.T.G. Lutz, G.
van Koten, Angew. Chem., Int. Ed. Engl. 35 (1996) 1959.
[52] J.M. Forward, Z. Assefa, R.J. Staples, J.P. Fackler Jr., Inorg. Chem.
35 (1996) 16.
[93] M. Glaser, H. Spies, T. LuÈgger, F.E. Hahn, J. Organomet. Chem.
503 (1995) C32.
[53] M. Mukanata, L.P. Wu, M. Yamamoto, T. Kuroda-Sowa, M.
Maekawa, J. Am. Chem. Soc. 118 (1996) 3117.
[94] W.P. Fehlhammer, M. Fritz, Chem. Rev. 93 (1993) 1243.
[95] DENZO: The HKL Manual ± A description of programs DENZO,
XDISPLAYF, and SCALEPACK, written by D. Gewirth, with the
cooperation of the program authors Z. Otwinowski, W. Minor,
1995.
[54] O.M. Yaghi, H. Li, T.L. Groy, J. Am. Chem. Soc. 118 (1996) 9096.
[55] A.D. Burrows, M.P. Mingos, A.J.P. White, D.J. Williams, J. Chem.
Soc., Dalton Trans. (1996) 149.
[56] M.M. Chowdhry, D.M.P. Mingos, A.J.P. White, D.J. Williams, J.
Chem. Soc., Chem. Commun. (1996) 899.
[96] TeXsan: Crystal Structure Analysis Package, Molecular Structure
Corporation, 1985, 1992.
[57] M.C. Etter, Acc. Chem. Res. 23 (1990) 120.
[58] J. Bernstein, R.E. Davis, L. Shimoni, N.-L. Chang, Angew. Chem.
107 (1995) 1687.
[97] B. Lal, R.M. Gidwani, J. Reden, N.J. de Souza, Tetrahedron Lett.
25 (1984) 2901.
[59] J. Bernstein, R.E. Davis, L. Shimoni, N.-L. Chang, Angew. Chem.,
Int. Ed. Engl. 34 (1995) 1555.
[98] W.E. Smith, J. Org. Chem. 37 (1972) 3972.
[99] H. Eckert, B. Forster, Angew. Chem. 99 (1987) 922.
[100] H. Eckert, B. Forster, Angew. Chem., Int. Ed. Engl. 26 (1987) 894.
[101] M.E. Squires, A. Mayr, Inorg. Chim. Acta 264 (1997) 161.
[102] F. Bachechi, L. Zambonelli, Acta Crystallogr., Sect. B 29 (1973)
2598.
[60] J. Perlstein, K. Steppe, S. Vaday, E.M.N. Ndip, J. Am. Chem. Soc.
118 (1996) 1996.
[61] I. Ugi, U. Fetzer, U. Eholzer, H. Knupfer, K. Offermann, Angew.
Chem. 77 (1965) 492.
[62] C. Grundmann, Methoden Org. Chem. (Houben Weyl), 4th ed.,
1952±1985, vol. E5, pp. 1611±1658.
È È
È
[63] W.A. Boll, F. Gerhart, A. Nurrenbach, U. Schollkopf, Angew.
[103] A. Gieren, B. Dederer, Acta Crystallogr., Sect. B 33 (1977) 3296.
[104] V. Bertolasi, G. Gilli, A.C. Veronese, Acta Crystallogr., Sect. B 38
(1982) 502.
Chem. 82 (1970) 482.
È È
È
[64] W.A. Boll, F. Gerhart, A. Nurrenbach, U. Schollkopf, Angew.
[105] L. Chertanova, C. Pascard, A. Sheremetev, Acta Crystallogr., Sect,
B 50 (1994) 708.
Chem., Int. Ed. Engl. 9 (1970) 458.
È
È È
[66] U. Schollkopf, P. Bohme, Angew. Chem., Int. Ed. Engl. 10 (1971)
[106] F.J. Hoogesteger, L.W. Jenneskens, H. Kooijiman, N. Veldman,
A.L. Spek, Tetrahedron 52 (1996) 1773.
È
[107] C.B. Aakeroy, A.M. Beatty, D.S. Leinen, J. Am. Chem. Soc. 120
È
[65] U. Schollkopf, P. Bohme, Angew. Chem. 83 (1971) 490.
491.
(1998) 7383.
[67] Y. Ito, K. Kobayashi, T. Saegusa, Tetrahedron Lett. (1979) 2087.
[68] G.O. Spessard, A.R. Ritter, D.M. Johnson, A.M. Montgomery,
Tetrahedron Lett. 24 (1983) 655.
[108] P. Murray-Rust, W.D.S. Motherwell, J. Am. Chem. Soc. 101 (1979)
4374.
[109] C.A. Hunter, J.K. Sanders, J. Am. Chem. Soc. 112 (1990) 5525.
[110] Y. Aoyama, K. Endo, T. Anzai, Y. Yamaguchi, T. Sawaki, K.
Kobayashi, N. Kanehisha, H. Hashimoto, Y. Kai, H. Masuda, J.
Am. Chem. Soc. 118 (1996) 5562.
[69] W.P. Fehlhammer, K. Bartel, B. Weinberger, U. Plaia, Chem. Ber.
118 (1985) 2220.
[70] W.P. Fehlhammer, K. Bartel, Angew. Chem. 86 (1974) 588.