SCE Paper

Abstract:

The reaction of [HB(3,5-Me2-pz)3]InCl2 •THF (pz=pyrazolyl ring) with

[Fe(C2H4(NH2)2)3][Fe2(CO)8] in THF yields [HB(3,5-Me2-pz)3]In[Fe2(CO)8] •THF in

58.58% yield.

The reaction of [HB(3,5-Me2-pz)3]InCl2 •THF with [Fe(C2H4(NH2)2)3][Fe3(CO)11] in THF

yields [HB(3,5-Me2-pz)3]In[Fe3(CO)11]. in 46.30% yield.

Infrared spectroscopy monitoring the shifts in the carbonyl regions of these new

complexes show results that new indium to iron bonds are taking place as these two

complexes coordinate with the Indium tris(3,5-dimethyl)-1 Pyrazolylborate Moiety. In

monitoring the shifting IR bands of the CO region of the respective spectra, starting with

the neutral parent compounds, the ethylenediamine dianions, and the final coordinated

complexes with the Indium Pyrazolylborate Moiety, it is been shown that these multi

metal centered carbonyl dianions react with the Indium Pyrazolylborate Moiety forming

new inorganic complexes.

The [HB(3,5-Me2-pz)3]In[Fe2(CO)8] •THF complex is predicted to have either a

octahedral or a distorted octahedron molecular geometry and the [HB(3,5-Me2-

pz)3]In[Fe3(CO)11] is predicted to have either an octahedral or a distorted octahedron

molecular geometry.

Introduction & Background:

In recent years the pyrazolylborate family of ligands have been used to create compounds

that exhibit a number of interesting features. The most interesting feature of the

pyrazolylborate ligand (Figure 1) is its capability to bond or coordinate to a central metal

atom, like indium. In the family of pyrazolylborate stems from research and synthesis

done by Trofimenko, et. al at DuPont.1 More notably known as the scorpinate family of

ligands, the pyrazolylborate acts like a scorpion, coordinating to a central metal atom

with two of the nitrogens from the first two pyrazolyl rings and the final coordination site

is achieved by “stinging” the metal center from the last nitrogen on the last pyrazolyl

ring.

-1
-1 -1
N

N
N N N N
N

N B
H B H B N
N
N
H N
N N N N N

N

“tris pyrazolylborate “bis” pyrazolylborate “tetrakis” pyrazolylborate

Figure 1 pyrazolylborate family of ligand

This process of the three nitrogens attaching themselves, is only limited by the type of

ligand chosen to synthesize. There are three different types of pyrazolylborate ligands

that can be made. The bis ligand, with two hydrogen and two pyrazolyl rings attached to

the central boron, the tris ligand with one hydrogen and three pyrazolyl rings attached to

the central boron, and lastly the tetrakis with all four pyrazolyl rings attached to the

central boron. Depending on the type of chemistry performed on the metal center of

interest, any of these ligands can coordinate to them.

There is also a realm of steric control with these set of ligands. This can be achieved by

choosing to make a substitution of an “R” Group onto the 3 and 5 positions of the

pyrazolyl rings. (Figure 2) Depending on the type of control, a range of “R” groups from

a hydrogen, to a methyl group, or even a t-butyl. Having this set of control allows, for

instance, to control how the ligand binds to a metal center and more importantly the

geometry and chemistry relative to the metal center of interest.

4

3
5

N N

H B

N

N N N

Figure 2—Location of “R” groups

Specifically the chosen pyrazolylborate ligand of interest in this research is the tris(3,5

dimethyl) pyrazolylborate ligand. By doing this, the tris ligand is achieving an interesting

property of stability that contributes to ideal formation the nitrogen to metal bonds. Using

the (3,5 dimethyl) pyrazolborate allows for a six member ring structure to be formed with

a central metal atom of choice. Looking at a coordinated pyrazolylborate close in detail

allows for illustration of this property. Starting with a metal center and counting to

adjacent nitrogen and continuing to the central boron, it is within this structure that

stability is achieved.

Reger, et. al. have explored this interesting capability in their class of pyrazolylborate

ligand system known collectively as the indium pyrazolylborate family.2,3.4 Focusing on

an indium center, Reger et. al. have designed a ligand system containing the

pyrazolylborate moiety and a indium metal center. Moreover they have used this ligand

system to stabilize highly reactive metal carbonyl anionic species, such as Collman’s

Reagent.5 In their accomplishments, not only have they stabilized these metal carbonyl

anions. Also they have also shown some of the first and shortest indium to metal bonds.

Two of the components involves synthesizing, first the “tris” ligand (i.e. three pyrazolyl

rings) and then attaching this ligand to the indium metal center. In this reaction InCl3 and

the tris ligand are placed into a round bottomed flask charged with THF, and allowed to

stir overnight, thereby making the indium tris (3,5 dimethyl)-1 pyrazolylborate ligand.3

This ligand family coordinates in three positions relative to the indium metal center,

leaving two chlorine ligands and a THF solvent ligand, allowing for chemistry to be

applied to the other three coordinate sites of the indium metal center. As stated, Reger, et.

al. have used this to stabilize metal carbonyl anions, and more specifically those that are

dianionic in nature, such as Collman’s Reagent. In coordinating Collman’s Reagent to the

indium pyrazolylborate, the bond formed between the indium and the iron atoms is “the

shortest indium to iron bond to date”5 Also in doing this, Reger, et. al. have also

synthetically determined the first indium to tungsten bond; using the indium tris(3,5

dimethyl) pyrazolylborate ligand and reduced tungsten carbonyl to make the indium

pyrazolylborate-tungsten carbonyl complex.

In order for the indium pyrazolylborate to coordinate to the carbonyl compounds, the

carbonyl compounds must first be in a reduced state. Collman’s Reagent can be made by

taking commercial iron pentacarbonyl and in a solvent, typically THF with naphthalene,

and sodium metal under an inert atmosphere.6,7 These reactions are extracted with

pentane to crash out the solid product. The order of addition of products at cold (-70C)

temperatures is important. Having a reversal of order would cause a contamination of

unwanted side product contamination.7

The danger of Collman’s reagent or any other metal carbonyl dianion is that they are

pyrophoric in nature and must be kept in an inert atmosphere to prevent their

decomposition.. (Figures 3 & 4) When these reduced carbonyl compounds are introduced

to the indium pyrazolylborate ligand they react and coordinate to the central indium, and

restores their geometry, but not without some distortion.5 Reger, et. al. showed that the

indium pyrazolylborate-tungsten carbonyl complex “conforms to a distorted octahedron”5

The reason for this is because one of the carbon atoms in the tungsten complex is in close

contact with a methyl group on one of the pyrazolyl ring.5

Figure 3- ORTEP Drawing of [(HB(Me2-pz)3]In-W(CO) 5

Figure 4- ORTEP Drawing of [(HB(Me2-pz)3]In-Fe(CO) 4

In this work, more was explored other than just geometrical configurations. There was

work done on looking at the indium to metal bonds established in these metal carbonyl

dianions. Reger, et. al. reported that the indium-iron bond length was 2.463Å and

established that the indium-tungsten bond was 2.783Å, being the “first complex to be

structurally characterized.”5 These short indium to a transition metal bonds have been

proven to be extremely short in nature. The reasoning behind this is primarily due to the

six coordinate character favored by the indium metal center itself. As a post transition

metal indium preferably bonds in a six coordinate fashion. The displacement of the two

chlorine ligands and the solvent THF ligand gets replaced by a metal carbonyl dianion.

The characteristics of this short bond distance are primarily due to the triple bond

character inside of the indium to metal bond, promoting this short characteristic.

Analysis of the carbonyl complexes can be easily monitored using IR spectral techniques.

In the metal carbonyl complexes the carbonyl stretches can be observed, but unlike

organic carbonyls their spectras do not produce a strong band at ~1710cm-1. Some of the

bands can be between the range of the double bond (organic) carbonyl region and the

triple-bond carbonyl region. (Free CO triple bond spectral region is at ~2143cm-1 and the

organic carbonyl double bond region is at ~1710cm-1.) The reason for this effect is

because in select metal complexes, the d-orbitals that are present in the metal can overlap

with the pi-anti-bonding orbitals. The electrons begin to feed into these anti-bonding

orbitals and, in effect, cancel out some of the triple bond character. This begins to make

the triple-bond exhibit some slight double-bond character. This canceling out is known as

back-bonding.8 In the tungsten and iron carbonyl complexes Reger, et. al., synthesized

exhibit this effect. The carbonyls that are trans to the indium atom contain this feature.

Research is on going in the field of these six coordinate indium pyrazolylborate

complexes. Specifically looking at the indium tris(3,5 dimethyl)-1 pyrazolylborate

moiety in providing stability to dianionic metal carbonyl species. Previous dianion metal

species have been synthesized, including Collman’s Reagent and others, as reported by

Ellis, et. al. 9 In narrowing down the list of dianionic metal carbonyls, the group of iron

carbonyl dianions can be synthesized in situ and brought together with the one pot

synthesis stated by Reger, et. al.5 (Equation 1) The results of these reactions look

promising in stabilizing the group of iron metal carbonyl dianions stemming originally

from Reger, et. al. research completed with Collman’s Reagent.

LInCl2 THF + Na2(CO)x LIn-M(CO)x

M= Fe, W

L=tris ligand, [HB-(Me2 –pz)3]

Equation 1- “One pot” synthesis of indium pyrazolylborate

coordinating to a metal carbonyl dianion, as stated by Reger, et. al.

This research started with the inclination of looking at different types of metal carbonyl

dianions, including the ones proposed by Ellis, et. al.9 Upon initial investigation, it was

discovered that multi-iron metal carbonyls that were neutral have been synthesized in

high yield from commercial iron pentacarbonyl. Such synthesis such as photolysis of

commercial iron pentacarbonyl produces the dimer, diiron nonacarbonyl in high yield

(Equation 1). Also gentle heating of this dimer produces the trimer—triiron

dodecacarbonyl, but care must be taken in order not to decompose the trimer into iron

metal and free carbon monoxide. (Equations below) These neutral parents synthesized

have indeed been made into their dianionic counterparts. In recent times it is not

necessary to synthesize these neutral parents because they can be purchased from

commercial suppliers.

Fe(CO)5 hv Fe2(CO)9

Equation 2- Photolysis of Iron Pentacarbonyl

Heat
Fe2(CO)9 Fe3(CO)12
Equation 3-Gentle Heating of Diiron nonacarbonyl

Fe3(CO)12

1. Fe(CO)5 + 3OH- HFe(CO)4-

2. HFe(CO)4- + 2MnO2 Fe3(CO)12

Equation Set 4- Alternative pathway to the neutral trimer via oxidation of the anion as

stated by Kleinberg.(Source)

Upon further investigation the neutral metal carbonyl compounds of diiron nonacarbonyl

(diiron eannacarbonyl, in older literature) and triiron dodecacarbonyl have been

successfully made into their dianioic counter parts.7, 9 ,12 Interestingly enough, these

dianions, when made similarly to Collman’s reagent, exhibit extreme pyrophoricity. In

this research a synthesis was carried out to make both of these dianionic forms of the

multi-iron centered carbonyl compounds. Both the diiron dianion carbonyl complex and

the triiron carbonyl complex was synthesized according to Heiber et. al.7, 11 The

investigation of this research explores coordinating these multi-iron metal carbonyl

dianions to the indium tris( 3,5 dimethyl)-1 pyrazolyl borate moiety.

Experimental:

All reactions were carried out under an inert Nitrogen environment using Schlenk
techniques.

Infrared Spectrophotometer: Perkin-Elmer FT-IR
NMR Spectrophotometer: Varian EM 360A, EFT Anasazi

Synthesis of hydrotris(3,5 dimethylpyrazol) borate:

KBH4 is added in excess of molten pyrazolyl and evolution of hydrogen gas continues

until 3 equivilants of hydrogens are evolved. The temperature for this synthesis occurs

between 180-210C.

100g of (3,5 dimethyl)pyrazolyl (Fluka) and 20g of KBH4 (Aldrich, 98 %+) are heated

and stirred in a 1-L flask connected to a water cooled condenser. The melt is then poured

into 200mL of toluene until solid precipitated. The product is filtered and washed with

hot toluene, then hexanes, and then allowed to air dry. Sublimation was completed to

remove excess pyrazolyl. Final product K[HB(Me2-pz)3]. (46.51 % yield)

H1NMR (CDCl3, Acros): δ 4.75 (1.00, s, 4-H); 1.50, 1.40 (3.60, 3.60; s,s Me)

-H2 "tris" ligand
KBH4 + H-pz K[HB-pz3]
~180 C H-pz3= 3,5-dimethylpyrazole
-1

N N

H B
N N

Adopted from: Trofimenko, J.
N 1967, JACS. 89, 3176.
N

Synthesis of [Hydrotris(3,5-dimethylpyrazolyl)borato]dichlorindium(III)

0.5g InCl3 (Strem , 99.999%) is added with 0.914g of K[HB(Me2-pz)3] into a round

bottomed flask and 25mL of dried, distilled THF (Fisher) is added via syringe and stirred

overnight. The THF was removed under vacuum and the product was extracted with

toluene to form a white solid. (41.66% yield)

(CDCl3) δ5.97 (1.23, s, 4-Hpz*); 3.80, 1.90 (1.00, 1.90, m, m; THF); 2.60, 2.95 (7.10,

7.10,s,s; 3,5Me-pz*)

FT-IR (KBr) 2243.51 cm-1 (B-H)

MP (68.0º-77.5ºC): with decomposition

KL + InCl3 LInCl2 THF + KCl
THF

N N
Cl

H B N N In THF

Cl
N N

L=tris ligand, [HB-pz3]

Adopted from : Reger, et. al., Inorganic Chem. 1994, 33, 805.

Synthesis of Fe2(CO)9

A 10 mL round bottomed flask was dried in an oven at 110C, sealed with a septum, and

cooled to room temperature. The flask was charged with commercial iron pentacarbonyl

(Acros, 99.50 %) via syringe, 5mL and placed onto a foil wrapped cork ring. This vessel

was then placed into a larger container that had water cooled down with liquid nitrogen.

A syringe was placed in the top of the septum to allow CO to liberate from the flask. The

procedure was repeated, with constant rotation of the round bottomed flask done by a

rotovap. The flask was charged with the same starting material and hooked up to a

rotovap and rotated in the nitrogen cooled water bath. Orange crystals were collected

with filtration and dried in vacuo. (94.50 % yield)

Crystals were analyzed via FT-IR (Perkin-Elmer) and exhibited strong carbonyl bands

comparable to commercial sources and literature (source)

FT-IR (KBr, IR Grade Mallerckrodut) 2081.52 cm-1, 2017.95 cm-1, 1985.92 cm-1,

1826.57cm-1 .

2Fe(CO)5 Fe2(CO)9 + CO
hv

O
C
OC CO
OC Fe Fe CO
OC CO
CO
C
O

Synthesis of Na2[Fe2(CO)8]

A solution of commercial iron pentacarbonyl (14.04 g) was added to dry distilled THF

(200mL). A separate solution was prepared of sodium (Baker) and naphthalene (Eastman,

9.90g) in 500 mL of THF, all reagents were charged into separate round bottomed flasks

evacuated under a nitrogen environment. The sodium naphthalene was cooled to 0ºC and

stirred for ~2hours until a dark green color was observed. The iron pentacarbonyl/THF

solution was added slowly over a 30 minute period via syringe and was stirred for an

additional hour. The green color disappeared as the iron pentacarbonyl solution was

titrated to the mixture, a small incremental amount of iron pentacarbonyl was added at

this time to ensure all the sodium had reacted with the iron pentacarbonyl. Reddish

orange crystals resulted and an extraction with 200ml of pentane was used. The product

was dried in vacuo and changed color as the solvent was removed. They exhibited more

of a yellowish-orange as opposed to the darker reddish orange. Under positive nitrogen

pressure the septa was removed and a small spatula full was removed from the flask to

test for pyrophoricity. The crystals were indeed pyrophoric.

2 Fe(CO)5 + 2Na Na2Fe2CO8 + CO
THF

Synthesis Adopted from: Strong, et. al.

Synthesis of ([Hydrotris[(3,5 dimethylpyrazolyl)borato]indium]octacarbonyldiiron

Starting with 1.01 g of [Hydrotris(3,5-dimethylpyrazolyl)borato]dichlorindium(III) and

0.52g of disodium diiron ocatcarbonyl are charged into a round bottomed flask evacuated

with nitrogen. 30mL of THF is added to the reaction allowed to stir overnight. Product.

Crystals were light brown and were extracted with toluene. HB(3,5 Me2-pz)3InFe2(CO)8.

FT-IR (KBr) 2739.50 cm-1 (B-H); 2063.96, cm-1 2010.34 cm-1, 1974.97cm-1,

1973.05 cm-1 (CO).

Na2Fe2CO8 + HB[(Me2-pz)3]InCl2 THF HB[(Me2-pz)3]In[Fe2(CO)8] + 2NaCl

Small Yielding Product: (10.40 % yield)

Synthesis of Triethylenediamine undodecacarbonyl ferrate.

7.5g of commercial triirondodecacarbonyl (Strem, 99 %) is charged into a round

bottomed flask equipped with a stir bar. The flask is then charged with 10mL of

ethylenediamine (Eastman) and allowed to stir for ten minutes until a color change is

observed, from deep green to red, the reaction will foam when this occurs. When the

reaction has a syrup like consistency 5mL of water is added and the crystals are filtered

with a glass fritted filter. (~ 1/3 of the material) These crystals are then collected and

recharged into a round bottomed flask with 100mL of water and stirred in a water bath

and warmed to 40C. After 15 minutes the crystals are cooled to just above 0C, suction

filtered, and then dried in vacuo. Crystals are stored cold at 0C. Crystals are moderately

air sensitive. Crystals were orange in color and were extracted with toluene. IR via KBr

was preformed on the commercial triirondodecacarbonyl. [Fe(C2H4(NH2)2)3][(Fe3(CO)11]

(67.85 % yield)

IR (KBr): 1921.67 cm-1, 1800cm-1 (CO)

IR (KBr) Fe3(CO)12 : 2000cm-1 (CO) ; 1826.58cm-1 (CO bridged)

9 C2H4(NH2)2 + 4 Fe3(CO)12 3 [Fe(C2H4(NH2)2)3][(Fe3(CO)11] + 15 CO

Synthesis Adopted from: Heiber, et. al. Chem. Ber.

Synthesis of ([Hydrotris[(3,5 dimethylpyrazolyl)borato]indium]
undodecacarbonyltriiron

0.830 g of [Fe(C2H4(NH2)2)3][(Fe3(CO)11] and ~.80 g of HB[(Me2-pz)3]InCl2 THF was

charged into a flask, equipped with a stirbar and ~25mL of THF and was allowed to stir

overnight. Crystals changed from an orange color to a deep red in the solution after ~12

hours. Crystals were extracted with toluene and dried in vacuo. Crystals were light

yellow to brown in color. (46.30 % yield)

[Fe(C2H4(NH2)2)3][Fe3(CO)11] + HB[(Me2-pz)3]InCl2 THF
THF

OC CO
OC CO
N N CO
Fe CO
H B N N In Fe
CO
Fe
CO
N N OC
CO
CO
+ [Fe(C2H4(NH2)2)3]Cl2

Product: HB[(Me2-pz)3]In[Fe3(CO)11]

MP: 285ºC-299ºC with decomposition

IR (KBr): 2623.31 cm-1 (B-H); 2001.44 cm-1, 1941.10 cm-1, 1893.64 cm-1 (CO)

Synthesis of Triethylenediamine ocacarbonyl ferrate.

2.5 g of commercial diiron nonacarbonyl (Strem 99%) was charged into a round

bottomed flask charged with a stir bar. ~3mL of ethylenediamine was added via syringe

and a color change from orange to a deep red/orange took place. This was followed with

bubbling and foaming of the slurry like mixture. After ~15 minutes 5mL of water was

added to the mixture and was filtered with a red/orange solid left behind. Another 5mL of

water was charged into the flask and was filtered one more. Heating of this product was

avoided to prevent the dimer from being converted to the trimer. (58.58 % yield)

6 C2H4(NH)2 + 3 Fe2(CO)9 2 [Fe(C2H4(NH2)2)3][Fe(CO)8] + 11 CO

Product: [Fe(en)3][Fe2(CO)8]

IR (KBr): 2009.83 cm-1 , 1924.24 cm-1 , 1852.04 cm-1 (CO)

Synthesis of ([Hydrotris[(3,5 dimethylpyrazolyl)borato]indium]octacarbonyldiiron

2.55 of [Fe(C2H4(NH2)2)3][(Fe2(CO)8] and ~3g of HB[(Me2-pz)3]InCl2 THF was charged

into a flask equipped with a stirbar and ~50mL of THF was added and allowed to stir

overnight. The dark red solution was allowed to stop stirring and crystals formed at the

bottom of the flask. The crystals were extracted with toluene. Crystals were yellow

brown in appearance. (58.58 % yield)

HB(3,5 Me2-pz)3InFe2(CO)8

IR (KBr) : 2557.79cm-1 (BH) ; 2011.18 cm-1, 1971.58 cm-1, 1928.14 cm-1,1891.38 cm-1
(CO)

NMR (CD3SOCD3): δ 5.505, 5.137 (s,s, 2.87, 2.09; 4-H); 3.388, 2.162 (m,m 18.89,
20.39; THF), 2.706, 1.883, (s-s, 45.84, 44.32 Me), 1.507, 0.869, (s-s, Me 15.89, 8.49)

MP: (278ºC-282ºC) with decomposition

THF

OC CO
N N THF CO
Fe
CO
H B N N In
Fe CO + [Fe(C2H4(NH2)2)3]Cl2
N N OC CO
CO

Discussion:

[HB(3,5Me2-pz)3]In[Fe2(CO)8]. The reaction Na2[Fe2(CO)8] with HB[(Me2-

pz)3]InCl2·THF yielded a small yielding product based on the carbonyl stretches for the

final compound. The synthesis of the final product HB[(Me2-pz)3]In[Fe2(CO)8] via this

route produced weak bands in the CO region of the IR spectra for this compound. After

the synthesis was repeated, stronger bands in the CO region appear, but they are still not

as strong as the following method below produced. Reasons for the minor product came

from the preparation and reaction of naphthalene and sodium metal in THF to produce

the radical carrier, since it is hard to see when all the sodium dissolves when this solution

changes color. The sodium metal itself may have not reacted all the way with the neutral

parent to produce a high yield dianion. This dianion is extremely pyrophoric and hard to

handle when making transfers to or from the container it is in, oxidizing it to an Fe(0)

product. The ethylenediamine dianion complex is much more stable and easier to handle

both in crystal form and in situ.

THF

CO
OC CO
N N
Fe CO
H B N N In
Fe CO
N
+ [Fe(C2H4(NH2)2)3]Cl2
N OC CO
CO

The reaction of [Fe(C2H4(NH2)2)3][Fe2(CO)8] with HB[(Me2-pz)3]InCl2·THF yielded a

major product with carbonyl bands 2011.18 cm-1, 1971.58 cm-1, 1928.14 cm-1,1891.38

cm-1 .

The neutral parent Fe2(CO)9 had carbonyl bands at 2081.52 cm-1, 2017.95 cm-1, 1985.92

cm-1, 1826.57cm-1. The ethylenediamine dianion complex had carbonyl bands at 2009.83

cm-1 , 1924.24 cm-1 , 1852.04 cm-1.

The shifts in the IR spectra in the CO region is expected to shift from the synthesis of the

neutral parent to the dianion as more electron density is given to the central iron atoms.

The CO shifts between the dianion and the iron indium pyrazolylborate complex shifted

slightly (comparatively to the dianion and neutral parent) as the two lone pairs (one from

each iron) is donated to the central indium atom. The predicted geometry of this complex

(with respect to the indium atom) could be either octahedral or a distorted octahedron,

depending upon how the irons sit relative to the indium center. There is a twofold axis of

rotation and a threefold axis of rotation between the iron atoms and the indium

respectfully and a vertical plane of symmetry passing through the two iron centers.

The 1HNMR of this compound provided an insight as to the structure of this compound.
1
HNMR (CD3SOCD3): δ 5.505, 5.137 (s,s, 2.87, 2.09; 4-H); 3.388, 2.162 (m-m 18.89,

20.39; THF), 2.706, 1.883, (s-s, 45.84, 44.32 Me), 1.507, 0.869, (s-s, Me 15.89, 8.49).

The peaks at 5.505 and 5.137 ppm indicate the 4-H position on the Pyrazolyl rings, the

peaks at 3.388 and 2.162 provide that a weakly bound THF solvent ligand is attached,

keeping the indium octahedral, the peaks at 2.706 and 1.883 show the two equivalent

methyl groups on two of the Pyrazolyl rings and the peaks at 1.507 and 0.869 show the

nonequivelent methyl groups on the last Pyrazolyl ring.

Comparing these 1HNMR peaks to the ones for the initial Indium tris(3,5-dimethyl)-1

Pyrazolylborate: 1HNMR (CDCl3): HB[(Me2-pz)3]InCl2·THF δ5.97 (1.23, s, 4-Hpz*);

3.80, 1.90 (1.00, 1.90, m, m; THF); 2.60, 2.95 (7.10, 7.10,s,s; 3,5Me-pz*) the peaks have

shifted, indicating that the Indium tris(3,5-dimethyl)-1 Pyrazolylborate has coordinated to

the diiron complex .Depending upon further crystal analysis and symmetry elements, the

complex seems to have been made with success.

[HB(Me2-pz)3]In[Fe3(CO)11] The reaction of [Fe(C2H4(NH2)2)3][Fe3(CO)11] with

HB[(Me2-pz)3]InCl2·THF yielded a major product [HB(Me2-pz)3]In[Fe3(CO)11] with

carbonyl bands at 2001.44 cm-1, 1941.10 cm-1, 1893.64 cm-1. The [Fe(C2H4(NH2)2)3]

[Fe3(CO)11] compound was made from the procedure provided by Heiber, et. al. 11 and

provides a convenient synthesis and the complex is much more stable and easier to

handle both in crystal form and in situ.

THF

OC CO
OC CO
N N
Fe CO

H B N N In Fe CO
Fe CO
N N OC CO
OC CO
+ [Fe(C2H4(NH2)2)3]Cl2

The neutral parent Fe3(CO)12 had carbonyl bands at 2000cm-1 (CO) ; 1826.58cm-1 (CO

bridged) and the ethylenediamine dianion complex had carbonyl bands at 2009.83 cm-1 ,

1924.24 cm-1 , 1852.04 cm-1.

The shifts in the IR spectra in the CO region is expected to shift from the synthesis of the

neutral parent to the dianion as more electron density is given to the central iron atoms.

The CO shifts between the dianion and the iron indium pyrazolylborate complex shifted

slightly (comparatively to the dianion and neutral parent) as the two lone pairs are

donated from the irons to the central indium atom. The predicted geometry of this

complex (with respect to the indium atom) could be either octahedral or a distorted

octahedron, depending upon how the irons sit relative to the indium center. There is a

threefold axis of rotation around the indium. Acquiring and NMR of this product was

difficult and different duterated solvents may need to be tried. Duterated DMSO seems to

dissolve the crystals but acquiring an NMR is difficult. Depending upon further crystal

analysis and symmetry elements, the complex seems to have been made with success.

Conclusions:

Two new complexes, HB[(Me2-pz)3]In[Fe2(CO)8] and [HB(Me2-pz)3]In[Fe3(CO)11], have

been prepared from the reaction of the iron metal carbonyl ethylenediamine dianions, and

HB[(Me2-pz)3]InCl2·THF. In each of the complexes the metal-metal bonding is described

as dative, arising from two lone pair of electrons being donated from the respective iron

carbonyl dianions directly to the indium atom. Early molecular modelings of both

compounds using GAUSSIAN are being completed for a confirmation of a theoretical

gas phase IR spectra.

Acknowledgements:

Mount Union College, Department of Chemistry:
Faculty:
Dr. Scott Mason
Dr. Jeffery Draves

Mount Union College, Department Foreign Languages
Faculty:
Dr. Mark Himmelien for the translation of the Heiber article.11

Case Western Reserve University
Dr. Yan Sun

References:

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2. Reger, Daniel L.; Mason, Scott S.; Reger, Lance B.; Rheingold, Arnold L.; Ostrander, Robert L.
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5. Reger, Daniel L.; Mason, Scott S.; Rheingold, Arnold L.; Haggerty, Brian S.; Arnold, Frederick
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Me2pz)3]InW(CO)5 (pz = Pyrazolyl Ring). Intermetallic Complexes with Short Metal-Metal
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6. Collman, J.P. “Disodium Tetracarbonyl Ferrate—a Transition-Metal Analog of a Gringnard
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10. Bhattacharyaa, N.K. ; Coffy, T.J, Quintana, W; Salupo, T.A.; Bricker, J.C. ; Shay, T.B.; Payne, M.
; Shore, S.G. Syntheses of dinuclear carbonylates of the iron subgroup: [M2(CO)8]2- (M = Ru,
Os) and [FeRu(CO)8]2-. Structures of [PPh4]2[FeRu(CO)8] CH3CN and [PPh4]2[Fe2(CO)8]
2CH3CN. Organometallics. 1990, 9, 2368-2374.
11. Heiber, W., et. al. “Über Metallcarbonyle. 79. Mitteil. Neuere Anschauungen Uber
Entstehung und Konstitution Äthylendiamin-Haltiger Eisencarbonyle” Chem. Ber. 1957, 90.
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12. Heiber, W., R. Werner. “Über Vierkernige Carbonyl Ferrate.” Chem. Ber. 1957, 90. (2).
286-296. Translated.

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