Organometallic compounds Questions in English

(C) To determine the oxidation state of iron $(Fe)$ in each compound:
$1$. In $FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O$ (Mohr's salt),the oxidation state of $Fe$ is $+2$.
$2$. In $K_4[Fe(CN)_6]$,the oxidation state of $Fe$ is $+2$ (since $4(+1) + x + 6(-1) = 0 \implies x = +2$).
$3$. In $Fe(CO)_5$,$CO$ is a neutral ligand,so the oxidation state of $Fe$ is $0$.
$4$. In $Fe_2O$,the oxidation state of $Fe$ is $+0.5$ (since $2x - 2 = 0 \implies x = +1$).
Comparing these values,$Fe$ has the lowest oxidation state $(0)$ in $Fe(CO)_5$.

(C) Tetraethyl lead $(Pb(C_2H_5)_4)$ is used as a petroleum additive to prevent knocking in internal combustion engines.

(A) Knocking is the abnormal combustion in internal combustion engines that produces a metallic sound.
Knocking causes engine damage,reduces efficiency,and leads to carbon deposition.
To prevent this,anti-knocking agents are added to fuel.
Tetraethyllead $(TEL)$,represented by the chemical formula $({C_2H_5})_4Pb$,is a well-known organometallic compound historically used as an effective antiknock agent in gasoline.

(D) The correct answer is $(d)$.
Tetraethyl lead $(TEL)$ is an antiknock compound.
When mixed with petrol,it improves the octane number of the fuel.
This process decreases the knocking in the cylinder of an internal combustion engine.

(C) An amalgam is a specific type of alloy formed by the reaction of mercury $(Hg)$ with other metals.
Therefore,amalgams are alloys which contain mercury as one of the components.

(A) . Finely divided iron reacts with carbon monoxide $(CO)$ under high pressure to form iron pentacarbonyl.
$Fe + 5CO \to [Fe(CO)_5]$ (Iron pentacarbonyl).

(A) The reaction of iron with carbon monoxide is a specific process used in the extraction of iron.
When iron oxides are reduced by carbon monoxide in a blast furnace,the primary product is metallic iron.
However,the question asks for the reaction of iron with carbon monoxide.
Actually,iron reacts with carbon monoxide to form iron pentacarbonyl,$Fe(CO)_5$,which is a volatile complex.
Therefore,the correct option is $A$.

(C) Polynuclear metal carbonyls are those that contain more than one metal atom bonded together by metal-metal bonds.
$Mn$ forms $Mn_2(CO)_{10}$,$Co$ forms $Co_2(CO)_8$,and $Fe$ forms $Fe_2(CO)_9$ and $Fe_3(CO)_{12}$.
$Cr$ forms a mononuclear carbonyl,$Cr(CO)_6$,but does not form stable polynuclear carbonyls under standard conditions.
Therefore,the correct answer is $Cr$.

(C) Wilkinson's catalyst is a coordination complex with the formula $[Rh(PPh_3)_3Cl]$.
It contains the metal Rhodium $(Rh)$ as the central metal atom.
Therefore,the correct option is $C$.

(A) The reaction between finely divided iron and carbon monoxide $(CO)$ is a direct synthesis method used to prepare metal carbonyls.
$Fe + 5CO \xrightarrow{\text{Heat, Pressure}} [Fe(CO)_5]$
The product formed is iron pentacarbonyl,which is $Fe(CO)_5$.

(A) An organometallic compound is defined as a compound containing at least one direct metal-carbon $(M-C)$ bond.
$A$. Cis-platin is $[Pt(NH_3)_2Cl_2]$. It contains $Pt-N$ and $Pt-Cl$ bonds,but no direct $Pt-C$ bond. Therefore,it is not an organometallic compound.
$B$. Ferrocene is $Fe(\eta^5-C_5H_5)_2$. It contains direct $Fe-C$ bonds.
$C$. Zeise's salt is $K[PtCl_3(\eta^2-C_2H_4)]$. It contains a direct $Pt-C$ bond (between $Pt$ and the ethylene ligand).
$D$. Grignard reagent is $R-Mg-X$. It contains a direct $Mg-C$ bond.

(D) is the correct answer.
$CH_3Li$ (Methyl lithium) is an organometallic compound because it contains a direct metal-carbon bond $(Li-C)$.
In contrast,lithium methoxide $(CH_3OLi)$,lithium dimethyl amide $((CH_3)_2NLi)$,and lithium acetate $(CH_3COOLi)$ contain $Li-O$ or $Li-N$ bonds,not $Li-C$ bonds.

(C) An organometallic compound is defined as a compound containing at least one carbon-metal bond. In $CH_3MgI$ (Methylmagnesium iodide),the carbon atom of the methyl group is directly bonded to the magnesium atom. Therefore,the presence of the $C - Mg$ bond makes it an organometallic compound.

(A) Zeise's salt is a well-known organometallic complex with the chemical formula $K[PtCl_3(\eta^2-C_2H_4)] \cdot H_2O$.
In this complex,the platinum atom is coordinated to three chloride ions and one ethylene molecule $(C_2H_4)$ acting as an $\eta^2$-ligand.
The correct structural representation of the anion is $[PtCl_3(\eta^2-C_2H_4)]^-$,making the full salt $K^+ [PtCl_3(\eta^2-C_2H_4)]^-$.
Thus,option $A$ is the correct structural formula.

(C) In metal carbonyls,the metal-carbon bond possesses both $\sigma$ and $\pi$ character.
The $\sigma$ bond is formed by the donation of lone pairs of electrons from the carbonyl carbon to the vacant orbital of the metal.
The $\pi$ bond is formed by the back-donation of electrons from the filled metal $d$-orbitals into the vacant antibonding $\pi^*$ orbitals of the $CO$ ligand.
This is known as $d\pi - p\pi$ back-bonding.
Therefore,the statement that $d\pi - p\pi$ overlap is not observed is false,and the statement that metal carbonyls are single bonded species is also incorrect as they exhibit multiple bond character.
However,in the context of standard chemistry problems,the statement that metal carbonyls are single bonded species is the most fundamentally incorrect description of their bonding nature.

(D) In organometallic compounds,back bonding is a characteristic feature of metal carbonyls and metallocenes where the metal atom donates electron density from its filled $d$-orbitals into the vacant antibonding $\pi^*$-orbitals of the ligand.
In the case of ferrocene,$[(C_5H_5)_2Fe]$,the $Fe$ atom interacts with the $\pi$-electron system of the cyclopentadienyl rings. The bonding involves the donation of electrons from the ligand to the metal and back-donation from the metal $d$-orbitals to the ligand $\pi^*$-orbitals,which stabilizes the complex.
Therefore,back bonding is involved in $[(C_5H_5)_2Fe]$.

(B) The complexes in which the metal and ligand form a bond that involves the $\pi$-electrons of the ligand are known as $\pi$-complexes.
For example,Ferrocene $Fe(\eta^{5}-C_{5}H_{5})_{2}$ and Zeise's salt $K[PtCl_{3}(\eta^{2}-C_{2}H_{4})]$ are $\pi$-complexes.

(D) The Ziegler-Natta catalyst is a mixture of an organometallic compound of a Group $13$ element (typically triethylaluminum,$(C_2H_5)_3Al$) and a transition metal compound of a Group $4$ element (typically titanium tetrachloride,$TiCl_4$).
Therefore,the transition metal involved is $Titanium$.

(C) The reaction between $n$-butyl lithium $(C_4H_9Li)$ and tin$(II)$ chloride $(SnCl_2)$ involves the alkylation of the metal center.
The balanced chemical equation is: $4C_4H_9Li + 2SnCl_2 \to ({C_4H_9})_4Sn + Sn + 4LiCl$.
Thus,the product formed is tetrabutyltin,represented as $({C_4H_9})_4Sn$.

(B) An organometallic compound is defined as a compound containing at least one direct metal-carbon bond.
In $C_2H_5ONa$ (sodium ethoxide),the sodium atom is bonded to an oxygen atom,not a carbon atom.
Therefore,$C_2H_5ONa$ is not an organometallic compound.

(B) An olefinic organometallic compound contains a metal-alkene bond ($\pi$-complex).
$K[C_2H_4PtCl_3] \cdot 3H_2O$ is Zeise's salt,which contains an ethylene ligand bonded to $Pt$.
$C_4H_4Fe(CO)_3$ is cyclobutadiene iron tricarbonyl,which contains a metal-alkene $\pi$-complex.
$Be(CH_3)_2$ is a simple organometallic compound with $Be-C$ $\sigma$-bonds,but it does not contain an olefin (alkene) ligand.
Therefore,$Be(CH_3)_2$ is not an olefinic organometallic compound.

(A) $(CH_3)_4Sn$ (Tetramethyltin) contains only $\sigma$-bonds between the metal and the carbon atoms of the alkyl groups.
$K[PtCl_3(\eta^2 - C_2H_4)]$ (Zeise's salt) contains a $\pi$-bonded ethylene ligand.
$Fe(\eta^5 - C_5H_5)_2$ (Ferrocene) is a sandwich compound with $\pi$-bonded cyclopentadienyl rings.
$Cr(\eta^6 - C_6H_6)_2$ (Dibenzenechromium) is a sandwich compound with $\pi$-bonded benzene rings.
Therefore,$(CH_3)_4Sn$ is the only $\sigma$-bonded organometallic compound among the given options.

(B) An organometallic compound is defined as a compound containing at least one direct metal-carbon bond.
$C_2H_5Li$ (Ethyl lithium) contains a direct bond between the $Li$ atom and the carbon atom of the ethyl group.
Therefore,it is an organometallic compound.
Lithium ethoxide $(C_2H_5OLi)$,lithium acetate $(CH_3COOLi)$,and lithium carbide $(Li_2C_2)$ do not contain a direct metal-carbon bond in the same manner as organometallic reagents.

(A) An organometallic compound is defined as a compound containing at least one direct metal-carbon bond.
In $Ti(C_2H_5)_4$,the titanium atom is directly bonded to the carbon atoms of the ethyl groups.
In the other options ($Ti(OC_2H_5)_4$,$Ti(OCOCH_3)_4$,and $Ti(OC_6H_5)_4$),the metal is bonded to oxygen atoms,not carbon atoms.
Therefore,$Ti(C_2H_5)_4$ is an organometallic compound.

(C) Organometallic compounds are those compounds in which a carbon atom is directly linked to a metal atom.
In $C_2H_5MgBr$ (Ethyl magnesium bromide),$C_2H_5Pb(C_2H_5)_4$ (Tetraethyl lead),and $Al(CH_3)_3$ (Trimethyl aluminium),the carbon atom is directly bonded to the metal.
However,in sodium ethoxide $(C_2H_5ONa)$,the sodium atom is bonded to the oxygen atom $(C_2H_5-O-Na)$,not directly to the carbon atom.
Therefore,it is not an organometallic compound.

(A) An organometallic compound is defined as a compound containing at least one direct metal-carbon bond.
$1$. Ferrocene $[Fe(\eta^5-C_5H_5)_2]$ contains $Fe-C$ bonds.
$2$. Tetraethyl lead $[Pb(C_2H_5)_4]$ contains $Pb-C$ bonds.
$3$. $CaC_2$ (Calcium carbide) is an ionic carbide containing the $C_2^{2-}$ ion and is generally not considered an organometallic compound.
Since both Ferrocene and $TEL$ are organometallic,and the question asks for 'an' organometallic compound,the options provided are slightly ambiguous. However,in many contexts,both $A$ and $C$ are correct. Given the structure of such questions,if only one must be chosen,$A$ is a classic example,but $C$ is also correct. Since $D$ is 'All of these' and $B$ is incorrect,the question likely intends to identify organometallic compounds. Given the standard definition,$A$ and $C$ are organometallic.

(C) Organometallic compounds are defined as compounds containing at least one metal-carbon bond.
$K[Pt(C_2H_4)Cl_3]$ is Zeise's salt,which contains a $Pt-C$ bond.
$Ni(CO)_4$ is a metal carbonyl,which contains a $Ni-C$ bond.
$C_2H_5MgBr$ is a Grignard reagent,which contains a $Mg-C$ bond.
$Al(OC_2H_5)_3$ is aluminum ethoxide,where the aluminum atom is bonded to oxygen atoms $(Al-O-C)$,not directly to carbon.
Therefore,it does not contain a metal-carbon bond.

(A) Zeise's salt is a $\pi$-bonded organometallic compound with the formula $K[PtCl_3(\eta^2-C_2H_4)]$.
It contains an ethene $(C_2H_4)$ molecule coordinated to the platinum $(Pt)$ metal center through its $\pi$-electrons.
Ferrocene contains cyclopentadienyl rings,dibenzene chromium contains benzene rings,and tetraethyl tin is a $\sigma$-bonded organometallic compound.
Therefore,the correct option is $A$.

(B) The complex compounds formed by the coordination of carbon monoxide $(CO)$ with transition metals are known as metal carbonyls.
Examples include $Fe(CO)_5$ and $Ni(CO)_4$.

(B) The organometallic compound $[Fe(\eta^5 - C_5H_5)_2]$,also known as ferrocene,contains both $\sigma$ and $\pi$ bonds.
In ferrocene,the cyclopentadienyl rings are bonded to the iron atom through $\pi$-electron clouds ($\pi$-bonding) and the metal-carbon interactions involve $\sigma$-bonding character.

(C) In metal carbonyls,the oxidation state of the central metal atom is always zero.
In the complex $[Ni(CO)_4]$,$CO$ is a neutral ligand.
Let the oxidation state of $Ni$ be $x$.
$x + 4(0) = 0$
$x = 0$.

(D) An organometallic compound is defined as a chemical compound containing at least one chemical bond between a carbon atom of an organic molecule and a metal.
In the case of $CH_3MgI$ (Methylmagnesium iodide),the carbon atom of the methyl group is directly bonded to the magnesium metal atom.
Therefore,the presence of the $C - Mg$ bond makes it an organometallic compound.

(B) The complex formed by the coordination of carbon monoxide $(CO)$ as a ligand is known as a metal carbonyl. Examples include $Fe(CO)_5$ and $Ni(CO)_4$.

(A) An organometallic compound is defined as a compound containing at least one direct metal-carbon bond.
$1$. $Cis-platin$ is $[Pt(NH_3)_2Cl_2]$. It does not contain any metal-carbon bond,so it is not an organometallic compound.
$2$. $Ferrocene$ is $[Fe(\eta^5-C_5H_5)_2]$,which contains $Fe-C$ bonds.
$3$. $Zeise's$ $salt$ is $K[PtCl_3(\eta^2-C_2H_4)]$,which contains a $Pt-C$ bond.
$4$. $Grignard$ $reagent$ is $R-Mg-X$,which contains a $Mg-C$ bond.
Therefore,$Cis-platin$ is the correct answer.

(B) The mixture of $TiCl_4$ (titanium tetrachloride) and trialkylaluminium (e.g.,$Al(C_2H_5)_3$) is a well-known organometallic catalyst system used in the industrial production of polyethylene and polypropylene. This specific catalyst is known as the $Ziegler-Natta$ catalyst.

(D) Organometallic compounds are those in which there is at least one direct metal-carbon bond.
$(I)$ Grignard reagent $(R-Mg-X)$ contains a $C-Mg$ bond,so it is an organometallic compound.
$(II)$ Trimethylboron $((CH_3)_3B)$ contains a $C-B$ bond. Since boron is a metalloid,its organic derivatives are generally classified as organometallic compounds,so it is an organometallic compound.
$(III)$ Sodium methoxide $(CH_3ONa)$ contains a $C-O-Na$ bond. There is no direct $C-Na$ bond,so it is not an organometallic compound.
$(IV)$ $TEL$ (Tetraethyllead,$(C_2H_5)_4Pb$) contains a $C-Pb$ bond,so it is an organometallic compound.
Therefore,$(I), (II),$ and $(IV)$ are organometallic compounds.

(A) Ferrocene is an organometallic compound with the formula $Fe(\eta^5 - C_5H_5)_2$.
It consists of an iron atom sandwiched between two cyclopentadienyl rings,where each ring is bonded to the iron atom through all five carbon atoms (hapticity $\eta^5$).

(A) An organometallic compound is defined as a compound containing at least one direct carbon-metal bond.
In $CH_3MgBr$ (Grignard reagent),there is a direct covalent bond between the carbon atom of the methyl group and the magnesium atom.
Therefore,the presence of a $C-Mg$ bond makes it an organometallic compound.

(A) In metal carbonyls like $Fe(CO)_5$,there is a synergistic bonding effect.
The metal atom donates electron density from its filled $d$-orbitals into the empty antibonding $\pi^*$ orbitals of the $CO$ ligand.
This back-bonding increases the electron density in the antibonding orbital of $CO$,which decreases the $C-O$ bond order.
As the bond order decreases,the $C-O$ bond length increases compared to free $CO$ $(1.128 \ \mathring{A})$.
In $Fe(CO)_5$,the observed $C-O$ bond length is approximately $1.16 \ \mathring{A}$.

(C) The Wilkinson catalyst is $Rh(PPh_3)_3Cl$.
It is a square planar complex of $Rh(I)$.
Therefore,it contains the metal $Rhodium$ $(Rh)$.

(C) An organometallic compound is defined as a compound containing at least one direct metal-carbon bond.
In $CH_3Li$ (methyl lithium),there is a direct covalent bond between the carbon atom of the methyl group and the lithium metal atom.
Therefore,$CH_3Li$ is an organometallic compound.
Lithium methoxide $(CH_3OLi)$,lithium acetate $(CH_3COOLi)$,and lithium carbonate $(Li_2CO_3)$ contain metal-oxygen bonds,not metal-carbon bonds.

(D) In the metal carbonyl complex $Fe(CO)_5$,the $Fe-C$ bond is formed by two processes:
$1$. The $CO$ ligand donates a lone pair of electrons from the carbon atom into an empty orbital of the $Fe$ metal,forming a $\sigma$-bond.
$2$. The $Fe$ metal donates a pair of electrons from its filled $d$-orbital into the empty antibonding $\pi^*$ orbital of the $CO$ ligand,forming a $\pi$-bond (back-bonding).
Therefore,the $Fe-C$ bond possesses both $\sigma$- and $\pi$-bond character.

(C) The compound $[Fe(\eta^5-C_5H_5)_2]$,also known as ferrocene,is an organometallic compound that contains both $\sigma$ and $\pi$ bonds.
In ferrocene,the metal atom is bonded to the cyclopentadienyl rings through $\pi$-electron clouds ($\pi$-bonding) and also exhibits metal-carbon $\sigma$-bonding character.

(B) An organometallic compound is defined as a compound containing at least one metal-carbon bond.
$(1)$ $Al_4C_3$ (Aluminum carbide) is an ionic carbide,not an organometallic compound,as it does not contain a direct metal-carbon covalent bond.
$(2)$ Metal carbonyls (e.g.,$Ni(CO)_4$) are organometallic compounds because they contain metal-carbon bonds.
$(3)$ $TEL$ (Tetraethyl lead,$Pb(C_2H_5)_4$) is a $\sigma$-bonded organometallic compound,not a $\pi$-bonded one.
$(4)$ Frankland reagent $(R_2Zn)$ is a $\sigma$-bonded organometallic compound.
Therefore,statements $(1)$ and $(3)$ are incorrect.

(D) Polynuclear carbonyls are metal carbonyls that contain more than one metal atom per molecule,often linked by metal-metal bonds or bridging carbonyl groups.
$Mn_2(CO)_{10}$ is a well-known polynuclear carbonyl.
$Co_2(CO)_8$ is a well-known polynuclear carbonyl.
$Fe_2(CO)_9$ and $Fe_3(CO)_{12}$ are well-known polynuclear carbonyls.
$Cr(CO)_6$ is a mononuclear carbonyl,meaning it contains only one metal atom per molecule. Therefore,$Cr$ does not form a polynuclear carbonyl.

(D) An organometallic compound is defined as a compound containing at least one direct carbon-metal bond.
In the Grignard reagent $CH_3-Mg-Br$,there is a direct covalent $\sigma$-bond between the carbon atom of the methyl group and the magnesium metal atom.
Therefore,it is classified as an organometallic compound.

(B) In metal carbonyls like $Fe(CO)_5$,the $M-C$ bond possesses both $\sigma$ and $\pi$ character.
The $\sigma$ bond is formed by the donation of electron pairs from the $CO$ ligand to the empty $d$-orbital of the metal.
The $\pi$ bond is formed by the back-donation of electrons from the filled $d$-orbitals of the metal into the empty antibonding $\pi^*$ orbitals of the $CO$ ligand.

(B) An organometallic compound is a compound containing at least one chemical bond between a carbon atom of an organic molecule and a metal.
$(1)$ Grignard reagent $(R-Mg-X)$ contains a $C-Mg$ bond,so it is an organometallic compound.
$(2)$ Sodium methoxide $(CH_3ONa)$ contains an $O-Na$ bond,not a $C-Na$ bond,so it is not an organometallic compound.
$(3)$ Trimethylboron $(B(CH_3)_3)$ contains a $C-B$ bond. Boron is often considered a metalloid,and its compounds with organic groups are classified as organometallic.
$(4)$ $Al_2(CH_3)_6$ (Trimethylaluminum dimer) contains $C-Al$ bonds,so it is an organometallic compound.
Therefore,$(1), (3),$ and $(4)$ are organometallic compounds.

(C) An organometallic compound is defined as a compound containing at least one direct metal-carbon $(M-C)$ bond.
In $Ti(OCOCH_3)_4$,the metal is bonded to oxygen ($Ti-O$ bond).
In $Ti(OC_6H_5)_4$,the metal is bonded to oxygen ($Ti-O$ bond).
In $Ti(OC_2H_5)_3(C_2H_5)$,the titanium atom is directly bonded to the ethyl group $(C_2H_5)$ via a $Ti-C$ bond,making it an organometallic compound.
In $[Fe(CN)_6]^{4-}$,although it contains carbon,the metal is bonded to the nitrogen atom of the cyanide ligand ($Fe-C$ bond is present,but it is a coordination complex where the ligand is bonded through carbon,yet organometallic compounds specifically refer to metal-alkyl or metal-aryl bonds in this context).
Therefore,$Ti(OC_2H_5)_3(C_2H_5)$ is the correct organometallic compound.