Organometallic Chemistry: Foundations, Core Ligands, Elementary Steps, and Homogeneous Catalysis

Comprehensive review flashcards covering organometallic foundations, electron counting, core ligand classes (CO, phosphines, carbenes, hydrides, arenes, Cp), elementary mechanistic steps (substitution, oxidative addition, reductive elimination, migratory insertion), and cross-coupling catalysis.

According to the IUPAC definition, an organometallic compound strictly contains a bond between a __________ and a __________.

metal atom; carbon atom

The 2010 Nobel Prize in Chemistry was awarded jointly to Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki for __________.

palladium-catalyzed cross couplings in organic synthesis

The 1973 Nobel Prize in Chemistry was awarded to Ernst Otto Fischer and Geoffrey Wilkinson for their pioneering work on the chemistry of __________.

organometallic, so-called sandwich compounds

In the Haber-Bosch process, the synthesis of ammonia from nitrogen and hydrogen ($N_2 + 3H_2 \rightleftharpoons 2NH_3$) is industrially catalyzed using __________.

promoted iron (Fe)

In the Covalent/Neutral method of electron counting, an $X$-type ligand is treated as donating __________ electron(s), whereas in the Ionic method, it is treated as an anion donating __________ electron(s).

$1$; $2$

In coordination notation, the symbol $\\eta^n$ indicates that $n$ contiguous atoms interact with one metal, whereas the symbol __________ designates that a single ligand bridges $n$ metal centers.

$$\mu_n$$

In the synergic bonding model of transition-metal carbonyls, metal-to-carbonyl backbonding involves donation from filled metal $d_\pi$ orbitals into the empty __________ orbitals of carbon monoxide.

$$2\pi^*$$

The Tolman Electronic Parameter (TEP) evaluates the net electron-donating ability of a ligand by measuring the high-frequency $A_1$ carbonyl stretching frequency ($\nu_{CO}$) of the reporter complex __________.

$$Ni(CO)_3L$$

Reducing the neutral complex $Fe_2(\mu\text{-}PPh_2)_2(CO)_6$ by two electrons to form the dianionic complex $[Fe_2(\mu\text{-}PPh_2)_2(CO)_6]^{2-}$ shifts the average $\nu_{CO}$ infrared stretching frequency almost __________ to lower energy.

$$150\,cm^{-1}$$

Ligand behavior in homogeneous catalysis emerges from four coupled properties: electrons ($\sigma/\pi$ interactions), space (size + distribution), dynamics (lability + motion), and __________ (denticity + bite angle).

connectivity

The chelating diphosphine dmpe (bis(dimethylphosphino)ethane) has a calculated bite angle of $107^\circ$, whereas dppp (bis(diphenylphosphino)propane) forms a six-membered chelate ring with a bite angle of __________.

$$127^\circ$$

In $^{31}P$ NMR spectroscopy, chemical shifts are reported relative to an external reference of __________ set at $0\,ppm$.

$$H_3PO_4$$

An amido ligand ($NR_2^-$) acting as a terminal donor can function as a $2e^-$ donor in a pyramidal geometry or as a $4e^-$ donor when adopting a __________ geometry with metal-nitrogen $\pi$ donation.

trigonal planar

Tris(pyrazolyl)borate ($Tp^-$) is a monoanionic, tripodal nitrogen ligand that commonly coordinates in a $\kappa^3$ facial mode, contributing __________ electrons in the ionic counting method.

$$6$$

In square-planar platinum(II) complexes, the relative rate of substitution of a chloride ligand trans to a hydride ($H^-$) is ${10^4}$, whereas trans to a methyl ($CH_3^-$) it is __________.

$$10^3$$

Comparing $Mo(CO)_3[P(OMe)_3]_3$ with $Mo(CO)_3(\text{pyridine})_3$, the pyridine complex exhibits lower carbonyl stretching frequencies ($1888, 1746\,cm^{-1}$ vs $1977, 1888\,cm^{-1}$) because __________.

more backbonding remains available to CO (pyridine does not compete for backbonding)

Due to the indenyl effect, ligand substitution on an indenyl rhodium complex proceeds with a relative rate of $3.8 \times 10^8$ compared to $1$ for Cp, while a fluorenyl analogue accelerates the rate to __________.

$$> 10^{10}$$

In iron nitrosyl complexes, bending of a linear $NO^+$ ligand to a bent $NO^-$ ligand formally changes the valence electron count at the iron center from $18e^-$ to __________.

$$16e^-$$

During a typical mononuclear oxidative addition where both fragments bind to the metal, the metal oxidation state increases by $2$ and the metal d count __________.

decreases by $2$

When $[Re(CO)_5]^-$ ($18e^-, Re(-I)$) reacts with allyl chloride via oxidative addition, it yields $Re(CO)_5(\eta^1\text{-allyl})$ ($18e^-, Re(+I)$), which then undergoes CO dissociation and an $\eta^1$ to __________ hapticity change.

$$\eta^3$$

In the reductive elimination of $H_2$ from an octahedral $Ir(III)$ ($18e^-$) dihydride complex, the formal oxidation state and electron count of the resulting iridium product are __________ and __________.

$Ir(+1)$; $16e^-$

Oxidative addition of chlorine across a dinuclear gold(I) complex ($Au-Au = 3.0\,\text{\AA}$) oxidizes both gold centers to form a $Au(II)-Au(II)$ bonded intermediate with a shortened $Au-Au$ distance of __________.

$$2.6\,\text{\AA}$$

In the migratory insertion of $CpFe^*(CO)(PPh_3)(Et)$, the reaction in $CH_3NO_2$ proceeds by ethyl migration with __________ of configuration at iron, whereas in HMPA, CO inserts with __________ of configuration.

inversion; retention

In the reaction of a rhodium silyl complex with acetonitrile, C-C bond cleavage occurs via an unusual __________ elimination step, releasing methane and forming a coordinated silyl isocyanide.

methyl

The complex $[Re_2(CH_3)_8]^{2-}$ possesses a formal metal-metal quadruple bond ($\sigma^2\pi^4\delta^2$) with a short $Re-Re$ bond distance of __________ and an eclipsed conformation.

$$2.18\,\text{\AA}$$

The isolobal principle, introduced by Nobel laureate __________, states that molecular fragments are isolobal if the number, symmetry properties, approximate energy, and shape of their frontier orbitals are similar.

Roald Hoffmann

In cross-coupling chemistry, the transmetalation partner in a Kumada-Tamao-Corriu coupling is an organomagnesium reagent ($R-MgX$), while in a Stille coupling it is an __________ reagent.

organotin ($R-SnR'_3$)

In Stille cross-coupling reactions, substituting triphenylphosphine ($PPh_3$) with the softer and weaker $\sigma$-donor ligand $AsPh_3$ accelerates the relative observed rate ($k_{obs}$) by a factor of __________.

$$1100$$

In $^1H$ NMR spectroscopy, transition-metal hydride ligands typically resonate at characteristic __________ chemical shifts, often falling between $0\,ppm$ and $-30\,ppm$.

negative (upfield)

Stryker's reagent is a copper hydride hexamer with the chemical formula __________.

$$[(PPh_3)CuH]_6$$

Alkyl ligands such as methyl, neopentyl, benzyl, and __________ resist $\beta$-hydride elimination because they lack hydrogen atoms on a $\beta$-carbon.

trimethylsilylmethyl ($-CH_2SiMe_3$)

Fischer carbenes generally feature low-valent late metals with $\pi$-donor heteroatom substituents and an __________ carbene carbon, whereas Schrock alkylidenes feature high-valent early metals and a __________ carbene carbon.

electrophilic; nucleophilic

Upon two-electron reduction of the $18e^-$ complex $[Ru(\eta^6\text{-}C_6Me_6)_2]^{2+}$ to neutral $Ru(0)$, the complex maintains an $18e^-$ configuration by undergoing ring slippage of one arene ring to an __________ coordination mode.

$$\eta^4$$

In the laboratory, monomeric cyclopentadiene is prepared immediately prior to use through the thermal cracking of __________ via a retro-Diels-Alder reaction.

dicyclopentadiene

In quantitative catalytic evaluation, turnover frequency (TOF) is calculated by dividing the turnover number (TON) by the __________.

elapsed reaction time

The enantiomeric excess ($\text{ee}$) of a chiral catalytic product formed with enantiomer molar amounts $n_R$ and $n_S$ is defined by the formula __________.

$$\frac{|n_R - n_S|}{n_R + n_S} \times 100\%$$