organometallic

• Organometallic chemistry is the chemistry of compounds containing at least one metal-carbon bond.
• Organometallic compounds are used on a large scale as precursors for generation of semiconductors such as AlN and GaAs.
• Organometallic chemistry is the basis for understanding important steps in heterogeneous catalysis reactions such as olefin hydrogenation and CO oxidation.
• Metal hydrides are often included in organometallic chemistry, as H is considered the "smallest organic group" (as in propyl, ethyl, methyl, hydride).
• Metal-carbon bonds are often formed temporarily or potentially, so many compounds are included in organometallic chemistry that do not actually contain metal-carbon bonds.
• Organic chemistry is characterized by more or less covalent C-X bonds, rigid element environments, and fixed oxidation states (better: valencies).
• Knowledge of inorganic and coordination chemistry is useful to understand geometries, electron counts and oxidation states of organometallic compounds.
• Organometallics are more covalent and often less symmetric than coordination compounds, so orbital symmetry arguments are not as important.
• Organometallic chemistry is concerned with all metals, in combination with all "organic" elements.
• There are many metals, and generalization is important, as the chemistry of Fe is not much more complicated than that of C, but after that there are 80 more metals.
• Organometallic chemistry concentrates on the M side of the M-C bond, and on how to tune its reactivity.
• Organic elements and main group metals are elements of interest in organometallic chemistry.
• The “Donor Pair” method of electron counting assigns common organometallic ligands an electron count and charge.
• Total ligand charge in M — M Bond is 0, so Mn 0 = d 7.
• The 18-electron rule is most valid with octahedral complexes of large D orbital ligands.
• Bonding Mode in Infrared Spectroscopy is determined by the number of electrons in the bonding orbital.
• In Cr(CO) 6 , the total charge on ligands is 0, so charge on Cr is 0, so Cr = d 6.
• When MO Theory predicts that 18 electrons fill bonding orbitals, this number is more stable than more or less.
• Infrared Spectroscopy determines the position of IR Bands, with electron density determining wavenumbers.
• Proton NMR in Hydride Complexes gives M — H hydrogens strongly shielded (-5 to -20 ppm), M — CH 3 hydrogens 1 - 4 ppm, and cyclic p system hydrogens 4 - 7 ppm and large integral because all the same.
• 13 C NMR is useful because it “sees” all C ligands and has a wide range (ppm), with CO: terminal = 195 - 225 ppm, bridging slightly larger.
• The charge on ligands helps determine d-electron count of metal.
• 5 CO ligands per metal give a total of 18 electrons for a Mn.
• In M — M Bond, each bond between metals counts 1 electron per metal: Mn — M = 1 e -.
• In [Mn(CO) 6 ] +, the total ligand charge is 0, so Mn + = d 6.
• 6 CO ligands x 2 electrons each give a total of 12 electrons.
• Infrared Spectroscopy of Cr(CO) 6 gives n = 2000 cm - 1 for [V(CO) 6 ] - and n = 1858 cm - 1 for [Mn(CO) 6 ] +.
• Other ligands are important in Infrared Spectroscopy, such as CO and CH 3 hydrogens.
• Neutral Ligand Method: This method uses the number of electrons donated by the ligands if they were neutral.
• Examples of Electron Counting include Cr(CO) 6 and [Mn(CO) 6 ] +.
• Add up all electrons from Metal d orbitals and ligands to find total e-count.
• Total of 18 electrons.
• 12 electrons from 6 CO ligands give a total of 18 electrons.
• Exceptions to the 18-electron rule are common, such as weak field ligands with small D orbital and p-donor ligands.
• Donor Pair Method: Method considers ligand donating electron pairs to the metal.
• Organometallic chemistry: C is the negative end of the M - C bond ("umpolung"), reactivity is dominated by electrophilic attack at C or nucleophilic attack at M, and associative and dissociative substitution at M is possible.
• Silicone rubbers are one of the few classes of organometallic compounds used as "final products".
• Organic chemistry: C - C / C - H are nearly covalent, while C d + - X d - is polar (partly ionic) and reactivity is dominated by nucleophilic attack at C.
• Organic chemistry: C - C / C - H are nearly covalent, while C d + - X d - is polar (partly ionic) and reactivity is dominated by nucleophilic attack at C.

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• Organometallic chemistry: X represents a Lewis acid, S represents a sigma bond, and T represents a pi bond.