Oxidation and reduction of carbonyls

Key points: Most metal carbonyls can be reduced to metal carbonylates; some metal carbonyls disproportionate in the presence of a strongly basic ligand, producing the ligated cation and a carbonylate anion; metal carbonyls are susceptible to oxidation by air; metal-metal bonds undergo oxidative cleavage.

Most neutral metal carbonyl complexes can be reduced to an anionic form known as a met al carbonylate. In monometallic carbonyls, two-electron reduction is generally accompanied by loss of the two-electron donor CO ligand, thus preserving the electron count at 18:

The metal carbonylate contains Fe with oxidation number 2, and it is rapidly oxidized by air. That much of the negative charge is delocalized over the CO ligands is confirmed by the observation of a low CO stretching band in the IR spectrum at about 1730 cm1. Polynuclear carbonyls, which obey the 18-electron rule through the formation of MM bonds, are generally cleaved by strong reducing agents. The 18-electron rule is obeyed in the product and a mononegative mononuclear carbonylate results:

Some metal carbonyls disproportionate in the presence of a strongly basic ligand, producing the ligated cation and a carbonylate. Much of the driving force for this reaction is the stability of the metal cation when it is surrounded by strongly basic ligands. Octacarbonyldicobalt (0) is highly susceptible to this type of reaction when exposed to a good Lewis base such as pyridine (py):

It is also possible for the CO ligand to be oxidized in the presence of the strongly basic ligand OH, the net outcome being the reduction of a metal centre:

Carbonyl compounds that have only 17 electrons are particularly prone to reduction to give 18-electron carbonylates. Metal carbonyls are susceptible to oxidation by air. Although uncontrolled oxidation produces the metal oxide and CO or CO₂, of more interest in organometallic chemistry are the controlled reactions that give rise to organometallic halides. One of the simplest of these is the oxidative cleavage of an MM bond:

In keeping with the loss of electron density from the metal when a halogen atom is attached, the CO stretching frequencies of the product are significantly higher than those of [Mn₂(CO)₁₀].

اخر الاخبار

اخبار العتبة العباسية المقدسة

لزيادة المساحات الخضراء.. قسم الحزام الأخضر الثاني يشرع بحملة تشجير في جامعة العميد

اللجنة التحضيرية لمهرجان روح النبوة تعلن تمديد موعد تسلم البحوث الخاصة بالمسابقة البحثية

المجمع العلمي يطلق جلستين قرآنيتين لطلبة العلوم الدينية في النجف

قسم الشؤون الفكرية يقدم محاضرة حول أساليب الحوار الإيجابي لوفد شبابي من البصرة

المزيد

الآخبار الصحية

هل ممارسة الرياضة على معدة فارغة تحرق الدهون أكثر؟

العلم يوضح الوقت "الأمثل" لشرب القهوة

دراسة: "طريقة سهلة" لحماية رئتيك من آثار تلوث الهواء

بالذكاء الاصطناعي.. أداة جديدة لتحسين علاج الصرع عند الأطفال

المزيد

الآخبار التكنلوجية

إيلون ماسك يعتزم إطلاق "غروكيبيديا" كمنافس لـ "ويكيبيديا"

"قرار" من أبل لحماية هواتف آيفون 17 من الخدوش

ميزة جديدة على "تشات جي بي تي".. شراء المنتجات من المحادثة

الصين تكشف عن توربين رياح طائر يغير قواعد الطاقة المتجددة

المزيد

مواضيع ذات صلة

Isolobal analogies

Structure of clusters

Bent metallocene complexes

Fluxional behaviour of metallocenes

Bonding in bis(cyclopentadienyl)metal complexes

Synthesis and reactivity of cyclopentadienyl compounds

Spectroscopic properties of carbonyl compounds

Reactions of the CO ligand

Metal carbonyl basicity

Properties of homoleptic carbonyls

Synthesis of homoleptic carbonyls

Homoleptic carbonyls