Carbonyl complexes 210 Subject

Cationic Group 11 carbonyl complexes have been implicated in catalytic carbony-lation reactions of alkenes, arenes, alcohols, saturated hydrocarbons and aldehydes under acidic conditions [106]. While the mono- and di-carbonyls [M(CO)] and [M(C0)2] (M = Cu, Ag, Au) can be formed at atmospheric pressure of CO, only Cu(I) forms a tricarbonyl cation under such conditions [107]. Strauss and co-workers reported the observation of [Ag(CO)3] when a Fluorolube mull of Ag[Nb(OTep5)5] was subjected to 13 bar CO in an HP IR transmission cell [108]. 

Because of its relevance to the mechanisms of catalytic processes of organometallic reagents, interest in the substitution mechanisms of carbonyl complexes has been considerable since the first work of Basolo in 1961.85 The subject has been generally and specifically reviewed from time to time86"93 and has experienced a recent resurgence of interest. Because it is impossible to discuss this area without moving rapidly outside the scope of this chapter, only the simplest systems will be considered. 

The first thionitrosyl complex was discovered by chance during an attempted synthesis of molybdenum nitrido complexes in the presence of a source of sulfur, tetrathiuram sulfide.168 This work of Dilworth and Chatt was reported in 1974 and ultimately led to the syntheses of a range of Mo, Re and Os thionitrosyl complexes starting with the respective nitrido complexes.143,164 Nitrosyl complexes, like carbonyls, had been known for decades, and the more recent syntheses of thio-carbonyl complexes forebode the advent of thionitrosyl complexes. However, convenient synthetic routes based on analogies with syntheses of NO complexes were generally not available because the requisite precursors did not exist or were inconvenient to handle. Sulfiliminato complexes (M=N=SR2) of transition metals are as yet unknown. The chemistry of thionitrosyl complexes was the subject of a recent review.179... 

Dienes form very stable complexes with a variety of metal caibonyls, particularly Fe(CO)s, and the neutral V-diene metal carbonyl complexes are quite resistant to normal reactions of dienes (e.g. hydrogenation, Diels-Alder). However, they are subject to nucleophilic attack by a variety of nonstabilized carbanions. Treatment of -cyclohexadiene iron tricarbonyl with nonstabilized carbanions, followed by protonolysis of the resulting complex, produced isomeric mixtures of alkylated cyclohexenes (Scheme 15).24 With acyclic dienes, this alkylation was shown to be reversible, with kinetic alkylation occurring at an internal position of the complexed dienes but rearranging to the terminal position under thermodynamic conditions (Scheme 16).2S By trapping the kinetic product with an electrophile, overall carbo-... 

Formation of polynuclear compounds with chalcogen atoms as bridging ligands between metal atoms is a characteristic feature of chalcogen metal carbonyl complexes. Such polynuclear complexes, in which often an additional metal-metal bond is assumed so as to account for the diamagnetism, have become known in increasing numbers because of the work of various research groups, and it is neither possible nor is it within the scope of this article to review this subject here. Only a few of our own results will be mentioned herein. 

In this section reactions of diphosphirene derivatives with transition metal carbonyl complexes, where also the ring skeleton was subject to transformations, are discussed. 

Since they are so clean, these reactions were the subject of in-depth mechanistic studies by electrochemistry [336-338], including by derivative cyclic voltammetry (DCV) [337, 338]. Acetonitrile and other solvento complexes are accessible by photolysis of transition-metal carbonyl complexes in the desired solvent. Such ETC catalyzed reactions are also of interest because they are practical and easily generalized, for instance to the series M(CO)3L3 (M = Cr, Mo, W L = MeCN, pyridine) [339]. 

All ligands receive a separate subject entry, e.g., 2,4-Pentanedione, iron complex. The headings Ammines, Carbonyl Complexes, Hydride complexes, and Nitrosyl complexes are used for the NH, CO, H, and NO ligands. 

The photochemical properties of organometallic compounds are investigated, but none to the depth to which metal-carbonyl complexes are subjected. Photosensitivity of the complexes often is cited, but there is little emphasis on synthetic utility. This section examines the synthetic potential of the photochemical transformations. Studies that are concerned solely with mechanistic aspects are excluded, as well as synthetic applications of the mixed compounds, such as h -CjHjCr(CO)3 and h -CjHjMnfCOjj, where the primary photochemical reaction is CO loss these are discussed in 13.2.4. 

In this contribution we shall present several applications of the new method, which we shall refer to as LSD/NL, to the calculation of bond energies of transition metal complexes. We shall focus on trends along a transition period and/or down a transition triad. The following subjects will be discussed a) metal-metal bonds in dimers of the group 6 transition metals b) metal-ligand bonds in early and late transition metal complexes c) the relative strength of metal-hydrogen and metal-methyl bond in transition metal complexes d) the metal-carbonyl bond in hexa- penta-and tetra-carbonyl complexes. 

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