Carbonyls block metal

Since the discovery of nickel carbonyl in 1890 (15), carbonyls of many other metals have been prepared. Nickel and iron are the only metals that combine direcdy with CO to produce carbonyls in reasonable yields. At least one carbonyl derivative is known for every t5 -block metal. A number of the neutral complexes that have been reported ate Hsted in Table 4. 

The 18-electron rale is not obeyed as consistently by these types of oiganome-tank compounds a by the carbonyl and nitrosyl complexes and their derivatives. For example, in addition to ferrocene. M(i 5-CsHs)2 compounds are known for most of the other elements of the first transition series (M — V, Cr, Mn.Co, Ni) and these cannot obey ihe 18-electron rule. However, only ferrocene shows exceptional thermal stability (stable to 500 C) and is not oxidized by air. Furthermore, cobaltocene, a 19-electron species, is readily oxidized to the 18-electron cobaltocenium ion. (Co(ip-CsH )3)4 , which reflects much of the thermal stability of ferrocene. Mixed cyclopentadienyl carbonyl complexes are common K -CjHjMCO) ]. [(if-CjH )-Cr(CO), . [( -CjHOMnCCOjJ, [(>r-C,H,>Fe(CO ,, . [fo -CjiyCoCoy. and (ip-CsH,)Ni(CO) 2. Of interest is the fact that among these compounds, the odd-atomic-number elements (V. Mn, and Co) form monomers and the even-atomic-number elements (Cr. Fe. and Ni) Ibrm dimers, which is in direct contrast to the behavior shown by the simple carbonyl complexes. Cyclopentadienyl derivatives are now known for every main group and transition metal of the periodic table and for most of the -block metals.89... 

Oxathiolane 2,2-dioxide undergoes metallation with n-butyllithium as expected at the 3-position (81JOC101). The anion may be alkylated with alkyl halides or carbonyl compounds. The isomeric 1,3-oxathiolane 3,3-dioxides also undergo metallation ortho to the sulfone and, when the 4-position is blocked, metallation at the 2-position may be used as an efficient conversion of alkyl halides into aldehydes as shown in Scheme 22 (79TL3375). 

CO can bridge two or more li-block metals and some cases are known when the metal carbonyl oxygen also binds to strongly electropositive metals. 

A large number of J-block metal complexes containing coordinated N2 are known (see Figure 14.9 and equations 22.95 and 22.96 and discussion) N2 is isoelectronic with CO and the bonding in complexes containing the N2 ligand can be described in a similar manner to that in metal carbonyl complexes (see Chapter 23). 

Table 23.3 lists many of the stable, neutral, d-block metal carbonyl compounds containing <6 metal atoms. A range... 

Table 23.3 Neutral, low-nuclearity (

G. Frenking (2001) Journal of Organometallic Chemistry, vol. 635, p. 9 - An assessment of the bonding in d-block metal complexes including carbonyls which considers the relative importance of a and tt, as well as electrostatic, contributions to the metal-ligand bonds. 

Organolanthanoid chemistry is a rapidly expanding research area, and an exciting aspect of this area is the number of efficient catalysts for organic transformations that have been discovered (see Box 24.5). In contrast to the extensive carbonyl chemistry of the d -block metals (see Sections... 

In a series of papers entitled Structural Systematics, Orpen and co-workers used the GSD to examine a number of geometric aspects of /7-block metal complexes including torsional flexibility and conformer interconversion pathways for phosphine and diphosphine ligands, carbonyl ligand migration between metal centers (see also Figure 9,... 

An analysis of more than 20000 crystal structures of J-block metal carbonyl complexes confirms a clear correlation between C O and M-C bond distances, i.e. as the M-C bond distance decreases, the C bond distance (rfco) increases. Ninety per cent of the structural data fall into a region in which 117.0 pm > dco > 112.8 pm, and for these M-CO interactions, the M-C bonding contributions are approximately in balance. For 4%, w-bonding dominates and dco > 117.0 pm, while for 6%, cr-bonding and ionic contributions dominate and dco < 112.8 pm. 

Table 24.3 lists many of the stable, neutral, el-block metal carbonyl compounds containing six or fewer metal atoms. A range of unstable carbonyls have been obtained by matrix isolation the action of CO on metal atoms in a noble gas matrix at very low temperatures or the photolysis of stable metal carbonyls under similar conditions. Among species made this way are Ti(CO)5, Pd(CO)4, Pt(CO)4, Cu2(CO)6, Ag2(CO)fi, Cr(CO)4, Mn(CO)5, Zn(CO)3, Fe(CO)4, Fe(CO)3 and Ni(CO)3 (those of Cr, Mn, Fe and Ni being fragments formed by decomposition of stable carbonyls). In the rest of this section, we discuss compounds isolable at ordinary temperatures. 

Despite the extreme air and moisture sensitivity of organo-lanthanoid compounds, this is a rapidly expanding research area. An exciting aspect of organolanthanoid chemistry is the number of efficient catalysts for organic transformations that have been discovered (see Box 25.5). In contrast to the extensive carbonyl chemistry of the J-block metals (see Sections 24.4 and 24.9), lanthanoid metals do not form complexes with CO under normal conditions. Unstable carbonyls such as Nd(CO)g have been prepared by matrix isolation. Since organolanthanoids are usually air- and moisture-sensitive and may be pyrophoric, handling the compounds under inert atmospheres is essential. ... 

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