Group 4 metals simple complexes

The ahphatic alkyleneamines are strong bases exhibiting behavior typical of simple aUphatic amines. Additionally, dependent on the location of the primary or secondary amino groups iu the alkyleneamines, ring formation with various reactants can occur. This same feature allows for metal ion complexation or chelation (1). The alkyleneamines are somewhat weaker bases than ahphatic amines and much stronger bases than ammonia as the piC values iadicate (Table 2). 

Two classes of promoter have been identified for iridium catalysed carbonylation (i) transition metal carbonyls or halocarbonyls (ri) simple group 12 and 13 iodides. Increased rates of catalysis are achieved on addition of 1-10 mole equivalents (per Ir) of the promoter. An example from each class was chosen for spectroscopic study. An Inis promoter provides a relatively simple system since the main group metal does not tend to form carbonyl complexes which can interfere with the observation of iridium species by IR. In situ HP IR studies showed that an indium promoter (Inl3 Ir = 2 1) did not greatly affect the iridium speciation, with [MeIr(CO)2l3] being converted into [Ir(CO)2l4] as the batch reaction progressed, as in the absence of promoter. 

Nucleophilic substitutions of simple aromatic compounds which formally involve a hydride displacement are difficult to achieve because of the poor leaving group and the high electron density of the aromatic nucleus which repels approach of a nucleophile. However, rc-electron deficient aromatic compounds such as metal carbonyl complexes are susceptible to attack by certain carbon nucleophiles. Studies of this chemistry have shown [16] an opposite jegioselectivity to the corresponding electrophilic substitutions, in agreement with the polarity alternation rule. 

Dioxygen binds to metal porphyrins in the three expected modes, i.e. u-superoxo, peroxo and bridging peroxo. In contrast to die simple complexes discussed previously, dioxygen coordination occurs with a wide range of transition metals from titanium and niobium through to the Group VIII metals. 

With the notable exception of rhodium, Group VIII metal-peroxo complexes are generally reluctant to react with simple alkenes by nonradical pathways. However, such an oxygen transfer has been shown to occur in the reaction of 180-labeled [(AsPh3)4Rh02]+C104" with terminal alkenes under 02-free, anhydrous conditions, producing lsO-labeled methyl ketone (equation 52).131... 

A similar situation arises when the metal-ion-catalysed base hydrolyses of aminoacids and peptides are studied. Such hydrolyses contrast with the base hydrolyses of simple esters, which are not catalysed by metal ions. Again, metal ion complexes with the aminoacid esters or the peptides are involved in the catalyses. The presence of the metal ion increases the electron-withdrawing power of the carbonyl group and helps attack by the hydroxide ion, leading to efficient hydrolysis. 

There are many reactions of metal-tin complexes where the tin group is a spectator ligand. The majority of these reactions are simple ligand substitutions, typified by the chemistry outlined in equations 163382-386, 164387 and 165329,330. 

Tphe bright colors of the coordination complexes of transition metal elements, including the platinum group metals, were of great assistance to pioneer workers with these materials. Thus, chemical changes could be followed visually it was frequently very easy from their colors to demonstrate the existence of isomers upon which Alfred Werner was able to base his monumental theory of coordination. Such early studies were limited to a simple qualitative visual evaluation of the color. 

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