Chemistry Reactions of Complexes

S213 As discussed in Section 21.6, the Eigen-Wilkins mechanism for substitution in octahedral complexes suggests the formation of an encounter complex [V(H20)6] Cl , in the first, fast step  

The second, slow step of the mechanism is producing the product  

1 If the mechanism of substitution were to be associative, the nature of incoming ligand should affect the rate of the reaction. This is because the rate-limiting step would require the formation of M-X bonds (X = incoming ligand). In the present case, however, the rate of the reaction does not vary much with the nature or the size of the incoming ligand. Therefore, the more likely mechanism would be dissociative. 

2 The rate of an associative process depends on the identity of the entering ligand and, therefore, it is not an inherent property of [M(OH2)s] . 

The rate law will be the same regardless of whether the transformation of the encounter complex into products is dissociatively or associatively activated. However, you can distinguish d from a by varying the nature of X. If k varies as X varies, then the reaction is a. If k is relatively constant as X varies, then the reaction is d. Note that k cannot be measured directly. It can be found using the expression k = kK and an estimate of K, . 

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Uson, R., Royo, P. and Laguna, A. (1974) Reactions of complexes of gold(I) with bis (pentafluorophenyl)thallium(III) halides. Journal of Organometallic Chemistry, 69(3), 361-365. 

When painting a wall, better coverage is assured when the roller passes over the same area several times from different directions. It is the opinion of the author that this technique works well in teaching chemistry. Therefore, a second objective has been to stress fundamental principles in the discussion of several topics. For example, the hard-soft interaction principle is employed in discussion of acid-base chemistry, stability of complexes, solubility, and predicting reaction products. Third, the presentation of topics is made with an effort to be clear and concise so that the book is portable and user friendly. 

The transformation predominates in Group 9 (Rh, Ir) chemistry. Reactions of RhCl(L)2 2 with 1-alkynes give the q -alkyne complexes which slowly convert to the hydrido(alkynyl)s at room temperature. The latter are sensitive to air and not often isolated. Addition of pyridine affords RhHCl(C=CR)(py)(L)2, which readily lose pyridine in hydrocarbon solvents to give square-planar fran.s-RhCl(=C=CHR)(L)2. Alternatively, the Cp complexes Rh(=C=CHR)(L)Cp can be obtained by reaction of the chloro complexes vdth TlCp. In the iridium series, heating for 36h in refluxing toluene afforded the vinylidenes in 80-90% yields. Table 1.2 lists several examples of reactions in which the q -alkyne complexes have been detected. 

The Tp hgands (i.e., tris(pyrazolyl)borates or scorpionates [13]) are close analogs to the Cp hgands (i.e., -cyclopentadienyl), and in connection with the chemistry of the Tp Cr complexes mentioned above, a recent example of O2-binding from vanadium chemistry is of interest, even though it is formally not organometalhc chemistry Reaction of the V(IV) complex... 

H. Taube, Electron Transfer Reactions of Complex Ions in Solution, Academic Press, New York 1970. >C.K. Ingold, Structure and Mechanism in Organic Chemistry, 2. Aufl. S. 406-417, Cornell University... 

A review of the Journal of Physical Chemistry A, volume 110, issues 6 and 7, reveals that computational chemistry plays a major or supporting role in the majority of papers. Computational tools include use of large Gaussian basis sets and density functional theory, molecular mechanics, and molecular dynamics. There were quantum chemistry studies of complex reaction schemes to create detailed reaction potential energy surfaces/maps, molecular mechanics and molecular dynamics studies of larger chemical systems, and conformational analysis studies. Spectroscopic methods included photoelectron spectroscopy, microwave spectroscopy circular dichroism, IR, UV-vis, EPR, ENDOR, and ENDOR induced EPR. The kinetics papers focused on elucidation of complex mechanisms and potential energy reaction coordinate surfaces. 

J Taube, H. Electron Transfer Reactions of Complex Ions In Solution Academic New York. 1970 Chapter 2. Haim A. Acc. Chem. Fes. 1975, 8, 264-272. Pennington, D. E. In Coordination Chemistry Martcll, A. E.. Ed. ACS Monograph 174 American Chemical Society Washington, DC. 1978 Yol. 2. pp 476-590. Taube. H. Science 1984.226, 1028-1036 (Professor Taube s Nobel Prize address). An Appreciation of Henry Taube, Prog. Invrg. Chem. 1983, 30. Rudolph A. Marcus Commemorative Issue, J. Phys. Chem, 1986, 90, 3453-3862. 

Other bis(cycloaurated) complexes related to 61 have been synthesised by closely related chemistry reaction of equimolar amounts of 29 and [Me4N][AuCl4] gave [Au(azo)2Cl] 62, which with Ag[C104] gave the corresponding cationic bis(cycloaurated)... 

One major reason for the great interest in the processes of thin metal-containing films is that reactions on the surface of small metal clusters can be studied. Indeed, prior to the development of thin-film chemistry, reactions of similar particles were studied only in the gas phase at rather high temperatures. Under these conditions, most of the primary products are unstable and decompose in the course of further reaction, which is non-selective. As a result, the information obtained on the routes and mechanisms of reactions of disperse metals appears to be scarce, while the use of such reactions in synthesis is inexpedient. Conversely, low-temperature reactions in the films of co-condensates are very promising from the standpoint of determining the detailed reaction mechanism, as well as for synthesis of previously unknown complexes and organometallic compounds. It is important that atoms of only a few metals react with organic compounds immediately at the instant of their contact on the cooled substrate. Rather often, atoms and/or small (molecular) clusters are first stabilized in the film, and then their transformations are observed. 

The field of acetylene complex chemistry continues to develop rapidly and to yield novel discoveries. A number of recent reviews 1-10) covers various facets including preparation, structure, nature of bonding, stoichiometric and catalytic reactions, and specific aspects with particular metals. The first part of this account is confined to those facets associated with the nature of the interactions between acetylenes and transition metals and to the insertion reactions of complexes closely related to catalysis. Although only scattered data are available, attempts will be made to give a consistent interpretation of the reactivities of coordinated acetylene in terms of a qualitative molecular orbital picture. 

Reactions of complexes of 1,2-cycloheptadienes have received only cursory attention. 1,2-cycloheptadiene is readily displaced from bisftriphenyl-phosphine)platinum(O)118 [Eq. (54)], but no reagent has been found that will displace the allene from iron.119 Reaction of the iron complex with alcohol in the presence of base (e.g., 312 — 322) is typical of Fp+ complexes of acyclic allenes.131132 The thermal chemistry of 312 is unusual in its decomposition to 324 (Scheme 41). This is probably attributable to the presence of the triflate counterion, since the corresponding fluoroborate salt is stable when warmed to 40°C for 16 h.119 A mechanism to 324 via carbene complex 321 appears likely. 

In the literature [615-619] there are the results of quantitative investigations into the reaction of complex formation of H2Se03 and aromatic ort/to-diamincs, -R-C6H3(NH2)2, which allow an accurate determination of the composition of the mixture at any pH, which is widely used in analytical chemistry of selenium. 

J. Meyer and H. Taube, Electton Transfer Reactions, in G. Wilkinson, R. D. Gillard, and J. A. McCleverty, eds., Pergamon, Comprehensive Coordination Chemistry, Vol. 1, London, 1987, pp. 331-384 H. Taube, Electron Transfer Reactions of Complex Ions in Solution, Academic Press, New York, 1970 Chem. Rev., 1952, 50, 69 J. Chem. Educ., 1968, 45,452. 

For several years, Streubel and coworkers have been exploring the chemistry of nitrilium phosphine ylides that contain low-valent organophosphorus fragments, such as complex (19) (Scheme 3). In their latest contributions to this area, they have investigated the reactions of complex (19) with phosphoranes and iminophosphoranes which have led to a number of new species containing ylidic moieties, such as the tricyclic complex (20), and 2H-l,2-azaphosphole complexes (21) and (22). Similarly, treatment of other low-valent organophosphorus complexes such as phosphinidine species (23) with stabilised phosphoranes produces new ylidic-aducts (24) and (25) (Scheme 4). ... 

Attempts have been made to isolate aluminohydride analogs in trivalent chemistry. Reaction of UCI3 with three equivalents of L1A1H4 yields a gray powder, proposed to be U(A1H4)3. The complex is reported to decompose at temperatures above —20 °C. 

Interest has also continued in phosphinidene (RP ) chemistry. Evidence from mass spectrometry has led to the conclusion that phenylphosphinidene, PhP , is a stable species in the gas phase.The existence of p-phenylenebi-sphosphinidene (332) has been considered from a theoretical standpoint. " The reactivity of coordinated phosphinidenes has received further study. The first examples of genuine 1,4-additions of the complex PhP=W(CO)5 with 1,3-dienes, giving phospholene complexes, e.g. (333), have been reported. " " Phosphiranes are formed as intermediate species in the reactions of complexed phosphinidenes with chloro-alkenes, which lead ultimately to vinylphosphorus compounds (334), essentially insertion products of the phosphinidene into the... 

The monoanion of this, trop, is a good 0,0 chelate, resembling the catecholato dianion in its platinum group chemistry. Reaction of [OsCl ] (generated from [OsCl ] " and silver powder) with tropolone gives the yellow Os(trop)3, for which IR, H and CNMR data were obtained. Similar data were obtained for the osmyl complex Os02trop2, made from fra s -K2[0s02(0H)4] and tropolone. ... 

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