Ammines complexes

Diamine Complexes. The reaction of tr ms-[Co(en)2Cl2] + with unidentate alkyl or aryl amines produces ds-[Co(en)2(amine)Cl]2+, the stereochemistry of the product being indicated by resolution.271 The spontaneous resolution of [Co(C204)(en)2]X, 

Hawkins and G. A. Lawrence, Inorg. Nuclear. Chem. Letters, 1973,9, 1183. 

Dellesbaugh and B. E. Douglas, Inorg. Nuclear Chem. Letters, 1973, 9, 1255. 

The [Co(en)3]3+ cation undergoes N-deprotonation to give [Co(en - 2H)3]3-when treated with MeLi or BunLi in diethyl ether or THF, from which acetic acid 

Cobalt(lll).—Complexes. Ammine complexes. Optical activity can be induced in the complexes [Co(NH3) ] and [Cofenlj] by means of outer-sphere association with chiral anions, e.g. (- - )-tartrate. Circular dichroism is observed in the d-d bands of the cations and it is suggested that this is due to (a) direct interaction between the chiral anion and the metal f/-orbitals and (b) the preferred conformation adopted by the inner-sphere ligands in the presence of a helical outer-sphere ligand. 

Solid-phase deaquation of cis-[Co(NH3)4(H20)2] has been studied. The sulphate trihydrate forms the dinuclear sulphate-bridged complex cis-cis-[(S04)(NH3)4Co(p-S04)Co(NH3)4(S04)], which is unstable in air and rapidly aquates to cis-[Co(NH3)4(H2G)S04]. The suggested mechanism for this reaction is  

Saburi. and S. Yoshikawa. Bull. Chem. Soc. Japan, 1971, 44, 3486. 

Historically, the most important ruthenium(II) ammine species is [Ru(NH3)5N2]2+, the first stable dinitrogen complex to be isolated (1965). It was initially obtained by refluxing RuC13 in hydrazine solution (but many 

X-ray diffraction confirms the terminal N2 geometry, with slight lengthening of the N—N bond (1.12A) compared to gaseous N2 (1.09A) with concomitant lengthening shown by the change in i/(N=N) in the IR spectrum (2110 cm-1, compared with 2331 cm-1 in nitrogen gas) [65], 

The N2 ligand is displaced by other ligands (e.g. py) and attempted oxidation to [Ru(NH3)5N2]3+ results in the loss of N2. 

The pentammine aqua ion [Ru(NH3)5(H20)]2+, best made by zinc amalgam reduction and aquation of [Ru(NH3)5C1]2+, undergoes extensively studied substitution reactions first order in both the ruthenium complex and the incoming ligand (e.g. NH3, py) and is a convenient source of other 

The ESR spectra of t2gRu(NH3)g+ on cubic sites in [Ru(NH3)6]BrS04 show an isotropic g value of 1.926 while in [Ru(NH3)6] (NCS)3 the g values are 2.357, 1.929 and 1.468 (gav = 1.918) in a low symmetry field. The results have been interpreted in a crystal field model with an orbital reduction factor of 0.94 [67], 

The mixed-valence ion has an intervalence charge transfer band at 1562nm not present in the spectra of the H-4 and +6 ions. Similar ions have been isolated with other bridging ligands, the choice of which has a big effect on the position and intensity of the charge-transfer band (e.g. L = bipy, 830 nm). 

The quantum yields for the photoaquation of these d hexammine complexes of the second- and third-row transition metals are independent of the excitation wavelength, and have values in the range of 0.07 to 0.09 for Rh(NH3)6 and Ir(NH3)6, and in the region of 0.25 for These quantum yields for 

The photochemistries of the mixed ligand cf complexes Rh(NH3)5X (X = Cl, Br, I), Rh(NH3)5L (L=CH3CN, py) and Ru(NH3)5L (L=N2, py, H2O) have been widely studied. In contrast to the photochemistry of cobalt(III) complexes where both substitution and redox reactions are observed, the photochemistry of the analogous rhodium(III) complexes results in substitution  

For the intermediate situation where X = Br, both halide and anunine substitution is observed. The quantum yields for these substitution reactions are shown in Table 3.1, and the energy level diagram in Fig. 3.4 has been used to explain the photoaquation of these haloammine complexes (see Ref. 49). As with the hexaam-mine complexes, initial singlet excitation is followed by relaxation to the lowest- 

The quantum yields for these reactions are low. When the chelating amine ethyle-nediamine (en) is used as ligand in the rhodium(III) complexes Rh(en)2X2, photoisomerization, in addition to photoaquation, must be considered [Eq. (3.12)].  

The photochemistry of the mixed ligand ruthenium(II) complexes of type Ru(NH3)sL can result in a range of different reactions. These involve photoaquation of the ligand L to give Ru(NH3)5(H20), or photoaquation of an anunine ligand to give either cis- or rran5 -Ru(NH3)4(H20)L .  

4 o is the primary quantum yield for bond cleavage and is assumed to be viscosity independent. In pure water I — d o and cage effects are negligible. ks decreases approximately inversely with increasing viscosity [ky const), and for the ammine complexes an / mechanism is most probable. For [M(CN)6] and [Cr(NCS)6], t I o and 7 ks. An Ij mechanism is most likely in these cases. For [Cr(NH3)sNCS] the volume of activation associated with ks (i.e., from plots of In 4 o versus pressure) is estimated to be -9.5 cm moF close to the value in pure water (-9.8 cm moF ). At high viscosities the dependence of In 4) on pressure is complex with maxima observed around 1 kbar. The reason for this is uncertain.  

Ligand-field photolysis of trans-[Cr(NH3)4(DMF)Cl] ion leads largely to the loss of DMF, with some loss of NH3 and CF as well. From the wavelength dependence of the quantum yields, the E and upper D2 states are inferred to be the main precursors to aquation of the axial ligands, and of NH3, respectively. Replacement of DMF and CF occurs with complete trans - cis isomerization, although charge transfer photolysis is less stereoselective.  

The structural data (Table 1.8) and spectroscopic information indicate that the 5 + ion has considerable delocalization with rapid electron transfer between the two centres ( 1012 s 1) [68]. 

Colors of coordination componnds depend on which metals and ligands are present. From left the [Ni(NH3)6l + ion is pnrple the [Ni(H20)el + ion is green the [Cu(H20)4l ion is light hine and the [Cu(NH3)4] + ion is deep hine. 

Ammine complexes contain NH3 molecules bonded to metal ions. Because the ammine complexes are important compounds, we will describe some of them briefly. 

Most metal hydroxides are insoluble in water, so aqueous NH3 initially reacts with nearly all metal ions to form insoluble metal hydroxides, or hydrated oxides. 

The careful addition of aqueous NH3 to the top of a light blue solution of Cu ions bottom of beaker) produces a grayish-white Cu(0H)2 precipitate middle) and the soluble dark blue tetraammine complex, [Cu(NH3)4f (fop). 

The hydroxides of some metals and some metalloids are amphoteric (see Section 10-6)., Aqueous NH3 is a weak base (i b = 1.8 X 10 ), so the [OH ] in an ammonia solution is too low to dissolve amphoteric hydroxides by forming hydroxo complexes. 

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As an example, the entries in Table 8.12 for the zinc ammine complexes represent these equilibria ... 

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

TABLE 11.35 Cumulative Formation Constants of Ammine Complexes at 20°C, Ionic Strength 0.1 ... 

Dispersed Metals. Bifimctional zeoHte catalysts, principally zeoHte Y, are used in commercial processes such as hydrocracking. These are acidic zeoHtes containing dispersed metals such as platinum or palladium. The metals are introduced by cation exchange of the ammine complexes, foUowed by a reductive decomposition (21) ... 

Coordination Compounds. A large number of indium complexes with nitrogen ligands have been isolated, particularly where Ir is in the +3 oxidation state. Examples of ammine complexes include pr(NH3)3] " [24669-15-6], prCl(NH3)] " [29589-09-1], and / j -pr(03SCF3)2(en)2]" [90065-94-4], Compounds of A/-heterocychc ligands include trans- [xCX py)][ [24952-67-8], Pr(bipy)3] " [16788-86-6], and an unusual C-metalated bipyridine complex, Pr(bipy)2(C, N-bipy)] [87137-18-6]. Isolation of this latter complex produced some confusion regarding the chemical and physical properties of Pr(bipy)3]3+ (167). 

Cobalt exists in the +2 or +3 valence states for the majority of its compounds and complexes. A multitude of complexes of the cobalt(III) ion [22541-63-5] exist, but few stable simple salts are known (2). Werner s discovery and detailed studies of the cobalt(III) ammine complexes contributed gready to modem coordination chemistry and understanding of ligand exchange (3). Octahedral stereochemistries are the most common for the cobalt(II) ion [22541-53-3] as well as for cobalt(III). Cobalt(II) forms numerous simple compounds and complexes, most of which are octahedral or tetrahedral in nature cobalt(II) forms more tetrahedral complexes than other transition-metal ions. Because of the small stabiUty difference between octahedral and tetrahedral complexes of cobalt(II), both can be found in equiUbrium for a number of complexes. Typically, octahedral cobalt(II) salts and complexes are pink to brownish red most of the tetrahedral Co(II) species are blue (see Coordination compounds). 

Copper hydroxide is almost iasoluble ia water (3 p.g/L) but readily dissolves ia mineral acids and ammonia forming salt solutions or copper ammine complexes. The hydroxide is somewhat amphoteric dissolving ia excess sodium hydroxide solutioa to form ttihydroxycuprate [37830-77-6] [Cu(011)3] and tetrahydroxycuprate [17949-75-6] [Cu(OH) ]. ... 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfldes (e.g. TI2S3) and polyiodides, etc. In other respects Tl resembles the more highly polarizing ion Ag+, e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

It should be noted that this method is only applicable to solutions containing up to 25 mg copper ions in 100 mL of water if the concentration of Cu2+ ions is too high, the intense blue colour of the copper(II) ammine complex masks the colour change at the end point. The indicator solution must be freshly prepared. 

Many of the ammine complexes are osmium(III) compounds the +2 state is less stable than with ruthenium, as expected, and osmium(II) compounds... 

Figure 2.44 Syntheses and reactions of rhodium(III) ammine complexes.

Figure 2.47 The limiting photosubstitution mechanism for rhodium(III) ammine complexes. (Reprinted from Coord. Chem. Rev., 94, 151, 1989, with kind permission from Elsevier Science S.A., P.O. Box 564, 1001 Lausanne, Switzerland.)...

Figure 2.48 Quantum yields for the photolysis of rhodium(IIl) ammine complexes.

Platinum ammine complexes have been a fertile area for studying transinfluence. Table 3.21 lists data for a range of ammines showing how /(195Pt-15N) depends upon the trans-atom [153]. (A further selection of data can be found in R.V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis-Horwood, Chichester, 1991, pp. 76, 87.) Possibly the most detailed study (of complexes of tribenzylphosphine) examined over a hundred neutral and cationic complexes [154] (Table 3.22). 

Another platinum(IV) ammine complex studied as a possible anti-tumour compound is shown in Figure 3.101 [171] m-(l,2-diaminocyclohexane)tetra-chloroplatinum has undergone clinical trials but was found to be too neurotoxic. 

Alkene complexes Alkynyl complexes Ammine complexes Aqueous chemistry Arsine complexes Auranofin Auride ion Aurophilicity Binary compounds Bond lengths acetylacetonate complex alkyls and aryls ammine complexes carboxylates cyanide complexes dialkyl sulphide complexes dithiocarbamates to gold... 

Alkene complexes Ammine complexes Aqueous chemistry Arsine complexes Binary compounds Bipyridyl complexes Bond lengths acetylacetonate alkene complexes alkyl and aryl complexes ammine complexes aqua ion... 

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