Yttrium stability constants

Compared to later elements in their respective transition series, scandium, yttrium and lanthanum have rather poorly developed coordination chemistries and form weaker coordinate bonds, lanthanum generally being even less inclined to form strong coordinate bonds than scandium. This is reflected in the stability constants of a number of relevant 1 1 metal-edta complexes ... 

The stability constants of yttrium tartrates have been determined and a mixed copper-yttrium tartaric (T) acid species, Y2CuT3H q unknown), was detected. ... 

The measurement of stability constants of complexes of yttrium, lanthanide, and actinide ions with oxalate, citrate, edta, and 1,2-diaminocyclohexanetetra-acetate ligands has revealed that there is a slight increase in the stability of complexes of the /-electron elements, relative to the others. A series of citric acid (H cit) complexes of the lanthanides have been investigated by ion-exchange methods and the species [Ln(H2cit)]", [Ln(H2cit)2] , [Ln-(Hcit)], and [Ln(Hcit))2] were detected. Simple and mixed complexes of dl- and jeso-tartaric acid have been obtained with La " and Nd ions, and the stability constants of lactate, pyruvate, and x-alaninate complexes of Eu and Am " in water have been determined. 

Sensor. The control of the exhaust composition was essential to maintain the air-to-fuel ratio close to stoichiometric for simultaneous conversion of all three pollutants. This control came about with the invention of the 02 sensor.21,22 The sensor head of this device was installed in the exhaust immediately at the inlet to the catalyst and was able to measure the 02 content instantly and precisely. It generates a voltage consistent with the Nemst equation in which the partial pressure of 02 (P02)exhaust in the exhaust develops a voltage (E) relative to a reference. The exhaust electrode was Pt deposited on a solid oxygen ion conductor of yttrium-stabilized zirconia (Zr02). The reference electrode, also Pt, was deposited on the opposite side of the electrolyte but was physically mounted outside the exhaust and sensed the partial pressure (P02)ref in the atmosphere. E0 is the standard state or thermodynamic voltage. R is the universal gas constant, T the absolute temperature, n the number of electrons transferred in the process, and F the Faraday constant. 

The position of yttrium in rare earth chemistry has always been interesting and this is also the case with respect to complex formation. The electrostatic model suggests placement of yttrium between holmium and thulium. It has been shown that it is not the case [14]. When one considers the stability constant data of group 1 ligands, yttrium is similar to the heavy rare earths. When the second group of ligands is considered, yttrium exhibits a behaviour similar to the lighter rare earth elements. 

Variation of the stability constant (ATm) of the mixed LnMEDTA-acetate complexes, the dissociation rate constant (jts Km ) and the calculated formation rate constant for the lanthanides (except Pm) and yttrium at 0.5 M... 

Both scandium and yttrium are electropositive metals with similar reduction potentials to the lanthanides ( °Sc +/Sc = -2.03 V ° Y +/Y = —2.37 V compare values of-2.37 V and -2.30 V for La and Lu, respectively). The ionic radii of Sc + and Y + are 0.745 A and 0.900 A, respectively (in six coordination). The former is much smaller than any Ln + ion but yttrium is very similar to Ho + (radius 0.901 A) purely on size grounds, it would be predicted that yttrium would resemble the later lanthanides but that scandium would exhibit considerable differences, and this expectation is largely borne out in practice. Table 7.1 lists stability constants for typical complexes of Sc + and Y +, together with values for La + andLu +. 

Selected stability constants for scandium, yttrium, lanthanum, and lutetium are shown in (Table 3) They show a preference for hard donor atoms, as might be expected for the trivalent metals, but complexes with softer donor atoms like nitrogen can be isolated by operating in nonaqueous solvents. 

The influence of chemical impurities showed that, of the five metalhc impurities investigated (Ca, Cd, Cu, Fe and Zn), the strongest competitor is Fe. For the assumed labelling yield (98% radiochemical purity), in the case of the labelling of Y-DOTATATE, the maximum concentration of Fe is 5 pg/Ci of °Y (Fig. 13.11). In the case of Lu-DOTATATE, the maximum concentration of Fe is approximately 100 gg/Ci of Lu (Fig. 13.12). This difference between the two maximum concentrations is probably due to the difference in stability constants for yttrium and lutetium complexes with DOTATATE. The stability constant for Lu-DOTA is ten times higher than that for Y-DOTA (Table 13.1). 

Liquid-liquid extraction has proved a practical technique for the isolation of rare earths and yttrium as a group and for the isolation of individual members of this group, the separation being accomplished especially easily in instances in which a valence other than +3 might be employed. It has proved useful in the determination of stability constants of lanthanide and actinide chloride and nitrate complexes. And it has demonstrated the existence of mixed extracted entities such as Th(N03)(HY2)3. 

Petit-Ramel MM, Khalil I (1974) Mixed bimetallic complexes II. Determination of the stability constants ofyttrium citrates of the bimetallic copper yttrium citrate. Bull Soc Chim (Fr) 1259-1263... 

There have only been two studies that have reported data for the stability constant of Y(0H)2 (Amaya, Kakihana and Maeda, 1973a Chirkst et al., 2009). The data from both of these studies lead to values of the second stepwise stability constant, log K2, that is greater than that of the first stability constant, log Ky This behaviour is not accepted in this review, and consequently, these data are not accepted. There have been no reported data on the formation and stability of Y(OH)3(aq). As such, no data are recommended for the higher monomeric species of yttrium (III). 

Shalinets and Stepanov (1972) measured the first hydrolysis constants of a number of trivalent metal ions including yttrium. They obtained values for the constants that were 3-4 orders of magnitude larger than in other studies that used similar experimental conditions. None of the data of Shalinets and Stepanov (1972) have been retained. Ivanov-Emin et al. (1970) also studied the hydrolysis of a number of metal ions and determined stability constants for the first six... 

There are only two studies that report data for the higher monomeric species of yttrium. Amaya, Kakihana and Maeda (1973a) determined a value for the stability constant of Y(OH)2" in 3moll LiC104 that was -16.87 (converted to 3.48 mol kg ). This value does not appear to be consistent with the value determined by Biedermann and Ciavatta (1964) for the first hydrolysis constant (see Table 8.8) since the second stepwise constant log K2 from Amaya et al. would be greater than log proposed by Biedermann and Ciavatta. Also, Amaya et al. did not detect the formation of in their solutions which is... 

There are two studies that have provided stability constants for polymeric species of yttrium (Biedermann and Ciavatta, 1964 Amaya, Kakihana and Maeda, 1973a). Both studies performed measurements at 25 C and in 3moll LiClO. ... 

Table 8.10 Data for the stability constants of polymeric species of yttrium(lll).

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