HSABHard and Soft Acids and bases软硬酸碱理论在分析化学中的应用
HardandSoftAcidsandBases
Hard and Soft Acids and Bases.We have already pointed out that the affinity that metal ions have for ligands is controlled by size, charge and electronegativity. This can be refined further by noting that for some metal ions, their chemistry is dominated by size and charge, while for others it is dominated by their elctronegativity. These two categories of metal ions have been termed by Pearson as hard metal ions and soft metal ions. Their distribution in the periodic table is as follows:Figure 1. Table showing distribution of hard, soft, and intermediate Lewis Acids in the Periodic Table, largely after Pearson.Pearson’s Principle of Hard and Soft Acids and Bases (HSAB) can be stated as follows: Hard Acids prefer to bond with Hard Bases, and Soft Acids prefer to bond with Soft Bases. This can be illustrated by the formation constants (log K1) for a hard metal ion, a soft metal ion, and an intermediate metal ion, with the halide ions in Table 1:Table 1. Formation constants with halide ions for a representative hard, soft, and intermediate metal ion .________________________________________________________________________ Log K1F-Cl-Br-I- classification________________________________________________________________________ Ag+0.4 3.3 4.7 6.6 softPb2+ 1.3 0.9 1.1 1.3 intermediateFe3+ 6.0 1.4 0.5 - hard________________________________________________________________________What one sees in Table 1 is that the soft Ag+ ion strongly prefers the heavier halide ions Cl-, Br-, and I- to the F- ion, while the hard Fe3+ ion prefers the lighter F- ion to the heavier halide ions. The intermediate Pb2+ ion shows no strong preferences either way. The distribution of hardness/softness of ligand donor atoms in the periodic Table is as follows:Figure 2. Distribution of hardness and softness for potential donor atoms for ligands in the Periodic Table. The diagram shows that hardness increases toward F-, and softness increases away from F-. However, this is not a smooth transition. There is, as shown, a major discontinuity between the lighter members of each group, namely, F-, O, and N, and their heavier congeners. Thus, Cl-, Br-, and I- are far more like each other, and far different from F-, in their bonding preferences, as can be seen in Table 1.The hardness of ligands tends to show, as seen in Figure 2, a discontinuity between the lightest member of each group, and the heavier members. Thus, one finds that the metal ion affinities of NH3 are very different from metal ion affinities for phosphines such as PPh3 (Ph = phenyl), but that the complexes of PPh3 are very similar to those of AsPh3. A selection of ligands classified according to HSAB ideas are:HARD: H2O, OH-, CH3COO-, F-,NH3, oxalate ( -OOC-COO-), en.SOFT: Br-, I-, SH-, (CH3)2S, S=C(NH2)2 (thiourea), P(CH3)3, PPh3, As(CH3)3, CN--S-C≡N (thiocyanate S-bound)INTERMEDIATE: C6H5N (pyridine), N3- (azide), -N=C=S (thiocyanate, N-bound), Cl-The softest metal ion is the Au+(aq) ion. It is so soft that the compounds AuF and Au2O are unknown. It forms stable compounds with soft ligands such as PPh3 and CN-. The affinity for CN- is so high that it is recovered in mining operations by grinding up the ore and then suspending it in a dilute solution of CN-, which dissolves the Au on bubbling air through the solution:4 Au(s) + 8 CN-(aq) + O2(g) + 2 H2O = 4 [Au(CN)2]-(aq) + 4 OH- [1]The aurocyanide ion is linear, with two-coordinate Au(I). This is typical for Au(I), that it prefers linear two-coordination. This coordination geometry is seen in other complexes of Au(I), such as [AuPPh3Cl], for example. Neighboring metal ions such as Ag(I) and Hg(II) are also very soft, and show the unusual preference for two-coordination.An example of a very hard metal ion is Al(III). It has a high log K1 with F- of 7.0, and a reasonably high log K1(OH-) of 9.0. It has virtually no affinity in solution for heavier halides such as Cl-. Its solution chemistry is dominated by its affinity for F- and for ligands with negative O-donors.One can rationalize HSAB in terms of the idea that soft-soft interactions are more covalent, while hard-hard interactions are ionic. The covalence of the soft metal ions relates to their higher electronegativity, which in turns depends on relativistic effects. What one needs to be able to comment on is sets of formation constants such as the following:Metal ion: Ag+Ga3+ Pb2+Log K1(OH-): 2.0 11.3 6.0Log K1(SH-): 11.0 8.0 6.0What is obvious here is that the soft Ag+ ion prefers the soft SH- ligand to the hard OH-ligand, whereas for the hard Ga3+ ion the opposite is true. The intermediate Pb2+ ion has no strong preference. Another set of examples is given by:Metal ion: Ag+H+Log K1(NH3): 3.3 9.2Log K1 (PPh3): 8.2 0.6Again, the soft Ag+ ion prefers the soft phosphine ligand, while the hard H+ prefers the hard N-donor.Thiocyanate (SCN-) is a particularly interesting ligand. It can bind to metal ions either through the S or the N. Obviously, it prefers to bind to soft metal ions through the S, and to hard metal ions through the N. This can be seen in the structures of [Au(SCN)2]- and [Fe(NCS)6]3- in Figure 3 below:Figure 3. Thiocyanate complexes showing a) N-bonding in the [Fe(NCS)6]3- complex with the hard Fe(III) ion, and b) S-bonding in the [Au(SCN)2]- complex (CSD: AREKOX) with the soft Au(I) ion.In general, intermediate metal ions also tend to bond to thiocyanate through its N-donors.A point of particular interest is that Cu(II) is intermediate, but Cu(I) is soft. Thus, as seen in Figure 4, [Cu(NCS)4]2- with the intermediate Cu(II) has N-bonded thiocyanates, but in [Cu(SCN)3]2-, with the soft Cu(I), S-bonded thiocyanates are present.Figure 4. Thiocyanate complexes of the intermediate Cu(II) ion and soft Cu(I) ion. Note that at a) the thiocyanates are N-bonded in [Cu(NCS)4]2- with the intermediate Cu(II), but at b) the thiocyanates in [Cu(SCN)3]2-, with the soft Cu(I), are S-bonded (CSD: PIVZOJ).。
HSAB 理论
HSAB 理论简介软硬酸碱理论：将酸和碱根据性质的不同各分为软硬两类的理论。
the theory of hard and soft acids and bases概念：体积小，正电荷数高，可极化性低的中心原子称作硬酸，体积大，正电荷数低，可极化性高的中心原子称作软酸。
将电负性高，极化性低难被氧化的配位原子称为硬碱，反之为软碱。
硬酸和硬碱以库仑力作为主要的作用力；软酸和软碱以共价键力作为主要的相互作用力。
分类将酸和碱根据性质不同分为软硬两类的理论。
1963年由R.G. 皮尔孙提出。
1958 年 S.阿尔兰德、J.查特和N.R.戴维斯根据某些配位原子易与 Ag+、Hg2+、Pt2+ 配位；另一些则易与Al3+、Ti4+配位，将金属离子分为两类。
a类金属离子包括碱金属、碱土金属 Ti4+、Fe3+、Cr3+、H+；b 类金属离子包括Cu+、Ag+、Hg2+、Pt2+。
皮尔孙在前人工作的基础上提出以软硬酸碱来区分金属离子和配位原子：硬酸包括a类金属离子（碱金属、碱土金属 Ti4+、Fe3+、 Cr3+、H+）硬碱包括F-、OH-、H2O、NH3、O2-、CH3COO-、PO43-、SO42-、CO32-、ClO4-、NO3-、ROH等软酸包括b类金属离子Cu+、Ag+、Hg2+、Pt2+ Au+;Cd2+; Pd2+、Hg2+及M0等软碱包括I-、SCN-、CN-、CO、H-、S2O32-、C2H4、RS-、S2-等交界酸包括Fe2+、Co2+、Ni2+; Zn2+、Pb2+、Sn2+、Sb3+、Cr2+、Bi3+ 、Cu2+等，交界碱包括N3-、Br- 、NO2-、N2 、SO32-等皮尔孙提出的酸碱反应规律为:“硬酸优先与硬碱结合，软酸优先与软碱结合。
”这虽然是一条经验规律，但应用颇广：①取代反应都倾向于形成硬 - 硬、软 - 软的化合物。
②软-软、硬-硬化合物较为稳定，软 - 硬化合物不够稳定。
③硬溶剂优先溶解硬溶质，软溶剂优先溶解软溶质，许多有机化合物不易溶于水，就是因为水是硬碱。
酸碱理论与溶剂化学
Hard
Borderline
Soft
Acids: H+, Li+, Na+, Acids: Fe2+, Co2+, Acids: Cu+, Ag+, K+, Be2+, Mg2+, Ca2+, Cr2+, Cr3+, Al3+, SO3, BF3 Bases: F–, OH–, H2O, NH3 , CO3
阿累尼乌斯提出的酸碱概念，对于化学科学的发展做出 了极大的贡献。这种概念只限于水溶液中。
2.1.1.2 酸碱溶剂理论 1905年美国化学家Franklin首先提出了溶剂体系的酸 碱定义，即： 在任何溶剂中， 酸：能增加和溶剂相同阳离子的物质； 碱：能增加和溶剂相同阴离子的物质； 酸碱中和反应：具有溶剂特征的阳离子与阴离子相互作 用形成溶剂分子。
b类：较低氧化态的过渡金属离子和氧化态小于+3的重过 渡金属离子 与电子对给予原子形成酸碱加合物稳定性的次序为：
优先与a类酸键合的Lewis碱为a类碱，优先与b类酸键合 的Lewis碱为b类碱 1963年，R.G.Pearson提出了软硬酸碱（SHAB）， 用“软”和“硬”表示a类和b类酸碱
硬酸：其接受电子对的原子（离子）正电荷高，半径小， 极化率小，变形性低，对外层电子拉得紧的物种。如：H+ 、 Be2+ 、Mg2+ 、 Al3+
N2O4
NH2OH
NO+
H+
NO3NHOH-
NOCl + AgNO3 = AgCl + N2O4
NH2OH.HCl + KNHOH = KCl + 2NH2OH
硬软酸碱规则的初步推导
硬软酸碱规则的初步推导1960年，Pearson第一次提出了化学中最重要的基本理论之一——硬软酸碱规则(HSAB)，即硬酸倾向于与硬碱通过离子键结合，而软酸通常与软碱通过共价键结合。
20年后，Parr和Pearson将化学硬度定义为能量对应电子数的二阶导数，即η≡(ð2EðN2)v(r)(1)。
化学硬度也可以通过η≈I−A (2)估算(其中I 为电离能，A为电子亲和能)。
自此，化学硬度的理论计算，尤其是与HSAB规则相关的计算工作大规模的开展起来。
虽然Parr和Pearson成功定义了硬度的概念，但科学家们还未弄清HSAB规则产生的根本原因。
有两种理论曾经被提出，但他们都不能很好的从数学推导或者从反应机理的角度解释HSAB规则。
第一种理论由Chattaraj和Parr提出，后经Gazquez等人修改而成。
他们认为，酸碱反应可以被分为两个步骤，(a)电荷在反应物中转移直至化学势相等，(b)生成部分的重排。
步骤(a)倾向于反应物的软度较大，而步骤(b)倾向软度较小。
在这种情况下，我们必须选择一个特定的模型来满足这两个步骤的要求，参数值f(y)才能达到一特定值，HSAB规则才能成立。
由于这种方法对于模型的要求非常高，而HSAB原则是普适性的，二者出现矛盾，理论一存在一定的问题。
理论二最初来源于Lee和Parr，是基于总正则配分函数而提出的，公式为Ω=E−μN (3) (其中E为能量，μ为系统的电化学势，通常由溶剂决定)。
理论二的推导建立在许多假设的基础上，然而这些假设均存在着一定的问题，不足以普适地证明HSAB规则。
由此，我们可以发现，建立一种简单有效的理论来解释HSAB规则是非常必要的。
我们使用了一种简单的二次模型来解释电子的给予与接受带来的反应物能量上的变化。
ΔE=μ(ΔN)+12η(ΔN)2(4) (其中η为硬度，μ为电化学势)。
又μ=(ðEðN )v(r)≈−(I+A2)=−χmulliken(5), 对公式(4)的高阶修正可被忽略。
HSAB(Hard-Soft-Acid-Base)理论
软硬酸碱理论简称HSAB（Hard-Soft-Acid-Base）理论，是一种尝试解释酸碱反应及其性质的现代理论。
20世纪60年代初，拉尔夫·皮尔逊介绍了HSAB的原理，作为一种尝试，用以统一有机和无机化学反应。
它目前在化学研究中得到了广泛的应用，其中最重要的莫过于对配合物稳定性的判别和其反应机理的解释。
软硬酸碱理论的基础是酸碱电子论，即以电子对得失作为判定酸、碱的标准（即路易斯酸碱理论）。
该理论可用于定性描述，而非定量的描述，这将有助于了解化学性质和反应的主要驱动因素。
尤其是在过渡金属化学，化学家们已经完成了无数次实验，以确定配体和过渡金属离子本身的硬和软方面的相对顺序。
原理概念：体积小，正电荷数高，可极化性低的中心原子称作硬酸，体积大，正电荷数低，可极化性高的中心原子称作软酸。
将电负性高，极化性低，难被氧化的配位原子称为硬碱，反之为软碱。
硬酸和硬碱以库仑力作为主要的作用力；软酸和软碱以共价键力作为主要的相互作用力。
此理论的中心主旨是，在所有其他因素相同时，“软”的酸与“软”的碱反应较快速，形成较强键结；而“硬”的酸与“硬”的碱反应较快速，形成较强键结。
大体上来说，“硬亲硬，软亲软”生成的化合物较稳定。
拉尔夫·佩尔森在六十年代首次提出了该理论。
自那以后，化学家们不断开拓该理论的应用范围，使之如今已成为了最重要的无机化学基础理论之一。
软硬酸碱酸碱硬软硬软氢离子H+汞CH3Hg+，Hg2+，Hg22+氢氧根OH−氢化物H−碱金属Li+，Na+，K+铂Pt4+醇盐RO−硫醇盐RS−钛Ti4+钯Pd2+卤素F−，Cl−卤素I−铬Cr3+，Cr6+银Ag+氨NH3膦PR3三氟化硼BF3硼烷BH3羧酸盐CH3COO−硫氰酸盐SCN−碳正离子R3C+四氯苯醌C6Cl4O2碳酸盐CO32−一氧化碳CO 重金属M0肼N2H4苯C6H6金Au+极端的情况下，还定义：交界酸（trimethylborane），二氧化硫和Fe（II），Co（II）， Cs（I）， Pb（II ）。
第七章 硬软酸碱原理
（四） 电子理论-路易斯（Lewis）
1923年，Lewis提出了更为广义的酸碱电子论：凡是能接受电子对的任何分
子、离子或原子团统称为酸，又称为电子对受体；凡是含有可给出电子对的分子、
离子或原子团统称为碱，又称为电子对给体。Lewis酸碱反应，实质上是形成配位 键，产生加合物。
Me H
BMe3 + NH3
Me B N H
Me H
BF3 + OEt2
F FB
F
Et O
Et
常见的Lewis酸有 SO3、 BF3、 AlCl3、 SnCl4、 FeCl3、 ZnCl2、 H+、 Ag+、 Ca2+、 Cu2+等等。
常见的Lewis碱有C5H5N、(C2H5)2O、NH3、(CH3)3N、C6H5NH2、OH－、 CO32－、HCO3－、SH－、CH3CO2－等。
缺点：（1） 把酸的性质局限于水溶液中，从而对当时已知的化学事实产生了一系列的问 题，如纯净的氯化氢气体是不是酸？熔融的碱是不是碱？
（2） 从理论和实践上看，质子（即氢正离子）在水溶液中难以独立存在，需与水 分子发生相互作用，生成水化离子。
（二）溶剂理论-富兰克林（ Franklin ）
1905年，英国化学家富兰克林提出了著名的酸碱溶剂理论。
这两种理论在有机化学中一直是兼容的，而且往往用于不同的场合。
重要性及优点：能说明不含质子的物质的酸碱性,如金属阳离子、缺电子化合 物、极性双键分子(典型的羰基分子)、价层可扩展原子化合物(某些P区元素的配 合物)、具有孤对电子的中性分子、含有C=C键分子(典型的蔡斯盐)；应用最为广 泛。
HSAB(Hard and Soft Acids and bases)软硬酸碱理论在分析化学中的应用
Ag(NH3)2+ Br- lgKsp= -12.3 AgBr
S2O32- lg
Ag(S2O3)23I- lgKsp= -16.03
AgI
CN- lg
Ag(CN)2S2- lgKsp= -48.70
Ag2S
2.4、解释有机试剂的选择性
碱的硬度：S’S<S’N<S’O~N’N<N’O<O’O 8-羟基喹啉(S’O)：Ag+, Hg2+, Cu2+（交
BiBr63Cu（NH3）42+ PdBr42-配位体（SCN-、 CNO-、CN-）配位原子选择的解释：
O、N——硬碱 [Fe-（NCS）6]3-
[Ta-（NCS）6]-
C、S——软碱 [Hg-（SCN）4]2-
[Cd-（SCN）4]2-
异双核配合物：Hg-（SCN）4-Co
HSAB(Hard and Soft Acids and
bases) 软硬酸碱理论
在分析化学中的应用
----陈德俊
一、理论原理
HSAB由1963年美国化学家Pearson根据 Lewis酸碱理论和实验观察而提出
应用于无机化学、有机化学、催化反应、 化学键理论等方面
Lewis 酸碱
硬酸碱 ：正电荷高、极化性低、 体积小、难氧化、不易变形
等的应用具有指导作用
Thank you!
界酸），Mg2+(硬酸),Al3+（硬酸） 8-巯基喹啉（S’N）：Ag+, Hg2+, Cu2+
（交界酸）
越软，选择性越好
2.5、掩蔽剂和解蔽剂的选择
Zn2+ Cd2+
CN掩蔽
硬软酸碱理论(HSAB理论)
硬软酸碱理论（HSAB理论）对于质子酸碱，我们可用pK来描述酸碱的强度，用pH或HO来表示溶液的酸度。
但是对于不涉及质子转移的路易斯酸碱，我们只能通过比较它们形成的配合物的热力学稳定性来估计它们的强度。
根据路易斯酸碱电子论的定义，认为在反应中能给出电子对的物质是碱，能接受电子对的物质是酸。
在配合物中，中心离子是电子对的接受体，是路易斯酸；配位体是电子对给予体，是路易斯碱。
1963年皮尔逊（Peauson）提出了软硬酸碱（Soft and Hard acids and bases，简称SHAB）概念，即根据酸、碱对外层电子控制的程度，应用了“软”和“硬”两字进行分类，把接受孤对电子能力强、对外层电子吸引得紧、没有易极化的电子轨道、电荷半径比较大的金属离子叫“硬酸”；把接受电子能力弱、对外层电子抓得松、易极化、电荷半径比较小的叫“软酸”，介乎二者之间的金属离子叫“交界酸”。
按同样道理也把配体分为软、硬和交界三类。
给出电子对的原子电负性大、对外层电子吸引力强、不易失去电子、变形性小的叫做“硬碱”；给出电子对的原子电负性小、对外层电子吸引力弱、易给出电子、变形性大的叫做“软碱”；介乎二者之间的为“交界碱”。
硬酸和硬碱之所以称为“硬”是形象化地表明它们的不易变形；软酸和软碱之所以称为“软”是表明它们较易变形.由于路易斯酸碱多种多样，分类比较粗糙，反应也较复杂，还没有大家公认的定量理论，目前只有一个软硬酸碱规则，其内容是：硬酸倾向于与硬碱相结合，而软酸倾向于与软碱结合。
用通俗的话来说，是“硬亲硬，软亲软，软硬交界就不管”。
所谓软硬交界就不管的意思是指中间酸（交界酸）与软、硬碱也能结合，中间碱与软、硬酸也能结合，但稳定性较前者差。
显然这一规则既不定量，而且有不少例外，但它仍是一个很有用的简单规则，能用它说明大量的事实，并能作一定的预测。
例如能对化合物相对稳定性给予较好的解释，如HF 和HCl很稳定，但HI不稳定。
Hard and Soft Acids and Bases (HSAB) Theory
302 Basic ConceptsIn the chapters below the chemistry, upon which the collected works in this thesis are built, is explained. The theories and definitions described herein are vital for coordination chemistry, but should not be taken as full descriptions of their respective areas as this falls outside the scope of this thesis.2.1 Hard and Soft Acids and Bases (HSAB) TheoryEven before Werner formulated his ideas for coordination chemistry, chemists had noticed that certain elements paired up more easily with some elements than others. In the early days, this observation was sometimes mixed up with other properties of the compounds involved, but the need to systematize chemistry has been an integral part of chemistry since Mendeleyev used some of the noted similarities in solving his puzzle for the first proper periodic table of elements.[7] Systematization attempts in coordination chemistry started in 1958 when a first proposal was put forth to classify various metal complexes by their complex formation stabilities. It was based on the complexes with halide ions (fluoride, chloride, bromide, and iodide), where class a and class b metal ions formed two separate groups: F- >> Cl- > Br- > I- (class a) and F- << Cl-, Br- < I- (class b).[65]An extended view of this way of looking at donor and acceptor atoms was introduced a few years later by Pearson, a model called hard and soft acids and bases or HSAB theory,[66] making use of Lewis’ definition of an acid (electronpair acceptors; metal ions and the proton) and a base (electron-pair donors; ligands). The hard acids and bases (non-polarizable, or class a in the previous terms) are those metal ions and ligands with weak electron-pair acceptor and donor properties forming bonds with mainly electrostatic interactions. The soft ones (class b) are those classified as strong electron-pair acceptors and donors establishing dominating covalent interactions between each another. There are a number of borderline cases, which means that the classification has been used as a guideline rather than law, but the general rule is that hard acids prefer hard bases and vice versa, useful information for many organic reactions.[67]Hard metal ions have multiple charges and are small, with a high charge density and thus high electrostatic interactions as a consequence. The scandium(III) and aluminium(III) ions serve as good examples for hard Lewis acids, which coordinate best to correspondingly small, electronegative ligands (Lewis bases) coordinating through fluorine or oxygen donor atoms. On the other side of the spectrum, we find that soft metal ions have low charge densities (often singly charged and large ionic radius), among them the noble metal ions gold(I), silver(I) and platinum(II), where the presence of the many d-electrons make them easier to polarize. The soft donor atom ligands (including phosphorous and sulfur), have low electronegativity. Table 7 lists the hard/borderline/soft designation for the metal ions and solvent ligands included in this thesis.31Table 7. The hard and soft acids and bases (HSAB) theory. The Lewis acids and bases presented in this thesis are included with a few examples as listed by Pearson (R = carbon chain of undetermined length).Hard Lewis acids Borderline Lewis acids Soft Lewis acidsH+, Na+, K+ Cu+, Ag+, Au+Be2+, Mg2+, Sr2+ Fe2+, Ni2+, Zn2+ Cd2+, Pd2+, Pt2+Sc3+, Fe3+, Ln3+ Tl3+Hard Lewis bases Borderline Lewis bases Soft Lewis basesH2O, NH3, R2O RSH, R2SCl-, NO3-, Br- I-, CN-2.1.1 Classification of solventsIn addition to the HSAB theory, a number of scales have been constructed for classification of the electron-donor capabilities of solvents. Gutmann’s donor number, D N, was the first one and is perhaps the best known of these scales.[68] It is based on calorimetric measurements and derives its values from the heat of reaction of antimon pentachloride and the ligand under study in benzene solution,SbCl5 + L →SbCl5L. A more relevant scale when dealing with strong electron-pair donors was developed by Sandstöm et al.[69], D S, which takes soft-ligand properties into consideration. The designated D S value for each solvent is obtained by studying the difference of the symmetric stretching vibration ofmercury(II)bromide, ν1(Hg-Br), in gaseous phase and the solvent under study,D S = ν(HgBr2) (g) - ν(HgBr2) (solv.). The D N and D S scales are oftentimes comparable, but there are some examples where they do differ significantly.[70] 2.1.2 Oxygen donor solventsLigands including an electron-pair donating oxygen atom are almost all hard, and among them we find some of the most common solvents in chemistry, e.g. water, alcohols, ethers, ketones, carboxylic acids, amides and sulfoxides. The physical chemical information available for these solvents, particularly water, is much too broad to be included in this thesis. Therefore, the main focus is an attempt to explain the difference between three main groups: water, other non-spacedemanding oxygen electron-pair donor solvents in general (DMSO in particular)and space-demanding oxygen donor solvents (with a focus on DMPU). A brief look at non-oxygen solvents (including DMTF) is included in the end.2.1.2.1 WaterThe most striking property of water is its hydrogen bonding ability. In solid state, water transforms to ice with an intricate system of hydrogen bonds, separating the water molecules at a slightly longer distance than in liquid water. This in turn makes ice less dense, resulting in the chemical abnormity of a solid that floats in its own liquid. Hydrogen bonds are also the reason why water is a liquid at room temperature. This tremendously important physical property is not seen in the related group 16 compounds H2S, H2Se, or H2Te.Table 7. The hard and soft acids and bases (HSAB) theory. The Lewis acids and bases presented in this thesis are included with a few examples as listed by Pearson (R = carbon chain of undetermined length).Hard Lewis acids Borderline Lewis acids Soft Lewis acidsH+, Na+, K+ Cu+, Ag+, Au+Be2+, Mg2+, Sr2+ Fe2+, Ni2+, Zn2+ Cd2+, Pd2+, Pt2+Sc3+, Fe3+, Ln3+ Tl3+Hard Lewis bases Borderline Lewis bases Soft Lewis basesH2O, NH3, R2O RSH, R2SCl-, NO3-, Br- I-, CN-。
高中化学竞赛课程 无机化学第八章 酸碱平衡
解: (1)
(2) 求0.1 mol dm-3 NaOH 溶液的pH = ? [OH-] = Kw = 10-14/0.1 = 10-13 mol dm-3
[H+]
pOH = -lg10-13 = 13
(2)
[H+] = Kw = 10-14/0.1 = 10-13
[OH-]
pH = 13
三、 弱酸弱碱电离平衡
1. 一元弱酸弱碱的电离平衡
一元弱酸：如
HAc + H2O
简写为：
HAc
H3O+ + AcH+ + Ac-
T 一定时： Ka0 =
[H+] / c o [Ac-] / c o [HAc] / c o
简写为：
[H+] [Ac-]
Ka =
[HAc]
Ka 越大，酸性越强。或pKa (-lgKa)越小，酸性越强。
H3O+ + OH-
298 K时测得：[H+] = [OH-] = 10-7
平衡常数Kw [H O][OH ] 1.0 10-14 3 水的离子积（Ionization product of water)
理论上求水的离子积：
H2O (l) + H2O(l)
H3O+ (aq) + OH-(aq)
HPO42- + OH-
Kb1=
[HPO42- ][OH-] [PO43- ]
=
Kw Ka3
H2PO4 - + OH-
Kb2 =
[ H2PO4-][OH-] [HPO42-]
=
Kw Ka2
H3PO4 + OH-
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HSAB原则对掩蔽、解蔽剂的选择具有一定 的指导作用
其他领域的应用
HSAB原则还对
分离性质相似的离子/富集痕量离子
选择共沉淀载体
溶液萃取中对萃取剂的选择
等的应用具有指导作用
Thank you!
2.2、判断溶解度
AlF3<AlCl3<AlBr3<AlI3 AgF>AgCl>AgBr>AgI
而
碱的硬度：F->Cl->Br->I酸的硬度：Ba2+>Fe2+>Hg2+ BaS>FeS>HgS
Ag+
2.3 、定性分析中的应用
Cl-
lgKsp= -9.75
AgCl NH3 lg Ag(NH3) 2+ Br- lgKsp= -12.3 AgBr S2O32lg
越软，选择性越好
2.5、掩蔽剂和解蔽剂的选择
Zn2+ Cd2+ CN掩蔽 Zn(CN)42+ Cd(CN)42+ HCHO 解蔽 Zn2+ Cd2+
Ag+（软） Ni(CN)42+ 解蔽
Ni2+
软亲软
OO（硬）：EDTA，酒石酸，柠檬酸 掩蔽：Ca2+, Ba2+,Fe3+, Al3+
SS，SN，SO（软）：二巯基丙醇，巯基 乙酸 掩蔽：Hg2+，Ag+
更更 软软 的的 碱酸 结倾 合向 与
Ag(S2O 3)23IlgKsp= -16.03 AgI CNlg
Ag(CN) 2S2lgKsp= -48.70
Ag2S
2.4、解释有机试剂的选择性
碱的硬度：S’S<S’N<S’O~N’N<N’O<O’O 8-羟基喹啉(S’O)：Ag+, Hg2+, Cu2+（交 界酸），Mg2+(硬酸),Al3+（硬酸） 8-巯基喹啉（S’N）：Ag+, Hg2+, Cu2+ （交界酸）
BiBr63Cu（NH3）42+ PdBr42-
生成物较稳定
反应速度适中
对配合物中异性双基配位体（SCN-、 CNO-、CN-）配位原子选择的解释：
O、N——硬碱 [Fe-（NCS）6]3
[Ta-（NCS）6]-
C、S——软碱 [Hg-（SCN）4]2
[Cd-（SCN）4]2-
异双核配合物：Hg-（SCN）4-Co
Al3+(硬酸）+6F-（硬碱）
Hg2+(软碱）+4SCN-（软酸）
AlF63Hg(SCN)42-
生成稳定配合ห้องสมุดไป่ตู้ 反应速度快
Al3+(硬酸）+S2O32-（软碱）
不能形成
生成物不稳定或不能 形成，反应速度慢
Bi3+（交界酸）+6Br-（交界碱） Cu2+（交界酸）+4NH3（硬碱） Pd2+（软酸）+4Br-（交界碱）
Lewis 酸碱
HASB原则：
硬亲硬，软亲软，交界酸 碱两边管
生成物稳定性高 反应过程速度快
二、在分析化学中的应用
2.1、配合物的形成规律 2.2、判断溶解度 2.3、定性分析中的应用 2.4、解释有机试剂的选择性 2.5、掩蔽剂和解蔽剂的选择 其他应用
2.1、配合物的形成规律
HSAB(Hard and Soft Acids and
bases) 软硬酸碱理论
在分析化学中的应用
----陈德俊
一、理论原理
HSAB由1963年美国化学家Pearson根据 Lewis酸碱理论和实验观察而提出 应用于无机化学、有机化学、催化反应、 化学键理论等方面 硬酸碱 ：正电荷高、极化性低、 体积小、难氧化、不易变形 交界酸碱：界于软硬之间 软酸碱：与硬酸碱相反