Coordination Chemistry | 配位化学考点精讲

📚 Coordination Chemistry | 配位化学考点精讲

Coordination chemistry is a fascinating branch of chemistry that explores how transition metals form complex compounds with surrounding molecules or ions called ligands. In the GCSE WJEC Chemistry syllabus, understanding the basics of coordination chemistry helps explain many properties of transition metals, such as their vibrant colours, variable oxidation states, and catalytic behaviour.

配位化学是化学中一个迷人的分支，研究过渡金属如何与周围被称为配体的分子或离子形成复杂的化合物。在 GCSE WJEC 化学大纲中，掌握配位化学的基础知识有助于解释过渡金属的许多性质，比如它们鲜艳的颜色、可变的氧化态以及催化行为。

1. Transition Metals – The Foundation | 过渡金属——配位化学的基础

Transition metals are elements found in the d-block of the periodic table, such as iron, copper, and chromium. They have partially filled d orbitals, which allow them to form a large number of stable complex ions by accepting lone pairs of electrons from ligands.

过渡金属是位于元素周期表 d 区的元素，例如铁、铜和铬。它们具有部分填充的 d 轨道，这使得它们能够通过接受配体的孤对电子形成大量稳定的配离子。

Unlike s-block metals that usually form simple ionic compounds, transition metals can bind to several ligands simultaneously, creating coordination compounds with characteristic shapes and properties.

与通常形成简单离子化合物的 s 区金属不同，过渡金属可以同时与多个配体结合，生成具有特征形状和性质的配位化合物。

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2. The Coordinate Bond | 配位键

A coordinate bond (also called a dative covalent bond) is a covalent bond in which both electrons come from the same atom. In a complex, the ligand donates a lone pair to an empty orbital on the central metal ion, forming the bond.

配位键（又称配位共价键）是一种共价键，其中两个电子都来自同一个原子。在配合物中，配体提供一个孤对电子给中心金属离子的空轨道，从而形成化学键。

For example, in the hexaaquacopper(II) ion [Cu(H₂O)₆]²⁺, each water molecule donates a lone pair from its oxygen atom to the Cu²⁺ ion. This type of bonding is the essence of coordination chemistry.

例如，在六水合铜(II)离子 [Cu(H₂O)₆]²⁺ 中，每个水分子都从氧原子提供一对孤对电子给 Cu²⁺ 离子。这种成键方式是配位化学的核心。

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3. Ligands and Their Types | 配体及其类型

A ligand is any molecule or ion that can donate at least one lone pair of electrons to a central metal atom or ion. Ligands are classified by the number of donor atoms they possess.

配体是能够提供至少一对孤对电子给中心金属原子或离子的任何分子或离子。配体根据它们拥有的供体原子数目进行分类。

• Monodentate ligands – donate one lone pair. Examples: H₂O:, :NH₃, :Cl⁻, :CN⁻.

  单齿配体 – 提供一对孤对电子。实例：H₂O:、:NH₃、:Cl⁻、:CN⁻。

• Bidentate ligands – donate two lone pairs from two different atoms. Example: ethane-1,2-diamine (en), C₂O₄²⁻ (oxalate).

  双齿配体 – 从两个不同的原子提供两对孤对电子。实例：乙二胺(en)、草酸根离子 C₂O₄²⁻。

• Polydentate ligands – can donate more than two lone pairs, such as EDTA⁴⁻, which can form six bonds.

  多齿配体 – 能提供两对以上的孤对电子，例如 EDTA⁴⁻ 可以形成六个键。

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4. Coordination Number and Shape | 配位数与形状

The coordination number is the number of coordinate bonds formed between the central metal ion and ligands. It largely determines the shape of the complex.

配位数是指中心金属离子与配体之间形成的配位键的数目。它在很大程度上决定了配合物的形状。

Coordination Number | 配位数	Common Shapes | 常见形状	Bond Angles | 键角
2	Linear | 直线形	180°
4	Tetrahedral or square planar | 四面体形或平面四边形	109.5° / 90°
6	Octahedral | 八面体形	90°

For GCSE, the most common coordination number is 6, giving an octahedral shape, as seen in [Cu(H₂O)₆]²⁺. Four-coordinate complexes can be tetrahedral, like [CuCl₄]²⁻, or square planar, like cisplatin.

在 GCSE 阶段，最常见的配位数是 6，得到八面体形状，如 [Cu(H₂O)₆]²⁺ 所示。四配位配合物可以是四面体形，如 [CuCl₄]²⁻，或是平面四边形，如顺铂。

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5. Naming Coordination Compounds | 命名配位化合物

The rules for naming complexes are systematic. The number of ligands is indicated by prefixes (di-, tri-, tetra-, penta-, hexa-), ligands are named first in alphabetical order, then the metal, with its oxidation state in Roman numerals in brackets.

配合物的命名规则是系统性的。配体的数目用前缀表示（二、三、四、五、六），配体按字母顺序命名，然后写出金属名称，并在括号内用罗马数字标出其氧化态。

Example: [Cu(H₂O)₆]²⁺ is hexaaquacopper(II) ion. [CoCl₂(NH₃)₄]⁺ is tetraamminedichlorocobalt(III) ion. Remember that anionic ligands end in -o (e.g., chloro for Cl⁻, cyano for CN⁻).

示例：[Cu(H₂O)₆]²⁺ 是六水合铜(II)离子。[CoCl₂(NH₃)₄]⁺ 是四氨二氯合钴(III)离子。记住阴离子配体的名称以 -o 结尾（例如氯为 chloro，氰为 cyano）。

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6. Isomerism in Complexes | 配合物中的异构现象

Coordination compounds can show isomerism, where the same formula represents different spatial arrangements. Two important types for GCSE are geometric (cis-trans) isomerism and optical isomerism.

配位化合物可以表现出异构现象，即同一分子式对应不同的空间排列。GCSE 中两种重要的类型是几何异构（顺反异构）和旋光异构。

Cis-trans isomerism occurs in square planar and octahedral complexes with two different types of ligands. For example, cisplatin [PtCl₂(NH₃)₂] is the cis isomer, which is an effective anticancer drug, while the trans isomer is inactive.

顺反异构出现在含有两种不同配体的平面四边形和八面体配合物中。例如，顺铂 [PtCl₂(NH₃)₂] 是顺式异构体，是一种有效的抗癌药物，而反式异构体则无活性。

Optical isomers are non-superimposable mirror images, often resulting from bidentate ligands creating a chiral complex. These isomers can rotate plane-polarised light in opposite directions.

旋光异构体是不可重叠的镜像，通常由双齿配体产生手性配合物而形成。这些异构体能够使平面偏振光向相反方向旋转。

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7. Colour in Transition Metal Complexes | 过渡金属配合物的颜色

One of the most striking features of transition metal complexes is their colour. This arises from the splitting of d orbitals in the ligand field, allowing electrons to absorb visible light as they jump between energy levels.

过渡金属配合物最显著的特征之一就是它们的颜色。这源于配体场中 d 轨道的分裂，使得电子在能级之间跃迁时能够吸收可见光。

Different ligands cause different amounts of splitting (spectrochemical series), thus changing the colour. For example, [Cu(H₂O)₆]²⁺ is blue, while adding ammonia gives the deep blue [Cu(NH₃)₄(H₂O)₂]²⁺. Anhydrous copper(II) chloride is yellow-brown, but its hydrated form is green-blue.

不同的配体引起不同程度的分裂（光谱化学序列），从而改变颜色。例如，[Cu(H₂O)₆]²⁺ 为蓝色，加入氨水后生成深蓝色的 [Cu(NH₃)₄(H₂O)₂]²⁺。无水氯化铜(II)是黄棕色的，而其水合形式是绿蓝色的。

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8. Applications of Coordination Compounds | 配位化合物的应用

Coordination chemistry is not just theory; it has real-world applications. Cisplatin is a chemotherapy drug. EDTA is used to treat lead poisoning by chelating the toxic metal. Haemoglobin contains an iron(II) complex that transports oxygen in blood. Chlorophyll is a magnesium complex essential for photosynthesis.

配位化学不仅仅是理论，它有着实际的应用。顺铂是一种化疗药物。EDTA 通过螯合有毒金属来治疗铅中毒。血红蛋白含有一种铁(II)配合物，在血液中运输氧气。叶绿素是光合作用必需的一种镁配合物。

In industry, transition metal complexes act as catalysts, for example in the Haber process and the Contact process. They are also used in electroplating and as dyes and pigments.

在工业上，过渡金属配合物用作催化剂，例如在哈伯法和接触法中。它们还用于电镀以及作为染料和颜料。

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9. Common Exam Questions and Pitfalls | 常见考题与易错点

WJEC GCSE questions often demand definitions of key terms like ligand, coordination number, and coordinate bond. Students are frequently asked to draw the shape of a complex given its formula, or to name a complex following IUPAC rules.

WJEC GCSE 试题经常要求对关键术语进行定义，如配体、配位数和配位键。学生经常被要求根据给定的化学式画出配合物的形状，或按照 IUPAC 规则命名配合物。

Watch out for common mistakes: confusing oxidation state with charge on the complex ion; omitting brackets around the metal oxidation state; forgetting that water as a ligand is named ‘aqua’ not ‘hydroxo’; misidentifying the number of donor atoms in a bidentate ligand.

注意常见错误：混淆氧化态与配离子的电荷；忘记在金属氧化态上加上括号；忘记作为配体的水命名为 ‘aqua’ 而不是 ‘hydroxo’；错误判断双齿配体中供体原子的数量。

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10. Revision Checklist | 复习清单

• Can I define a coordinate bond and a complex ion?

  我能否定义配位键和配离子？

• Can I give examples of monodentate and bidentate ligands?

  我能否举出单齿配体和双齿配体的例子？

• Do I know the shapes associated with coordination numbers 2, 4, and 6?

  我是否知道与配位数 2、4 和 6 相关的形状？

• Can I name a complex given its formula, and vice versa?

  我能根据化学式命名配合物，反之亦然吗？

• Can I explain why transition metal complexes are coloured?

  我能解释为什么过渡金属配合物有颜色吗？

• Can I describe the use of cisplatin and its stereoisomerism?

  我能描述顺铂的用途及其立体异构现象吗？

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Published by TutorHao | Chemistry Revision Series | aleveler.com

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