配合物、配体及颜色变化
引入
词汇
| English | 释义 | 拼音 |
|---|---|---|
| ligand/ˈlɪɡænd/ | 配体 | pèi tǐ |
| coordination number/kəʊˈɔːdɪneɪʃn ˈnʌmbə/ | 配位数 | pèi wèi shù |
| octahedral/ˌɒktəˈhiːdrəl/ | 八面体的 | bā miàn tǐ de |
| Absorption/əbˈsɔːpʃn/ | 吸收 | xī shōu |
English
Count what actually bonds
- A ligand 配体 donates an electron pair to a metal ion. Coordination number 配位数 counts donor atoms directly attached to that metal.
- Three bidentate en ligands have six donor atoms. A six-coordinate complex often has octahedral 八面体的 geometry.
练习
三个双齿配体不一定给出配位数为三。
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每个配体提供两个供体原子，总计六个。
English
Keep atom and ion configurations separate
- Chromium is [Ar]3d⁵4s¹ and copper is [Ar]3d¹⁰4s¹. Remove 4s electrons before 3d to form positive ions.
- Cu²⁺ is d⁹ and meets the transition-element criterion. Zn²⁺ is d¹⁰; zinc does not meet that definition.
练习
哪种离子具有未充满的d亚层？
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铜(II)为d⁹，满足未充满d层的条件。
English
Solve charge before interpreting colour
- In [Cr(H₂O)₄Cl₂]⁺, neutral waters contribute zero and two chlorides contribute −2. Chromium is +3.
- Four water donors plus two chloride donors give coordination number six. Neither colour nor ligand count alone determines every structural detail.
Example
For [Co(en)₃]³⁺, three neutral en ligands leave cobalt at +3 and give six donor atoms.
练习
求[Cr(H₂O)₄Cl₂]⁺中铬的氧化态。
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x − 2 = +1，因此 x = +3。
English
Explain colour using energy levels
- Ligands split d-orbital energy levels. Absorption 吸收 of suitable visible light promotes an electron between levels.
- Changing ligand, oxidation state or coordination number can change the gap. A d⁰ or d¹⁰ ion has no suitable d–d transition.
练习
哪两种改变可以影响d轨道分裂？
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配体环境和氧化态会影响d轨道能级差。
English
Separate ammonia’s two roles
- A small amount of ammonia precipitates copper hydroxide by accepting protons from coordinated water.
- Excess ammonia replaces water ligands and dissolves the precipitate to give a deep blue solution. The copper remains +2.
Watch out
Four-coordinate complexes may be tetrahedral or square planar; the same count can have different geometry.
Key idea
Count donor pairs and coordination sites, track the metal oxidation state, and distinguish precipitation from ligand replacement before interpreting a colour change.
练习
过量氨水使铜(II)形成深_____溶液。
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溶解后的氨合配合物呈深蓝色，不同于初始的浅蓝色沉淀。