北京化工大学：《无机化学》课程电子教案（课件讲稿，2015）Chapter 13 The elements of boron family

Chapter 13 The elements of boron family 13.1 Outline on boron family 13.2 The elemental substances of boron family 13.3 The compounds of boron -*13.4 The compounds of aluminum

Chapter 13 The elements of boron family *13.4 The compounds of aluminum 13.3 The compounds of boron 13.2 The elemental substances of boron family 13.1 Outline on boron family

13.1 Outline on boron family Boron family (IA):B,Al,Ga,In,TI Valence electron configuration:ns2npl Electron deficient elements:number of valence electrons number of valence orbits Electron deficient compounds:number of electron pairs in bonding molecular orbits number of valence orbits(即：还有空的成键轨道) Example:BF3(sp3),H3BO3.B:2S22pl HBF is not electron deficient compound

13.1 Outline on boron family Boron family (ⅢA)：B，Al，Ga，In，Tl Valence electron configuration：ns 2np 1 Electron deficient elements: number of valence electrons < number of valence orbits Electron deficient compounds: number of electron pairs in bonding molecular orbits < number of valence orbits(即：还有空的成键轨道). Example：BF3 (sp3 ), H3BO3。 B: 2S22p1 HBF4 is not electron deficient compound

21p 2P 2s1 excited 2s↑↑)( $p2 B:2s22p1 sp-hybridization The formation of BF

of BF3 The formation 2s 2p 2p 2s sp 2 sp2 hybridization B ： 2s 22p 1 excited

The features of electron deficient compounds Example a.forming coordination compound HBF4 HF→BF3 Example b.forming Al2Cl6 molecules in gas phase Al:ns2npl C (sp3杂化) Cl:2s22p5

Cl Cl Al Cl Cl Cl Cl Al The features of electron deficient compounds Example b. forming Al2Cl6 molecules in gas phase HF BF3 Example a. forming coordination compound HBF4 Al：ns2np1 (sp3杂化) Cl：2s22p5

General properties of boron family elements Except for B which is a metalloid(非金属)，Al, Ga,In,Tl are all metals. Oxidation numbers:B,Al,Ga:(+3) In:(+1,+3) T:(+1) Maximum coordination numbers: B:4 example:HBF4(sp3杂化) others:6 example:Na3AlF6(sp3d2杂化)

General properties of boron family elements • Except for B which is a metalloid(非金属), Al， Ga，In，Tl are all metals. • Oxidation numbers：B，Al，Ga：(+3) In：(+1，+3) Tl：(+1) • Maximum coordination numbers： B：4 example：HBF4 (sp3杂化) others：6 example：Na3AlF6 (sp3d 2杂化)

13.2 The elemental substances of boron family 硼B metalloid 铝Al meta 镓Ga metal 铟In metal

13.2 The elemental substances of boron family metalloid metal metal metal

The elemental substances of boron (denote B) Allotropes(同素异形体)：amorphous B-→brown powder (a few types)crystalline B->black-gray Properties:high chemical activity,high hardness high m.p and b.p a一菱形硼(B12)(one of the crystalline type of B): Atomic crystal 12 vertices,20 faces

The elemental substances of boron (denote B) Allotropes(同素异形体)：amorphous B  brown powder (a few types) crystalline B  black-gray Properties: high chemical activity, high hardness high m.p and b.p α -菱形硼 (B12) (one of the crystalline type of B): Atomic crystal 12 vertices, 20 faces

13.3 The compounds of boron 1.Boron hydrides(borane) General formula of boranes:B Hn+4 and BHn+6 Example:B2H6 B4H10。。。。。o diborane borobutane H H No existence of BH B:2s22p1 H-BB-H The simplest borane:B2H HH The structure of B,H cannot be depicted as the right figure:

13.3 The compounds of boron 1. Boron hydrides (borane) General formula of boranes: BnHn+4 and BnHn+6 Example： B2H6 B4H10。。。。。。 diborane borobutane 。。。。 No existence of BH3 The simplest borane：B2H6 The structure of B2H6 cannot be depicted as the right figure： H H B B H H H H B:2s22p1

The structure of boranes B:one sp3 orbital from each boron overlaps a hydrogen's 1s orbital to give a three center bond to which two electrons are assigned(三中心两电子键).(B-H-B bridge) H H H Sp3 p denote: B B H SD 1s 要点：B的杂化方式， 三中心两电子键、氢桥

• The structure of boranes B: one sp3 orbital from each boron overlaps a hydrogen’s 1s orbital to give a three center bond to which two electrons are assigned (三中心两电子键). (B-H-B bridge) denote： H H B B H H H H 要点：B的杂化方式， 三中心两电子键、氢桥

The structure of BHio molecule B:sp3 hybridization Note:a B-B bond 119pm H 143pm 13 H H 110pm B (a)） (b)

The structure of B4H10 molecule 119pm 110pm 137pm 143pm 122。 171pm H B ( b ) B B B B H H H H H H H H H H H ( a ) B: sp3 hybridization Note: a B-B bond