周四金属有机office

1、Name: 梁福顺, 教授 博士生导师Ph D: 中国科学院长春应用化学研究所Postdoc: 日本早稻田大学Visiting fellow: 加拿大国家研究院化学加工与环境技术研究所Phone： E-mail： Self-IntroductionMajor: 有机化学；高分子化学Research interests: 有机合成方法；有机太阳能电池Organometallic Chemistry 金属有机化学ReferencesThe Organometallic Chemistry of the Transition Metals, Robert H. Crabtree, John Wile

2、y & Sons: New York, 3rd Edition, 2001.课程要求：不缺课： 15%记笔记： 5%作业： 10%考试： 70%Course OutlineGeneral properties of organometallic complexes Complexes with metal-carbon s bond: Metal alkyls, aryl, hydride and related s-bonded ligands3.Carbonyls, phosphine complexes and substitution reactions 4.Complexes of

3、p-ligands 5.Oxidative addition and reductive elimination Insertion and eliminationCarbene and carbyne complexesOutline1.What is organometallic chemistry ?2.Why organometallic chemistry?3. Review on coordination chemistry4.The 18-electron rule5.Limitations of 18-electron rule6.Oxidation numberEffect

4、of complexationChapter 1. General properties of organometallic complexes 1. What is organometallic chemistry? Chemistry: structures, bonding and properties of moleculesOrganometallic chemistry: chemistry of organometallic compoundsorganometallic compounds: containing direct metal-carbon bonds. e. g.

5、 Some compounds do not contain metal-carbon bond, but they are usually included in the field of organometallic chemistry. They include: Metal hydride complexes, e.g. plexes, e.g. Phosphine complexes, e.g. Organosilicon and organoboron compounds, e.g.In general, metals in organometallic compounds inc

6、lude: main group metals transition metals f-block metals. (e.g. Lanthanide; Actinide)In this course, transition metals are our main concern. Lanthanide 镧系元素; actinide 锕系金属有机化学是无机化学和有机化学相互交叉渗透的学科,它的发展打破了传统的有机化学与无机化学的界限,成为一门新兴的学科和当代化学的前沿领域.Organometallic chemistry combines aspects of inorganic chemist

7、ry and organic chemistry.交叉学科当今有机化学的热点之一无机化学材料科学催化科学有机化学2. Why organometallic chemistry ? a). From practical point of view: * Organometallic chemistry is related to many industrial processes e.g. fine chemicals chemicals * Organometallic chemistry is related to material science. e.g. Organometallic

8、Polymers* Organometallic chemistry may help us to understand some enzyme-catalyzed reactions. e.g. B12 catalyzed reactions. b). From academic point of view: * Organometallic compounds display many unexpected behaviors discover new chemistry New structures e.g.New reactions, reagents, catalysts, e.g.

9、Ziegler-Natta catalyst, Wilkinson catalystSharpless epoxidation. metathesis method in organic synthesisC-H bond activationolefin metathesis: 烯烃复分解History: first organometallic compoundfirst organometallic compound1827 Zeises salt is the first platinum - olefin complex 1890 Ludwig Mond discovers Ni(C

10、O)4 1893 Alfred Werner develops the modern ideas of coordination chemistry1899 introduction of Grignard reagents1912 Nobel prize Victor Grignard and Paul Sabatier1917 Schlenk prepares Li alkyls via transalkylation from R2Hg并发展了无水无氧操作技术Schlenk技术 1930 Ziegler and Gilman simplify organolithium preparat

11、ion, using ether cleavage and alkyl halide metallation, respectively.1951 1952 Discovery of ferrocene, Fe(h5-C5H5)2Keally, Pauson, and Miller report the synthesisWilkinson and Woodward report the correct structure1973 Nobel prize Geoffrey Wilkinson and Ernst Otto Fischer on sandwich compounds1955Zie

12、gler and Natta develop olefin polymerization at low pressure using mixed metal catalysts (transition metal halide / AlR3)1963 Nobel prize for Karl Ziegler and Giulio Natta on Ziegler-Natta catalysts1962: Vaskas complex1964: Fischer reports the first metal carbene.17沃什卡配合物 Vaskas complex can undergo

13、oxidative addition and is notable for its ability to bind to O2 reversibly. It is a bright yellow crystalline solid.1964: Banks reports the first example of olefin metathesis.烯烃复分解1965年 G. Wilkinson和 R. S. Goffey采用 (Ph3P)3RhCl 作为均相催化剂研究了烯烃的氢化反应。1973: Fischer synthesizes first metal carbyne complex.1

14、983 年 R. G. Bergman 和 W. A. Graham发现在过渡金属化合物存在下CH 键的活化。1981 年 Nobel奖授予R. Hoffmann和 K. Fukui以表彰它们在无机、有机、有机金属化合物分子结构及其反应活性分子轨道理论处理上的成就，即等瓣相似理论(isolobal analogies)。 Nobel -Prize Winners related to the area: Victor Grignard and Paul Sabatier (1912) the discovery of Grignard reagent K. Ziegler, G. Natta

15、(1963) Ziegler-Natta catalyst E. O. Fisher, G. Wilkinson (1973) the chemistry of Sandwich compounds W. S. Knowles, K. B. Sharpless, R. Noyori (2001) Asymmetric hydrogenation/oxygenation Yves Chauvin, Robert H. Grubbs, Richard R. Schrock (2005) olefin metathesis R. Heck, E. Negishi, A. Suzuki (2010)P

16、alladium catalyzed cross coupling reactions不对称催化氢化反应: 在手性催化剂作用下氢分子将含有碳碳、碳氮、碳氧双键的烯烃、亚胺和酮类等潜手性底物加成转化为手性中心含氢的产物。如：治疗神经系统帕金森病的药物左旋多巴，以及孟山都公司年销售额达10亿美元的高效消炎解热镇痛药(s)荼普生。不对称催化氧化反应双键不对称催化氧化在手性药物生产中具有重要地位它包括不对称环氧化和不对称双羟基化。1988年，Sharpless用手性配体金鸡纳碱与四氧化饿进行烯烃的不对称催化羟基化反应，现己成功用于抗癌药物紫杉醇边链的不对称合成。. W. S. Knowles, K.

17、B. Sharpless, R. Noyori (2001) Asymmetric hydrogenation/oxygenationYves Chauvin, Robert H. Grubbs, Richard R. Schrock (2005)烯烃复分解反应是有机化学中最重要也是最有用的反应之一，今天，烯烃复分解反应已被广泛应用在化学工业，尤其是制药业和塑料工业从中受益无穷。R. Heck, E. Negishi, A. Suzuki (2010)Palladium catalyzed cross coupling reactions有机化学如今已经发展成了一种艺术形式，化学家们在试管中制

18、造了非凡的化学“作品”。人类以医学、电子学及高级科技材料的形式获益。这一化学工具极大地促进了制造复杂化学物质的可能性，比如碳基分子，其复杂性可媲美天然分子。思考题：1. 什么是金属有机化学？2. 了解金属有机化学发展的历史。3. 知道在金属有机领域获得诺贝尔奖的事件。3. Review on coordination chemistry Complexes or coordination compounds are compounds composedof a metal and ligands which donate electrons to the metal, e.g.Ligands:

19、 a molecule or ion that has at least one electron pair thatcan be donated. Condensed-Phase, Halogen-Bonded CF3I and C2F5I Adducts for Perfluoroalkylation ReactionsDr. Filippo Sladojevich, Dr. Eric McNeill, Jonas Brgel, Dr. Shao-Liang Zheng and Prof. Dr. Tobias RitterArticle first published online: 4

20、 FEB 2015 | DOI: 10.1002/anie.201410954Its (no longer) a gas! A family of practical, liquid trifluoromethylation and pentafluoroethylation reagents enabled by halogen bonding is described. The synthetic utility of these reagents is exemplified by a novel direct arene trifluoromethylation reaction as

21、 well as adaptations of other perfluoroalkylation reactions.Classification of ligands Based on nature of the donating electron pairs, ligands may be classified as lone pair donor, p-bonding electron pair donors, s-bonding electron pair donors. 1) Lone pair donors Note: Ligands that donate electron p

22、airs to form M-L s bond are also called s donors. Some lone pair donor ligands may have orbitals to form M-L p bonds. = p acceptor. accept e- to form p bond (dp back bonding)e.g. CO is not only a s donor, but also a p acceptor.Head to headshoulder to shoulder Some lone pair donor ligands may have or

23、bitals to form M-L p bonds. = p donor. e.g. RO- is a s donor and also a p donorR-O- donates e- to form a p bond s donorp donorEvidences for dp-pp interactions.* Take M-CO complexes as an example for p accepterNi(CO)42066 cm-1首先，CO向金属原子的空轨道提供电子形成键。键的形成有助于提高co。其次，金属原子又反馈d电子给CO的空反键轨道形成键，这有助于降低co。当金属处于较

24、低的氧化态时，协同作用的净结果是电子从金属向CO迁移，因而会造成金属羰基配合物的co一般比游离的CO的低。* Take M-OR complexes as an example for p donor.Normally, O atom has sp3 hybridization, leading to the A-O-B angle being about 104.5. However, in the above two complexes the angles are 120 and 180, respectively. Why ? Types of lone pair donor liga

25、nds2). p-bonding electron pair donorsHow can these ligands interact with M ?Take CH2=CH2 as an example. CH2=CH2 acts as both a s donor and a p acceptor. 3). s-bonding electron pair donors Relatively fewer stable complexes are known. Typical examples:agostic bond: 抓氢键; agostic: 抓住仅靠其近旁 agostic bond:

26、抓氢键M: 过渡金属原子。它用空轨道接受从C-H s 键上的电子形成的三中心两电子键。作用：抓氢键C-H M消弱了C-H s键，在金属有机反应中，能使H原子转移到金属原子上，容易进行消除反应How can these ligands interact with M?Take H2 as an example. Further Notes:* Relative basicity of electron pairs: lone pairs p bonding electron pairs s bonding electron pairs* Therefore usual order of bind

27、ing ability: lone pair donor p bonding electron pair donor s bonding electron pair donor. Consequence:* Some ligands have several types of electron pairs. The types of e- pairs to be used to bind metal will depend on metals. e.g. In addition, based on the nature of bonding interaction, ligands may b

28、e classified as soft or hard.Hard ligands: have low polarizability, especially those containing period 2 donor atoms N, O, F, e.g. O2H, NH3, F-Soft ligands: have high polarizability, they include:. Those with period three or subsequent donor atoms, e.g. Cl, Br, S, P.b). -acceptors, e.g. CO, CS (carb

29、on sulfide), H2, CN- (cyanide)c). Those containing p-electrons, e.g.极化率(polarizability) Importance of the concepts of soft and hard ligands: * Hard ligands tend to form stable complexes with hard metal ions, (usually those at high oxidation state, e.g. Al3+, Fe3+, Cu2+, Ti4+, Pt(IV). Example: AlF63-

30、, Ti(OR)4 are very stable complexes, but Pt(0)-F, Pt(0)-OR, W(0)-F are very rare. * Soft ligands tend to form stable complexes with soft metal ions, (usually those at low oxidation state, e.g. Mn(I), Co(I), Fe(II), Pt(II), Pt(0) ) Example:(Olefins are soft base; Pt(II) is soft but Pt(IV) is hard) 4.

31、 The 18 electron rule 1) Thermodynamically stable transition metal organometallic compounds are formed when the sum of the metal d electrons plus the electrons supplied by the ligands equals 18.In this way, the metal formally attains the electronic configuration of the next noble gas.The 18 electron

32、 rule= 18 VE rule = inert gas rule = effective atomic number rule (EAN rule)e.g. Simple reasons:2) Ways to count valence electrons (VE)# VE = valence e- of M (or Mn+) + e- from ligandsTwo Models: covalent model and ionic modelCovalent model : Both M and L are considered as neutral# VE = valence e- o

33、f M + e- from ligands + chargee.g. Ionic model : Metal complexes are formed from Mn+ + L + X-# VE = valence e- of Mn+ + e- from ligands + charge5. Limitations of the 18 electron ruleMost OMC follow 18e rule. But there are many stable compounds thatdo not have 18 valence electrons. e.g. WMe6 (12e) Pt

34、(PCy3)2 (14e) Cu(NH3)62+ (21e) RhCl(PPh3)3 (16e)Some general observations:1). Many main group complexes do not follow 18e rule: e.g.ZnMe2 (14e), Cp2Be (12e), IF7 (24e), SbF6- (22e)2). F-block metals do not follow 18e rule. e.g. (because electrons can go to (n-2)f orbitals)Common exceptions to the 18

35、 electron rules: d8 metals: The d8 metals (groups 8 - 11) have a tendency to form square-planar 16 electron complexes. This tendency is weakest for group 8 (Fe(0), Ru(0), and Os(0) and is very strong for groups 10 and 11 (Pd(II), Rh(I), Pt(II), Au(III). (because one of the 9th orbital is very high-l

36、ying and is usually empty.)* Steric effect may prevent the formation of 18e complexes. e.g.The rule is particularly useful for Groups 6-8 The oxidation state of a metal in a complex is simply the charge that the metal would have on the ionic model.6. Oxidation number of metalse.g. What is the oxidat

37、ion number of metals in the following complexes?Problems with O. S. : a) Ambiguous oxidation statesConsider complexes W(CO)6 and WH6(PMe3)3. Which one would you expect to have a higher positive charge on W?W(CO)6 W(0): W CO backdonationWH6(PMe3)3 W(VI): actually more e-richThere is no strict correla

38、tion between charge density and formaloxidation states! Oxidation states in organometallic complexes are merely formalisms that may bear little resemblance to the actual positive charge on the metal. b) charge density and formal oxidation statesOxidation number can never be higher than group number

39、!= predict if a compound/intermediate is possible= Help to formulate the structure of a compound.Any uses of formal oxidation states?e.g. (1) Are the following species possible? WMe6 TiMe6 VH7(PMe3)2(2) WH6(PMe3)3 + HBF4 WH7(PMe3)3 BF4 Which one below is not the likely structure for WH7(PMe3)3+ ?Van

40、adium: 钒W(VIII) W(VI) W(IV)7. Effect of complexation M-L: Complexation of L on M may cause:* the change of electron density distribution on L* new reactivity of L: unreactive = reactiveExamples:Change the electron density on LComplexation reduces the e- density on olefin.Complexation reduces the e-

41、density on C6H6. Reactivity towards Nu-: increaseReactivity towards E+: decreaseChange the electron density distribution on L (e- lies on both atoms)(e- from only C atom)I. 给出下列络合物中金属的形式氧化态和d-电子数.a) (h6-C6H6)2Mo b) Cp2ZrCl(OMe)c) (CO)5ReEt d) Cp(PMe3)3WH2+II. 指出下列每个络合物的金属价电子层中的电子数,并确认你认为这些络合物中哪些是足够稳

42、定.a) (h6-C6H6)2Fe b) Ru(PPh3)2(CO)2 c) Cp2NbH(C2H4) d) HFe(CO)4-e) Re(CO)5 f) Pt(PBu3)3g) PtCl3(C2H4)- h) Cp(CO)2Fe(PhCCH)+练习_1III. Determine the valence electron count of the following complexes. IV. 下列每两个络合物中哪一个在红外光谱中具有较低能量的CO伸缩振动频率?请合理地说明你的选择.a) W(CO)5Cl- or Re(CO)5Clb) Fe(CO)5 or Fe(CO)4Br2c) Mo

43、(CO)6 or Mo(CO)4(PPh3)2Chapter 2Complexes with metal-carbon s bondsMetal alkyls, aryls, hydridesOutline1. The stability of transition metal-carbon s bonds2. Preparation of complexes with metal-carbon s bonds3. Chemical properties of complexes with metal-carbon s bonds4. Metal hydridesPrior to 1960s:

44、 Non-transition metal alkyls are well known, e.g.AlMe3ZnEt2Transition metal alkyls are rare. Only a few transition metal alkyls were prepared. e.g.Cubic 立方的Prior to 1960s，transition metal alkyls are rare.Are transition metal-carbon bonds weak and unstable?But today: Transition metal-carbon bonds are

45、 known for virtually all transition metals. Questions Are transition metal carbon s bonds really unstable? What affects M-C bond strength? What causes the earlier failure to obtain transition metal alkyls? 1). Thermal stability of transition metal-carbon bondsThe thermal stability can be related to

46、bond dissociation energy.M-X (g) M(g) + X(g) DH = BDE (M-X) If BDE (M-X) is large, M-X is thermally more stable.Range of M-C bond dissociation energy (BDE).(See next two pages)BDE (M-C) values in MRn complexes (KJ/mol)Non-transition metals Transition metals M-C bond BDE Compound M-C bond BDELi-Et209

47、Ti(CH2C(CH3)4Ti-CH2R 170Li-Bu248Ti(CH2Ph)4 Ti-CH2R 240Zn-Me176Ti(CH2Si(CH3)4 Ti-CH2R 250Zn-Et145Cp2Ti(CH3)2 Ti-CH3 250Cd-Me139Cp2TiPh2 Ti-Ph 350Hg-Me122(CO)5MnCH3 Mn-CH3 150Hg-Et101(CO)5ReCH3 Re-CH3 220Hg-i-Pr 89Zr(CH2C(CH3)4 Zr-CH2R 220Hg-Ph136Zr(CH2Ph)4 Zr-CH2R 380B-Me363Zr(CH2Si(CH3)4 Zr-CH2R 225

48、B-Et342CpPt(CH3)3Pt-CH3 165Al-Me276(Et3P)2PtPh2 Pt-Ph 250Al-Et242Ta(CH3)5 Ta-CH3 260Ga-Et237W(CH3)6 W-CH3 160Non-transition metals:BDE(M-C): 89-280 kJ/mol Except B-CTransition metals:BDE (M-alkyl) :150 - 260 kJ/molBDE (M-aryl): 250 - 350 kJ/molNormally, BDE (M-alkyl) M-Br M-H = or M-I)Electron densi

49、ty: Cl Br IM-H M-CF3 M-Ar M-CH3 M-CO-CH3M-C-R: stability increases with more electron-withdrawing R.* M-H is stronger than M-CR3 s orbital is indirectional and more dense.* M-CF3 is stronger than M-CR3 -CF3 is electron withdrawing.* M-Ar is stronger than M-CR3. More effective back-donation for M-Ar.

50、Would you expect M-CH3 bond be stronger or weaker than (answer: M-CH3 M-CH=CH2 M-CCH)Why?* M-CH3: no dp-pp interaction; M-CHCH2: one dp-pp interactions; M-CCH: two dp-pp interactions* Evidence: Stability of the following M-C bonds:M-CH3 D(M-CF3) D(M-Ph) D(M-CH3) D(M-CH2CH3) D(M-CH2Ph).The earlier fa

51、ilure in obtaining TM alkyls is not due to thermodynamic reasons !congeners: 同族元素Exercises Which one has the strongest stability of the following complexes ?Answer: a) last one b) last one c) first one3). Origin of earlier failure in obtaining TM alkyls: (Kinetic consideration)General questions.Q1.

52、Why could many TM alkyl complexes not be isolated? The reason for the instability of TM alkyl complexes is that there are many pathways that TM alkyl complexes can be posed. Q2. What are the common posing pathways for transition metal alkyls?*. b-elimination (The most common route!) *. Reductive eli

53、mination*. Others, e.g. a,g-eliminations, intramolecular reactions.Q3. How can we obtain stable M-alkyl complexes? Stable M-alkyl complexes could be obtained if the above posing pathways can be prevented. a) b-elimination.The most common position pathway for alkyls is b-H elimination, which converts

54、 a metal-alkyl into a hydrido-olefin complex.hydrido-olefin complexWhat is the condition for b-H elimination to occur ?A. There must be a b-H.B. The complex should be able to form four-membered co-planar transition state. (see (A) C. There is a vacant site cis to the alkyl (e.g. (B). but not (C). (n

55、eed an empty orbital to accept C-H electron.)D. The olefin formed is stable.E. The metal has e- to go to s*(C-H).Exercises. (a). It is difficult for the following compounds to undergo b-hydrogen eliminations. Suggest main reasons. answer: (1) can not form a four-membered TS(2) no vacant site cis to

56、the alkyl group, and CO is usually tightly bound to metal.(3) the vacant site is not cis to the alkyl group.Further notes on b-elimination. (i) b-H elimination on d0 (electron deficient) metal complexes may not occur. e.g. agostic bond: 抓氢键M: 过渡金属原子。它用空轨道接受从C-H s 键上的电子形成的三中心两电子键。作用：抓氢键C-H M消弱了C-H s键

57、，在金属有机反应中，能使H原子转移到金属原子上，容易进行消除反应no d electron, so cant undergo -elimination.s- donation-backdonation(ii) Other b-elimination is also possible, e.g.because: M-H M-CH3 (by 15-25 kcal/mol); M-F M-Hb) Reductive elimination* Coordination number decreased by 2. * Oxidation number decreased by 2. The proce

58、ss is the second most common position pathway for metal alkyls. e.g. c) Other pathwaysa-H eliminationAlpha-hydride elimination is the transfer of a hydride (hydrogen atom) from the alpha-position on a ligand to the metal center. Example,?note: (b) is incorrect due to Ta(VII).g-H elimination. e.g. Su

59、mmary: Common pathways of posing M-alkyls: b-H elimination Reductive elimination others.Exercises. 1) For each pair of complexes listed below, which one is less stable?answer: (1) a reductive elimination. (2) b b-H elimination. 2) Which one is least stable ? answer: (b)3) which one is most stable ?A

60、. Synthesis by alkyl transfer reactions.R- + M-X M-R + X-B. Synthesis from anionic transition metal complexes. M- + R-X M-R + X-C. Synthesis by oxidative addition reactions.M + R-X X-M-RD. Synthesis involving insertion Reactions. M-X + A M-A-XE. Synthesis involving elimination reactions. M-A-R M-R +