配位化学总结

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,配合物的命名法(Nomenclature of coordination compounds(IUPAC),阳离子在前，阴离子在后,在配离子中，配体的命名总是在金属离子前,带负电的配体结尾常用”,o”,中性配体不变。,每一种配体的数目常用希腊语前缀,括号中的罗马数字或零表示金属离子的氧化态,如果配合物是一个阴离子，在金属名字后加后缀,-ate. titanate, vanadate, chromate, manganate, ferrate, cobalatate, nickelate, cuprate, zincate,1,K,3,Cr(C,2,O,4,),3,.,3H,2,O 三水合三草酸合铬(III)酸钾,Potassium tris(oxalato)chromate(III) trihydrate,Potassium trioxalatochromate(III) trihydrate,NiCl,2,(PPh,3,),2,二氯,双（三苯基膦）合镍（II),dichloridobis(triphenylphosphane)nickel(II),如果有两个以上的配体，则按照配体名称的字母顺序来命名。,2,配合物中的异构Isomerism in Coordination Complex,Werner 很早就预测Co(en),2,ClNH,3,2+,存在两种,互为镜面的结构。,3,异构体的分类The classification of iosmers,结构异构,(structural isomerism),(1),电离异构,(ionization isomerism),组成相同，由于阴离子处于内界或外界不同而引起的异构现象。,Co(NH,3,),5,BrSO,4, Co(NH,3,),5,Br,2+,+SO,4,2-,Co(NH,3,),5,SO,4,Br Co(NH,3,),5,SO,4,+,+Br,-,4,(2),水合异构(hydrate isomerism),化学组成相同，由于水分子处于内界或外界不同而引起的异构现象。,Cr(H,2,O),4,Cl,2,Cl,.,2H,2,O,bright-green,Cr(H,2,O),5,ClCl,2,.,H,2,O,grey-green,Cr(H,2,O),6,Cl,3,violet,(3),键合异构(linkage isomerism),配体用不同的配位原子与中心原子键合而产生的异构。,例： (NH,3,),5,Co-NO,2,Cl,2,、(NH,3,),5,Co-O-N=OCl,2,(H,2,O),5,Cr-SCN,2+,、 (H,2,O),5,Cr-NCS,2+,5,(4)配合异构,由于配体在配阳离子和配阴离子之间分配不同而引起的异构。,例： Co(NH,3,),6, Cr(CN),6,Cr(NH,3,),6, Co(CN),6,立体异构(stereoisomerism),(1),几何异构现象 (geometric isomerism),几何异构：配合物组成相同，由于配体在空间的位置不同而产生的异构现象。(平面四方形，八面体),6,平面正方形配合物,Pt(NH,3,),2,Cl,2,顺式(cis) 反式(trans),7,Pt(gly),2, gly=H,2,NCH,2,CO,2,-,（不对称二齿配体）(甘氨酸）,8,八面体构型的配合物,Co(NH,3,),4,Cl,2,+,的几何异构体,cis,顺式（绿色）,trans,反式（紫色）,9,Rh(py),3,Cl,3,的几何异构体,面式（facial） 经式（meridinal）,10,(2) 旋光异构（Optical isomerism),相互成为镜象而不能重合的一对分子称为旋光,异构体（又称对映异构体）。,分子具有旋光异构体的对称性判据,可以证明：分子具有旋光异构体的充分必要条,件是该分子不具备任意次的旋转反映轴（非真,轴）S,n,。,S,n,的定义：先转动2/n，然后再通过垂直于,转动轴的平面进行反映。,11,L(表示左旋), D(表示右旋),12,旋光异构体实例,* 平面正方形配合物不存在旋光异构体。,Rh(en),2,Cl,2,+,除存在顺、反几何异构体外，其顺式,几何异构体还可分出两种旋光异构体：,13,Co(en),3,3+,也存在两种旋光异构体,14,旋光异构体的拆分,定义：从两个旋光异构体的混合物中分离出单,一异构体的过程。,（1）自然拆分法：,若混合物从溶液中析出结晶时，两种晶体分别,结晶出来，且两种结晶外形不同，则可将其分,开。,例：Co(C,2,O,4,)(en),2,2,(C,2,O,4,),.,8H,2,O,15,（2）化学拆分法,该方法将对映体首先转化为非对映体，然后再,利用非对映体溶解度或其它物理性质的不同来,进行分离。,例：拆分Rh(en)33+的两种异构体(Werner的工作)：,I: 配合物的制备,NaRhCl,4,.,12H,2,O + enRh(en),3,Cl,3,+,NaCl + H,2,O,16,II: 使对映体转化为非对映体：,拆分试剂：硝基樟脑磺酸钠（NaL）,d,l-Rh(en),3,3+,+NaL l-Rh(en),3,L,3,+,d-Rh(en),3,L,3,(aq),III: 除去拆分试剂：,l-Rh(en),3,L,3,+NaIl-Rh(en),3,I,3,+NaL,溶解度较大的d-异构体可从溶液中回收。,17,在1929年由Bethe提出，in 1935 为van Vleck等所,发展, 与Puling的价键理论处于同一时代.,晶体场理论是一种静电理论, 它把配合物中中心原子,与配体之间的相互作用, 看作类似于离子晶体中正负,离子间的相互作用(pure electrostatic interaction)。,Ligands : point charges. Somewhat unrealistic.,Metal,d,orbitals are degenerate (,间并的) in gaseous,gas. 如果一个球形对称的负电核放在金属周围,则这,些轨道的能量会提高,但仍然是兼并的.,Crystal Field Theory,18,但如果是非球形对称的负电荷呢? d轨道发生分裂,(splitting).,CFT for Octahedral Geometry,19,The electron-electron interactions must be taken into,account.,For d,1,-d,3,systems, Hunds rule predicts that the electrons will not pair and occupy the same t,2g,set.,For d,4,-d,7,systems, two possibilities: electrons in the t,2g,set (electrons pairing), low spin or strong field situation; electrons in the e,g,set (electrons unpairing) , high spin or weak field situation( the pairing energy（,电子成对能,）,(,P,) and the splitting energy (10Dq).,20,电子成对能P 包括两部分：,The Coulombic repulsion(相互排斥能）,4d和5d过渡金属总是低自旋的,The loss of exchange energy (交换能的损失）。自旋平行的电子越多，交换能越大。因此，Fe,3+, Mn,3+,（d,5,)的配合物高自旋的情况越多。,21,2 正四面体场,在正四面体场中，过渡金属离子的五条d轨道同样分裂为两组，一组包括d,xy,、d,xz,、d,yz,三条轨道，用t,2,表示，,这三条轨道的极大值分别指向立方体棱边的中点。距配体较近，受到的排斥作用较强，能级升高，,另一组包括d,z,2,和d,x,2,y,2,，以e表示,，这两条轨道的极大值分别指向立方体的面心，距配体较远，受到的排斥作用较弱，能级下降。,四面体场中的d轨道,e,t,2,22,由于在四面体场中，这两组轨道都在一定程度下避开了配体、没有像八面体中d轨道与配体迎头相撞的情况，可以预料分裂能,t,将小于,o,，计算表明,t,(4/9),o,同样，根据重心守恒原理可以求出t,2,及e轨道的相对能量:,四面体场中的d轨道,e,t,2,t,(4/9),o,23,3 拉长的八面体,相对于正八面体而言，,在拉长八面体中，,z轴方向上的两个配体逐渐远离中心原子，排斥力下降，即d,z,2,能量下降。同时，为了保持总静电能量不变，在x轴和y轴的方向上配体向中心原子靠拢，从而d,x,2,y,2,的能量升高，这样e,g,轨道发生分裂。在t,2,g,三条轨道中，由于xy平面上的d,xy,轨道离配体要近，能量升高，xz和yz平面上的轨道d,xz,和d,yz,离配体远因而能量下降。结果，轨道也发生分裂。这样，,5条d轨道分成四组，能量从高到低的次序为:, d,x,2,y,2,， d,z,2, d,xy,， d,xz,和d,yz,。,24,4 平面正方形场,设四个配体只在x、y平面上沿x和y轴方向趋近于中心原子，因d,x,2,y,2,轨道的极大值正好处于与配体迎头相撞的位置，受排斥作用最强，能级升高最多。其次是在xy平面上的d,xy,轨道。而d,z,2,仅轨道的环形部分在xy平面上，受配体排斥作用稍小，能量稍低，简并的d,xz,、d,yz,的极大值与xy平面成45,角，受配体排斥作用最弱，能量最低。,总之，,5条d轨道在S,q,场中分裂为四组，由高到低的顺序是,：, d,x,2,y,2, d,xy, d,z,2, d,xz,和d,yz,。,25,Crystal Field Theory,In crystal field theory, the electron pairs on the ligands are viewed as point negative charges that interact with the,d,orbitals on the central metal.,The nature of the ligand and the tendency toward covalent bonding is ignored.,26,d Orbital Splitting,_ _ _ _ _,Spherical field,_ _,d,z,2,d,x,2,-,y,2,_ _ _,d,xy,d,xz,d,xz,o,0.6,o,0.4,o,Octahedral field,e,g,t,2g,27,d Orbital Splitting,In some texts and articles, the gap in the d orbitals is assigned a value of 10Dq. The upper (e,g,) set goes up by 6Dq, and the lower set (t,2g,) goes down by 4Dq.,The actual size of the gap varies with the metal and the ligands,.,28,d Orbital Splitting,The colors exhibited by most transition metal complexes arises from the splitting of the,d,orbitals. As electrons transition from the lower t,2g,set to the e,g,set, light in the visible range is absorbed.,29,d Orbital Splitting,The splitting due to the nature of the ligand can be observed and measured using a spectrophotometer. Smaller values of ,o,result in colors in the green range. Larger gaps shift the color to yellow.,30,The Spectrochemical Series,The complexes of cobalt (III) show the shift in color due to the ligand.,(a) CN, (b) NO,2, (c) phen, (d) en, (e) NH,3, (f) gly, (g) H,2,O, (h) ox,2, (i) CO,3,2,.,31,Magnetic Moments,A magnetic balance can be used to determine the magnetic moment of a substance. If a substance has unpaired electrons, it is,paramagnetic, and attracted to a magnetic field.,For the upper transition metals, the spin-only magnetic moment,s, can be used to determine the number of unpaired electrons.,s,= n(n+2),1/2,32,Magnetic Moments,The magnetic moment of a substance, in Bohr magnetons, can be related to the number of unpaired electrons in the compound.,s,= n(n+2),1/2,Where n is the number of unpaired electrons,33,Magnetic Moments,Complexes with 4-7 electrons in the,d,orbitals have two possibilities for the distribution of electrons. The complexes can be,low spin, in which the electrons occupy the lower t,2g,set and pair up, or they can be,high spin,. In these complexes, the electrons will fill the upper e,g,set before pairing.,34,Summary,1. All ligands are, donors. In general, ligand that engage solely in bonding are in the middle of the spectrochemical series. Some very strong donors, such as CH,3,-,and H,-,are found high in the series.,2. Ligands with filled,p,or,d,orbitals can also serve as, donors. This results in a smaller value of ,o,.,35,Summary,3. Ligands with empty,p,d,or,* orbitals can also serve as acceptors. This results in a larger value of ,o,.,I,-,Br,-,Cl,-,F,-,H,2,ONH,3,PPh,3,CO, donor weak donor only 6 common,Middle Transition,Metals,18e configurations,are common,CN = 6 common,Late Transition,Metals,16e and sub-16e,Configurations,are common,CN, 5 common,41,Electron Counting: Donor Pair Method,Consider ligands to donate electron pair(s) to metal thus must know how many electrons ligands donate (and their charge when electrons of M-L bond are put back on ligand),Must take into account the overall charge on complex as well as those of bound ligands to determine oxidation state of metal,Add up the electron counts for the metal center and the ligands (donated electrons),42,Complexes with 18e,-,counts are referred to as saturated,because there are no low-lying orbitals that another,incoming ligand can coordinate.,Complexes with counts lower than 18e,-,are called,unsaturated and can electronically bind additional ligands.,Electron Counting: Donor Pair Method,43,Ligand Charges & Donor Number of Electrons,First, know charges and e donated for the common ligands (below):,NO,+,(Nitrosyl bound in linear,fashion MNO),:NR,3,(amines),:PR,3,(phosphines),:CO,(carbonyl),R,2,C=CR,2,(alkenes),RC,CR,(alkynes, can also be 4e),:NCR,(nitriles),Cationic 2e donors:,Neutral 2e donors:,44,Ligand Charges & Donor Number of Electrons,Halides,(F,-, Cl,-, Br,-, I,-,),R,3,C,-,(alkyls),Ph,-,(phenyl),H,-,(hydride),RO,-,(alkoxide),RS,-,(thiolate),NO,-,(Nitrosyl, bound in bent fashion MNO),O,2-,(oxide),S,2-,(sulfide),RN,2-,(inorganic imide),C,3,H,5,-,(,3,-,allyl),N,3-,(nitride),P,3-,(phosphide),Cp,-,(,5,-,cyclopentadienyl),Anionic 2e donors:,Anionic 4e- donors:,Anionic 6e- donors:,45,Other notes:,M-M count 1e- per bond (1 for single, 2 for double, etc.)M=CR,2,carbene count as 2e- and considered Neutral.,M,CR,carbyne count as 3e- and considered,Neutral.,2,-CO, bridging carbonyl count as 1e- per Metal.,Ligand Charges & Donor Number of Electrons,46,18e- Rule & Application to Middle/Late TM,Coordinatively unsaturated complexes (e.g. 14e and 16e species),We will see many stable 14e- and 16e- species however, as their maximum coordination number (i.e. not 18e- species) is not achieved, they are capable of coordinating other ligands and are therefore rather reactive (and very important to reactivity of TM complexes),where,n,is the number of valence electrons of metal (,d,n,), and CN is coordination number.,n,+ 2(CN),max,= 18,or,(CN),max,= 18 ,n,2,47,One can write down:,d,n,0246810,(CN),max,98765 4,Applies for simple monometallic, spin-paired complexes, when n is even,18e- Rule & Application to Middle/Late TM,48,There is no overall charge on complex so metal must exactly balance ligand charges,Are there any charged ligands?,What is metal oxidation state?,What is,d,n,configuration?,Now that charges are known, do electron counting,18e- Rule & Application to Middle/Late TM,49,There is a +2 charge on the complex that must be,accounted for,Are there any charged ligands?,What is metal oxidation state?,What is,d,n,configuration?,Now that charges are known, do electron counting,18e- Rule & Application to Middle/Late TM,50,Then,What is metal oxidation state?,What is,d,n,configuration?,Now that charges are known, do electron counting,So,3-C,3,H,5,- (allyl) ligand is anionic and donates 4e- to metal center in above case,51,Are there any charged ligands?,What is metal oxidation state?,What is,d,n,configuration?,Now that charges are known, do electron counting,There is no charge on the complex,52,