KOMPLEKS BIRIKMALARDA KIMYOVIY BOG’LARNING TABIATI

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   Kompleks birikmalarning  tuzilishini 3 xil yo’l bilan tushuntirish mumkin.

                  1) kristall maydon nazariyasi

                  2) valent bog’lanish usuli (VBU)

                  3) molekulyar orbitallar usuli (MOU)

1. Kristall  maydon  nazariyasi kompleks hosil qiluvchi va ligandlar orasidagi elektrostatik ta’sir kuchlariga asoslangan. Bunda kompleks hosil qiluvchining

 d-orbitallarining fazoviy shakli hisobga olinadi. Ligandlar hosil qilgan elektr maydoni kuchiga qarab kompleks hosil  qiluvchining d-orbitallari har xil energetik orbitalga ajraydi.  Shu tufayli kompleks birikmaning fazoviy shakli ham turlicha bo’ladi.Erkin ionda  markaziy atomning d-orbitallari bir xil energiyaga ega bo’ladi.

                                                                                           b)ligandlarning oktaedrik

                                                                                                                                  maydoni ta’siridagi ion

                                                      b)sferik ion                                      d_z² d_x²_y²

                                                                                                __  __       d_g

1.   a) Erkin ion                     d_xy d_xz d_yz d_z² d_x²_y²

                                                          __  __  __ __  __                  

                                                                                                                    Ñ

              d_xy d_xz d_yz d_z² d_x²_y²

               __  __  __ __  __                                                       d_xy d_xz d_yz

                                                                                                   __  __  __ d_e

             Agar markaziy ion atrofida ligandlarning oktaedrik joylashuvi yuzaga kelsa  markaziy atomdagi dz²  va d x²y²  ligandlarga nisbatan kucliroq itarilishga uchrab  ularning energiyalari doira maydon ta’siridagi iondan anchagina yuqori bo’ladi.

              Ayni paytda, d_xy,d_xz va  d_yz orbatallarning energetik holati  doira maydon ta’siridan kuchsiz bo’ladi.Shu sababga kora  markaziy atomning d orbatallari  oktaedrik maydon ta’sirida ikkiga bo’linadi(d_g  va  d_e). Bu enehgiyalarning farqi

 (Ñ) – parchalanish enehgiyasi deyiladi. Bu qiymat  kompleks birikmalarning yutilish spektrlari orqali aniqlanadi.

               Ligandlar parchalanish spektrlarini qiymati bo’yicha  quyidagi spektrokimyoviy qatorni hosil qiladi.

CO,CN  ^->  En    >   NH₃ > CSN^-  > H₂O > OH^-   > F^- > Cl^-  > Br^- >  J^-

  Kucli                                      o’rtacha maydon                                                 kuchsiz

  maydon      ½                                          ½                            maydon

 

             [CoF₆] ^3- paramagnit kompleks hosil qilishi  va [Co(CN)₆]^3- ning  diamagnit kompleks hosil qilish sabaini  ligandlarning spektrokimyoviy qatori asisida tusuntirish mumkin. CN^- ioni kuchli maydon hosil qiluvchi ligandlar qatorida joylashganligi uchun  uning parchalanish energiyasi anchagina yuqori bo’ladi. [CoF₆]^3-  yuqori  spinli kompleksga kirib paramagnit xossaga ega.

 [Co(CN)₆]^3-     da bo’lsa elektronlarning joylasuvi boshqacha yuzaga keladi.

 

 

                                                                                            d_z² d_x²_y²

                                              [CoF₆]^3-                                  ___ ___    d_g

 

                                                          maydoni ta’siridagi ion

        b)sferik ion                                       d_z² d_x²_y²       d_g

                                                    ­  ­                                                    

        d_z² d_x²_y²   d_xy d_xz d_yz                                                Ñ                     [Co(CN)₆]^3-                             Ñ

 

        ­¯  ­    ­ ­  ­                  

                                                  d_xy d_xz d_yz      d_e

                                                   ­¯  ­    ­              

                                                                                            d_xy         d_xz         d_yz

                                                                                            ­¯__ ­ ¯__  ­¯__ d_e

 

 

        

2. Valent bog’lanishlar usuli.Bu nazariyaga binoan kompleks hosil qiluvchi  va  ligandlar orasida kovalent   bog’  donor-aktseptor  mexanizmida  sodir  bo’ladi.Kompleks hosil qiluvchining bo’sh orbitallari bo’ladi,  ya’ni u aktseptor bo’ladi. Ligandlarda esa umumlashmagan elektron juftlari bo’lib uni kompleks hosil  qiluvchining bo’sh  orbitaliga  beradi,  ya’ni donor bo’ladi.  Ammiak  molekulasida  azot  atomi sp ³ gibridlangan holda bo’lib,  gibrid orbitallaridan  birida bo’linmagan  elektron jufti bor. Shu tufayli ammiak molekulasi H⁺  ioni bilan NH ₄⁺  ni hosil qiladi va u tetraedrik kofiguratsiyaga ega. [NiCl₄]^2- ioni ham xuddi shunday tuzilishga ega. Bunda Cl^-  ioni elektronodonor, Ni²⁺  molekulasi aktseptor bo’ladi.

 

          Ni    - 2e   ® Ni²⁺                                 K₂[NiCl₄]

 3s²3p ⁶3d ⁸ 4s²    ®  3s² 3p⁶3d⁸4s⁰

            Cl ClCl

     Cl  ┌─┬─┬─┐          [NiCl₄] ^2-    sp ³  gibridlanish

     ┌─┼─┴─┴─┘

     └─┘  4p

      4s

       ┌─┬─┬─┬─┬─┐

   3d└─┴─┴─┴─┴─┘ 

   2ta  juftlashmagan elektron hisobiga bu kompleks birikma magnit xossaga ega.

         [Zn(NH₃)₄]Cl₂ kompleks birikma tetraedr shakliga ega.

      [Zn(NH₃)₄]²⁺ , [Cd(NH₃)₄]²⁺ , [HgJ₄]²⁺ lar ega.

                   Zn - 2e ® Zn ²⁺

    3s²3p⁶3d¹⁰4s² ®    3s²3p⁶3d¹⁰

 

                          NH₃NH₃NH₃

                       NH₃         ┌─┬─┬─┐

     [Zn(NH3)4]²⁺      ┌─┼─┴─┴─┘    sp³ gibridlanish

                                 └─┘     4p

                                  4s

     d- elementlarning 4ta d -orbitallari  band  bo’lgan  ionlarda,koordinatsion soni 4 ga teng bo’lsa,  bitta d,  bitta s va ikkita d-orbital ishtirok etadi.

     [Pt(NH₃)₄]²⁺            Pt -2e   ®    Pt²⁺

                    5s²5p⁶5d⁹6s¹  ®  5s²5p⁶5d⁸

                                                                     ┌─┬─┬─┐

                                                               ┌─┼─┴─┴─┘

                                   ┌─┬─┬─┬─┬─┼─┘  6p

                  ┌─┬─┬─┼─┴─┴─┴─┴─┘6s

            ┌─┼─┴─┴─┘   5d

            └─┘ 5p

             5s

 

     Bunda dsp² gibridlanish bo’lib, molekula tekis kvadrat shaklida bo’ladi. Ligandlar kvadratning uchlarida joylashadi.

     Koordinatsion son 6 ga teng bo’lganda d²sp³ gibridlanish  bo’ladi. Kompleks birikma oktaedr shaklida bo’lib, ligandlar oktaedr uch-larida joylashadi.

     [Pt(NH₃)₆]⁴⁺          Pt - 4e ®     Pt ⁴⁺

                    5s²5p⁶5d⁹6s¹   ®5s ²5p⁶ 5d⁶

                                                                      ┌─┬─┬─┐

                                                                ┌─┼─┴─┴─┘

                                   ┌─┬─┬─┬─┬─┼─┘  6p

                  ┌─┬─┬─┼─┴─┴─┴─┴─┘6s

            ┌─┼─┴─┴─┘   5d

            └─┘ 5p

             5s

      Shunga o’xshash konfiguratsiya  [Co(NH₃)₆] ³⁺ ,  [Fe(CN)₆]³⁺   larda

bo’ladi.

     Agar koordinatsion son 2 ga teng bo’lsa,  sp gibridlanish kuzatiladi, chiziqli konfiguratsiya bo’ladi.

     [Ag(NH₃)₄]Cl     Ag - 1e ® Ag ⁺

                       4s²4p⁶4d¹⁰5s¹ ®  4s²4p⁶ d¹⁰5s^o5p^o

     Bu misollar  valent valent bog’lanish metodi kompleks birikmalarning koordinatsion soni, geometrik shakli va magnit xossalarini to’g’ri tushuntiradi. Lekin yutilish spektrlarini valent boglanish usuli bilan tushuntirib bo’lmaydi. Shunday ligandlar borki, ular metaldagi elektronlarni o’zining vakant orbitallariga qabul qila oladi.

    PF₃  yoki SnCl₄  ioni o’zining bo’shashtiruvchi orbitallariga CO,NO kabi  molekulalarni qabul qila oladi.  Bu kompleks birikmalarning tuzilishini molekulyar orbitallar nazariyasi tushuntirib beradi.