$\begingroup$ My issue with cyano ligands is that although they are isoelectronic to carbonyls, they have a negative charge.

If we bond this methyl anion to the metal, the lone pair forms our metal-carbon bond and the methyl group acts as a two-electron donor ligand. Notice that to keep charge neutrality we must oxidize the metal by one electron (i.e. All types of bipyridine synthons have been used for the formation of chelating pyridine–pyridylidene complexes, including 2,1′-pyridine-pyridinium salts, 2,2′-, 2,3′-, and 2,4′-bipyridine-derived precursors. Add up the group number of the metal center and the e- count of the ligands, then take into consider the overall charge of the complex to obtain the final electron count. Count one pair of electrons per ligand. A density functional theoretical (DFT) study (B3LYP) has been carried out on 20 organometallic complexes containing η5- and/or η3-coordinated cyclopentadienyl anions (Cp–) and 2,2′-bipyridine (bpy) ligand(s) at varying oxidation levels, i.e., as the neutral ligand (bpy0), as the π-radical monoanion (bpy•–)−, or as the diamagnetic dianion (bpy2–)2–. This is the metal's formal oxidation state. Ru(CO) 5: Total electron count = 10 + 8 = 18, predicted to be stable. There is a wrinkle in this process if charges are involved. X-type ligands are those that donate one electron to the metal and accept one electron from the metal when using the neutral ligand method of electron counting, or donate two electrons to the metal when using the donor pair method of electron counting. Practice Questions . c) bis(η 4 –cyclooctadiene)nickel(0) Ni(0) is d 10 in this complex. balance the ligand charges with an equal opposite charge on the metal. d) hexacyanoferrate(III) Fe(III) is d 5 in this complex. assign a positive charge to the metal).

This, in turn, reduces the d-electron count of the metal center by one. c) bis(η 4 –cyclooctadiene)nickel(0) Ni(0) is d 10 in this complex. 2,2′-Bipyridine (bipy or bpy, pronounced / ˈ b ɪ p iː /) is an organic compound with the formula C 10 H 8 N 2.This colorless solid is an important isomer of the bipyridine family. Determining Coordination Number. There are many definitions of the term coordination number, but there is no one simple unambiguous definition that works in all cases.For simple monodentate and chelating ligands, the coordination number can be defined as the number of atoms or ligands directly bonded to the metal atom.For example, [Fe(NH 3) 6] 3+ and [Fe(en) 3] 3+ are both 6-coordinate … At the presence of metal-metal bond, one electron is counted towards each metal center in a bond. Also, we must count the valence electrons that the metal brings itself. The rate constant for the reaction of 2,2'-bipyridine with photochemically-produced hydroxyl radicals in water has been measured to be 6.2X10+9 M-1 sec-1 at 21 °C and a pH of 9.3(2), which corresponds to an aqueous half-life of about 129 days at a hydroxyl radical concn of 1X10-17 M(3). Total electron count = 10 + 8 = 18, predicted to be stable.

To obtain the total number of electrons add up the metal d electron count, electron count of the ligands, charges and metal-metal bonds (if present). Once the complex has been deconstructed, we count a pair of electrons for each ligand, since they are each donating a pair to the metal in the complex.
d) hexacyanoferrate(III) Fe(III) is d 5 in this complex.
Each η 4 –COD contributes 4 electrons: total = 2(4) = 8.

Each CN – contributes 2 electrons: total = 6(2) = 12 The total is the electron count in the metal in … d-Electron count (dn) n = Valence of neutral metal – charge on the metal Rh(0) has 9 valence electrons, so Rh(I) has (9-1= 8) Rh(I) has 8 d-electrons and is said to be d8 d Total electron count d The total electron count at the metal is given by: (metal electrons + ligand electrons). Total electron count = 12 + 4 = 16, predicted to be stable.

Each η 4 –COD contributes 4 electrons: total = 2(4) = 8.

To determine ligand charges, create an ionic model by assigning each M-L electron pair to the more electronegative atom (L). Total electron count = 12 + 4 = 16, predicted to be stable. It is a bidentate chelating ligand, forming complexes with many transition metals.