Rhodium electron configuration

The most common oxidatiou states and corresponding electronic configurations of rhodium are +1 which is usually square planar although some five coordinate complexes are known, and +3 (t7 ) which is usually octahedral. Dimeric rhodium carboxylates are +2 (t/) complexes. Compounds iu oxidatiou states —1 to +6 (t5 ) exist. Significant iudustrial appHcatious iuclude rhodium-catalyzed carbouylatiou of methanol to acetic acid and acetic anhydride, and hydroformylation of propene to -butyraldehyde. Enantioselective catalytic reduction has also been demonstrated. 

The most common oxidation states, corresponding electronic configurations, and coordination geometries of iridium are +1 (t5 ) usually square plane although some five-coordinate complexes are known, and +3 (t7 ) and +4 (t5 ), both octahedral. Compounds ia every oxidation state between —1 and +6 (<5 ) are known. Iridium compounds are used primarily to model more active rhodium catalysts. 

In class (1), a range of small molecules adds to rhodium, usually with the loss of one PPh3, thus maintaining the 16-electron configuration, rather than an 18-electron species unable to bind a substrate. 

Before turning to specific results we will have a look at the properties of rhodium(II) acetates/carboxamidates as catalysts for reactions with diazocompounds as the substrates via carbenoid intermediates. Rhodium(II) has a d7 electron configuration, forming the lantern type dimers with bridging carboxylates. The single electrons in the respective dz2 orbitals form an electron... 

From the results published on the hydrogenation of benzene (29, 30, 31), it appears that ruthenium and rhodium are more active than palladium. By adapting the scheme proposed by Dalla Betta and Boudart (9), we could suppose that the electron-deficient character of palladium on oxidizing sites leads to an electronic configuration very similar to that of rhodium, and, thus, to an increase in catalytic activity. 

RhCl(PPh3) 3 The chlorine radical (Cl ) accepts an electron from rhodium metal (electronic configuration Ad1,5s2) to give Cl and Rh+. The chloride ion then donates two electrons to the rhodium ion to form a dative or a coordinate bond. Each PPh3 donates a lone pair of electrons on the phosphorus atom to the rhodium ion. The total number of electrons around rhodium is therefore 8 + 2 + 3X2=16, and the oxidation state of rhodium is obviously 1 +. The other way of counting is to take the nine electrons of rhodium and add one electron for the chlorine radical and six for the three neutral phosphine ligands. This also gives the same electron count of 16. 

The oxidative addition of methyl iodide to an unsaturated cobalt carbonyl according to Equation (27) was proposed by Wender, CO insertion gives an acetyl species (28) which is thought to be hydrogenated by cobalt carbonyl hydride or H to yield acetaldehyde [4]. Numerous examples of the oxidative addition of methyl iodide to transition metal complexes with a electron configuration (e.g. Rh Ir ) ate known from the literature [66, 67]. For the carbonytaiion of methanol, the rate has been found to be the oxidative addition of methyl iodide to rhodium(l) [68]. 

However, its bine chloride solntion had been previously observed by Vauquehn in Paris in 1804. Rnthenium is the least abundant platinum metal (10 to 10 ppm) after rhodium. In 2002, the demand for ruthenium was 11.6 tons, an increase of 1.8 tons compared to 2001, mainly becanse of increased sales of rnthenium paste to the electronics industry, for the manufacture of chip resistors and hybrid integrated circuits (HIC). Its atomic number is 44, its atomic weight 101.07, and its electronic configuration [Kr]4d 5s. Seven stable isotopes are known. Some physical data are reported in Table 1 (see Coordination Chemistry History mA Coordination Numbers Geometries). 

Increasing the number of electrons reduces the activation of N2, because the electrons occupy the orbitals which are bonding with respect to the NN bond, and actually stabilize it. In agreement with this prediction dinitrogen is sufficiently activated to be reduced by protonation by dinuclear complexes of titanium(II), zirco-nium(Il), niobium(III), tantalum(III), molybdenum(IV), and tungsten(IV), whereas it is not reduced by protonation by certain d -d complexes, such as those of molybdenum(O), ruthenium(II), or rhodium(I). Apparently dinuclear complexes M-N=N-M in which M has the d electronic configuration can be intermediates in dinitrogen reduction in protic media, particularly if they represent part of polynuclear complexes (vide infra). 

The UV-vis spectra of sarcophaginates and sepulchrates of the platinum subgroup metal ions are much less informative. In most cases, the d-d transition bands have been observed as a shoulder at CO 4000 cm- to more intensive CTB. Only spectra of rhodium(III) complexes with electronic configuration d oi the encapsulated metal ion show the Aig—> Tigand d-d transition bands at 33 000... 

The strengthening of the C-O bond, which is revealed by the blue shift over the doped catalysts, implies that the rhodium particles have an electronic configuration that does not favor the formation of Rh-CO bonds, as compared to the undoped... 

Organometallic compounds of rhodium have the metal center in oxidation states ranging from +4 to -3. but the most common oxidation states are +1 and +3. The Rh(I) species have a d electron configuration and both four coordinated square planar and five coordinated trigonal bipyramidal species exist. Oxidative addition reactions to Rh(I) form Rh(III) species with octahedral geometry. The oxidative addition is reversible in many cases, and this makes catalytic transformations of organic compounds possible. Presented here are important reactions of rhodium complexes in catalytic and stoichiometric transformations of organic compounds. 

It has been demonstrated that RhBr,-doped AgBr crystals give rise to centers upon exposure to light. These rhodium(II) centers become more stable with decreasing temperatures and at 35 K it was shown that the low spin Rh center was in a Z>4 environment. However, it was believed that the Z>4/, symmetry observed for photolytically generated Rh + centers in LiH or LiD lattices was an artifact of site symmetry. It is reasonable to assume less than ideal geometry for a ion since Jahn-Teller effects will be prominent for such an electronic configuration and a static Jahn-Teller effect has been observed for Rh in a CaO matrix at 4.2... 

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