Dinuclear complexes rhodium

Metal basicity and cooperative effects in the reactions of dinuclear pyrazolato rhodium complexes 98PAC779. 

Complex [(CXI )Ir(/j,-pz)(/i,-SBu )(/j,-Ph2PCH2PPh2)Ir(CO)] reacts with iodine to form 202 (X = I) as the typical iridium(II)-iridium(II) symmetrical species [90ICA(178)179]. The terminal iodide ligands can be readily displaced in reactions with silversalts. Thus, 202 (X = I), upon reaction with silver nitrate, produces 202 (X = ONO2). Complex [(OC)Ir(/i,-pz )(/z-SBu )(/i-Ph2PCH2PPh2)Ir(CO)] reacts with mercury dichloride to form 203, traditionally interpreted as the product of oxidative addition to one iridium atom and simultaneous Lewis acid-base interaction with the other. The rhodium /i-pyrazolato derivative is prepared in a similar way. Unexpectedly, the iridium /z-pyrazolato analog in similar conditions produces mercury(I) chloride and forms the dinuclear complex 204. 

Phenylacetylene 13 reacts with Rh4(CO)i2 to give 112 under an Ar or GO atmosphere. Complex 112 gives ( )-15 as the sole organic product by the reaction with Mc2PhSiH under GO atmosphere. Under CO pressure, 112 is transformed to dinuclear complex 7, which is directly formed from the reaction of 13 with Rh4(CO)i2 under GO pressure, irrespective of the quantity of 13 used (Scheme 7). No specific indication of CO insertion into the Rh-C bond in 7 is observed at this stage. Coordination of 13 to rhodium metal in 7 is relatively stable and the coordinated 13 is not replaced by the free 13 in solution. ... 

IX. Equilibria between Mono- and Dihydroxo-Bridged Dinuclear Complexes of Chromium(III), Rhodium(III), and Iridium(III)... 

G. Dinuclear Indenyl Rhodium Complexes with Bridging OFCOT Ligands... 

The complexes of rhodium will primarily be considered in order of increasing oxidation state. However, complexes in which the oxidation state of the metal is uncertain (e.g. nitrosyls) or dinuclear complexes of mixed oxidation state will be dealt with last. 

The reaction of RhCls with an excess of the anion of TIPT in MeCN also generated a dinuclear complex in high yield, in which the bridging aromatic thiolate also binds via an arene substituent, but in this case the two rhodium atoms are not equivalent (76). A representation of the overall crystal and molecular structure is shown in Fig. 18. A simplified view of the coordination sphere of one rhodium atom is shown in Fig. 19. The structure comprises two distinct metal atoms, with... 

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). 

An example of the H-2/C=C ligand metal coordination was reported by Siebert and co-workers <1998JOM107, 2001JOM7>, who reacted 2,3-dihydro-l/7-l,3-diborole derivatives 31a-c with dirhodium-/r-dichlorotetraethylene in tetrahydrofuran (THE) at room temperature to give the dinuclear complexes bis 7 -[l,3,4,5-tetramethyl-2-(2,4,6-trimethylbenzyl)-2,3-dihydro-l,3-diborole]- and bis[77 -(4,5-diethyl-l,2,3-trimethyl-2,3-dihydro-l,3-diborole)rhodium chloride 34a-c, respectively (Equation 3). 

The rhodium and cobalt complexes 13 and 14, which contain labile ethylene ligands, also cleave the central CSp2-CSp2 bond of biphenylene to afford dinuclear complexes 15 and 16, respectively [28]. Treatment of the cobalt complex 16 with carbon monoxide furnishes fluorenone. However, both complexes are resistant to hydrogenation. 

Chelation v. cyclometalation in a cationic dipyridylpyridazine-Rh(I) complex. Milstein and co-workers reported the results of a study of the interaction of rhodium norbomadiene tetrafluoroborate (Rh(NBD)2) with the tetradentate ligand 3,6-bis-(2-pyridyl)pyridazine (DPPN) (241). Mononuclear complexes, 242, were obtained quantitatively. Treatment of the complex of DPPN Rh(NBD)2BF4 with a second equivalent of the metal precursor (Rh(NBD)(CH3CN)2)BF4 led to a dinuclear complex, 243, that involves a unique rearrangement of the norbomadienyl moiety. 

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