143890-17-9Relevant articles and documents
Steric effects of the 2-(diphenylphosphino)-6-methoxypyridine short-bite bridging ligand in the synthesis of binuclear complexes. Crystal and molecular structure of [Rh2Cu(CO)2(Ph2PPyOMe) 2(μ-Cl)2]BF4·CH2Cl 2
Arena, Carmela Grazia,Faraone, Felice,Lanfranchi, Maurizio,Rotondo, Enrico,Tiripicchio, Antonio
, p. 4797 - 4802 (2008/10/08)
Treatment of [Rh(COD)(μ-Cl)]2 (COD = cycloocta-1,5-diene) with 2-(diphenylphosphino)-6-methoxypyridine (Ph2PPyOMe) in benzene solution yielded the complex [Rh(COD)(Ph2PPyOMe)Cl] (1), in which Ph2PPyOMe acts as an η1 P-bonded ligand. The COD ligand was easily displaced when CO was bubbled into a CH2Cl2 solution of 1, and the presence in solution of cis-[Rh(CO)2(Ph2PPyOMe)Cl] (2) was established by IR and NMR spectroscopy. By the addition of Ph2PPyOMe to a CH2Cl2 solution containing 2 (molar ratio 1:1) or [Rh(CO)2(μ-Cl)]2 (molar ratio 4:1), trans-[Rh(CO)(Ph2PPyOMe)2Cl] (3) was obtained. The lack of formation in these reactions of the A-frame complex [Rh2(μ-CO)(Ph2PPyOMe)2Cl2], as was observed in the analogous reactions with 2-(diphenylphosphino)pyridine (Ph2PPy), is discussed. The reaction of 3 with [Cu(NCCH3)4]BF4, in CH2Cl2 solution, gave nearly quantitatively the complex [Rh2Cu(CO)2(Ph2PPyOMe) 2(μ-Cl)2]BF4·CH2Cl 2 (4), whose structure was established by an X-ray diffraction study. Attempts to obtain a Rh2Au complex, analogous to 4, failed. Crystals of 4 are monoclinic, of space group P21/a with Z = 4 in a unit cell of dimensions a = 32.852 (8) A?, b = 10.452 (4) A?, c = 12.945 (5) A?, and β = 97.17 (2)°. The structure was solved from diffractometric data by Patterson and Fourier methods and refined by full-matrix least-squares techniques on the basis of 4842 observed reflections to R and Rw values of 0.0500 and 0.0661, respectively. The cationic complex of 4 is a trinuclear Rh2Cu species containing two rhodium atoms linked by two bridging chloride ligands; the CO and the Ph2PPyOMe (P-bonded to Rh) ligands complete the coordination of each rhodium center. The two CO ligands are mutually trans. The copper center is almost linearly coordinated by the pyridine nitrogen atoms of the Ph2PPyOMe ligands. The copper and rhodium atoms are not involved in a metal-metal bond. The reaction of 1 with [AuPPh3]PF6 afforded [Rh(COD)(μ-C l)]2 and [Au(PPh3)(Ph2PPyOMe)]PF6 (6). Transfer of the Ph2PPyOMe ligand from one metal center to another occurred also in the reactions of 1 with cis-[Pd(CNtBu)2Cl2] and [Pd(COD)Cl2]. The reaction products were [Rh(CO)2(μ-Cl)]2 and respectively cis-[Pd(CNtBu)(Ph2PPyOMe)Cl2] (7) and [Pd(Ph2PPyOMe)Cl(μ-Cl)]2 (8), Ph2PPyOMe acting as an η1 P-bonded ligand in the last two. The effect of the small bite angle of the Ph2PPyOMe ligand on the pathway of these reactions is discussed, and a comparison with the results of analogous reactions of complexes containing the Ph2PPy ligand is made.
