TY - JOUR

T1 - The structure and dynamic behaviour of disubstituted derivatives of [Rh6(CO)16] containing bidentate phosphorus ligands

AU - Farrar, David H.

AU - Grachova, Elena V.

AU - Haukka, Matti

AU - Heaton, Brian T.

AU - Iggo, Jonathan A.

AU - Pakkanen, Tapani A.

AU - Podkorytov, Ivan S.

AU - Tunik, Sergey P.

PY - 2003/10/30

Y1 - 2003/10/30

N2 - The solution structure and dynamic behaviour of [Rh6(CO) 14(μ,η2-dppm)] (1), [Rh6(CO) 14(μ,η2-dppe)] (2) and [Rh6(CO) 14(μ,η2-dppef)] (3) containing bridging diphosphine ligands have been examined using 1D 13C, 31P and 2D 13C-{103Rh}, 31P-{103Rh} HMQC and 13C EXSY NMR techniques. It has been shown that the solid state structure of these clusters remains unchanged in solution, including the close non-bonding intramolecular interactions of the perfluorinated phenyl rings with adjacent terminal carbonyls. In solution, two different dynamic processes have been found: for 2 and 3, the P-CH2-CH2-P chain of the coordinated dppe and dppef is non-rigid and this leads to the interchange of the two enantiomeric forms of the clusters through a 'rocking' motion of the bridging diphosphine; the rate of this exchange depends strongly on the non-bonding van der Waal's interactions between the phosphorus substituents and adjacent carbonyl ligands which results in substantially slower dynamics for 3 because the steric requirements of the fluorinated phenyl rings considerably hinder this racemization. The second type of dynamics found in 1-3 involves exchange of terminal/face-bridging CO's associated with the unsubstituted rhodium atoms. Regioselectivity of these exchanges is essentially similar for all three clusters, whereas the rates of these CO-exchanges are substantially higher in 3, which may be due to the lower net donicity of the per-fluorinated diphosphine.

AB - The solution structure and dynamic behaviour of [Rh6(CO) 14(μ,η2-dppm)] (1), [Rh6(CO) 14(μ,η2-dppe)] (2) and [Rh6(CO) 14(μ,η2-dppef)] (3) containing bridging diphosphine ligands have been examined using 1D 13C, 31P and 2D 13C-{103Rh}, 31P-{103Rh} HMQC and 13C EXSY NMR techniques. It has been shown that the solid state structure of these clusters remains unchanged in solution, including the close non-bonding intramolecular interactions of the perfluorinated phenyl rings with adjacent terminal carbonyls. In solution, two different dynamic processes have been found: for 2 and 3, the P-CH2-CH2-P chain of the coordinated dppe and dppef is non-rigid and this leads to the interchange of the two enantiomeric forms of the clusters through a 'rocking' motion of the bridging diphosphine; the rate of this exchange depends strongly on the non-bonding van der Waal's interactions between the phosphorus substituents and adjacent carbonyl ligands which results in substantially slower dynamics for 3 because the steric requirements of the fluorinated phenyl rings considerably hinder this racemization. The second type of dynamics found in 1-3 involves exchange of terminal/face-bridging CO's associated with the unsubstituted rhodium atoms. Regioselectivity of these exchanges is essentially similar for all three clusters, whereas the rates of these CO-exchanges are substantially higher in 3, which may be due to the lower net donicity of the per-fluorinated diphosphine.

KW - Dynamic behaviour

KW - NMR

KW - Rhodium disubstituted carbonyl clusters

KW - X-ray structures

UR - http://www.scopus.com/inward/record.url?scp=0142186326&partnerID=8YFLogxK

U2 - 10.1016/S0020-1693(03)00315-3

DO - 10.1016/S0020-1693(03)00315-3

M3 - Article

AN - SCOPUS:0142186326

VL - 354

SP - 11

EP - 20

JO - Inorganica Chimica Acta

JF - Inorganica Chimica Acta

SN - 0020-1693

ER -