New Racemic Planar-Chiral Metalloligands Derived from Donor-Substituted Indenes:  A Synthetic, Structural, and Catalytic Investigation

• Published in: Organometallics Vol. 26; no. 25; pp. 6418 - 6427
• Main Authors: Wechsler, Dominik, Rankin, Matthew A., McDonald, Robert, Ferguson, Michael J., Schatte, Gabriele, Stradiotto, Mark
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 03.12.2007; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; ASYMMETRIC CATALYSIS; HYDROBORATION; HYDROGENATION; FORMALLY ZWITTERIONIC RHODIUM(I); LIGANDS; IRIDIUM(I) DERIVATIVES; TRANSITION-METAL; COMPLEXES; HOMOGENEOUS CATALYSIS; ISOMERIZATION BEHAVIOR
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om700832f

The synthesis and characterization of a new family of (η5-indenyl)MLn complexes (MLn = Mn(CO)3, Cp*Ru, or Cp*Fe; Cp* = η5-C5Me5) derived from 3-P i Pr2-indene, 1-P i Pr2-2-NMe2-indene (1a[H]), or 1-P(S) i Pr2-2-NMe2-indene (1b[H]) are described. Lithiation of 1b[H] followed by treatment with BrMn(CO)5, 0.25 equiv of [Cp*RuCl]4, or Cp*Li/FeCl2 provided the corresponding (η5-1b)MLn complexes (MLn = Mn(CO)3, 2a, 96%; Cp*Ru, 2b, 87%; or Cp*Fe, 2c, 55%). Similarly, treatment of 1a[Li] with 0.25 equiv of [Cp*RuCl]4 or Cp*Li/FeCl2 provided the corresponding (η5-1a)MLn complexes (MLn = Cp*Ru, 3b, 74%; or Cp*Fe, 3c, 62%). Whereas combination of 3b and 0.5 equiv of [(COD)RhCl]2 afforded [(COD)Rh(κ2-P,N-3b)]+Cl- ([4b] + Cl - ; 49% isolated yield), under similar conditions 3c was observed to undergo a decomposition reaction resulting in the formation of the zwitterionic complex (COD)Rh(κ2-P,N-1a) (5; COD = η4-1,5-cyclooctadiene). Each of 3a−c was observed to react cleanly with [(COD)Rh(THF)2]+BF4 - (prepared in situ) to give the corresponding [(COD)Rh(κ2-P,N-3a−c)]+BF4 - complex ([4a − c] + BF 4 - ; 87%, 96%, and 89% isolated yield, respectively). Whereas lithiation of 3-P i Pr2-indene followed by the addition of BrMn(CO)5 generated a complex mixture of products, similar reactions employing 0.25 equiv of [Cp*RuCl]4 or Cp*Li/FeCl2 afforded 6b or 6c in 98% and 43% yield, respectively. Treatment of 6b with 0.5 equiv of [(COD)RhCl]2 allowed for the isolation of (COD)RhCl(κ1-P-6b) 7 in 96% isolated yield. Each of [4a − c] + BF 4 - proved to be an active catalyst for addition of pinacolborane to styrene, with the observed regioselectivity being dependent on the nature of the η5-coordinated metal fragment, as well as the solvent employed. Single-crystal X-ray diffraction data for 2a, 2b, 2c, 3b, [4c] + BF 4 - , and 7 are provided.