TY - JOUR
T1 - Synthesis, Structure, and Solution Dynamics of (η5-2,4-Dimethylpentadienyl)Co[P(C2H5)3]2 and (anti-η3-2,4-Dimethylpentadienyl)Co[P(CH3)3]3
AU - Bleeke, John R.
AU - Peng, Wei Jun
PY - 1984/3
Y1 - 1984/3
N2 - Reaction of CoCl2 with P(C2H5)3, potassium 2,4-dimethylpentadienide, and a reducing agent (zinc dust or additional potassium 2,4-dimethylpentadienide) results in the formation of (η5-2,4-dimethylpentadienyl) Co[P(C2H5)3]2,1. The crystal structure of 1 has been determined by X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c with a = 7.928 (2) Å, b = 18.041 (7) Å, c = 15.592 (4) Å, β = 92.81 (2)°, and Z = 4. The two P(C2H5)3 ligands in 1 are oriented with one eclipsing the open edge and the other eclipsing the central carbon atom of the 2,4-dimethylpentadienyl ligand. The five cobalt-bound carbon atoms of the U-shaped 2,4-dimethylpentadienyl ligand are essentially coplanar. Reaction of ClCo[P(CH3)3]3 with potassium 2,4-dimethylpentadienide produces (anti-η3-2,4-dimethylpentadienyl) Co[P(CH3)3]3,2a. The crystal structure of 2a has been determined by X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c with a = 8.927 (2) Å,b = 15.008 (6) Å, c = 16.694 (4) Å,β = 104.33 (2)°, and Z = 4. The geometry about the cobalt atom approximates a square pyramid, with two of the allylic carbon atoms of the 2,4-dimethylpentadienyl ligand (C1 and C3) occupying adjacent basal sites, two of the P(CH3)3 phosphorus atoms (P1 and P2) occupying the remaining basal sites, and the final P(CH3)3 phosphorus atom (P3) residing in the axial site. The mouth of the allylic portion of the 2,4-dimethylpentadienyl ligand faces the axial P(CH3)3 ligand; as a result, the vinylic portion of the 2,4-dimethylpentadienyl ligand lies above the basal plane. The 2,4-dimethylpentadienyl ligand is U-shaped. However, it is not planar; the vinylic moiety is bent substantially out of the plane of the allylic moiety away from the cobalt atom. In solution, 2a equilibrates with its syn isomer, (syn-η3-2,4-dimethylpentadienyl) Co[P(CH3)3]3, 2b, producing a 70:30 mixture of 2a-2b. Spin saturation transfer NMR experiments suggest that the mechanism for interconversion of 2a and 2b involves a C3-bound (η1-2,4-dimethylpentadienyl) Co[P(CH3)3]3 intermediate.
AB - Reaction of CoCl2 with P(C2H5)3, potassium 2,4-dimethylpentadienide, and a reducing agent (zinc dust or additional potassium 2,4-dimethylpentadienide) results in the formation of (η5-2,4-dimethylpentadienyl) Co[P(C2H5)3]2,1. The crystal structure of 1 has been determined by X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c with a = 7.928 (2) Å, b = 18.041 (7) Å, c = 15.592 (4) Å, β = 92.81 (2)°, and Z = 4. The two P(C2H5)3 ligands in 1 are oriented with one eclipsing the open edge and the other eclipsing the central carbon atom of the 2,4-dimethylpentadienyl ligand. The five cobalt-bound carbon atoms of the U-shaped 2,4-dimethylpentadienyl ligand are essentially coplanar. Reaction of ClCo[P(CH3)3]3 with potassium 2,4-dimethylpentadienide produces (anti-η3-2,4-dimethylpentadienyl) Co[P(CH3)3]3,2a. The crystal structure of 2a has been determined by X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c with a = 8.927 (2) Å,b = 15.008 (6) Å, c = 16.694 (4) Å,β = 104.33 (2)°, and Z = 4. The geometry about the cobalt atom approximates a square pyramid, with two of the allylic carbon atoms of the 2,4-dimethylpentadienyl ligand (C1 and C3) occupying adjacent basal sites, two of the P(CH3)3 phosphorus atoms (P1 and P2) occupying the remaining basal sites, and the final P(CH3)3 phosphorus atom (P3) residing in the axial site. The mouth of the allylic portion of the 2,4-dimethylpentadienyl ligand faces the axial P(CH3)3 ligand; as a result, the vinylic portion of the 2,4-dimethylpentadienyl ligand lies above the basal plane. The 2,4-dimethylpentadienyl ligand is U-shaped. However, it is not planar; the vinylic moiety is bent substantially out of the plane of the allylic moiety away from the cobalt atom. In solution, 2a equilibrates with its syn isomer, (syn-η3-2,4-dimethylpentadienyl) Co[P(CH3)3]3, 2b, producing a 70:30 mixture of 2a-2b. Spin saturation transfer NMR experiments suggest that the mechanism for interconversion of 2a and 2b involves a C3-bound (η1-2,4-dimethylpentadienyl) Co[P(CH3)3]3 intermediate.
UR - https://www.scopus.com/pages/publications/0038625578
U2 - 10.1021/om00087a019
DO - 10.1021/om00087a019
M3 - Article
AN - SCOPUS:0038625578
SN - 0276-7333
VL - 3
SP - 1422
EP - 1426
JO - Organometallics
JF - Organometallics
IS - 9
ER -