TY - JOUR
T1 - Structural and spectroscopic comparisons in two series of cobalt(III)-monodentate phosphine complexes
T2 - Trans-[Co(acac)2(PMe(3 - n)Ph(n))(H2O)]PF6 and trans-[Co(acac)2(PMe(3 - n)Ph(n))2]PF6 (acac = pentane-2,4-dionate; n = 0, 1, 2 and 3)
AU - Suzuki, Takayoshi
AU - Kaizaki, Sumio
AU - Kashiwabara, Kazuo
N1 - Funding Information:
The authors wish to thank Professor Claus E. Schäffer (University of Copenhagen) for valuable discussion. They appriciate the 31 P and 59 Co NMR measurements by Mr Seiji Adachi (Osaka University). The present work was supported in part by a Grant-in-Aid for Scientific Research Nos. 09740489 and 11640562 from Ministry of Education, Science, Sports and Culture, Japan.
PY - 2000/2/15
Y1 - 2000/2/15
N2 - The X-ray crystal structures and spectroscopic properties of two series of cobalt(III)-monodentate phosphine complexes, trans-[Co(acac)2(PM(3 - n)Ph(n)(H2O)]PF6 (na) and trans-[Co(acac)2(PMe(3 - n)Ph(n))2]PF6 (nb), have been compared in variation of methyl/phenyl substituents of phosphines. The Co-P bond lengths in complexes nb are found to be remarkably longer (> 0.095 Å) than those in the corresponding complexes na. Complex trans-[Co(acac)2(PPh3)(H2O)]PF6 (3a) shows an unusually long Co-P bond (2.243(1) Å) and an anomalous distortion of the equatorial acac planes, owing to a severe steric interaction associated with three phenyl rings of PPh3. It appears that the PPh3 in 3a is bound more closely to cobalt(III) in solution than in the solid state, as suggested by comparison of the absorption spectra of the solution and the solid. The ligand spectral parameters of phosphines, d(Co)(PMe(3-n)Ph(n)), are estimated by using the energy of the a1E(g) ← 1A(1g) transition, which is observed as an absorption band for complexes na or a broad shoulder for complexes nb, and evaluated in relation to the 59Co NMR chemical shifts. The estimated d(Co)(PMe(3 - n)Ph(n)) values indicate that the ligand-field strengths of the phosphines become considerably reduced as the number of phenyl substituents increases. Also, the ligand-field strengths of the phosphines in complexes nb are smaller than those in the corresponding complexes na. Furthermore, the low-lying (18500-25000 cm-1) LMCT band of complexes nb can be explained by the estimated parameters. (C) 2000 Elsevier Science S.A.
AB - The X-ray crystal structures and spectroscopic properties of two series of cobalt(III)-monodentate phosphine complexes, trans-[Co(acac)2(PM(3 - n)Ph(n)(H2O)]PF6 (na) and trans-[Co(acac)2(PMe(3 - n)Ph(n))2]PF6 (nb), have been compared in variation of methyl/phenyl substituents of phosphines. The Co-P bond lengths in complexes nb are found to be remarkably longer (> 0.095 Å) than those in the corresponding complexes na. Complex trans-[Co(acac)2(PPh3)(H2O)]PF6 (3a) shows an unusually long Co-P bond (2.243(1) Å) and an anomalous distortion of the equatorial acac planes, owing to a severe steric interaction associated with three phenyl rings of PPh3. It appears that the PPh3 in 3a is bound more closely to cobalt(III) in solution than in the solid state, as suggested by comparison of the absorption spectra of the solution and the solid. The ligand spectral parameters of phosphines, d(Co)(PMe(3-n)Ph(n)), are estimated by using the energy of the a1E(g) ← 1A(1g) transition, which is observed as an absorption band for complexes na or a broad shoulder for complexes nb, and evaluated in relation to the 59Co NMR chemical shifts. The estimated d(Co)(PMe(3 - n)Ph(n)) values indicate that the ligand-field strengths of the phosphines become considerably reduced as the number of phenyl substituents increases. Also, the ligand-field strengths of the phosphines in complexes nb are smaller than those in the corresponding complexes na. Furthermore, the low-lying (18500-25000 cm-1) LMCT band of complexes nb can be explained by the estimated parameters. (C) 2000 Elsevier Science S.A.
KW - Co NMR spectroscopy
KW - Cobalt(III) complexes
KW - Crystal structures
KW - Monodentate tertiary phosphines
KW - Spectral parameters
KW - Trans influence
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U2 - 10.1016/S0020-1693(99)00399-0
DO - 10.1016/S0020-1693(99)00399-0
M3 - Article
AN - SCOPUS:0034651446
SN - 0020-1693
VL - 298
SP - 131
EP - 140
JO - Inorganica Chimica Acta
JF - Inorganica Chimica Acta
IS - 2
ER -