Springer Online Journal Archives 1860-2000
Abstract The crystal and molecular structures of three derivatives of [(η 5-C5H4Me)Fe(CO)(L)I] [L=2,6-Me2C6H3NC, P(OMe)3, and P(C6H11)3] have been determined. [(η 5-C5H4Me)Fe(CO)(CNC6H3Me2-2,6)I] (1): Space groupP¯1,Z=2,a=13.193(7),b=8.183(5),c=7.465(4) Å,α=95.13(5),β=94.39(5), γ=91.09(5)°. [(η 5-C5H4Me)Fe(CO)[P(OMe)3]I] (2): Space groupP21/c,Z=4,a=7.296(3),b=24.471(6),c=8.877(3) Å,β=111.92(4)°. [(η 5-C5H4Me)Fe(CO)[P(C6H11)3]I] (3): Space groupP21/c,Z=4,a=9.809(3),b=14.147(2),c=8.276(3) Å,β=103.07(2)°. The structures were refined toR values of 0.045, 0.070, and 0.061, respectively. Disorder was observed in the P(OMe)3 ligands on2. Structural data for1 and3 reveal (i) a small movement of the Fe atom away from the ringC atom containing the methyl group, (ii) a larger movement of ring C atoms away from the ring least-squares plane for3 than for1, and (iii) a shift toward an allyl-ene bond length variation in the ring distances for3. Molecular mechanics calculations performed on2 produce a low-energy conformation similar to that found in the crystal structure determination of2 with an energy barrier to ring rotation of ±5 kcal mol−1. A correlation of the structural and molecular mechanics data with the nmr spectra of complexes1 to3 indicates that the steric influence ofL on the ring rotation could be due to ring distortion and/or interaction with the ring methyl group.
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