I +-abstraction versus I −-displacement in the reactions of diiodocethylene with metal carbonyl anions: X-ray structure of [(OC) 5MneCCMn(CO) 5

Abstract

Solid diiodoacetylene, ICCI, reacts with THF solutions of the highly basic, third row, metal carbonyl anion, RE(CO) 5 −, exclusively by a formal I +-abstraction process producing ReI(CO) 5 and Re 2I 2(CO) 8. Under the same conditions, the less basic, first row, metal carbonyl anion, Mn(CO 5 − reacts to produce not only Mn 2I 2(CO 8) by formal I +-abstraction but also (OC) 5MnCCMn(CO 5 by I −-displacement. These results may be rationalized by HSAB arguments and consideration of charge distribution in the substrate as indicated by molecular orbital calculations. The X-ray structure of (OC) 5MnCCMn(CO) 5 is reported. Crystals are triclinic, space group P 1 , with Z = 1 in a unit cell of dimensions a 6.421(2), b 6.425(2), c 9.520(2) Å, α 81.86(2), β 88.55(2), γ 82.06(2)°, and D calc 1.79 g cm −3. The structure was solved by the Patterson and Fourier methods and refined by full-matrix least squares to R = 0.024, R w = 0.033 for 1372 observed reflections with F 2 o > 30σ( F 2 o). The complex is centrosymmetric and thus exhibits an eclipsed in the solid state.