Notes. Carbon-13 nuclear magnetic resonance study of the properties of the unsaturated anion [Re3(µ-H)4(CO)9(NCMe)]– at low temperature

Abstract

The carbonyl resonances of [Re₃(µ-H)₄(CO)₉(NCMe)]^– have been assigned and the ¹³C spin–lattice relaxation times measured at different field strengths (20.15,50.31, and 75.43 MHz) at 238 K. The results indicate that scalar coupling of the second kind with rhenium isotopes is the dominant relaxation mechanism at this temperature. Values of T₁^Q(Re) and ¹J(¹⁸⁷Re–C) were calculated. The presence on the H₂Re(CO)₃(NCMe) moiety of a poor π-acceptor ligand doubles ¹J(¹⁸⁷Re–C) with respect to the unsubstituted H₂Re(CO)₄ moiety in the precursor [Re₃(µ-H)₄(CO)₁₀]^–.