NO bond length/stretching frequency realtionships in C-nitroso compounds and their coordination complexes

The mode of coordination of monomeric C-nitroso compounds to metals is discussed. In contrast to previous studies it is proposed that an understanding of the v(NO)/r(NO) and r(CN)/r(NO) relationships in the non-coordinated nitrosocompounds is of primary importance for assesment of the coordination mode. It is concluded that both v(NO)/R(NO) and r(CN)/r(NO) have linear interrelationships in C-nitroso compounds that the coordination compounds of RNO have the same v(NO)/r(NO) relationship as the non-coordinated monomers. Previous correlations of ?v(NO) with coordination mode are therefore correlations of r(NO) with coordination mode. s-N and s-O complexes of aromatic RNO conform to the same R(CN)/r(NO) equation (within a very small error) as the non-coordinated monomers. The extent of deviation from the r(CN)/(r(NO) relationship for complexes of aliphatic RNO is of a similar order of magnitude to that which occurs when C-nitroso monomers form the trans-dimer. The coordination mode of aliphatic RNO is, with one exception, s-N. Nitrosobenzene has a variety of coordination modes to transition metals but does not display s-O coordination. p-Nitrosodimethylaniline undergoes s-O coordination to d¹⁰ metals. © 1991.