NO BOND LENGTH STRETCHING FREQUENCY RELATIONSHIPS 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 nu-(N-O)/r(N-O) and r(C-N)/r(N-O) relationships in the non-coordinated nitrosocompounds is of primary importance for assessment of the coordination mode. It is concluded that both nu-(N-O)/r(N-O) and r(C-N)/r(N-O) have linear interrelationships in C-nitroso compounds and that the coordination compounds of RNO have the same nu-(N-O)/r(N-O) relationship as the non-coordinated monomers. Previous correlations of DELTA-nu-(N-O) with coordination mode are therefore correlations of r(N-O) with coordination mode. sigma-N and sigma-O complexes of aromatic RNO conform to the same r(C-N)/r(N-O) equation (within a very small error) as the non-coordinated monomers. The extent of deviation from the r(C-N)/r(N-O) 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, sigma-N. Nitrosobenzene has a variety of coordination modes to transition metals but does not display sigma-O coordination. p-Nitrosodimethylaniline undergoes sigma-O coordination to d10 metals.