The new complexes rner-[Cr(CO),(q'-L-L) (0-L-L)] [where L-L = Ph,PCH,PPh, (dppm), Ph,P-NHPPh, (dppa) or Ph,PNMePPh, (dppma)] were synthesized by treating [Cr(CO),(C,H,)] (C,H, = cyclohepta-l,3,5-triene) with the appropriate diphosphine. The complexes were characterized by i.r. and by 31P-{1H} and "H-{,lP} n.m.r. spectroscopy. The electrochemical and chemical oxidation of these complexes was investigated and the products identified by electrochemical techniques and by e.s.r. and i.r. spectroscopy. The one-electron oxidation of mer-[Cr( CO),(q2-L-L) (0-L-L)] gives the 17-electron chromium(i) complex mer-[Cr(CO),(q2-L-L)(o-L-L)] +. These chromium(i) complexes have only limited stability and have been shown to follow two reaction pathways, disproportionation (electron transfer) as in equation (i) and intramolecular displacement of CO as in equation (ii). The rates of these reactions increase markedly from L-L = dppm to dppa or dppma. A second one-electron oxidation process [equation (iii)] has been observed but the dications are very unstable and decompose to give solvated Cr2+, free diphosphine, and CO gas.
Solutions of LiNCS, NaNCS, KNCS and (Bu2N)NCS in methanol, at various concentrations and four temperatures, have been studied in the C-N stretching region by infrared spectroscopy. The spectra have been analysed to show t h e presence of a minimum of six species in solution, which are identified as t h e thiocyanate ion with 0, 1, 2 or 3 hydrogen bonds. It is proposed that t h e thiocyanate ion has donor sites for hydrogen bonding on both the nitrogen atom and on the n electron cloud. Some fine structure is observed in t h e spectra which indicates that there is also hydrogen bonding from the sulfur atom. In solutions of lithium thiocyanate an additional band was observed at ca. 2101 cm-', which is attributed to a contact ion pair in which the nitrogen atom is attached to Li+ and t h e sulfur atom is hydrogen bonded, or vice versa. Equilibrium constants for this ion-pair and for hydrogen bonding have been determined from the absorption intensity at ca. 2101 cm-'. There is evidence for t h e existence of solvent-shared ion pairs in solutions of LiNCS, NaNCS and KNCS.We have reported that lithium thiocyanate forms both contact ion pairs and solvent-shared ion pairs in acetonitrile solution.2 In other solvents monomeric, dimeric or tetrameric ion pairs have beenWe now report the results of a quantitative study of the thiocyanates of the Li+, Na+, K + and (Bu:N)+ cations in methanol solution using IR spectroscopy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.