Chemistry of polyfunctional molecules. 133. X-ray crystal structural, solid-state P-31 CP/MAS NMR, TOSS, P-31 COSYNMR, and mechanistic contributions to the co-ordination chemistry of octacarbonyldicobalt with the ligands bis(diphenylphosphanyl)amine, bis(diphenylphosphanyl)methane, and 1,1,1-tris(diphenylphosphanyl)ethane

Co-2(CO)(8) reacts with bis(diphenylphosphanyl)amine, HN(PPh2)(2) (Hdppa, 1 ), in two steps to afford the known compound [Co(CO)(Hdppa-kappa(2)P)(2)][C o(CO)(4)]. 2THF (6a . 2THF). The intermediate [Co(CO)(2)(Hdppa-kappa(2)P).( Hdppa-kappa(2)P)][Co(CO)(4)]. dioxane . n-pentane (5 . dioxane . n-pentane) was isolated for the first time and was characterized by X-ray analysis. T he cation 5(+) exhibits a slightly distorted trigonal-bipyramidal geometry. Detailed P-31-NMR investigations (solid-state CP/MAS NMR, TOSS, P-31-COSY, P-31-EXSY) showed that the additional tautomer [Co(CO)(2)(Hdppa-kappa(2)P) (Ph2P-N=P(H)Ph-2-kappa P)(+) (5'(+)) is present in solution. The tautomer equilibrium is slow in the NMR time scale. In contrast to the solid state o nly tetragonal pyramidal species of 5 are found in solution. At -90 degrees C there is slow exchange between the three diastereomeric species 5a(+)-5c (+). Compound 5 forms [Co(CO).(Hdppa-kappa(2)P)(2)]BPh4. THF (6b . THF) in THF with NaBPh4 under GO-Elimination. A X-ray diffraction investigation sho ws that the cation 6(+) consists of a slightly distorted trigonal-bipyramid al co-ordination polyeder. However, a distorted tetragonal-pyramidal struct ure has been found for the cation 7(+) of the related compound [Co(CO)(dppm )(2)][Co(CO)(4)]. 2 THF (7 . 2 THF; dppm = bis(diphenylphosphanyl)methane, Ph2PCH2PPh2). A comparison with the known [8] trigonal-bipyramidal stereois omer, ascertained for 7(+) of the solvent-free 7, is described. In solution s of 6a . 2 THF and 7 . 2 THF C-13{H-1}- and P-31{H-1}-NMR spectra indicate an exchange of all CO and organophosphane molecules between cobalt(I) cati on and cobalt(-I) anion. A concerted mechanism for the exchange process is discussed. CO elimination leads to discontinuance of the cyclic mechanism b y forming binuclear substitution products such as the isolated Co-2(CO)(2). (mu-CO)(2)(mu-dppm)(2). 0.8 (3) over bar THF (8 . 0.8 (3) over bar THF), wh ich was characterized by spectroscopy and X-ray analysis. For the dissolved [Co(CO)(2)CH3C(CH2PPh2)(3)][Co(CO)(4)]. 0.8 (3) over bar n-pentane (9a . 0 .8 (3) over bar n-pentane) no CO and triphos exchange processes between the cation and the anion are observed. Metathesis of 9a . 0.8 (3) over bar n-p entane with NaBPh4 yields [Co(CO)(2)CH3C(CH2PPh2)(3)]BPh4 (9b) which has be en characterized by single-crystal X-ray analysis. The cation shows a small distorted tetragonal-pyramidal structure.