A series of diazo complexes with the compositions M(N2R)L2 (M = Ni, L = t-BuNC; M = Pt, L = PPh3; N2R = N2C5C14, N2CsBr4) and Ru(CO)2(N2R)(PPh3)2 (N2R = N2C5C14, N2C5Br4, 9-diazofluorene, or 2, 7-dibromo-9-diazofluorene) has been prepared by the direct reaction of the given neutral diazo molecule with an appropriate transition-metal system. The complexes have been characterized spectroscopically and in the case of Ru(CO)2(N2C5Cl4)(PPh3)2-CH2Cl2 crystallographically. In this complex the tetrachlorodiazocyclopentadiene molecule is coordinated to the Ru atom in the η2 fashion. Some relevant metrical parameters are Ru-N(1) = 2.062 (4) Å, Ru-N(2) = 2.141 (5) Å, Ru-P(1) = 2.390 (2) Å, Ru-P(2) = 2.385 (2) Å, Ru-C(CO) = 1.886 (6) and 1.925 (6) Å, N(1)-N(2) = 1.224 (6) Å, N(1)-C(1) = 1.372 (7) Å, P(1)-Ru-P(2) = 168.80 (5)°, C-Ru-C(carbonyl) = 95.1 (2)°, N(1)-Ru-N(2) = 33.8 (2)°, and N(1)-N(2)-C(1) = 131.6 (5)°. The compound crystallizes with four formula units in the monoclinic space group C6 2h-P21/c in a cell of dimensions a = 14.66 (1) Å, b = 10.891 (7) Å, c = 26.73 (2) Å, and β = 94.11 (2)°. On the basis of 5728 unique reflections collected at -159 °C the structure was refined by full-matrix, least-squares techniques to a final value of the conventional R index of 0.057. The entire series of complexes shows a reduction of the N-N stretching frequency from ca. 2100 cm-4 in the free diazo molecules to ca. 1500 cm-1 in these complexes. The correspondence of these reduced stretching frequencies strongly suggests that in each of these complexes the diazo molecule has η2 coordination to the transition metal and may be described as 7t bound through the N-N multiple bond. Although the complexes Ni(N2R)(PPh3)2 (N2R = N2C5C14, N2C5H4) could not be isolated, they were generated in situ from Ni(C2H4)(PPh3)2 and the diazo molecule. Reaction of these diazo complexes with diethyl maleate at 100 °C did not produce cyclopropanation products; however with the N2C5H4 complex, an ylide, (triphenylphosphonium)cyclopentadienylidene, was obtained.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry