Reactions of di-isopropylcarbodi-imide with some ruthenium and osmium hydrides, leading to ready dehydrogenation of an isopropyl group; crystal and molecular structure of carbonylchloro(N-isopropenyl-N′-isopropylformamidinato)bis(triphenylphosphine)ruthenium(II)

Abstract

The reactions of PrⁱNCNPrⁱ with the complexes [RuH(X)(CO)(PPh₃)₃](X = Cl or Br) in boiling benzene involve insertion of the carbodi-imide moiety into the Ru–H bond and concomitant dehydrogenation of an isopropyl group to yield the derivatives [RuX{CH₂C(Me)N CH NCHMe₂}(CO)(PPh₃)₂]. A single-crystal X-ray diffraction study of the chloro-complex (X = Cl) has confirmed the presence of an N-isopropenyl-N′-isopropylformamidinate ligand in which the isopropenyl skeleton is essentially coplanar with, and conjugated to, the formamidinate group. The crystals are monoclinic, space group P2₁/a, with a= 17.836(2), b= 18.443(3), c= 12.607(1)Å, β= 104.59(3)°, and Z= 4. The structure has been solved via the heavy-atom method and refined by least squares using 4 381 observed [I > 1.5σ(l)] diffractometer intensities to a final R of 0.086. The octahedral molecule comprises two trans phosphines [Ru–P 2.383(4) and 2.400(4)Å], a chelating formamidinate ligand [Ru–N 2.048(10) and 2.242(10)Å], a carbonyl group [Ru–C 1.805(12)Å], and a chlorine atom [Ru–Cl 2.434(4)Å], the latter being trans to the more strongly bound nitrogen atom. The complex [OsH₂(CO)(PPh₃)₃] reacts with PrⁱNCNPrⁱ to afford the intermediate product [OsH(Me₂HCN CH NCHMe₂)(CO)(PPh₃)₂] which, on further heating, dehydrogenates to [OsH{CH₂C(Me)N CH NCHMe₂}(CO)(PPh₃)₂] in good yield.