Mixed alkyl isocyanide-1,4-diaza-1,3-butadiene complexes of molybdenum(II) and tungsten(II)

Abstract

The reactions of M(CO) 4(R′-DAB) (M = Mo) or W; R′-DAB = R′-NCHCHNR′ (R′ = i-propyl, t-butyl, or cyclohexyl) with SnCl 4 in dichloromethane solution result in the formation, in high yield, of the orange, diamagnetic, seven-coordinate oxidative-addition products M(CO) 3(R′-DAB)(SnCl 3)Cl. The reactions of Mo(CO) 3(R′-DAB)(SnCl 3)Cl (R′ = i-Pr or Cy) with an excess of alkyl isocyanide RNC (R = CHMe 2, CMe 3, or C 6H 11) in the presence of KPF 6 lead to the formation of [Mo(CNR) 4(R′-DAB)Cl]PF 6 or [Mo(CNR) 5(R′-DAB)](PF 6) 2 depending upon the reaction stoichiometry and reaction conditions. The monocationic chloro species are converted to [Mo(CNR) 5(R′-DAB)](PF 6) 2 upon reflux with the stoichiometric amount of RNC. Under similar reactions conditions M(CO) 3(t-Bu-DAB)(SnCl 3)Cl (M = Mo or W) derivatives react with alkyl isocyanides with the reductive-elimination of the elements of SnCl 4 and the formation of octahedral M(CO) 3(CNR)(t-Bu-DAB). The dark red compounds [Mo(CNCMe 3) 5(R′-DAB)](PF 6) 2 (R′ = i-Pr or Cy) react readily with cyanide ions at ambient temperatures in methanol to yield [Mo(CNCMe 3) 4(R′-DAB)(CN)]PF 6. Attempts to thermally dealkylate the parent complexes [Mo(CNCMe 3) 5(R′-DAB)](PF 6) 2 (R′ = i-Pr or Cy) to these same cyano species were unsuccessful.