Datensatz

Zusammenfassung

The coordinatively unsaturated (16e) (ethene)nickel(0) stannylene complex (C₂H₄)₂Ni=Sn{CH(SiMe₃)₂}₂ (1) reacts with 1,6-heptadiene with preservation of the Ni=Sn bond to yield quantitatively the 1,6-diene derivative (η²,η²-C₇H₁₂)Ni=Sn-{CH(SiMe₃)₂}₂ (2). The alkene ligands of both 1 and 2 are readily displaceable. Compounds 1 and 2 react with butadiene at −50°C by a 4-e oxidation of the metal-metal pair Ni(0)/Sn(II) to Ni(II)/Sn(IV) and concomitant reduction of two butadiene molecules to butenediyl moieties to afford stereo-selectively the 16-e complex Ni-cis-{η³(Ni),η¹(Sn)-anti-C₃H₄CH₂}₂Sn{CH(SiMe₃)₂}₂ (3). Similarly, the reaction of 1 or 2 with isoprene yields regio- and stereoselectively the derivative Ni-cis-{η³(Ni,η¹(Sn)-anti-C₃(3-Me)H₃CH₂}₂Sn{CH-(SiMe₃)₂}₂ (4). These reactions imply the cleavage of one formal Ni-Sn bond and the formation of two new Sn-C bonds. Upon reaction of 3 with PMe₃ the configuration of the allyl system changes and, again fully stereoselectively, the 18-e addition compound (Me₃P)Ni-cis-{η³(Ni),η¹(Sn)-syn-C₃H₄-CH₂}₂Sn{CH(SiMe₃)₂}₂ (5) is formed. When 5 is treated with BPh₃, the phosphane ligand is trapped and, kinetically controlled, Ni-cis-{η³(Ni),η¹(Sn)-syn-C₃H₄CH₂}₂Sn{CH(SiMe₃)₂}₂ (6) is obtained as a stereoisomer of 3. At 40°C 6 slowly rearranges into the thermodynamically stable stereoisomer Ni-trans-{η³(Ni),η¹(Sn)-syn-C₃H₄CH₂}₂Sn{CH(SiMe₃)₂}₂ (7). Mild protolysis of 3 with pyridine hydrochloride or hydrobromide affords region and stereoselectively (Me₃Si)₂CH}₂(X)SnNi-(η³-1-MeC₃H₄)(NC₅H₅) (X = C1, 8a; Br, 8b). In the course of this protonation reaction one butadiene molecule is eliminated, accompanied by a 2-e reduction of the metal-metal pair Ni(II)/Sn(IV) to Ni(II)/Sn(II) and, at the expense of two Sn-C bonds, reformation of a Ni-Sn bond. All compounds are isolated in high yield and fully characterized by ¹H-, ¹³C-, and ³¹P-NMR spectroscopy.