(BIS[BIS(TRIMETHYLSILYL)METHYL]STANNIO(II))BIS(ETA(2)-ETHENE)NICKEL(0) AND RELATED-COMPOUNDS .2.

The coordinatively unsaturated (16e) (ethene)nickel(0) stannylene complex (C2H4)(2)Ni=Sn{CH(SiMe(3))(2)}(2) (1) reacts with 1,6-heptadiene with preservation of the Ni=Sn bond to yield quantitatively the 1,B-diene derivative (eta(2),eta(2)-C7H12)Ni=Sn-{CH(SiMe(3))(2)}(2) (2). The alkene ligands of both 1 and 2 are readily displaceable. Compounds 1 and 2 react with butadiene at -50 degrees 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 stereoselectively the 16-e complex Ni-cis-{eta(3)(Ni),eta(1)(Sn)-anti-C3H4CH2}Sn-2{CH(SiMe(3))(2)}(2) (3) Similarly, the reaction of 1 or 2 with isoprene yields regio- and stereoselectively the derivative Ni-cis-{eta(3)(Ni), eta(1)(Sn)-anti-C-3(3-Me)H3CH2}Sn-2{CH-(SiMe(3))(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 PMe(3) the configuration of the allyl system changes and, again fully stereoselectively, the 18-e addition compound (Me(3)P)Ni-cis-{eta(3)(Ni),eta(1)(Sn)-syn-C3H4-CH2}Sn-2{CH(SiMe(3))(2)}(2) (5) is formed. When 5 is treated with BPh(3), the phosphane ligand is trapped and, kinetically controlled, Ni-cis-{eta(3)(Ni),eta(1)(Sn)-syn-C3H4CH2}2Sn{CH(SiMe(3)) (2)}(2) (6) is obtained as a stereoisomer of 3. At 40 degrees C 6 slowly rearranges into the thermodynamically stable stereoisomer Ni-trans-{eta(3)(Ni),eta(1)(Sn)-syn-C3H4CH2}Sn-2{CH(SiMe(3))(2)}(2) (7). Mild protolysis of 3 with pyridine hydrochloride or hydrobromide affords regio- and stereoselectively {(Me(3)Si)(2)CH}(2)(X)SnNi-(eta(3)-1-MeC(3)H(4))(NC5H5) (X=Cl, 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(TV) 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 H-1-, C-13-, and P-31-NMR spectroscopy.