UNUSUAL CHLOROPALLADATION OF 1,2,3-TRI-TERT-BUTYL-3-VINYL-1-CYCLOPROPENE TO GIVE AN ETA-3-(CHLOROMETHYL)CYCLOBUTENYL LIGAND - CRYSTAL-STRUCTURES AND MOLECULAR-STRUCTURES OF DI-MU-CHLOROBIS[(1-3-ETA)-4-ENDO-(CHLOROMETHYL)-1,2,3-TRI-TERT-BUTYLCYCLOBUTENYL]DIPALLADIUM AND TETRA-MU-CHLOROBIS[(1-3-ETA)-4-ENDO-(CHLOROMETHYL)-1,2,3-TRI-TERT-BUTYLCYCLOBUTENYL]TRIPALLADIUM

Treatment of [PdCl2(PhCN)(2)] with 1.5 equiv of 1,2,3-tri-tert-butyl-3-vinyl-1-cyclopropene (1) afforded the dimeric eta 3-cyclobutenyl compound 2. Although the reaction required only a 1:1 ratio of 1 to [PdCl2(PhCN)(2)], use of only a slight excess of vinylcyclopropene in the initial reaction solution resulted in a mixture of 2 and the tripalladium compound 3. Compound 2 converts to 3 in the presence of added [PdCl2(PhCN)(2)]. Solid state structures of 2 and 3 were determined by X-ray crystallography. 2: monoclinic, P2(1)/c, a = 14. 113(4) Angstrom, b = 11.032(3) Angstrom, c = 13.752(4) Angstrom; beta = 118.90(2)degrees, V = 1874.5(9) Angstrom(3), and Z = 2. 3: monoclinic, P2(1)/c, a = 14.923(3) Angstrom, b = 10.189(3) Angstrom, c = 17.559(5) Angstrom; beta = 111.24(2)degrees, V = 2488(1) Angstrom(3), and Z = 2. Both complexes contain the same cyclobutenyl ligand eta(3)-bound to palladium, with a pendant chloromethyl group on its endo face. The mechanism of formation of the endo-(chloromethyl)cyclobutenyl ligand is discussed.