Cobalt-complexed conjugated diyne salts: A family of rigid masked dielectrophiles. Syntheses, structures, and double nucleophilic substitutions

A family of dicationic diyne salts of the general formula (Co-2(CO)(6))(2)- mu,eta (2),eta (2)-(Nu-CH2C dropC-C drop CCH2-Nu)]-[BF4](2) {Nu= SMe2 (3); Nu = NC6H7, 3-picoline, (5); Nu = NC9H7, quinoline (7)} were prepared and f ully characterized. Three X-ray molecular structures of 3, 5, and the neutr al starting material 2,4-hexadiyne-1,6-diol complex [(Co-2(CO)(6))(2)-mu,et a (2),eta (2)-(HO-CH2C dropC-C drop CCH2-OH)] (1) are presented. Complex 1 crystallizes in the triclinic space group P (1) over bar with a = 14.722(2) Angstrom, b = 14.571(3) Angstrom, c = 14.722(2) Angstrom, alpha = 105.17(1 )degrees, beta = 113.30(1)degrees, gamma = 99.20(1)degrees, and Z = 4. Comp lex 3 crystallizes in the monoclinic space group P2(1)/n with a = 12.758(3) Angstrom, b = 13.360(3) Angstrom, c = 20.494(3) Angstrom, beta = 91.44(1)d egrees, and Z = 4, and compound 5 also crystallizes in the monoclinic space group P2(1)/n with a = 9.426(2) Angstrom, b = 21.739(5) Angstrom, c = 18.7 04(3) Angstrom, beta = 94.86(1)degrees, and Z = 4. The X-ray structures pro vide us with valuable information on the arrangement of the Co-2-alkyne uni ts, which have a cis geometry and are in sharp contrast to that observed ge nerally for diyne-tetracobalt compounds. Complex [(Co-2(CO)(6))(2)-mu,eta ( 2),eta (2)-(Me2S-CH2C dropC-C drop CCH2-SMe2)][BF4](2) (3) reacts with N-, S-, and P-centered nucleophiles and affords the related substituted complex es in high yields. The stability and reactivity of the disulfonium diyne co mplex 3 toward nucleophiles are compared to those of the analogous disulfon ium-yne complex [(Co-2(CO)(6))(2)-mu,eta (2),eta (2)-(Me2S-CH2-C dropC-CH2- SMe2)][BF4](2) (4).