U(2),ETA(2)-ALKYNYL-HEXACARBONYLDICOBALT]ORGANOTIN COMPLEXES AND THE MOLECULAR-STRUCTURE OF (2)-ETA(2)-ETHYNYLHEXACARBONYLDICOBALT]DIPHENYLTIN

mu(2)-,eta(2)-alkynyl-hexacarbonylcobalt]organotin complexes of the ty pe (mu(2)-,eta(2)-HC2SnR3)Co-2(CO)(6) (R=Et (fb), Bu-t (Tc)), R2Sn[(mu (2)-,eta(2)-C2H>Co-2(CO)(8)](2) (R = Me (2a), Et (2b), Bu-t (2c), Ph ( 2d)), Me4-nSn[(mu(2)-,eta(2)-C2Me)Co-2(CO)(8)](n) (n = 1 (3), 2 (4), 3 (5)), and MeC=CSn[(mu(2)-,eta(2)-C2Me)Co-2(CO)(8)] (6) were prepared and studied by H-1, C-13 and Sn-119 NMR. The signs of coupling constan ts (1)J(Sn-119,C-13) < 0, (2)J(Sn-119,C-13(cluster))> 0, (3)J(Sn-119,H -1(cluster)) > 0 were determined for these complexes by modified 2D H- 1 detected H-1/Sn-119 and H-1/C-13 heteronuclear shift correlations. T he molecular structure of 2c was determined by X-ray structural analys is (orthorhombic; space group Pbca; a = 19.46(1) Angstrom, b = 15.992( 7) Angstrom, c = 20.10(I) Angstrom, Z= 8). The bond angles at the subs tituted carbon atoms of the dicobaltatetrahedrane Sn-C(I)-C(2) (151.3( 3)degrees) and Sn-C(3)-C(4) (150.5(5)degrees) are significantly larger than in all other known molecular structures of dicoboltatetrahedrane s.