MOLYBDENUM AND TUNGSTEN CYCLOPENTADIENONE COMPLEXES .1. SYNTHESIS ANDCHARACTERIZATION

The labile complexes M(CO)(3)(CH3CN)(3)(M = Mo, W) undergo facile oxid ative addition reactions with 4-bromo-2-cyclopentenone to give M(eta(3 )-C5H5O)(CO)(2)(CH3CN)(2)Br 1a and 2. Complex 1a crystallizes in space group P2(1)/m (No. 11) with a = 8.631 (2) Angstrom, b = 12.852 (3) An gstrom, c = 6.659 (2) Angstrom, beta = 109.27 (1)degrees, V = 697.3 (3 ) Angstrom(3), and Z = 2. The structure was refined to R(F) = 0.023 (F greater than or equal to 4 sigma F). 1 and 2 react with potassium tri s(pyrazolyl)borate (K[HBpz(3)]), 2,2'-bipyridyl (bipy), and bis(diphen ylphosphino)methane (dppm) to give neutral eta(3)-cyclopentenoyl compl exes of types M(eta(3)-C5H5O)(CO)(2)(HBpz(3)) 3a and 4, M(eta(3)-C5H5O )(CO)(2)(bipy)-Br 5 and 6, and M(eta(3)-C5H5O)(CO)(2)(dppm)Br 7 and 8, respectively, in high yields. Single crystal structural studies have been carried out for complexes 3a, 4, and 8. 3a crystallizes in space group Pbca (No. 61) with a = 19.819 (3) Angstrom, b = 13.899 (3) Angst rom, c = 13.088 (2) Angstrom, V = 3605 (1) Angstrom(3), and Z = 8, and the structure was refined to R(F) = 0.026 (F greater than or equal to 4 sigma F). 4 is isostructural with 3a and crystallizes in space grou p Pbca (No. 61) with a = 19.726 (6) Angstrom, b = 13.924 (6) Angstrom, c = 13.080 (4) Angstrom, V = 3593 (2) Angstrom(3), and Z = 8, and the structure was refined to R(F) = 0.028 (F greater than or equal to 4 s igma F). 8 crystallizes in space group <P(1)over bar> (No. 2) with a = 10.143 (3) Angstrom, b = 10.972 (4) Angstrom, c = 13.708 (5) Angstrom , alpha = 82.52 (2)degrees, beta = 85.07 (2)degrees, gamma = 84.77 (1) degrees, V = 1502.0 (9) Angstrom(3), and Z = 2. The structure was refi ned to R(F) = 0.029 (F greater than or equal to 4 sigma F). Treatment of complexes 3-8 with Ph(3)C(+)PF(6)(-) in methylene chloride solution led to facile hydride abstraction and formation of the stable cationi c eta(4)-cyclopentadienone complexes [M(eta(4)-C5H4O)(CO)(2) (HBpz(3)) ]PF6 9a and 10, [M(eta(4)-C5H4O)(CO)(2)(bipy)Br]PF6 11 and 12, and [W( eta(4)-C5H4O)(CO)(2)(dppm)Br]PF6 (13). Complex 10 has been found to cr ystallize in space group Pcab (No. 61) with a = 18.242 (4) Angstrom, b = 17.145 (4) Angstrom, c = 13.188 (3) Angstrom, V = 4125 (2) Angstrom (3), and Z = 8. The structure was refined to R(F) = 0.029 (F greater t han or equal to 4 sigma F). 13 crystallizes in space group P2(1)/n (No . 14) with a = 11.796 (3) Angstrom, b = 17.512 (7) Angstrom, c = 17.21 0 (5) Angstrom, beta = 93.67 (1)degrees, V = 3548 (2) Angstrom(3), and Z = 4. The structure was refined to R(F) = 0.040 (F greater than or e qual to 4 sigma F).