COORDINATION OF THE (MU-ETA(2)-AS-2) LIGAND TO GROUP-6 TRANSITION-METAL CARBONYL FRAGMENTS AND CRYSTAL-STRUCTURES OF CP(2)CR(2)(CO)(4)AS-2[M(CO)(5)](2) (M=CR, W)

[CpCr(CO)(2)](2)(mu-eta(2)-As-2) (1) reacts with 2 mol equiv. of M(CO) (5)(THF) to give the adducts [CpCr(CO)(2)](2)(mu-eta(2)-As-2)[M(CO)(5) ](2) (2A, M = Cr; 2B, M = W) in 55-60% isolated yields. The adducts ar e isostructural, possessing a crystallographic C-2 axis through the mi dpoints of the As-As and Cr-Cr bonds. Bonding parameters are indicativ e of a small degree of steric effects imposed by the coordinated M(CO) , fragments.