Trindenyl Trimolybdenum and Tritungsten Complexes: Crystal Structure of (trindenyl)[(OC)3W–W(CO)3]W(CO)3Bn

Trindenyl trimolybdenum and tritungsten complexes, syn,syn,anti-Td­[M­(CO)3R]3 (Td = dihydro-1H-trindene trianion; M = Mo, W; R = methyl, benzyl, p-xylyl), have been prepared where two M­(CO)3R groups are forced into close proximity by bonding to the same side of the trindenyl ligand. Intramolecular Mo–Mo and W–W bonds form readily either photochemically or thermally between the two syn-M­(CO)3 groups of Td­[M­(CO)3R]3, exclusive of any intermolecular M–M bond formation. The intramolecular W–W bond-forming reaction of Td­[W­(CO)3benzyl]3, as enforced by the trindenyl ligand, is 148 times faster than the intermolecular W–W bond-forming reaction of (cyclopentadienyl)­W­(CO)3benzyl. The crystal structure of the W–W product, Td­[(OC)3W–W­(CO)3]­W­(CO)3benzyl, was determined: orthorhombic, Pn21a, a = 29.188(8) Å, b = 10.387(3) Å, c = 9.599(3) Å, V = 2910.2(15) Å3, Z = 4, R1 = 3.93%. The W–W bond length of 3.276(2) Å is among the longest W–W bonds reported. The trindenyl ligand is twisted from planarity by 19.1°, which allows the carbonyl ligands on the adjacent tungsten atoms to be staggered.