The Fischer carbyne complexes [(η-C 5R 5)(CO) 2WC( p-totyl)] (R = H ( 1c)) (R = Me ( 2c)) react with H 2B 2Et 4 to afford the boryl substituted η 3-benzyl complexes [(η-C 5R 5) (CO) 2W(α,1,2-η 3{α-BEt 2}( p-methyl)benzyl)] (R = H ( 5b)) (R = Me ( 6b)). On a column of silica, 5b is slowly converted to the η 3-benzyl complex [η-C 5H 5)(CO) 2W(α, 1,2-η 3-{( p-methyl)benzyl}] ( 7). Complex 5b crystallizes in the monoclinic space group P2 1/ n with a = 8.930(4), b = 14.490(8), c = 14.022(7) Å, β = 98.70° and Z = 4. The structure was refined to R = 0.026 using 2649 unique observed diffractometer data. Complex 6b crystallizes in the monoclinic space group P2 1/ a with a = 16.124(3), b = 8.728(2), c = 18.190(3) Å, β = 114.56(1)° and Z = 4. The structure was refined to R = 0.033 using 2064 unique observed diffractometer data. The gross structures of the two complexes are very similar, with α-BEt 2-( p- methyl)benzyl ligands bound in an α,1,2-η 3-enylic fashion to the tungsten atoms. In 6b, one of the ethyl substituents is disordered. In both derivatives there is a weak attractive interaction between the boron atom of the boryl group and the carbon atom of one of the carbonyl ligands. In solution, 5b exists as a mixture of two isomers. Extended Hückel (EH) and Fenske-Hall (FH) self-consistent field (SCF) molecular orbital (MO) calculations were conducted on several model complexes, [(η-C 5H 5)(CO) 2W(α,1,2-η 3-benzyl)] ( 9), [(η-C 5H 5)(CO) 2W{α,1,2-η 3-( anti-1-BH 2)allyl}] ( 10) and [(η-C 5H 5) (CO) 2W{α,1,2-η 3-( anti-α-BH 2)benzyl}] ( 11) as well as on 5b. The bonding of the η 3- benzyl ligand to the metal was found to be similar in all cases and comparable with [(η-C 5H 5)(CO) 2W(α,1,2- η 3-allyl)]. Bonding overlap between empty π orbitals on the boryl group and two of the four π* ligand group orbitals of the two CO molecules was found in 5b.