2 Homometallic Alkoxides

Metal Aryloxides 469
Table 6.1 Metal–ligand bond lengths for mixed alkyl, aryloxides of niobium and
tantalum
Bond length ( ˚A)
Compound M–O M–C 1O,C ( ˚A) Ref.
[Ta⊲OC6H3Bu t 2 -2,6⊳2Me3] 1.930 (6)
1.945 (6)
2.14 (1)
2.14 (1)
2.25 (1)
[Ta⊲OC6H2Bu t 2 -2,6-OMe-4⊳2Me3] 1.925 (4) 2.151 (8)
2.169 (8)
[Nb⊲OC6H3Ph2-2,6⊳2⊲CH2C6H4Me-4⊳3] 1.915 (2)
1.917 (2)
[Ta⊲OC6H3Ph2-2,6⊳2⊲CH2C6H4Me-4⊳3] 1.903 (4)
1.906 (4)
[Ta⊲OC6H3Me2-2,6⊳2⊲CH2C6H5⊳3] 1.919 (4)
1.887 (4)
[Ta⊲OC6HPh2-2,6-Me2-3,5⊳2⊲CH2SiMe3⊳3] 1.89 (1)
1.90 (1)
[Ta⊲OC6HPh2-2,6-Pr i 2 -3,5⊳2⊲CH2SiMe3⊳3] 1.922 (3)
1.908 (3)
[Ta⊲OC6H3Ph2-2,6⊳3⊲CH2SiMe3⊳2] 1.912 (3)
1.918 (3)
1.930 (3)
[Ta⊲OC6H3Me2-2,6⊳3⊲C6H5⊳2] 1.848 (5)
1.879 (4)
[Ta⊲OC6H3Pri 2-2,6⊳3⊲C6H5⊳2] 1.852 (3)
1.881 (3)
1.880 (3)
2.219 (8)
2.181 (3)
2.181 (3)
2.192 (4)
2.154 (7)
2.192 (4)
2.181 (3)
2.204 (7)
2.204 (6)
2.10 (2)
2.16 (2)
2.13 (1)
2.121 (5)
2.130 (5)
2.180 (5)
2.090 (6)
2.122 (5)
0.24 i
0.25 i
0.27 ii
0.27 ii
0.30 iii
0.24 iv
0.23 iv
0.19 iv
2.181 (6) 0.32 v
2.206 (5)
2.209 (5)
0.34 v
[Ta⊲OC6H3Me2-2,6⊳4Me] 1.899 (4) 2.15 (1) 0.25 iii
iL. Chamberlain, J. Keddington, I.P. Rothwell, and J.C. Huffman, Organometallics, 1, 1538
(1982).
iiR.W. Chesnut, G.G. Jacob, J.S. Yu, P.E. Fanwick, and I.P. Rothwell, Organometallics, 10, 321
(1991).
iiiL.R. Chamberlain, I.P. Rothwell, K. Folting, and J.C. Huffman, J. Chem. Soc., Dalton Trans.,
155 (1987).
ivJ.S. Vilardo, M.A. Lockwood, L.G. Hanson, J.R. Clark, B.C. Parkin, P.E. Fanwick, and
I.P. Rothwell, J. Chem. Soc., Dalton Trans., 3353 (1997).
vB.D. Steffey, P.E. Fanwick, and I.P. Rothwell, Polyhedron, 9, 963 (1990).
distance found between alkyl and alkylidene derivatives of these metals, cf. distances
of 2.246 (12) ˚A and2.026 ⊲10⊳ ˚A in[Cp2Ta(CH2)(CH3)]. 179
In the case of tungsten there are a variety of eighteen electron aryloxides
to consider. Some examples include the carbonyl anions [W(OAr)(CO)5] , the
hydrido aryloxide [W(OPh)(H)3(PMe3)4], the cyclometallated derivatives [W(O-
1 -C6H4)(H)2(PMe3)4] and [W(O- 1 -C6H3Me-CH2)(H)2(PMe3)4] and the chelated
2,6-diphenylphenoxides [W(OC6H3Ph- 6 -C6H5)(H)(PMePh2)2] and [W(OC6H3Ph- 6 -
C6H5)(Cl)(PMePh2⊳2] (Table 6.3). For all these compounds the W–OAr distances fall