The interaction of chlorides of V, Cr, Mo, and W with the lithium or Grignard reagents derived from chloromethyltri rn et h y 1 si I a n e produces the r m a I I y stab I e a I ky Is of form u I a V ( C H 2S i Me,) 1, VO ( C H , S i M e, ) 3, Cr ( C H , S i M e3) 4, and M,(CH2SiMe,)s ( M = Mo or W). The compounds have been investigated, where feasible, by i.r., Raman, electronic, e.s.r., and n.m.r. spectroscopy and the various spectral assignments are discussed in terms of proposed structures for the compounds.Laboratories, Imperial College, London SW7 2AY EARLY efforts to prepare simple alkyls and aryls of transition metals showed that, generally, these have low thermal stability.2 It has often been taken implicitly, and sometimes explicitly, that the transition metal to carbon bond is weak and that, following the preparation of the first extensive series of o-bonded alkyls and aryls3 in which additional ligands were present, the presence of ligands such as CO, x-C,H,, PR,, etc. may increase the strength. Thus, ( By any simple criterion, simple transition-metal alkyls are very unstable,' ( in contrast to the simple alkyls some metal complexes bearing other ligands in addition to alkyl and aryl groups are strikingly stable ' 4a and ( in these compounds [of type x-( C,H,),TiR,] the electronic energy levels of the metal are filled by x electrons of the 7 No reprints available.