The reaction of Li,[Me,Si(C,H,),] with 2 equivalents of [ZrLCI,] (L = C,Me, or C,H,But2) in toluene under reflux gave the known [{Zr(C,Me,)CI,},{p-Me,Si(C,H,),}] 1 and the new chloro derivative [{Zr(C,H,-But,)CI,},{p-Me,Si(C,H,),}] 2 in good yields. Addition of 4 equivalents of LiMe (or MgMeCI) to a pentane solution of 1 or 2 afforded the tetramethyl derivatives [{Zr(C,Me,) Me,},{p-Me,Si(C,H,),}]3 and [{Zr(C,H,But,) Me,},{p-Me,Si(C,H,),}] 4. Compound 3 is extremely moisture sensitive leading to the p-0x0 dinuclear complex [{Zr(C,Me,)Me},(p-O){p-Me,Si(C,H,),}] 5, as demonstrated by 'H N M R spectroscopy. Compound 4 reacted with water, in pentane or toluene, to give the p-0x0 dimethyl complex [{Zr(C,H,Bu',) Me},(p-O){p-Me,Si(C,H,),}] ' . I J. CHEM. SOC. DALTON 2 MC13 + Li2[Me2Si(C5H,)d -1 L = C5Me5 2 L = C5H3But2 Me, Me ' . f Me, Me ' . 1 5 L = C5Me5 3 L = C5M% 6 L = C5H3B~t2 4 L = C5H3But2 Scheme 1 (i) LiMe or MgMeC1; (ii) water