The synthesis of group IV metallocene dichlorides with variable sterics, conformational mobility and geometric shapes.

New chiral doubly bridged bis(tetrahydroindenyl)zirconium dichloride 285 has been synthesized from chiral doubly bridged 284 in excellent yield. These complexes give access to rigid ansa-bis(indenyl)- and ansa-bis(tetrahydroindenyl)zirconium dichlorides. The structures of 284 and 285 were determined by X-ray diffraction and have confirmed the closed shape of these metallocene dichlorides.We have prepared several novel metallocene dichlorides bridged at the $7,7\sp\prime$ position of the indenyl moiety. The new metal complexes include the methylene bridged dl-bis(4,6-dimethylinden-7-yl) methylidenetitanium dichloride 349, and dl-bis(4,6-dimethylinden-7-yl)$\rbrack$methylidenezirconium dichloride 348 which were prepared from m-xylene. In addition, dl-1,2-bis(4-methylinden-7-yl)$\rbrack$ethylidene, dl-1,2-bis(4-isopropylinden-7-yl)$\rbrack$ethylidenezirconium dichlorides (dl-339) and (dl-340) and dl-1,2-bis(4-isopropylinden-7, yl)$\rbrack$ethylidenetitanium dichloride (dl-341) were synthesized from p-cymene and p-xylene, respectively. The structure of metallocene dichlorides dl-339, dl-340, and dl-341 were determined by X-ray crystallography and found to have $\rm C\sb1$-symmetry in the solid state, but in solution exhibit $\rm C\sb2$-symmetry as seen in their $\rm\sp1 H$ NMR spectra at room temperature. The synthesis of these new titanocene and zirconocene dichlorides will be discussed.$2,2\sp\prime$-$\rm Bis\lbrack 1$-(4,7-dimethyl-indenylmethyl)) -$1,1\sp\prime$-binaphthyltitanium and -zirconium dichlorides have been synthesized from $2,2\sp\prime$-bis(bromomethyl)-$1,1\sp\prime$-binaphthalene 221. $2,2\sp\prime$-Bis(bromomethyl)-$1,1\sp\prime$-binaphthalene 221 was alkylated with 4,7-dimethylindene 229 to yield $2,2\sp\prime$-$\rm bis\lbrack 1$-(4,7-dimethyl-indenylmethyl)$\rbrack$-$1,1\sp\prime$-binaphth alene (S)-(${\bf -}$)-212. The dilithio salts were formed and metallated with titanium trichloride and zirconium tetrachloride to give ansa-$\rm bis\lbrack 1$-(4,7-dimethyl-indenylmethyl)$\rbrack$-$1,1\sp\prime$-binaphth yltitanium dichloride (S)-(+)-232 and -zirconium dichloride 233