SYNTHESIS OF HIGHLY CROWDED CYCLOPENTADIENES VIA REACTIONS OF CP(2)NIAND CPSN(CH3)(3) WITH TRIARYLMETHYLHALOGENIDES - MOLECULAR-STRUCTURE OF 1-(CH3)(3)SI-(3-PH(3)C)-C5H4

Triphenylmethylcyclopentadiene Ph(3)CC(5)H(5) (1) and 2-[tris-(2'-meth oxyphenyl)methyl]cyclopentadiene 2-((2'-CH3OC6H4)(3)C)-C5H5 (2) have b een prepared in high yields via reactions of the corresponding triaryl methyl-halogenides with Cp(2)Ni (and CpSn(CH3)(3) in the case of 1). I t is shown that 3-tritylsubstituted 6,6-dimethylfulvene formed exclusi vely in the reaction between the lithium salt of 1 and acetone. Cyclop entadiene 2 exists only as the 2-triarylmethylsubstituted isomer in a mixture of two enantiomeric forms caused by the C-3v-asymmetry type in the relative orientation of the aryl groups. Cyclopentadiene 1-Si(CH3 )(3)-(3-Ph(3)C)-C5H4 was obtained by reaction of the sodium salt of 1 with (CH3)(3)SiCl; it crystallizes from hexane in the monoclinic space group P2(1)/c with cell dimensions a = 11.635(5), b = 12.400(7), c = 15.531(7) Angstrom, V = 2240.09(9) Angstrom(3) and Z = 4; the Si atom is in the allylic position with d(C-Cp-Si) = 1.891(8) Angstrom, Si-C(3 )-C(2) = 109.7(6)degrees, Si-C(3)-C(4) = 110.3(6)degrees, C(2)-C(3)-C( 4) = 100.2(7)degrees.