Synthesis of highly crowded cyclopentadienes via reactions of Cp2Ni and CpSn(CH3)3 with triarylmethylhalogenides. Molecular structure of 1-(CH3)3Si(3-Ph3C)C5H4

Abstract Triphenylmethylcyclopentadiene Ph 3 CC 5 H 5 ( 1 ) and 2-[tris-(2′-methoxyphenyl)methyl]cyclopentadiene 2-((2′-CH 3 OC 6 H 4 ) 3 C) C 5 H 5 ( 2 ) have been prepared in high yields via reactions of the corresponding triarylmethyl-halogenides with Cp 2 Ni (and CpSn(CH 3 ) 3 in the case of 1 ). It is shown that 3-tritylsubstituted 6,6-dimethylfulvene formed exclusively in the reaction between the lithium salt of 1 and acetone. Cyclopentadiene 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(CH 3 ) 3 -(3-Ph 3 C)-C 5 H 4 was obtained by reaction of the sodium salt of 1 with (CH 3 ) 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)A, V = 2240.09(9)A 3 and Z = 4; the Si atom is in the allylic position with d(C Cp Si) = 1.891(8)A,Si C(3) C(2) = 109.7(6)°,Si C(3) C(4) = 110.3(6)°,C(2) C(3) C(4) = 100.2(7)°.