SYNTHESIS, STRUCTURES, AND REACTIVITY OF (R(6)-ACEN)ZRR'(2) AND (R(6)-ACEN)ZR(R')(+) COMPLEXES (R=H, F, R'=CH(2)CME(3), CH(2)PH

The synthesis, structures, and reactivity of neutral and cationic Zr(I V) alkyl complexes incorporating acen and hexafluoroacen ligands are d escribed. Alkane elimination reactions of H-2(R(6)-acen) (6a, R = F; 6 b, R = H) and ZrR'(4) afford (R(6)-acen)ZrR'(2) (11a, R = F, R'= CH(2) CMe(3); 11b, R = H, R'= CH(2)CMe(3); 12, R = F, R' = CH(2)Ph) in high yield. 11a has been characterized by X-ray diffraction: space group P ($) over bar 1, a 12.280(3) Angstrom, b = 12.731(3) Angstrom, c = 8.82 5(3) Angstrom, a = 96.66(2)degrees, beta = 97.21(2)degrees, gamma = 76 .68(2)degrees, V = 1327(1) Angstrom(3), Z = 2, R = 0.042, R(w) = 0.049 . 11a adopts a trigonal prismatic structure with a twisted F-6-acen li gand and a large angle (129.9(2)degrees) between the neopentyl groups. Solution NMR data for 11a,b and 12 are in accord with similar structu res. The reaction of 11a,b. with [HNMe(2)Ph][B(C6F5)(4)] yields cation ic amine adducts 6)-acen)Zr(CH(2)CMe(3))(NMe(2)Ph)][B(C6F5)(4)(13a, R = F; 13b, R = H). Similarly, the reaction of 11a with [HNEt(2)Ph][B(C6 F5)4] yields [(F-6-acen)Zr(CH2-CMe(3))(NEt(2)Ph)][B(C6F5)4] (14) Howev er, the reaction of 11a with [HNMePh(2)][B(C6F5)(4)] in benzene yields the base-free complex [(Fs-acen)Zr(CH(2)CMe(3))][B(C6F5)(4)] (15). Co mplex 14 decomposes in CH2Cl2 to [NEt(2)Ph(CH2Cl)][B(C6F5)(4)] (18), a n unusual chloride-bridged dinuclear cation {(F-6-acen)Zr(CH(2)CMe(3)) }(2)(mu-Cl)][B(C6F5)(4)] (19), and free NEt(2)Ph in 1:1:1.3 ratio. It is proposed that this reaction proceeds via nucleophilic attack of NEt (2)Ph on the CH2Cl2 ligand of an intermediate (F-6-acen)Zr(CH(2)CMe(3) )(CH2Cl2)(+) solvent adduct (formed by NEt(2)Ph dissociation from 14), followed by trapping of the resulting (F-6-acen>Zr(CH(2)CMe(3))-Cl (1 7) by a second equivalent of 14. 13a is stable toward this process bec ause the amine does not dissociate extensively. Direct chloride abstra ction from CH2Cl2 is not observed; base-free 15 is very stable in CH2C l2. 13a has been characterized by X-ray diffraction: space group = C2/ c, a = 39.707(4) Angstrom, b = 11.226(1) Angstrom, c = 30.045(3) Angst rom, beta = 126.667(9)degrees, V = 10742.6-(22) Angstrom(3), Z = 8, R = 0.0608, R(w) = 0.0880. The (F-6-acen)Zr(CH(2)CMe(3))(NMe(2)Ph)(+) ca tion of 13a adopts a distorted octahedral structure with a more planar F-6-acen ligand (vs that in 11a) and a large angle (144.7(2)degrees) between the neopentyl and amine ligands. 13a and 15 react with Lewis b ases to yield [(F-6-acen)Zr(CH(2)CMe(3))(L)(n)][B(C6F5)(4)] adducts (n = 1, PMe(2)-Ph (22); n = 2, L = PMe(3) (21), CH3CN (24)). 13a inserts CO, yielding a eta(2)-acyl cation Zr{eta(2)-C(=O)CH(2)CMe(3)}(NME(2)P h)][B(C6F5)(4)] (25, two isomers). 13a also reacts with 2 equiv of ben zophenone to yield an alkoxide ketone complex [(F-6-acen)Zr(OCPh(2)CH( 2)CMe(3))- (O=CPh(2))][B(C6F5)(4)] (26). Neither 13a nor 15 reads with ethylene or 2-butyne in the absence of Al cocatalysts.