SYNTHESIS OF 5-COORDINATE AND 6-COORDINATE ALKYLIDENE COMPLEXES OF THE TYPE MO(CHR)(NAR)[OCME(CF3)2]2SX AND THEIR USE AS LIVING ROMP INITIATORS OR WITTIG REAGENTS

Addition of a slight excess of 4-methoxy-1-hexene to Mo(CHCMe2Ph)(NAr)(ORF6)2 (1a) or Mo(CHCMe3)(NAr)(ORF6)2 (1b) in pentane (ORF6 = OCMe(CF3)2) yielded crystalline, red-orange anti-Mo[CHCH2CH(OMe)CH2CH3](NAr)(ORF6)2 (2). A similar reaction was used to prepare the difunctional complex anti-[(ArN)(ORF6)2Mo=CHCH2CH(OMe)]2C6H4(3). Styrene reacts with la or lb in DME over a period of 12 h to afford orange syn-Mo(CHPh)(NAr)-(ORF6)2(DME) (4) in good yield. 4-(Dimethylamino)styrene and 2,4,6-trimethoxystyrene react analogously to yield dark red syn-Mo(CH-4-C6H4-NMe2)(NAr)(ORF6)2 (DME) (5) and red anti-Mo[CH-2,4,6-C6H2-(OMe)3](NAr)(ORF6)2(DME) (6). 4 also can be synthesized from Mo(NAr)2Cl2(DME) via Mo(NAr)2(CH2Ph)2 and Mo(CHPh)(NAr)(OTf)2(DME). The reaction between 1 and 0.5 equiv of octatetraene in DME afforded syn-(DME)(RF60)2(ArN)Mo(CH)6-Mo(NAr)(ORF6)2(DME) (9a). A related complex, syn-(Et2O)(RF60)2(ArN)Mo(CH)6Mo(NAr)-(ORF6)2(Et2O) (9b), could be prepared directly in diethyl ether or by dissolving 9a in diethyl ether. anti-(THF)(RF60)2(ArN)Mo(CH)6Mo(NAr)(ORF6)2(THF) (9c) was observed upon dissolving 9a in THF. Addition of 4 equiv of LiO-t-Bu and 2 equiv of quinuclidine (quin) to 9a yields metallic green (quin)(t-BuO)2(ArN)Mo(CH)6Mo(NAr)(0-t-Bu)2(quin) (9d). 1,4-Divinylbenzene reacts smoothly with la or lb to give another conjugated difunctional alkylidene complex, 1,4-[(DME)(RF60)2(ArN)MoCH]2C6H4 (10a). Mo(CH2)(NAr)(ORF6)2(DME) (11a) could be generated and observed by H-1 NMR upon adding an excess of ethylene to a solution of lb in DME-d10 in a septum-sealed NMR tube. Addition of 2,2'-bipyridine (bpy) to 11a yielded isolable Mo(CH2)(NAr)(ORF6)2(bpy) (11b). 2,3-Dicarbomethoxynorbornadiene (100 equiv) could be polymerized in a living manner in DME using lb, 4, 5, 9a, 9b, or 10a as the initiator. 2,3-Bis(trifluoromethyl)norbomadiene (100 equiv) was also polymerized in a living manner by la in DME. Addition of an excess of LiO-t-Bu (8 equiv) to a solution of 3 in toluene, followed by 200 equiv of methyltetracyclododecene (MTD), gave low-polydispersity poly-MTD (M(W)/M(n) = 1.03) in 93% yield. Complexes 4,5,9a, 9b, and 10a react cleanly with pivaldehyde or benzaldehyde in CD2Cl2 or DME. A combination of Wittig reactions was used to prepare the di-tert-butyl-capped polyenes(t-Bu)(CH=CH)n(t-Bu)(n=4,6,8). The techniques described here should expand the opportunities for making polymers via living ROMP reactions and, in particular, should allow one to introduce conjugated sequences with a known, fixed length into a variety of polymers and to attach functional groups to both ends of a polymer.