Preparation and Chemical Reactions of Metal Vinylidene Complexes Pending with Olefinic Functionality
Date Issued
2009
Date
2009
Author(s)
Huang, Yu-Hao
Abstract
The reactivity of a series of cationic metal alkenyl-vinylidene complexes of ruthenium and osmium containing the cyclopentadienyl and phosphine ligand are explored. The methoxyvinylidene complex [Ru]{=C=CHCH(OMe)CH2C(Me)2CH=CH2}[PF6] (7, [Ru] = (η5-C5H5)(PPh3)2Ru) was prepared by treatment of propargyl alcohol 2 with [Ru]-Cl in the presence of excess NH4PF6 in MeOH. Complex 7 in CH2Cl2 afforded the alkenyl-vinylidene complex [Ru]{=C=CHCH=CHC(Me)2CH=CH2}[PF6] (10a). When CH2Cl2 was used as a solvent system for the reaction of [Ru]-Cl with compound 2, the mixture of complex 10a and alkenyl-phosphonio complex [Ru]-{C≡CCH(PPh3)CH2C(Me)2CH=CH2}[PF6] (11) were obtained. At higher temperature, complex 10a is the predominant product. With external free phosphine as PPh3 source, complex 11 was obtained exclusively. From the reaction of 10a with NaOMe or Al2O3, the ruthenium acetylide complex [Ru]-C≡CCH=CHC(Me)2CH=CH2 (9-trans) was obtained. Similarly, the osmium acetylide complex [Os]-C≡CCH=CHC(Me)2CH=CH2 (9b) was also acquired by the depronation of complex 10b. Besides, the cationic metal vinylidene complexes [M]{=C=CRCH=CHC(Me)2CH=CH2}[PF6] (12, R = CH2CH=CH2, 13, R = CH2C≡CH, 14, R = (Ph)C=C(CN)2, 15a, R = CH2C(O)OMe3, 15b, R = CH2C(O)OCEt) were prepared by the alkylation reactions of the acetylide complexes [M]-C≡CCH=CHC(Me)2CH=CH2 (9-trans, M = Ru, 9b, M = Os). Reaction of the terminal alkynyl group of complex [Ru]{=C=C(CH2 C≡CH)CH=CHC(Me)2CH=CH2}[PF6] (13a) with [Ru]-Cl afforded the dinuclear bisvinylidene complex {[Ru]=C=C(CH=CHC(Me)2CH=CH2)CH2CH=C=[Ru]}[PF6]2 (16aa). Then complex [Os]{=C=C(CH2C≡CH)CH=CHC(Me)2CH=CH2}[PF6] (13b) was reacted with [Ru]-Cl and excess NH4PF6 in methanol at reflux to yield the dinuclear vinylidene complex {[Os]=C=C(CH=CHC(Me)2CH=CH2)CH2CH=C=[Ru]}[PF6]2 (16ba) under nitrogen atmosphere. Another dinuclear vinylidene complex {[Os]=C=C(CH=CHC(Me)2CH=CH2)CH2CH=C=[Os]}[PF6]2 (16bb) was synthesized by a similar method. Deportonation of complexes [Ru]{=C=C(CH2COOR)CH=CHC(Me)2CH=CH2}[PF6] (15a, R = Me, 15b, R = Et) in the presence of nBu4NOH gave neutral furyl complexes [Ru]-C=C(CH=CHC(Me)2CH=CH2)CH=C(O)OR (17a, R = Me, 17b, R = Et). When complexes 17a and 17b in toluene were heated to reflux under nitrogen for two day, the furyl complexes completely transformed into complexes 18 with an allylic ligand binding to the ruthenium center in a η3 binding mode. Treatment of complex 18b with HCl (1M, in diethyl ether) afforded the neutral complex (Cp)Ru[Ph2PC6H4{2η-CHC(CH=CHC(Me)2CH=CH2)CH2C(O)OEt}]Cl (19). Furthermore, treatment of complex 19 with HCl afforded a new Ru(IV) complex (20). Complex 18b also was protonated via HBF4 to yield complex 21 without coordination of a chloride ligand. Treatment of [Ru]-Cl with propargyl ether 4 or 6 in presence of NH4PF6 in CH2Cl2 afforded the ruthenium alkenyl-alkylidene complex [Ru]{=CHCH=CHCH2C(Me)2CH=CH2}[PF6] (22). Complex 22 in the presence of Al2O3 transformed to yield [Ru]-CH=CHCH=CHC(Me)2CH=CH2 (23). Complex 22 was also reacted with NaOMe to yield [Ru]-CH=CHCH(OMe)CH2C(Me)2CH=CH2 (24). The product from treatment of complex 22 with sodium methoxide is not the same as the product obtained from passing complex 22 through a neutral Al2O3 column. The neutral alkenyl complex 24 was obtained in good yields in MeOH. The methoxy group of complex 24 is considered as a good leaving group and is eliminated leading to complex 23 under basic condition. Treatment of complex 23 with malononirtile in CH2Cl2 led to the neutral alkenyl complex [Ru]-{CH=CHCH(CH(CN)2)CH2C(Me)2CH=CH2} (25) which was formed by addition of malononitrile to 23. Differently, treatment of [Os]-Br ([Os] = (η5-C5H5)(PPh3)2Os) with propargyl alcohol 2 or propargyl ether 4 and 6 in the presence of excess NH4PF6 in MeOH or CH2Cl2 generated exclusively the osmium alkenyl-vinylidene complex [Os]{=C=CHCH=CHC(Me)2CH=CH2}[PF6] (10b). We also successfully synthesized 6,6-dimethyl-4-ethynyl-octa-1,7-dien-4-ol dieneyne 26a and 6,6- dimethyl-2-methyl-4-ethynyl-octa-1,7-dien-4-ol 26b which can be regarded as a combined 1,5-enyne and 1,6-enyne. The σ-arene complexes 27 were obtained from the mixture of [Ru]-Cl, NH4PF6 and dieneyne compounds 26a or 26b in MeOH. The formation of σ-arene complexes 27 is via a cyclization of the dienylvinylidene complexes.
Subjects
Ruthenium
vinylidene
ortho-metalation reaction
furyl
Type
thesis
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