Niobocene Alkyne Complexes: Synthesis and Characterization of Neutral and Cationic d2 Metal Alkyne Derivatives. X-ray Crystal Structure of [Nb(
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- 作者：Antonio Antiñ ; olo ; Antonio Otero ; Mariano Fajardo ; Cristina Garcí ; a-Yebra ; Carmen Ló ; pez-Mardomingo ; Avelino Martí ; n ; and Pilar Gó ; mez-Sal
- 刊名：Organometallics
- 出版年：1997
- 出版时间：June 10, 1997
- 年：1997
- 卷：16
- 期：12
- 页码：2601 - 2611
- 全文大小：391K
- 年卷期：v.16,no.12(June 10, 1997)
- ISSN：1520-6041
文摘
The paramagnetic niobocene alkyne complexesNb(
5-C5H4SiMe3)2(2(C,C)-RC
CR')(2)have been synthesized fromNb(5-C5H4SiMe3)2(2(C,C)-RCCR')(Cl)(1) and subsequentlyoxidized in the presence of different ligands to give stable cationicd2 derivatives, [Nb(5-C5H4SiMe3)2(2(C,C)-RCCR')(L)][BPh4](L = CH3CN, R = R' = Ph (3a); L =CH3CN, R =R' = CO2Me (3b); L =CH3CN, R = R' = Me (3c); L =CH3CN, R = Me, R' = CO2Me(3d);L = tBuCN, R = R' = Ph (4a); L = tBuCN, R = R' =CO2Me (4b); L = tBuCN, R = R' =Me(4c); L = tBuCN, R = Me, R' = CO2Me(4d); L = tBuNC, R = R' = Ph (5a); L =tBuNC, R= R' = CO2Me (5b); L = tBuNC, R =R' = Me (5c); L = THF, R = R' = Me (6c);L = THF,R = Me, R' = CO2Me (6d); L = Py, R= R' = Ph (7a); L = Py, R = R' = Me(7c)). Oxidationof the complexNb(5-C5H4SiMe3)2(2(C,C)-MeCCCO2Me)(2d) under different experimentalconditions gave rise to the divinylidene binuclear d2niobocene complex[(5-C5H4SiMe3)2(CO)Nb=C=C(CH3)(CH3)C=C=Nb(CO)(5-C5H4SiMe3)2][BPh4]2(8a). A mechanism involvingthe intermediacy of a 
-acetylide species is proposed for theformation of this compound.Thus, the divinylidene complex[(5-C5H4SiMe3)2(CO)Nb=C=C(Ph)(Ph)C=C=Nb(CO)(5-C5H4SiMe3)2][BPh4]2(8c) was easily synthesized by oxidation of thecorresponding Nb(III)alkynyl derivativeNb(5-C5H4SiMe3)2(CO)(CCPh)(13), obtained fromNb(5-C5H4SiMe3)2(CO)Cl and Mg(CCPh)2. Furthermore, theparamagnetic Nb(IV) complexes (2) undergoclean reactions with alkyl halides to give a mixture of bothalkyl-alkyne and halo-alkynecompounds. The former complexes,Nb(5-C5H4SiMe3)2(2(C,C)-RCCR')(R'')(R = R' = Ph,R'' = Me (9a); R = R' = R'' = Me (9c); R= H, R' = Ph, R'' = Me (9e); R = R' = Me, R''=Et (10c); R = R' = Me, R'' = CH2Ph(11c); R = H, R' = Ph, R'' = CH2Ph(11e); R = H, R' =Ph, R'' = CH2CH=CH2 (12e)),were also prepared by an alternative procedure in whichthecorresponding chloro derivatives 1 were reacted with theappropriate dialkylmagnesiumreagents. The structure of 11e was determined bysingle-crystal diffractometry.
5-C5H4SiMe3)2(2(C,C)-RCCR')(2)have been synthesized fromNb(5-C5H4SiMe3)2(2(C,C)-RCCR')(Cl)(1) and subsequentlyoxidized in the presence of different ligands to give stable cationicd2 derivatives, [Nb(5-C5H4SiMe3)2(2(C,C)-RCCR')(L)][BPh4](L = CH3CN, R = R' = Ph (3a); L =CH3CN, R =R' = CO2Me (3b); L =CH3CN, R = R' = Me (3c); L =CH3CN, R = Me, R' = CO2Me(3d);L = tBuCN, R = R' = Ph (4a); L = tBuCN, R = R' =CO2Me (4b); L = tBuCN, R = R' =Me(4c); L = tBuCN, R = Me, R' = CO2Me(4d); L = tBuNC, R = R' = Ph (5a); L =tBuNC, R= R' = CO2Me (5b); L = tBuNC, R =R' = Me (5c); L = THF, R = R' = Me (6c);L = THF,R = Me, R' = CO2Me (6d); L = Py, R= R' = Ph (7a); L = Py, R = R' = Me(7c)). Oxidationof the complexNb(5-C5H4SiMe3)2(2(C,C)-MeCCCO2Me)(2d) under different experimentalconditions gave rise to the divinylidene binuclear d2niobocene complex[(5-C5H4SiMe3)2(CO)Nb=C=C(CH3)(CH3)C=C=Nb(CO)(5-C5H4SiMe3)2][BPh4]2(8a). A mechanism involvingthe intermediacy of a -acetylide species is proposed for theformation of this compound.Thus, the divinylidene complex[(5-C5H4SiMe3)2(CO)Nb=C=C(Ph)(Ph)C=C=Nb(CO)(5-C5H4SiMe3)2][BPh4]2(8c) was easily synthesized by oxidation of thecorresponding Nb(III)alkynyl derivativeNb(5-C5H4SiMe3)2(CO)(CCPh)(13), obtained fromNb(5-C5H4SiMe3)2(CO)Cl and Mg(CCPh)2. Furthermore, theparamagnetic Nb(IV) complexes (2) undergoclean reactions with alkyl halides to give a mixture of bothalkyl-alkyne and halo-alkynecompounds. The former complexes,Nb(5-C5H4SiMe3)2(2(C,C)-RCCR')(R'')(R = R' = Ph,R'' = Me (9a); R = R' = R'' = Me (9c); R= H, R' = Ph, R'' = Me (9e); R = R' = Me, R''=Et (10c); R = R' = Me, R'' = CH2Ph(11c); R = H, R' = Ph, R'' = CH2Ph(11e); R = H, R' =Ph, R'' = CH2CH=CH2 (12e)),were also prepared by an alternative procedure in whichthecorresponding chloro derivatives 1 were reacted with theappropriate dialkylmagnesiumreagents. The structure of 11e was determined bysingle-crystal diffractometry.