Insertion and C-H Bond Activation of Unsaturated Substrates by Bis(benzamidinato)yttrium Alkyl, [PhC(NSiMe3)2]2YR (R = CH2Ph·THF, CH(SiMe3)<
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- 作者：Robbert Duchateau ; Cornelis T. van Wee ; and Jan H. Teuben
- 刊名：Organometallics
- 出版年：1996
- 出版时间：April 30, 1996
- 年：1996
- 卷：15
- 期：9
- 页码：2291 - 2302
- 全文大小：445K
- 年卷期：v.15,no.9(April 30, 1996)
- ISSN：1520-6041
文摘
The reactivity of benzamidinate-stabilized yttrium complexes[PhC(NSiMe3)2]2YR (R=CH2Ph·THF,CH(SiMe3)2) and{[PhC(NSiMe3)2]2Y(
-H)}2has been investigated. Thecomplexes are thermally stable showing no sign of decomposition, ligandor solventmetalation, or H/D exchange after hours at 100 
C incyclohexane-d12 orbenzene-d6. Thealkyls are also stable in ethereal solvents. However,{[PhC(NSiMe3)2]2Y(-H)}2induces C-Ocleavage in THF solutions. The complexes[PhC(NSiMe3)2]2YCH2Ph·THFand {[PhC(NSiMe3)2]2Y(-H)}2are modestly active in ethylene polymerization but are inactivetowardpropylene and 1-hexene. Terminal alkynes react stoichiometricallywith[PhC(NSiMe3)2]2YCH(SiMe3)2 and{[PhC(NSiMe3)2]2Y(-H)}2to give -acetylide dimers,{[PhC(NSiMe3)2]2Y(-C
CR)}2 (1, R = H; 2, R =Me; 3, R = n-Pr; 4, R =SiMe3; 5, R = Ph; 6, R =CMe3).Treatment with THF leads to cleavage of these dimers, yielding[PhC(NSiMe3)2]2YCCR·THF (7, R = H; 8, R = CMe3).[PhC(NSiMe3)2]2Y(-Me)2Li·TMEDAreacts with HCCCMe3to afford[PhC(NSiMe3)2]2Y(-CCCMe3)2Li·TMEDA.[PhC(NSiMe3)2]2YCH(SiMe3)2catalyzesthe regioselective dimerization of bulky 1-alkynes. With small1-alkynes, HCCR (R = H,Me, n-Pr), no dimerization was observed and the reactionstops with the formation of thealkynyl dimers{PhC(NSiMe3)2]2Y(-CCR)}2(1-3). Treatment of[PhC(NSiMe3)2]2YRwithacetonitrile gives either C-H bond activation or insertion. ForR = CH(SiMe3)2, C-H bondactivation occurs, yielding{[PhC(NSiMe3)2]2Y(-(N,N ')-N(H)C(Me)=C(H)CN)}2(10). ForR = CH2Ph·THF a mixture of C-H bondactivation (10, 10%) and insertion products,{[PhC(NSiMe3)2]2Y(-N=C(Me)CH2Ph)}2(11a, 50%) and{[PhC(NSiMe3)2]2Y(-N(H)C(Me)=C(H)Ph)}2 (11b, 40%), was obtained. Thehydride{[PhC(NSiMe3)2]2Y(-H)}2exclusively givesinsertion of acetonitrile, affording{[PhC(NSiMe3)2]2Y(-N=C(H)Me)}2(12). With pyridine,[PhC(NSiMe3)2]2YCH(SiMe3)2gives C-H bond activation, whereas[PhC(NSiMe3)2]2YCH2Ph·THF and{[PhC(NSiMe3)2]2Y(-H)}2undergo insertion yielding[PhC(NSiMe3)2]2Y(NC5H5R) (13, R = H; 14,R = CH2Ph). In contrast, with 
-picoline,[PhC(NSiMe3)2]2YR(R= CH(SiMe3)2,CH2Ph·THF) and{[PhC(NSiMe3)2]2Y(-H)}2afford the -picolyl derivative,[PhC(NSiMe3)2]2Y(
2-(C,N)-2-CH2NC5H4(15). The difference in reactivity of thebis(benzamidinate)-stabilized complexes compared to the correspondingCp*2YR systems, e.g.the low tendency to catalyze C-C bond formation, the reduced or eventhe absence of C-H/C-O activation properties, and the enhanced nucleophilic and Br
nstedbase reactivities,is interpreted in terms of the high ionicity of thebenzamidinate-stabilized yttrium complexes.The contracted yttrium orbitals are less exposed than in thedicyclopentadienyl derivativesand therefore not suited to establish the first initiating interactionwith substrate molecules.
-H)}2has been investigated. Thecomplexes are thermally stable showing no sign of decomposition, ligandor solventmetalation, or H/D exchange after hours at 100 C incyclohexane-d12 orbenzene-d6. Thealkyls are also stable in ethereal solvents. However,{[PhC(NSiMe3)2]2Y(-H)}2induces C-Ocleavage in THF solutions. The complexes[PhC(NSiMe3)2]2YCH2Ph·THFand {[PhC(NSiMe3)2]2Y(-H)}2are modestly active in ethylene polymerization but are inactivetowardpropylene and 1-hexene. Terminal alkynes react stoichiometricallywith[PhC(NSiMe3)2]2YCH(SiMe3)2 and{[PhC(NSiMe3)2]2Y(-H)}2to give -acetylide dimers,{[PhC(NSiMe3)2]2Y(-CCR)}2 (1, R = H; 2, R =Me; 3, R = n-Pr; 4, R =SiMe3; 5, R = Ph; 6, R =CMe3).Treatment with THF leads to cleavage of these dimers, yielding[PhC(NSiMe3)2]2YCCR·THF (7, R = H; 8, R = CMe3).[PhC(NSiMe3)2]2Y(-Me)2Li·TMEDAreacts with HCCCMe3to afford[PhC(NSiMe3)2]2Y(-CCCMe3)2Li·TMEDA.[PhC(NSiMe3)2]2YCH(SiMe3)2catalyzesthe regioselective dimerization of bulky 1-alkynes. With small1-alkynes, HCCR (R = H,Me, n-Pr), no dimerization was observed and the reactionstops with the formation of thealkynyl dimers{PhC(NSiMe3)2]2Y(-CCR)}2(1-3). Treatment of[PhC(NSiMe3)2]2YRwithacetonitrile gives either C-H bond activation or insertion. ForR = CH(SiMe3)2, C-H bondactivation occurs, yielding{[PhC(NSiMe3)2]2Y(-(N,N ')-N(H)C(Me)=C(H)CN)}2(10). ForR = CH2Ph·THF a mixture of C-H bondactivation (10, 10%) and insertion products,{[PhC(NSiMe3)2]2Y(-N=C(Me)CH2Ph)}2(11a, 50%) and{[PhC(NSiMe3)2]2Y(-N(H)C(Me)=C(H)Ph)}2 (11b, 40%), was obtained. Thehydride{[PhC(NSiMe3)2]2Y(-H)}2exclusively givesinsertion of acetonitrile, affording{[PhC(NSiMe3)2]2Y(-N=C(H)Me)}2(12). With pyridine,[PhC(NSiMe3)2]2YCH(SiMe3)2gives C-H bond activation, whereas[PhC(NSiMe3)2]2YCH2Ph·THF and{[PhC(NSiMe3)2]2Y(-H)}2undergo insertion yielding[PhC(NSiMe3)2]2Y(NC5H5R) (13, R = H; 14,R = CH2Ph). In contrast, with -picoline,[PhC(NSiMe3)2]2YR(R= CH(SiMe3)2,CH2Ph·THF) and{[PhC(NSiMe3)2]2Y(-H)}2afford the -picolyl derivative,[PhC(NSiMe3)2]2Y(2-(C,N)-2-CH2NC5H4(15). The difference in reactivity of thebis(benzamidinate)-stabilized complexes compared to the correspondingCp*2YR systems, e.g.the low tendency to catalyze C-C bond formation, the reduced or eventhe absence of C-H/C-O activation properties, and the enhanced nucleophilic and Brnstedbase reactivities,is interpreted in terms of the high ionicity of thebenzamidinate-stabilized yttrium complexes.The contracted yttrium orbitals are less exposed than in thedicyclopentadienyl derivativesand therefore not suited to establish the first initiating interactionwith substrate molecules.