Synthesis and Reactivity of d⁰Alkyl, Silyl, and Hydride Complexes of Titanium and Zirconium Featuring an Aryl-Substituted Tripodal Triamido Ligand Derived fromcis,cis-1,3,5-Triaminocyclohexane

Zirconium and titanium complexes containing the new chelating triamido ligand [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ] 3 - ( 1 ) are reported. The chloride complexes [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]TiCl ( 2 ) and [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrCl ( 3 ) were prepared by reaction of TiCl 4 (THF) 2 and ZrCl 4, respectively, with [ 1 ]Li 3 (prepared in situ). The diethyl ether adduct of 3 ( 3 ·OEt 2 ) was crystallographically characterized. The alkyl complexes [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrCH 2 SiMe 3 ( 4 ) and [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrCH 2 Ph ( 5 ) were prepared by reaction of the triamine ([ 1 ]H 3 ) with Zr(CH 2 SiMe 3 ) 4 and Zr(CH 2 Ph) 4, respectively. The aryl complexes [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrPh ( 6 ) and [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrMes ( 7, Mes = 2,4,6-Me 3 C 6 H 2 ) were prepared by the reaction of 3 with PhLi and MesLi, respectively. Similarly, [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]TiMe ( 8 ) was prepared by the reaction of 2 with MeMgBr. The alkyl and aryl complexes 4 − 8 did not react with hydrosilanes to give isolable silyl complexes. The titanium and zirconium silyl complexes [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]TiSi(SiMe 3 ) 3 ( 9 ), [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrSi(SiMe 3 ) 3 ( 10 ), [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]TiSiHMes 2 ( 11 ), and [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrSiHMes 2 (THF) ( 12 ) were prepared by the reaction of the corresponding titanium and zirconium chloride complexes with either KSi(SiMe 3 ) 3 or LiSiHMes 2 (THF) 2 . Although the alkyl and aryl complexes 4 − 8 did not react appreciably with H 2 (1 atm), the silyl complexes 9 and 10 reacted with H 2 (1 atm) over the course of only a few minutes to give d 0 hydride products. Hydrogenolysis of 9 yielded the monohydride complex [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]TiH ( 13 ), which was characterized in solution. Complex 13 readily inserted 1-hexene to give the hexyl insertion product [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]TiHex ( 14 ). Hydrogenolysis of 10 yielded a mixture of monomeric and dimeric hydride products, [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrH ( 17a ) and {[ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrH} 2 ( 17b ), both of which were characterized in solution. Upon addition of 1 equiv of PMe 3, a mixture of 17a and 17b reacted to give the adduct [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrH(PMe 3 ) ( 15 ), which binds PMe 3 reversibly in solution. In the presence of 1-hexene, the mixture of 17a and 17b was readily converted to the hexyl insertion product, [ cis,cis -1,3,5-(3,5- t Bu 2 C 6 H 3 N) 3 C 6 H 9 ]ZrHex ( 16 ). The hydride species 13 and 17a / 17b undergo H/D exchange with D 2 but exhibit low reactivities toward hydrosilanes.