Sterically demanding aryloxides as supporting ligands in organoactinide chemistry. Synthesis, structural characterization, and reactivity of Th(O-2,6-t-Bu(2)C(6)H(3))(2)(CH(2)SiMe(3))(2) and formation of the trimeric thorium hydride Th3H6(O-2,6-t-Bu(2)C(6)H(3))(6)

Reaction of ThBr4(THF)(4) with 2 equiv of KOAr (Ar = 2,6-t-Bu(2)C(6)H(3)) produces the bis(aryloxide) complex ThBr2(OAr)(2)(THF)(2) (1) in 67% yield. Alkylation of 1 with 2 equiv of Me(3)SiCH(2)MgCl allows the isolation of Th(OAr)2(CH(2)SiMe(3))(2) (2) in 61% yield. Thermolysis of 2 (benzene, 60 degrees C, 36 h) in the presence of NEt(3) results in the formation of the cyclometalated ligand redistribution product Th(OC6H3-t-BuCMe(2)CH(2))(OAr)(2) (3). Reaction of 2 with 1 equiv of 2,6-dimethylphenyl isocyanate leads to insertion into the Th-C bond to yield (ArO)(2)Th[OC(=NR)CH(2)SiMe(3)](CH(2)SiMe(3)) (4; R = 2,6-Me(2)C(6)H(3)) Aminolysis of 2 with 2 equiv of 2,6-diisopropylaniline allows the isolation of the bls(amido) species Th(OAr)(2)(NH2,6-i-Pr2C6H3)(2) (5) in 92% yield. 2 reacts with dihydrogen (1.5 atm) over a period of 7 days to form the trimeric dihydride complex Th-3(mu(3)-H)(2)(mu(2)-H)(4)(OAr)(6) (6) In the presence of 1 equiv of [HNMe(2)Ph][B(C6F5)(4)], 2 catalyzes the hydrogenation of 1-hexene (N-t = 1 h(-1)), while 6 is found to be a single-component catalyst for the analogous process (N-t = 3 h(-1)). Complexes 1-6 have been characterized by H-1 NMR and IR spectroscopy, microanalysis, and, in the case of 2 and 6, by single-crystal X-ray diffraction studies. 2 comprises a pseudotetrahedral thorium metal center bearing two aryloxide and two alkyl ligands. The O-Th-O angle between the aryloxide ligands (119.2(4)degrees) is significantly larger than the C-Th-C angle (101.4(6)degrees). Th-O and Th-C distances average 2.137(11) and 2.462(18)% respectively, while Th-C-Si angles are 125.9(8) and 122.8(8)degrees. The alkyl groups of 2 also display a reduced C-H coupling constant (J(CH) = 98 Hz), suggestive of cl-agostic interaction between the methylene group and the Th metal center. 6 exhibits a triangular arrangement of three thorium metal centers, each bearing two terminal aryloxide ligands. Two sides of the trimetallic core (Th-Th distances 3.781(1) and 3.818(1) Angstrom) are bridged by single mu(2)-hydride ligands, while the third side is bridged by two mu(2)-hydride ligands (Th-Th distance 3.588(1) Angstrom). Each face of the trimer is capped by a mu(3)-hydride ligand to produce a structurally unique M(3)(mu(3)-X)(2)(mu(2)-X)(4)X(6) geometry. Th-(mu(2)-H) and Th-(mu(3)-H) distances lie in the ranges 2.0(1)-2.3(1) and 2.3(1)-2.6(1) Angstrom, respectively, while Th-O distances range from 2.126(7) to 2.164(7) Angstrom.