Heterometallic polyhydride complexes containing yttrium hydrides with different Cp ligands: synthesis, structure, and hydrogen-uptake/release properties.

A new family of Y(4)/M(2) and Y(5)/M heterobimetallic rare-earth-metal/d-block-transition-metal-polyhydride complexes has been synthesized. The reactions of the tetranuclear yttrium-octahydride complex [{Cp''Y(μ-H)(2)}(4)(thf)(4)] (Cp'' = C(5)Me(4)H, 1-C(5)Me(4)H) with one equivalent of Group-6-metal-pentahydride complexes [Cp*M(PMe(3))H(5)] (M = Mo, W; Cp* = C(5)Me(5)) afforded pentanuclear heterobimetallic Y(4)/M-polyhydride complexes [{(Cp''Y)(4)(μ-H)(7)}(μ-H)(4)MCp*(PMe(3))] (M = Mo (2 a), W (2 b)). UV irradiation of compounds 2 a,b in THF gave PMe(3)-free complexes [{(Cp''Y)(4)(μ-H)(6)(thf)(2)}(μ-H)(5)MCp*] (M = Mo (3 a), W (3 b)). Compounds 3 a,b reacted with one equivalent of [Cp*M(PMe(3))H(5)] to afford hexanuclear Y(4)/M(2) complexes [{Cp*M(μ-H)(5)}{(Cp''Y)(4)(μ-H)(5)}{(μ-H)(4)MCp*(PMe(3))}] (M = Mo (4 a), W (4 b)). UV irradiation of compounds 4 a,b provided the PMe(3)-free complexes [(Cp''Y)(4)(μ-H)(4){(μ-H)(5)MCp*}(2)] (M = Mo (5 a), W (5 b)). C(5)Me(4)Et-ligated analogue [(Cp''Y)(4)(μ-H)(4){(μ-H)(5)Mo(C(5)Me(4)Et)}(2)] (5 a') was obtained from the reaction of 1-C(5)Me(4)H with [(C(5)Me(4)Et)Mo(PMe(3))H(5)]. On the other hand, the reaction of pentanuclear yttrium-decahydride complex [{(C(5)Me(4)R)Y(μ-H)(2)}(5)(thf)(2)] (1-C(5)Me(5): R = Me; 1-C(5)Me(4)Et: R = Et) with [Cp*M(PMe(3))H(5)] gave the hexanuclear heterobimetallic Y(5)/M-polyhydride complexes [({(C(5)Me(4)R)Y}(5)(μ-H)(8))(μ-H)(5)MCp*] (6 a: M = Mo, R = Me; 6 a': M = Mo, R = Et; 6 b: M = W, R = Me). Compound 5 a released two molecules of H(2) under vacuum to give [(Cp''Y)(4)(μ-H)(2){(μ-H)(4)MoCp*}(2)] (7). In contrast, compound 6 a lost one molecule of H(2) under vacuum to yield [{(Cp*Y)(5)(μ-H)(7)}(μ-H)(4)MoCp*] (8). Both compounds 7 and 8 readily reacted with H(2) to regenerate compounds 5 a and 6 a, respectively. The structures of compounds 4 a, 5 a', 6 a', 7, and 8 were determined by single-crystal X-ray diffraction.