Bonding and Reactivity of a Pair of Neutral and Cationic Heterobimetallic RuZn₂ Complexes

Abstract

A combined experimental and computational study of the structure and reactivity of two [RuZn 2 Me 2 ] complexes, neutral [Ru(PPh 3 )(Ph 2 PC 6 H 4 ) 2 (ZnMe) 2 ] ( 2 ) and cationic [Ru(PPh 3 ) 2 (Ph 2 PC 6 H 4 )(ZnMe) 2 ][BAr F 4 ] ([BAr F 4 ] = [B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ]) ( 3 ), is presented. Structural and computational analyses indicate these complexes are best formulated as containing discrete ZnMe ligands in which direct Ru–Zn bonding is complemented by weaker Zn···Zn interactions. The latter are stronger in 2 , and both complexes exhibit an additional Zn···C aryl interaction with a cyclometalated phosphine ligand, this being stronger in 3 . Both 2 and 3 show diverse reactivity under thermolysis and with Lewis bases (P n Bu 3 , PCy 3 , and IMes). With 3 , all three Lewis bases result in the loss of [ZnMe] + . In contrast, 2 undergoes PPh 3 substitution with P n Bu 3 , but with IMes, loss of ZnMe 2 occurs to form [Ru(PPh 3 )(C 6 H 4 PPh 2 )(C 6 H 4 PPhC 6 H 4 Zn(IMes))H] ( 7 ). The reaction of 3 with H 2 affords the cationic trihydride complex [Ru(PPh 3 ) 2 (ZnMe) 2 (H) 3 ][BAr F 4 ] ( 12 ). Computational analyses indicate that both 12 and 7 feature bridging hydrides that are biased toward Ru over Zn.

Zinc‐Promoted ZnMe/ZnPh Exchange in Eight‐Coordinate [Ru(PPh3)2(ZnMe)4H2]

“…Both the Ru−Zn and Ru−H bond paths show similar BCP ρ ( r ) values to those in 1 a and the computed Ru−H distances are again 1.70 Å. We have previously found delocalisation indices to be more discriminating for Ru−Zn bonding [5] and the significantly lower value computed for Ru−Zn1 suggests this Ru−Zn interaction is weakest [11] . QTAIM, ETS‐NOCV and NCI analyses again indicate that any Zn⋅⋅⋅Zn and Zn⋅⋅⋅H interactions in 2 b are weak (Supporting Information).…”

“…Both the RuÀ Zn and RuÀ H bond paths show similar BCP ρ(r) values to those in 1 a and the computed RuÀ H distances are again 1.70 Å. We have previously found delocalisation indices to be more discriminating for RuÀ Zn bonding [5] and the significantly…”

Zinc‐Promoted ZnMe/ZnPh Exchange in Eight‐Coordinate [Ru(PPh3)2(ZnMe)4H2]

“…The topology of the electron density in the equatorial {RuZn 4 H 2 } plane of 1 a taken from a QTAIM study shows the presence of Ru−Zn and Ru−H bond paths (Figure 1b). The Ru−Zn bond critical point (BCP) metrics are typical for direct Ru−Zn bonds, [5] while the Ru−H BCP data are consistent with terminal Ru–hydrides. The computed Ru−H distances are 1.70 Å, as expected for a trans ‐HRuH moiety [7] .…”

“…In contrast to the clean activation of H 2 by complexes A-D, we recently showed that exposure of [Ru(PPh 3 )-(Ph 2 PC 6 H 4 ) 2 (ZnMe) 2 ] to H 2 gave an inseparable mixture of species. [5] When the reaction was repeated in the presence of 10 equiv of ZnMe 2 , [Ru(PPh 3 ) 2 (ZnMe) 4 H 2 ] (1 a) was formed as the major metal-containing product, albeit over ca. The product exhibited a symmetrical structure (Figure 1a) with four ZnMe groups in the equatorial plane (RuÀ Zn = 2.4564(3)-2.4664(2) Å) and two axial PPh 3 groups (RuÀ P = 2.3209(5), 2.3210(5) Å).…”

Synthesis and reactivity of heterometallic complexes containing Mg- or Zn-metalloligands

“…In addition, the Ru–Zn heterobimetallic complex 56 was found to react with organozinc species constructing trimetallic [RuZn 2 ] complexes 80 and 82 (Scheme 27). 45,54 Their molecular structures revealed direct Ru–Zn bonds, discrete Zn–Me ligands and weak Zn⋯Zn interactions (2.59 and 2.68 Å). Moreover, the reaction of 80 with P n Bu 3 generated the ligand exchange product 81 , keeping the [RuZnZnMe] moiety intact.…”