One Bridge, Three Bonds: A Frontier in Multiple Bonding in Heterobimetallic Complexes

Abstract

A single bridging phosphinoamide ligand was shown to support a metal−metal triple bond in a Zr/Co heterobimetallic complex. The similarity of the bonding in this compound to previously synthesized Zr/Co species, and therefore the assignment of the Zr/Co triple bond, is supported by the structural parameters of the complex, the electronic structure predicted by density functional theory, and complete-active-space self-consistent-field (CASSCF) calculations. This demonstrates that metal− metal multiple bonds can be realized in heterobimetallic complexes without multiple bridging ligands to enforce the proximity of the two metals.

Assessing the activity and stereoselectivity of heterobimetallic Zr/Co complexes catalyzed terminal alkyne dimerization: A DFT study

“…Previous studies reported by Hunter et al 38 show that the Zr‐Co bond distances are 2.361, 2.273, and 2.170 Å, in A , B , and C , respectively. They also found that in the triple Zr‐Co bond A (WBI = 1.23), the WBIs are lower compared to B and C (WBI = 1.50, 1.52).…”

“…In the last decade, Thomas group has synthesized and characterized the Zr/Co heterobimetallic complexes with highly polarized Zr≡Co triplet bonds with tris-, bis-, and mono (phosphinoamide) bridging ligands (Scheme 1). [38][39][40][41][42] The tris (phosphinoamide) bridged (THF)Zr (MesNP i Pr 2 ) 3 CoN 2 (denoted as A) shows excellent reactivity and stereoselectivity in the dimerization of terminal alkynes, 43 and the Zr/Co bis (phosphinoamide) complex (denoted as B) displays even higher reactivity compared to the tris (phosphinoamide) counterparts in the hydrogenation of unsaturated hydrocarbons. 42 However, there are few studies on the reactivity of the Zr/Co mono (phosphinoamide) complex (denoted as C), which represents as the first example of a metal-metal triple bond in the heterobimetallic compound that is bridgeable with a phosphinoamide ligand in organic reactions.…”

“…42 However, there are few studies on the reactivity of the Zr/Co mono (phosphinoamide) complex (denoted as C), which represents as the first example of a metal-metal triple bond in the heterobimetallic compound that is bridgeable with a phosphinoamide ligand in organic reactions. 38 Overall, complex B demonstrates a higher reactivity than A, and with the reduced bridging ligand, the steric hindrance of complex C is also decreased, and its catalytic activity is expected to be better than A. Therefore, it is very interesting to clarify the catalytic performances of B and C in the dimerization reaction of alkyns, which are expected to show higher reactivity than A due to their increased coordinative unsaturation.…”

“… 38–42 The tris (phosphinoamide) bridged (THF)Zr (MesNP i Pr 2 ) 3 CoN 2 (denoted as A ) shows excellent reactivity and stereoselectivity in the dimerization of terminal alkynes, 43 and the Zr/Co bis (phosphinoamide) complex (denoted as B ) displays even higher reactivity compared to the tris (phosphinoamide) counterparts in the hydrogenation of unsaturated hydrocarbons 42 . However, there are few studies on the reactivity of the Zr/Co mono (phosphinoamide) complex (denoted as C ), which represents as the first example of a metal–metal triple bond in the heterobimetallic compound that is bridgeable with a phosphinoamide ligand in organic reactions 38 . Overall, complex B demonstrates a higher reactivity than A , and with the reduced bridging ligand, the steric hindrance of complex C is also decreased, and its catalytic activity is expected to be better than A .…”