Terminal zinc–hydrogen bonding. X-Ray and neutron diffraction studies of 2-dimethylaminoethyl(methyl)aminozinc hydride dimer

Abstract

The crystal structure of the title compound reveals that hydrogen bound to zinc occupies a terminal position and that each zinc atom is four co-ordinate by virtue of the formation of four-and five-membered rings with the diamine.

Accessing Zinc Monohydride Cations through Coordinative Interactions

“…A likely mechanism of this transformation involves first the binding of ketone to form [IPr·Zn(H)OCPh 2 ] + , followed by hydride transfer to the ketonic carbon to yield an alkoxide intermediate [IPr·Zn(OCPh 2 )] + that is later converted into 4 and silylether by known silane-mediated metathesis. [3,23] The presence of strongly donating DMAP groups about Zn in 5 appears to shut down the activity of this species as no catalytic reduction of benzophenone was observed, thus lending support to the abovementioned mechanism. [IPr·ZnH(m-H)] 2 (1) was also found to be active in the hydrosilylation of Ph 2 CO under similar conditions albeit with slightly lower activity (TOF = 190 h À1 ) relative to 4.…”

“…1) have been prepared with varying degrees of nuclearity depending on the steric bulk and denticity of the ligand present ( Figure 1). [3] Moreover, the use of the hydridic (H dÀ ) character within ZnÀH residues to activate substrates, such as CO 2 and imines, represents a promising low-toxicity approach for chemical synthesis. [4,5] One possible way to increase the reactivity of Zn hydrides is to open coordination sites for substrate binding/activation by the synthesis of complexes featuring formally cationic [ZnH] + moieties, while concurrently retaining the requisite hydridic character.…”

“…Thus our results portent well for the future use of [ZnH] + in abundant-metal catalysis. [22] Despite reacting quite rapidly with PhMeSiH 2 , attempts to instigate hydrosilylation (from 4) using tertiary silanes such as Et 3 SiH or (EtO) 3 SiH did not yield any catalysis; thus we are currently exploring analogous [ZnH] + complexes as 4 but with less-hindered carbene donors. Of added note, 4 was able to effect the hydroboration of benzophenone using the widely used reagent HBPin [Bpin = B(OCMe 2 ) 2 ] with a TOF of 1100 h À1 at 25 8C.…”

Direct Bonds Between Metal Atoms: Zn, Cd, and Hg Compounds with Metal–Metal Bonds

“…The most notable feature of these structures is the short ZnZn separation of approximately 2.30 Å (identical for 4 and 5 within experimental error), which, as discussed below (Section 2.3), is the shortest ZnZn separation found in the known ZnZn compounds. In characterized hydride‐bridged binuclear zinc compounds [{ZnL} 2 (μ‐H) 2 ],36a, 57, 58 the ZnZn separations are 2.40–2.45 Å.…”

An Organozinc Hydride Cluster: An Encapsulated Tetrahydrozincate?

“…The second type of zinc hydride species are neutral and typically incorporate bulky ligands to limit aggregation (see Figure 1,[2][3][4]. Examples of structurally characterized compounds include monomeric pyrazolylhydroborates of the type [Zn(L)(H)] (2), [11] the dimeric diamino compound [{Zn(m-L)(H)} 2 ] (3 a), [12] hydride-bridged compounds [{Zn(L)(m-H)} 2 ] (3 b, c), [13,14] and cubanes [{Zn(L)H} 4Àn {Li(L)} n ] (4, n = 0-3). [15] Although current applications of these compounds are somewhat limited, hydridozinc alkoxide cubane clusters have recently been used to promote the hydrogenation of CO 2 .…”