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Heterometallic hydride complexes are of growing interest due to their potential to contribute to highly active insertion-based catalysis; however, methods to modulate electron density within this class of molecules are underexplored. Addition of ancillary ligands to heterotrimetallic NiAl2H2 species (1) results in the formation of heterobimetallic NiAl-hydride complexes with varying phosphine donors (2-(L)2). Incorporation of sigma donating ancillary ligands of increasing strength led to contractions of the Ni–Al distances correlated to a strengthening of a back donation interaction to the Al–H sigma antibonding orbital, most prominently present in 2-(PMe3)2. Demethylation of the aryl ether from 2-(PMe3)2 provides access to a novel anionic nickel–aluminum complex (3) with a maintained bridged hydride moiety between Ni and Al. Increased negative charge in complex 3 results in an elongation of the Ni–Al interaction. Combined crystallographic, spectroscopic, and computational studies support a 3-center interaction within the Al–H–Ni subunits and were used to map the degree of Ni–H character of the series within the Al–H–Ni bonding continuum.
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Accessing Reactive Metal Hydrides through Designed Heterometallic Bridges
Abstract A methodology to access reactive hydride moieties is highly desirable, yet limited. Multimetallic hydride fragments are notable for their heightened reactivity and catalysis, but deliberate access to these species is lacking. In this highlight, we discuss recent developments by our group in the design of a new heterometallic complex that invokes an architecture designed to provide modular access to reactive hydride moieties by leveraging metal hydrides in combination with pendent donors to a model heterotrimetallic Ni–(Al–H)2 complex. An amplification of insertion-based reactivity has been examined in the hydrofunctionalization of quinolines, and our complex substantially outperformed the parent aluminum hydride LAlH (L = ligand). A potential rationale for the dramatically increased reactivity, and a further examination of these motifs and methodology in catalysis are also discussed. 1. Introduction 2. Heterometallic Hydride Design and Characterization 3. Amplification in Catalysis 4. Summary and Outlook
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- Award ID(s):
- 2316582
- PAR ID:
- 10527484
- Publisher / Repository:
- Thieme
- Date Published:
- Journal Name:
- Synlett
- ISSN:
- 0936-5214
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1055/a-2264-9040
