Publication Date

2019

Document Type

Dissertation/Thesis

First Advisor

Ryzhov, Victor

Second Advisor

Gilbert, Thomas M.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Chemistry and Biochemistry

Abstract

In this thesis, the chemistry of three groups of transition metal coordination complexes

is reported: A series of zinc–based catalysts was evaluated for eﬃciency in decomposing

formic acid into molecular hydrogen and carbon dioxide in the gas phase. The eﬀectiveness

of the catalysts in the series [LZn(H)]+, where L = terpyridine (tpy), phenantroline (phen)

or 2,2’-bipyrydine (bpy) was found to depend on the ligand used, which turned out to be fun

damental in tuning the catalytic properties of the zinc complex. Speciﬁcally, [(tpy)Zn(H)]+

displayed the fastest formic acid decomposition as observed inside a quadrupole ion trap mass

spectrometer. The catalysts [LZn(H)]+ can then be reformed by decarboxylating the zinc

formate complex [LZn(OOCH)]+ via tandem mass spectrometry. This process was nearly

independent of the nature of the ligand used. The decarboxylation reaction was found to be

reversible, as the zinc hydride complexes [LZn(H)]+ react with carbon dioxide leading back

to the zinc formate complex. This reaction was again substantially faster when L= tpy than

when L = phen or bpy. The energetics and mechanisms of these processes were modelled

using several levels of density functional theory (DFT) calculations. Experimental results

are fully supported by the computational predictions.

Unimolecular reactivity of palladium/diphospine complexes was studied in the gas-phase

via mass spectrometry experiments. Ions of [(L)Pd(OOC(R))]+ L=dppm, dppf, dppv, were

formed by electrospray ionization and their ability to undergo competitive deoxygenation

reactions (decarbonylation/decarboxylation) was studied via collision induced dissociation

(CID). The unimolecular reactivity of the decarbonylated intermediate ions, [(L)Pd(O)(R)]+,

was further explored and their capacity to achieve oleﬁns elimination determined. DFT cal

culation and IRMPD experiments, complemented MS experimental work in the determina

tion of the most stable isomer. It was found that decarbonylation is accompanied by ligand

oxidation (insertion of the oxygen in the Pd-P bond), and that it is therefore dependent on

the structure of the auxiliary ligand used. Furthermore, the eﬃciency of the decarbonylation

reaction over the competitive decarboxylation is shown to be dependent on the alpha satu

ration of the OOCR ligand; Carboxylic acids having a double bond alpha to the carbonyl

prefer the decabonylation/oleﬁn-elimination pathway over decarboxylation, while when sat

urated carboxylates are used decarbonylation is always in competition with decarboxylation

independently on the ligand used.

Gas-phase C-C coupling reactions catalyzed by Ni(II) complexes were carried out in

a linear quadrupole ion trap mass spectrometer. Ternary nickel cationic complexes with

1,10-phenantroline (phen) and a carboxylate, [(phen)Ni(OOCR1)]+, were formed by elec

trospray ionization. Upon collision-induced dissociation (CID), they extrude CO2 forming

an organometallic ion [(phen)Ni(R)1]+. Gas-phase ion-molecule reactions (IMR) of this

species with acetate esters CH3COOR2 lead to the reformation of the carboxylate complex [(phen)Ni(OOCCH3)]+ and a C-C coupling product R1-R2. The combination of CID and

IMR steps results in a CO2ExR (Extrusion-Recombination) class of reaction. In this work,

we show that Ni(II)-phenanthroline-catalyzed coupling reactions can be performed with a

variety of carbon substituents R1 and R2 (sp3, sp2, or aromatic), some of them functionalized.

Reaction rates do not seem to be strongly dependent on the nature of the substituents, as

sp3 - sp3 or sp2- sp2 coupling reactions proceed rapidly. Experimental results are supported

by density functional theory calculations