In the past 10-15 years, Augustana College has experienced a quantum leap in undergraduate Chemistry research because of a fortunate set of circumstances which converged at roughly the same time. Several factors were instrumental for establishing this research culture but the essential ingredients are a very organized and hard-working faculty dedicated to making a research culture a reality and students who are excited about research and willing to work to make it happen. Creative use of available facilities and efforts to secure financial support from a variety of sources is essential for maintaining and growing this research culture, where success breeds success in obtaining support. The decades long effort at Augustana was sustained at a moderate level until about 10 years ago. At that time several larger collaborations fueled growth, but participation in an NSF-URC entitled the Northern Plains Undergraduate Research Center (NPURC) provided the biggest boost. In a very real way, the impact of NPURC is still being perpetuated in the department. The intentional manner each program fed students into summer research as well as the funding support for students, faculty, instruments, and travel to meetings over the extended period of time effected a change in student expectations to one of entitlement. The details of these circumstances will be examined to see what effect they have had on the recognition, honors and placement of students in and after graduating from this department and its research program. The necessary elements of a successful research program will be discussed.

AbstractStille coupling of aryl halides with bis(stannyl)acetylene gives diarylacetylenes, which are studied with UV‐vis and fluorescence spectroscopy.

Bis(tri-n-butylstannyl)acetylene was synthesized and used to create a series of symmetric diarylacetylenes via a one-step Stille coupling protocol with Pd(PPh3)4 as the catalyst. In many cases, the product simply crystallized in good yields from the reaction mixture upon cooling after reflux at 100°C or upon removal of solvent. The diarylacetylenes were studied using UV–vis and fluorescence spectroscopies, which showed that naphthyl- and biphenyl-substituted acetylenes had very high solution-state fluorescence quantum yields.

A single-crystal neutron diffraction study at 20 K has revealed accurate hydride ligand positions in the first stable hydride derivative of a divalent group-14 metal, [2,6-Trip(2)C(6)H(3)Sn(mu-H)](2)-4C(6)H(6), Trip = 2,4,6-tri-isopropylphenyl [B.E. Eichler, P.P. Power, J. Am. Chem. Soc. 122 (2000) 8785]. In the solid state this dimeric complex assumes a trans C-2h geometry with two bridging hydrides (Sn-H 1.943(7) angstrom, angle C-Sn-H 92.4(2)degrees, angle Sn-H-Sn' 106.9(3)degrees, angle H-Sn-H' 73.1(3)degrees). The bulky Trip ligand serves to stabilize the Sn-H bonds. The tin atoms carry lone pairs, and, as determined previously by X-ray diffraction and reported by Eichler and Power, the tin coordination accordingly is pyramidal as evidenced by the sum of the three bond angles around tin of 257 degrees. To our knowledge this is the first neutron diffraction study of a tin hydride complex to be reported. The neutron diffraction measurements were carried out using the time-of-flight Laue SCD instrument at the Argonne Intense Pulsed Neutron Source.

Tin can form examples of rare organically substituted clusters whose structures are related to Zintl salts. The two new types of metal-rich organotin clusters, a neutral Sn9Ar3 (see picture) and two ionic [Sn10Ar′3]+ species, were structurally characterized and their bonding situation investigated by density functional calculations.

A series of very bulky 1,4-diiodo-2,3,5,6-tetraarylbenzenes I2Ar4C6 (Ar = 4-(BuC6H4)-Bu-t, 1; Ar = 3,5-(Bu2C6H3)-Bu-t, 2; Ar = 2,4,6-Me3C6H2, 3) have been prepared by a rapid, convenient procedure involving sequential reaction of hexabromobenzene with the appropriate Grignard reagent in excess, followed by addition of excess elemental iodine. The new materials 2 and 3 were isolated in 18 and 28% yields, respectively. The solid state structures of 1-3 have been investigated by single crystal X-ray techniques. Interesting distortions in the structures of these hexasubstituted benzenes are observed upon the increasing steric pressures in 1-3. For example, while the structures of 1 and 2 contain central planar benzene rings, steric interactions in 3 produce a non-planar central benzene ring. Regardless of these factors, the carbon iodine bond lengths in 1-3 are essentially constant (2.108-2.118 Angstrom).

The reaction of LiPh with Ar*SnPh (Ar* = C 6 H 3 -2,6-Trip 2 ; Trip = C 6 H 2 -2,4,6-Pr i 3) afforded either the monomeric etherate (Et 2 O)LiSnPh 2 Ar* (1) or the dimer (LiSnPh 2 Ar*) 2 (2). The reaction of 2 with SnCl 2 in a 1:1ratio in Et 2 O yielded the monomeric distannylstannylene Sn(SnPh 2 Ar*) 2 (3). The compounds 1-3 were characterized by 1 H, 7 Li, 1 3 C, and 1 1 9 Sn NMR and UV-vis spectroscopy. Complete single-crystal X-ray crystal structures of 2 and 3 were determined as well as a partial structure for 1. The structure of 1 showed that the tin was pyramidally coordinated by the three organic groups as well as by lithium. The lithium was found to be ligated by ether and η 6 -coordinated by one of the phenyl rings. The structure of 2 showed that it was dimerized through η 6 -interactions of a tin-coordinated lithium with a phenyl group of a partner monomer rather than through tin-tin bonding. The structure of 3 featured a central, two-coordinate tin(II) bound to two SnPh 2 Ar* groups with long Sn-Sn distances near 2.96 A and a very wide Sn-Sn-Sn angle of 115.19(2)°. The 1 1 9 Sn NMR chemical shift of the central tin is 3752 ppm, which is the furthest downfield 1 1 9 Sn NMR chemical shift recorded for a stannylene.

The metallostannylene compounds (η5-C5H5)(CO)3MSnC6H3-2,6-Mes2 (Mes = C6H2-2,4,6-Me3; M = Cr (1), Mo (2), W (3)), (η5-C5H5)(CO)3MSnC6H3-2,6-Trip2 (Trip = C6H2-2,4,6-Pri3; M = Cr (4), Mo (5), W (6)), and (η5-1,3-ButC6H3)MoSnC6H2-2,6-Trip2 (7) were synthesized by the reaction of the appropriate aryltin(II) halide with the alkali-metal salt of the cyclopentadienylcarbonylmetalate. The compounds, which were isolated as purple (1−6) or turquoise (7) crystals, are monomeric with V-shaped two-coordinate geometries at tin. The tin−transition-metal bonds are slightly longer than the distances predicted from metallic and covalent radii or those observed in related tin(IV)−transition-metal species. The compounds were also characterized by IR and UV−vis spectroscopy as well as 1H, 13C, and 119Sn NMR spectroscopy. The 119Sn NMR spectra displayed singlet resonances whose chemical shifts were in the range 2116−2650 ppm. These shifts were consistent with the two-coordination at tin. With use of 119Sn NMR and UV−visible spectroscopic data for 1−7, together with data for other two-coordinate tin(II) species, it was shown that there is a rough correlation between the 119Sn NMR chemical shift and the wavelength of the n−p transition. This correlation underlines the importance of the paramagnetic shielding term in determining 119Sn chemical shifts.

A series of group 13 metal complexes featuring the beta-diketiminate ligand [[(C(6)H(3)-2,6-i-Pr(2))NC(Me)](2)CH](-) (i.e., [Dipp(2)nacnac](-), Dipp = C(6)H(3)-2,6-i-Pr(2)) have been prepared and spectroscopically and structurally characterized. The chloride derivatives Dipp(2)nacnacMCl(2) (M = Al (3), Ga (5), In (8)) were isolated in good yield by the reaction of 1 equiv of Dipp(2)nacnacLi.Et(2)O (2) and the respective metal halides. The iodide derivatives Dipp(2)nacnacMI(2) (M = Al (4), Ga (6), In (9)), which are useful for reduction to afford M(I) species, were made by a variety of routes. Thus, 4 was obtained by treatment of the previously reported Dipp(2)nacnacAlMe(2) with I(2), whereas the gallium analogue 6 was obtained as a product of the reaction of "GaI" with Dipp(2)nacnacLi.Et(2)O, and 9 was obtained by direct reaction of InI(3) and the lithium salt. The methyl derivatives Dipp(2)nacnacMMe(2) (M = Ga (7), In (10)), which are analogous to the previously reported Dipp(2)nacnacAlMe(2), were synthesized by the reaction of GaMe(3) with Dipp(2)nacnacH (1) or by reaction of the indium chloride derivative 8 with 2 equiv of MeMgBr in diethyl ether. The compounds 3-10 exist as colorless, air- and moisture-sensitive crystalline solids. Their X-ray crystal structures feature nearly planar C(3)N(2) arrays in the Dipp(2)nacnac ligand backbone with short C-C and C-N distances that are consistent with a delocalized structure. However, there are large dihedral angles between the C(3)N(2) plane and the N(2)M metal coordination plane which have been attributed mainly to steric effects. The relatively short M-N distances are consistent with the coordination numbers of the metals and the normal/dative character of the nitrogen ligands. The compounds were also characterized by (1)H and (13)C NMR spectroscopy. (1)H NMR data for 7 revealed equivalent methyl groups whereas the spectrum of 10 displayed two In-Me signals which indicated that ring wagging was slow on the (1)H NMR time scale.

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The reaction of the beta -aminoimine compound (2,6-(Pr2H3C6)-H-i)NC(CH3)CHC(CH3)N(C6H3-2,6-Pr-2(i))H (1, Dipp(2)nacnacH; Dipp = C6H3-2,6-Pri2) with n-BuLi in diethyl ether or tetrahydrofuran afforded the solvates Dipp(2)nacnacLi(Et2O) (2) and Dipp(2)nacnacLi(THF) (3), respectively, which crystallized as monomers featuring the Li+ ions in a distorted trigonal planar environment and an essentially planar arrangement for the LiN2C3 ring. The lithiation of 1, in the absence of a donor solvent, afforded a Dipp(2)nacnacLi product that crystallized in two different types of associated structures, 4a and 4b. In the dimer 4a, the Li+ ion is coordinated to the two nitrogens of the Dipp(2)nacnac ligand, and it is associated by coordination of lithium to a carbon of the Dipp ring of the other Dipp(2)nacnac unit of the dimer. In the dodecamer 4b, the asymmetric unit consists of a chain of six LiDipp(2)nacnac units associated by interactions of the Li+ ions with one or two carbons from a Dipp ring of the next molecule in the chain. The hexamer is linked to an identical one (generated through an inversion center) by Li+-Dipp interactions involving the rst and third lithium atoms from each hexamer, thereby generating an overall dodecameric structure of a type that was previously unknown for lithium salts. An improved yield synthesis for 1 was also developed.

A series of group 13 metal complexes featuring the beta-diketiminate ligand [[(C(6)H(3)-2,6-i-Pr(2))NC(Me)](2)CH](-) (i.e., [Dipp(2)nacnac](-), Dipp = C(6)H(3)-2,6-i-Pr(2)) have been prepared and spectroscopically and structurally characterized. The chloride derivatives Dipp(2)nacnacMCl(2) (M = Al (3), Ga (5), In (8)) were isolated in good yield by the reaction of 1 equiv of Dipp(2)nacnacLi.Et(2)O (2) and the respective metal halides. The iodide derivatives Dipp(2)nacnacMI(2) (M = Al (4), Ga (6), In (9)), which are useful for reduction to afford M(I) species, were made by a variety of routes. Thus, 4 was obtained by treatment of the previously reported Dipp(2)nacnacAlMe(2) with I(2), whereas the gallium analogue 6 was obtained as a product of the reaction of "GaI" with Dipp(2)nacnacLi.Et(2)O, and 9 was obtained by direct reaction of InI(3) and the lithium salt. The methyl derivatives Dipp(2)nacnacMMe(2) (M = Ga (7), In (10)), which are analogous to the previously reported Dipp(2)nacnacAlMe(2), were synthesized by the reaction of GaMe(3) with Dipp(2)nacnacH (1) or by reaction of the indium chloride derivative 8 with 2 equiv of MeMgBr in diethyl ether. The compounds 3-10 exist as colorless, air- and moisture-sensitive crystalline solids. Their X-ray crystal structures feature nearly planar C(3)N(2) arrays in the Dipp(2)nacnac ligand backbone with short C-C and C-N distances that are consistent with a delocalized structure. However, there are large dihedral angles between the C(3)N(2) plane and the N(2)M metal coordination plane which have been attributed mainly to steric effects. The relatively short M-N distances are consistent with the coordination numbers of the metals and the normal/dative character of the nitrogen ligands. The compounds were also characterized by (1)H and (13)C NMR spectroscopy. (1)H NMR data for 7 revealed equivalent methyl groups whereas the spectrum of 10 displayed two In-Me signals which indicated that ring wagging was slow on the (1)H NMR time scale.

Eine verzerrte rhombisch-prismatische Anordnung, bei Hauptgruppenmetall-Clustern bisher nicht bekannt, liegt in [Sn8(2,6-Mes2C6H3)4] vor (siehe Struktur; nur die ipso-C-Atome der Terphenylliganden sind gezeigt). Synthetisiert wurde die Verbindung durch Reduktion von [{Sn(μ-Cl)(2,6-Mes2C6H3)}2] mit Kalium in THF. Mes=2,4,6-Me3C6H2.

The reaction of Et2O·LiC6H3-2,6–Trip2 (Trip=C6H2–2,4,6-i-Pr3) with SnCl2 afforded the two coordinate monomer Sn(Cl)C6H3-2,6–Trip2 (1), and its dimer {Sn(μ-Cl)C6H3–2,6-Trip2}2 (2), as orange and yellow crystals, respectively. Solution 119Sn NMR spectroscopy of 2 in C6D6 solution showed that it dissociated readily to give 1. The addition of pyridine (py) to a solution of 1 yielded the adduct py·Sn(Cl)C6H3–2,6-Trip2 (3) which featured tin in a three coordinate pyramidal environment. The reaction of the closely related bulky terphenyl lithium reagent LiC6H3–2,6-Dipp2 (Dipp=C6H3–2,6-i-Pr2) with SnCl2 afforded the mixed halide species {Sn(μ-Cl)0.35(μ-I)0.65C6H3–2,6-Dipp2}2 (4). This arose from the preparation of the lithium aryl precursor in situ from IC6H3–2,6-Dipp2 and n-BuLi. The monomeric nature of 1, and the weak association of 2 and 4, were attributed to the large size of the terphenyl ligands. All compounds were characterized by X-ray crystallography, 1H, 13C and 119Sn NMR spectroscopy, and IR and UV–Vis spectroscopy.