Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

Structure-function studies on the role of pendent Lewis acids in the reductive coupling of CO are reported. Cationic rhenium carbonyl complexes containing zero, one, or two phosphinoborane ligands (Ph_2P(CH_2)_nB(C_8H_(14)), n=1-3) react with the nucleophilic hydride [HPt(dmpe)_2]^+ to reduce [M-CO]^+ to M-CHO; this step is relatively insensitive to the Lewis acid, as both pendent (internal) and external boranes of appropriate acid strength can be used. In contrast, whether a second hydride transfer and C-C bond forming steps occur depends strongly on the number of carbon atoms between P and B in the phosphinoborane ligands, as well as the number of pendent acids in the complex: shorter linker chain lengths favor such reductive coupling, whereas longer chains and external boranes are ineffective. A number of different species containing partially reduced CO groups, whose exact structures vary considerably with the nature and number of phosphinoborane ligands, have been crystallographically characterized. The reaction of [(Ph -2P(CH_2)_2B(C_8H_(14)))_2Re(CO)4]^+ with [HPt(dmpe)_2]^+ takes place via a “hydride shuttle” mechanism, in which hydride is transferred from Pt to a pendent borane and thence to CO, rather than by direct hydride attack at CO. Addition of a second hydride in C_6D_5Cl at -40 ºC affords an unusual anionic bis(carbene) complex, which converts to a C-C bonded product on warming. These results support a working model for Lewis acid-assisted reductive coupling of CO, in which B (pendent or external) shuttles hydride from Pt to coordinated CO, followed by formation of an intramolecular B-O bond, which facilitates reductive coupling

Homogeneous CO Hydrogenation: Dihydrogen Activation Involves a Frustrated Lewis Pair Instead of a Platinum Complex

During a search for conditions appropriate for Pt-catalyzed CO reduction using dihydrogen directly, metal-free conditions were discovered instead. A bulky, strong phosphazene base forms a “frustrated” Lewis pair (FLP) with a trialkylborane in the secondary coordination sphere of a rhenium carbonyl. Treatment of the FLP with dihydrogen cleanly affords multiple hydride transfers and C−C bond formation

Trialkylborane-Assisted CO_2 Reduction by Late Transition Metal Hydrides

Trialkylborane additives promote reduction of CO_2 to formate by bis(diphosphine) Ni(II) and Rh(III) hydride complexes. The late transition metal hydrides, which can be formed from dihydrogen, transfer hydride to CO_2 to give a formateborane adduct. The borane must be of appropriate Lewis acidity: weaker acids do not show significant hydride transfer enhancement, while stronger acids abstract hydride without CO_2 reduction. The mechanism likely involves a pre-equilibrium hydride transfer followed by formation of a stabilizing formateborane adduct

Centrifugal and Centripetal Forces Shaping the American Midwest

Efforts to identify the essential identity or the defining features of the Midwest are interesting and valuable, but they are ultimately doomed to failure because the Midwest is many different things. It is necessarily complex, conflicted, and contradictory, in much the same way that America as a whole was depicted by historian Michael Kammen in The Contrapuntal Civilization. Citing examples from his 2014 book, Small-Town Dreams: Stories of Midwestern Boys Who Shaped America, John Miller describes the powerful impulses that led young men to leave their midwestern farms and hometowns to pursue their destinies in distant places, while at the same time many of them clung to fond memories of childhoods spent fishing, playing ball, and roaming the countryside. Movement and stasis, ambition and contentment, change and continuity, dynamism and stability—these were some of the tensions that constituted the centrifugal and centripetal forces that operated in many midwestern lives

Review of \u3ci\u3eRegionalism and the Humanities\u3c/i\u3e edited and with an introduction by Timothy R. Mahoney and Wendy J. Katz

Emerging out of a 2003 conference in Lincoln, Nebraska, organized by the Consortium of Regional Humanities Centers, the sixteen disparate essays included in this engaging volume, ably edited and introduced by Timothy Mahoney and Wendy Katz, testify to the catholicity and vitality of the new regionalism in American studies. They both illustrate and justify what has been labeled by some the local turn in humanities scholarship. Because of the location of the conference on the border between the Midwest and the Great Plains, half of these essays focus upon those two regions. Each author assumes that place matters-that in addition to the standard explanatory variables of class, race, ethnicity, gender, demography, and so forth, geography needs to be assigned high priority in any cultural analysis. These regionalist scholars have moved a long distance from the geographical determinists of an earlier day, such as Frederick Jackson Turner, who is mentioned in six of the essays. Both implicitly and sometimes explicitly they champion multiplicity, contingency, indeterminancy, permeability, contestedness, ambiguity, and change. Beyond that, they reflect a growing consensus that regional studies in the twenty-first century need to be interdisciplinary, methodologically flexible, and creative

The Continuing Relevance of C. Wright Mills: His Approach to Research and What We Can Learn From It

C. Wright Mills (1916-1962), remembered primarily for his 1956 book, The Power Elite, and for his 1960 essay “Letter to the New Left,” which helped launch the rising New Left in the America of the 1960s, was a major American sociologist, but he also had much to teach historians. Although he focused his research on national and global subjects, students and scholars of regionalism can also learn much from his wide-ranging, critical approach. Like all good sociologists, Mills always assumed that historical context was an essential element of any adequate analysis of society, economics, and politics. Born in Texas, educated at the University of Texas and the University of Wisconsin, Mills spent most of his career as a professor at Columbia University. His distinctive mantra as a teacher and writer was “Take it big!” His dozen or so books and many articles were both influential and highly controversial. Beyond thinking historically, Mills encouraged his students and followers to focus on big problems, connect personal problems to social structure, do comparative work, connect work and life, develop an organized system of notes, write simply and directly, and utilize multiple perspectives. In practice, he always took a pointedly critical approach to his subjects

John Brown to Bob Dole: Movers and Shakers in Kansas History

Review of: "John Brown to Bob Dole: Movers and Shakers in Kansas History," edited by Virgil W. Dean

The Funeral of Beloved Hoosier Poet, James Whitcomb Riley

The funeral of popular Indiana poet James Whitcomb Riley in July 1916 was more than a statewide event (before him, only Abraham Lincoln and a general who had fought in the Spanish-American War had been accorded the honor of having their body lie in state in the rotunda of the state capitol). It was a national commemoration, generating thousands of newspaper articles, editorials, and expressions of grief and appreciation. Eulogized as a secular saint for his cheerfulness, high-mindedness, insight, and generosity, he was beloved for the poems that he had written extolling the simple virtues and the hardy characters of the Midwestern rural, small-town people among whom he had lived. Dying just before the United States entered World War I and at a time of maximum cultural influence for the Midwest, Riley represented a way of life that would soon be overwhelmed by modern, industrialized, urban America