The compound (ButO)3W identical to N serves to exchange the nitrogen atoms between nitriles (MeC identical to N and PhC identical to N), itself and (ButO)3Mo identical to N in solution at room temperature.

M(2)(O(t)Bu)(6) compounds (M = Mo, W) react in hydrocarbon solvents with an excess of (t)BuSH to give M(2)(O(t)Bu)(2)(S(t)Bu)(4), red, air- and temperature-sensitive compounds. (1)H NMR studies reveal the equilibrium M(2)(O(t)Bu)(6) + 4(t)BuSH <==> M(2)(O(t)Bu)(2)(S(t)Bu)(4) + 4(t)BuOH proceeds to the right slowly at 22 degrees C. The intermediates M(2)(O(t)Bu)(4)(S(t)Bu)(2), M(2)(O(t)Bu)(3)(S(t)Bu)(3), and M(2)(O(t)Bu)(5)(S(t)Bu) have been detected. The equilibrium constants show the M-O(t)Bu bonds to be enthalpically favored over the M-S(t)Bu bonds. In contrast to the M(2)(O(t)Bu)(6) compounds, M(2)(O(t)Bu)(2)(S(t)Bu)(4) compounds are inert with respect to the addition of CO, CO(2), ethyne, (t)BuC triple bond CH, MeC triple bond N, and PhC triple bond N. Addition of an excess of (t)BuSH to a hydrocarbon solution of W(2)(O(t)Bu)(6)(mu-CO) leads to the rapid expulsion of CO and subsequent formation of W(2)(O(t)Bu)(2)(S(t)Bu)(4). Addition of an excess of (t)BuSH to hydrocarbon solutions of [Mo(O(t)Bu)(3)(NO)](2) and W(O(t)Bu)(3)(NO)(py) gives the structurally related compounds [Mo(S(t)Bu)(3)(NO)](2) and W(S(t)Bu)(3)(NO)(py), with linear M-N-O moieties and five-coordinate metal atoms. The values of nu(NO) are higher in the related thiolate compounds than in their alkoxide counterparts. The bonding in the model compounds M(2)(EH)(6), M(2)(OH)(2)(EH)(4), (HE)(3)M triple bond CMe, and W(EH)(3)(NO)(NH(3)) and the fragments M(EH)(3), where M = Mo or W and E = O or S, has been examined by DFT B3LYP calculations employing various basis sets including polarization functions for O and S and two different core potentials, LANL2 and relativistic CEP. BLYP calculations were done with ZORA relativistic terms using ADF 2000. The calculations, irrespective of the method used, indicate that the M-O bonds are more ionic than the M-S bonds and that E ppi to M dpi bonding is more important for E = O. The latter raises the M-M pi orbital energies by ca. 1 eV for M(2)(OH)(6) relative to M(2)(SH)(6). For M(EH)(3) fragments, the metal d(xz)(),d(yz)() orbitals are destabilized by OH ppi bonding, and in W(EH)(3)(NO)(NH(3)) the O ppi to M dpi donation enhances W dpi to NO pi* back-bonding. Estimates of the bond strengths for the M triple bond M in M(2)(EH)(6) compounds and M triple bond C in (EH)(3)M triple bond CMe have been obtained. The stronger pi donation of the alkoxide ligands is proposed to enhance back-bonding to the pi* orbitals of alkynes and nitriles and facilitate their reductive cleavage, a reaction that is not observed for their thiolate counterpart.

Green chemistry and sustainability concepts have been woven into the University of Toronto undergraduate curriculum for almost two decades. This has been achieved through (i) development of expository, discovery-based, and student-directed laboratory experiments; (ii) evolution of several upper-year courses; and (iii) strategic integration of these components into two academic programs. In conjunction with the establishment of a graduate student-run organization known as the Green Chemistry Initiative who assists with curricular redesign, a committed departmental attitude has developed toward sustainability education. The notion of systems thinking (where links are forged between varying systemic components which affect each other in different ways, and separate components are considered as a whole) influences both specific green instructional practices and the broader Department of Chemistry approach to sustainable education and research. This article outlines the departmental mindset in relation to green chemistry, and how systems thinking has inherently informed the progress made. The connection between systems thinking and green chemistry is solidified through discussion of the Green Chemistry Commitment (GCC) learning objectives. The GCC is a voluntary initiative designed by a nonprofit organization (Beyond Benign) to assist in the preparation of chemists whose skills are aligned with the needs of the planet and its inhabitants in the 21st century.

This communication describes a variety of virtual student assessment strategies employed at the University of Toronto during the academic disruption caused by the 2020 COVID-19 global pandemic. Instructors focused their efforts toward maintaining a positive learning environment and offering meaningful evaluation methods for students in each of three introductory organic chemistry courses. Assessment schemes were initially modified in response to moving courses to a virtual platform, and a variety of support measures were used while students completed the course material and prepared for online “final assignments”, which in two courses included a virtual rehearsal test. The readiness for and delivery of online final assignments is outlined (including methods to effectively maintain academic integrity), and the important roles of graduate student teaching assistants in successfully completing each course are highlighted. Specific outcomes and reflections are discussed, including approaches which, with hindsight, were considered unnecessary, and others that proved to be valuable virtual teaching and assessment tools.

No abstract