Transforming Sustainability Science to Generate Positive Social and Environmental Change Globally.

Despite the decades-long efforts of sustainability science and related policy and action programs, humanity has not gotten closer to global sustainability. With its focus on the natural sciences, sustainability science is not able to contribute sufficiently to the global transition to sustainability. This Perspective argues for transforming sustainability science into a transdisciplinary enterprise that can generate positive social and environmental change globally. In such transformation, the social sciences, humanities, and the arts can play an important role to address the complex problems of culture, institutions, and human behavior. To realize a truly integrated sustainability science, we need renewed research and public policies that reshape the research ecosystem of universities, funding agencies, science communications, policymaking, and decision making. Sustainability science must also engage with society and creatively employ all available sources of knowledge in favor of creating a sustainable Earth.

Coordination and Conversion of Urea at Dinuclear &mgr;-Acetato Nickel(II) Complexes with Symmetric and Asymmetric Cores.

A series of symmetric and asymmetric pyrazolate-based dinuclear Ni(II) complexes relevant to the active site of urease is reported, which have acetate ions as secondary bridges and which feature variations in the type (N or S) and number of donor sites provided within the individual coordination compartments of the primary pyrazolate ligand matrixes. X-ray crystallographic structures of the acetone adduct [L(1)Ni(2)(&mgr;-OAc)(acetone)(2)](ClO(4))(2) (1) as well as of the urea adducts [L(1)Ni(2)(&mgr;-OAc)(benzylurea)(2)](ClO(4))(2) (2c), [L(2)Ni(2)(&mgr;-OAc)(urea)](ClO(4))(2) (3a), and [L(3)Ni(2)(&mgr;-OAc)(N,N'-dimethylurea)(2)(MeOH)(2)](ClO(4))(2) (4) have been determined. They reveal that the urea substrates are tied up with the bimetallic cores by both O-coordination to the metal centers and hydrogen bonding between the urea NH and the O atoms of the bridging acetate. In a related complex [L(3)Ni(2)(&mgr;-OAc)(OAc)(2)Na]BPh(4) (5) a sodium ion is associated with the dinickel framework via binding to one O atom of each of the three acetates. The nickel(II) ions in 1 and 2a are weakly antiferromagnetically coupled (J = -2.6 and -1.9 cm(-)(1)), where the magnitude of the coupling appears to correlate with the tilting of the acetate moiety with respect to the plane of the pyrazolate. The superexchange in 3a and 4 is even weaker. The ability of the new complexes to mediate the ethanolysis of urea is examined and is found to be dependent on the number and stereochemical arrangement of the accessible coordination sites at the dinuclear core: the asymmetric species 3a is not capable of inducing any solvolysis of the substrate, and the activity of the symmetric systems 1 and 2b is less than stoichiometric, whereas 4 displays higher activity, albeit this is still very low and possibly proceeds via a one metal ion mechanism.

A Dinuclear Nickel(II) Complex with Readily Accessible Coordination Sites and Additional N-Functional Groups in Proximity to the Bimetallic Core.

A series of pyrazolate-based dinuclear Ni(II) complexes relevant to the active site of urease are reported. Deprotonation of HL(1) [HL(1) = 3,5-bis(R(2)NCH(2))-pyzH; R(2)N = Me(2)N(CH(2))(3)NMe] by means of 1 equiv of BuLi and subsequent reaction with 2 equiv of [Ni(H(2)O)(6)](ClO(4))(2) in the presence of NEt(i)Pr(2) affords the dinuclear complex [L(1)Ni(2)(OH)(MeCN)(2)](ClO(4))(2) (1). This is shown crystallographically to contain two five-coordinate nickel ions bridged by both the pyrazolate and a hydroxide, with an acetonitrile solvent molecule bound to each metal center. When HL(2) is employed {HL(2) = 3,5-bis(R(2)NCH(2))-pyzH; R(2)N = [Me(2)N(CH(2))(3)](2)N}, the additional ligand side arms act as proton acceptors forming an intramolecular N.H.N bridge to yield the complex [HL(2)Ni(2)(OH)(MeCN)(2)](ClO(4))(3) (2), whose basic bimetallic framework is essentially identical to 1. The two Ni(II) centers in 2 exhibit strong antiferromagnetic coupling (J = -46.7 cm(-)(1)). The labile acetonitrile donors in 2 are easily replaced by either neutral ligands such as dmf or anions such as thiocyanate, giving rise to the formation of complexes [HL(2)Ni(2)(OH)(dmf)(2)](ClO(4))(3) (3) and [HL(2)Ni(2)(OH)(NCS)(2)](ClO(4)) (4), respectively, where the overall dinuclear framework of 2 remains unchanged upon the substitution reaction.

Partially Oxidized Zintl Ions? The Characterization of [(µ3 -OH)(µ3 -O)3 (OEt)3 {(CO)5 W}7 Sn7 ]2.

A formally isoelectronic (µ3 -Sn)2- ion replaces the µ3 -O building block in the subvalent anion 1, which is a derivative of the known cage compound [(µ3 -OR)4 (µ3 -O)4 Sn6 ]. Thus, compound 1 forms a link between oxo metal clusters and Zintl ions. [(µ3 -OH)(µ3 -O)3 (OEt)3 {(CO)5 W}7 Sn7 ]2- 1.

Monomeric Bis(eta(2)-alkyne)copper(I) and -silver(I) Halides, Pseudohalides, and Arenethiolates.

The synthesis and characterization of the complexes [(eta(5)-C(5)H(4)SiMe(3))(2)Ti(C&tbd1;CSiMe(3))(2)]MX (M = Cu, X = OTf (2), SC(6)H(5) (4), SC(6)H(4)NMe(2)-2 (5), SC(6)H(4)CH(2)NMe(2)-2 (6), S-1-C(10)H(6)NMe(2)-8 (7), Cl (8), (N&tbd1;CMe)PF(6) (9); M = Ag, X = OTf (3)) are described. These complexes contain monomeric MX entities, which are eta(2)-bonded by both alkyne functionalities of the organometallic bis(alkyne) ligand [(eta(5)-C(5)H(4)SiMe(3))(2)Ti(C&tbd1;CSiMe(3))(2)] (1). The reactions of 2 with the Lewis bases N&tbd1;CPh and N&tbd1;CC(H)=C(H)C&tbd1;N afford the cationic complexes {[(eta(5)-C(5)H(4)SiMe(3))(2)Ti(C&tbd1;CSiMe(3))(2)]Cu(N&tbd1;CPh)}OTf (10) and {[(eta(5)-C(5)H(4)SiMe(3))(2)Ti(C&tbd1;CSiMe(3))(2)]Cu}(2)(N&tbd1;CC(H)=C(H)C&tbd1;N)(OTf)(2) (11), respectively. The X-ray structures of 2, 3, and 6 have been determined. Crystals of 2 are monoclinic, space group P2(1)/c, with a = 12.8547(7) Å, b = 21.340(2) Å, c = 18.279(1) Å, beta = 133.623(5) degrees, V= 3629.7(5) Å(3), Z = 4, and final R = 0.047 for 5531 reflections with I >/= 2.5sigma(I) and 400 variables. The silver triflate complex 3 is isostructural, but not isomorphous, with the corresponding copper complex 2, and crystals of 3 are monoclinic, space group P2(1)/c, with a = 13.384(3) Å, b = 24.55(1) Å, c = 13.506(3) Å, beta = 119.21(2) degrees, V = 3873(2) Å(3), Z = 4, and final R = 0.038 for 3578 reflections with F >/= 4sigma(F) and 403 variables. Crystals of the copper arenethiolate complex 6 are triclinic, space group P&onemacr;, with a = 11.277(3) Å, b = 12.991(6) Å, c = 15.390(6) Å, alpha = 65.17(4) degrees, beta = 78.91(3) degrees, gamma = 84.78(3) degrees, V = 2008(2) Å(3), Z = 2, and final R = 0.079 for 6022 reflections and 388 variables. Complexes 2-11 all contain a monomeric bis(eta(2)-alkyne)M(eta(1)-X) unit (M = Cu, Ag) in which the group 11 metal atom is trigonally coordinated by the chelating bis(eta(2)-alkyne) entity Ti(C&tbd1;CSiMe(3))(2) and an eta(1)-bonded monoanionic ligand X. The copper arenethiolate complexes 4-7 are fluxional in solution.