1. Fourth generation scorpionates: coordination behavior of a new class of conformationally flexible mixed-donor (pyrazol-1-yl)borates
Elena V Mutseneck, Susanne Bieller, Michael Bolte, Hans-Wolfram Lerner, Matthias Wagner Inorg Chem. 2010 Apr 5;49(7):3540-52. doi: 10.1021/ic100104t.
The coordination behavior, the conformational flexibility, and the stability of the novel (pyrazol-1-yl)borate ligands [Ph(pz)B(mu-N(Me))(mu-pz)B(pz)Ph](-) ([L(1)](-)), [Ph(pz)B(mu-O)(mu-pz)B(pz)Ph](-) ([L(2)](-)), and [Ph(pz)B(mu-O)(mu-OB(Ph)O)B(pz)Ph](2-) ([L(3)](2-)) have been experimentally assessed by investigating the following compounds: [Li(thf)L(1)], [Li(thf)L(2)], [Mg(Cl)(thf)(x)L(1)], [Mg(Cl)(thf)(2)L(2)], [Mn(CO)(3)L(2)], K(thf)[Mn(CO)(3)L(3)], [CoCl(2)(HL(1))], [L(1)Co(mu-Cl)(2)CoL(1)], [Zn(Br)L(1)], [Cu(Cl)L(1)], [Cu(Cl)L(2)]. The L(1)-complexes were prepared from a mixture of HL(1) and the appropriate metal salt by addition of a base. HCl elimination from [CoCl(2)(HL(1))], which gives [L(1)Co(mu-Cl)(2)CoL(1)], does not necessarily require the assistance of a base, but happens spontaneously when a solution of the complex is stored at room temperature for several days. K(thf)[Mn(CO)(3)L(3)] was obtained via in situ hydrolysis of HL(1)/[Mn(CO)(5)Br] in the presence of K(2)CO(3). In some other cases, formation of the coordination compounds proceeded with decomposition of a part of the ligand molecules and yielded pyrazole (e.g., [Zn(Cl)(Hpz)L(2)]) or pyrazolide (e.g., [L(2)Co(mu-Cl)(mu-pz)CoL(2)]) complexes. As evidenced by the crystal structure analyses of [Zn(Br)L(1)]/[Mg(Cl)(thf)(2)L(2)]/[Mn(CO)(3)L(2)] on the one hand and [L(1)Mg(mu-Cl)(2)Mg(thf)L(1)]/[Cu(Cl)L(1)]/[Cu(Cl)L(2)](2) on the other, [L(1)](-) and [L(2)](-) are able to adopt both a facial and a meridional conformation. Moreover, while many of the established design principles of scorpionate chemistry are still valid for [L(1)](-), [L(2)](-), and [L(3)](2-), the bonding situation of the central donor moiety (N(Me) in [L(1)](-); O in [L(2)](-), [L(3)](2-)) is distinctly different from the way the pyrazolyl rings are attached to the molecule, so that donor scrambling is not an issue in these [N,N,N] and [N,O,N] mixed-donor ligands.
2. Cyclolinear Oligo- and Poly(iminoborane)s: The Missing Link in Inorganic Main-Group Macromolecular Chemistry
Ozan Ayhan, Nicolas A Riensch, Clemens Glasmacher, Holger Helten Chemistry. 2018 Apr 17;24(22):5883-5894. doi: 10.1002/chem.201705913. Epub 2018 Mar 12.
The reaction of n-C8 H17 B[N(Me)SiMe3 ]2 (1) with n-C8 H17 BCl2 (2 a) yielded, instead of a linear poly(iminoborane), the aminoborane n-C8 H17 B(Cl)N(Me)SiMe3 (4) and after cyclotrimerization the borazine cyclo-(n-C8 H17 BNMe)3 (6). Side reactions that result in borazine formation were effectively suppressed if 1,3-bis(trimethylsilyl)-1,3,2-diazaborolidines 7 were employed as co-monomers in combination with dichloro- or dibromoboranes 2 or 8, respectively. Silicon/boron exchange polycondensation led to oligo(iminoborane)s 11 a,b,ac,d. Alternative synthetic routes to such species involve Sn/B exchange of 1,3-bis(trimethylstannyl)-2-n-octyl-1,3,2-diazaborolidine (16) and n-C8 H17 BBr2 (8 a), and the initiated polycondensation of the dormant monomer 14 in the presence of a Brønsted acid (HCl, HOTf, or HNTf2 ; Tf=trifluoromethylsulfonyl). Although an attempt to obtain an oligo-/poly(iminoborane) with phenyl side groups yielded only insoluble material, the incorporation of aryl groups was proven for a derivative with both phenyl and n-octyl boron substituents (11 ac), as well as for a derivative with 4-n-butylphenyl side groups (11 d). The highest-molecular-weight sample obtained was 11 ac. Featuring about 18 catenated BN units, on average, this is the closest approach to a poly(iminoborane) known.
3. Chronic repeated cocaine administration alters basal and opioid-regulated adenylyl cyclase activity
E M Unterwald, B M Cox, M J Kreek, T E Cote, S Izenwasser Synapse. 1993 Sep;15(1):33-8. doi: 10.1002/syn.890150104.
Repeated daily cocaine injections have been shown to alter mu-opioid receptor densities in the caudate putamen and nucleus accumbens of rat brain (Unterwald et al., 1991, 1992). Adenylyl cyclase activity was measured in rat rostral caudate putamen and nucleus accumbens following repeated cocaine administration to determine the functional consequences of cocaine-induced opioid receptor changes. Male Fischer rats were injected daily for 14 days with saline or cocaine HCl (30 or 45 mg/kg/day, i.p.) in three equal doses at 1-hr intervals. Basal adenylyl cyclase activity and the effects of the selective mu- and delta-opioid agonists [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO) and [D-penicillamine2,D-Penicillamine5]enkephalin (DPDPE), respectively, on adenylyl cyclase activity were examined 30 min after the last injection using a cAMP radioligand binding assay in crude membrane preparations. Basal adenylyl cyclase activity was 49% and 34% lower in the caudate putamen of animals treated with 30 and 45 mg/kg/day of cocaine, respectively, as compared to those receiving saline injections. Basal adenylyl cyclase activity was unchanged in the nucleus accumbens following cocaine treatment. DAMGO and DPDPE each maximally inhibited approximately 25% and 30%, respectively, of basal adenylyl cyclase in the caudate putamen and nucleus accumbens of saline-injected animals. Administration of cocaine attenuated the ability of DPDPE to inhibit adenylyl cyclase in both brain regions, but had no effect on the efficacy or potency of DAMGO for inhibiting adenylyl cyclase activity. These results suggest that chronic, repeated cocaine administration results in a selective impairment of delta-opioid receptor-mediated effector function in the caudate putamen and nucleus accumbens.
