IR spectroscopic methods for the investigation of the CO release from CORMs.

Carbon monoxide (CO) is a toxic gas for mammals, and despite this fact, it is naturally produced in these organisms and has been proven to be beneficial in medical treatments, too. Therefore, CO-releasing molecules (CORMs) are intensively developed to administer and dose CO for physiological applications. Nearly all of these compounds are metal carbonyl complexes, which have been synthesized and investigated. However, for most of these CORMs, the exact reaction mechanisms of CO release is not completely elucidated, although it is of utmost importance. The widely used myoglobin assay for testing the CO release has several disadvantages, and therefore, different methods have to be applied to characterize CORMs. In this work, different setups of IR absorption spectroscopy are used to analyze and quantify the CO release during the decay of various CORMs: IR spectroscopy of the gas phase is applied to follow the CO liberation, and attenuated total reflection (ATR) IR spectroscopy is used to record the decay of the metal carbonyl. IR spectroscopy supported by DFT calculations yields valuable insights in the CO release reaction mechanism. The focus is set on two different CORMs: CORM-2 (Ru2(CO)(6)Cl(4)) and on the photoactive CORM-S1 (photoCORM [Fe(CO)2(SCH2CH2NH2)2]). Our results indicate that the CO liberation from CORM-2 strongly depends on sodium dithionite, which is required for the commonly applied myoglobin assay and that CORM-S1 loses all its bound CO molecules upon irradiation with blue light.

Bis[µ-N-(tert-butyl-dimethyl-silyl)-N-(pyridin-2-ylmeth-yl)amido]-bis-[methyl-cobalt(II)].

The green title complex, [Co(2)(CH(3))(2)(C(12)H(21)N(2)Si)(2)], was obtained from bis-{[µ-N-tert-butyl-dimethyl-silyl-N-(pyridin-2-ylmeth-yl)amido]-chloridocobalt(II)} and methyl-lithium in diethyl ether at 195 K via a metathesis reaction. The dimeric cobalt(II) complex exhibits a crystallographic center of inversion in the middle of the Co(2)N(2) ring (average Co-N = 2.050 Å). The Co(II) atom shows a distorted tetra-hedral coordination sphere. The exocyclic Co-N bond length to the pyridyl group shows a similar value of 2.045 (4) Å. The exocyclic methyl group has a rather long Co-C bond length of 2.019 (5) Å.

Synthesis of heteroleptic iron(II) 2-pyridylmethylamides and 2-pyridylmethylideneamines via the reaction of [(thf)Fe{N(SiMe3)2}2Cl] with (2-pyridylmethyl)(trialkylsilyl)amines.

The deprotonation of (2-pyridylmethyl)(triorganylsilyl)amines of the type Py-CH(2)-N(H)-SiR(3) with SiR(3) = SiMe(2)tBu (1a), SiMe(2)(CMe(2)iPr) (1b), SiiPr(3) (1c) and SiPh(3) (1d) with (thf)Fe[N(SiMe(3))(2)](2)Cl in THF is accompanied by redox reactions and leads to the formation of iron(II) compounds. The products with lower solubility precipitated first and are the pale yellow and paramagnetic complexes chloro-(2-pyridylmethyl)(triorganylsilyl)amido iron(ii) [SiR(3) = SiMe(2)tBu (2a), SiMe(2)(CMe(2)iPr) (2b), SiiPr(3) (2c), and SiPh(3) (2d)]. These complexes crystallized dimeric with Fe(2)N(2) rings with different Fe-N bond lengths (average values of 211.1 and 203.2 pm). The Fe-Cl distances vary around an average value of 225.6 pm. Another isolated product consists of orange to blue crystals of dichloro-(2-pyridylmethylidene)(triorganylsilyl)amino iron(II) [SiR(3) = SiMe(2)tBu (3a), SiMe(2)(CMe(2)iPr) (3b), SiiPr(3) (3c), and SiPh(3) (3d)] which are obtained from very concentrated reaction solutions. These (2-pyridylmethylidene)(triorganylsilyl)amino ligands (imines) act as bidentate bases at FeCl(2) with average Fe-N and Fe-Cl bond lengths of 211.8 and 223.5 pm, respectively. The metallation of the (2-pyridylmethyl)(triorganylsilyl)amines with dimeric Fe[N(SiMe(3))(2)](2) yields homoleptic iron(II) bis[(2-pyridylmethyl)(triorganylsilyl)amides] (4) with distorted tetrahedrally coordinated iron centers. Metathesis reactions of FeCl(3) with lithium (2-pyridylmethyl)(triorganylsilyl)amide as well as employing a mixture of Fe[N(SiMe(3))(2)](2) and FeCl(3) with (2-pyridylmethyl)(triorganylsilyl)amine give similar results and the formation of chloro-(2-pyridylmethyl)(triorganylsilyl)amido iron(II) (2) and dichloro-(2-pyridylmethylidene)(triorganylsilyl)amino iron(II) (3) are observed.

Bis(N-triisopropyl-silyl-quinolin-8-aminato)nickel(II).

The reddish-brown title complex, [Ni(C(18)H(27)N(2)Si)(2)], was prepared via the salt-metathesis reaction of N-triisopropyl-silyl-8-amido-quinoline lithium with nickelocene (NiCp(2)). The asymmetric unit contains two symmetry-independent mol-ecules with the Ni atoms in distorted tetra-hedral environments.

A key step in the formation of acrylic acid from CO2 and ethylene: the transformation of a nickelalactone into a nickel-acrylate complex.

The reaction of a nickelalactone with dppm, resulting in the formation of a stable binuclear Ni(I) complex with an acrylate, a Ph2P- and a dppm bridge, models a key step in the formation of acrylic acid from CO2 and ethylene.