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Treatment of the complexes [Re(NO)2(PR3)2][BAr(F)4] (R = Cy, 1 a; R = iPr, 1 b) with phenyldiazomethane gave the cationic benzylidene species [Re{CH(C6H5)}(NO)2(PR3)2][BAr(F)4] (2 a and 2 b) in good yields. Upon reaction of 2 a and 2 b with acetonitrile, the consecutive formation of [Re(N[triple bond]CCH3)(N[triple bond]CPh)(NO)(OC(CH3)=NH)(PR3)][BAr(F)4] (3 a and 3 b) and [Re(NCCH3)(OC{CH3}NH{C6H5})(NO)(PR3)2][BAr(F)4] (4 a and 4 b) was observed. The proposed reaction sequence involves the coupling of coordinated NO, carbene and acetonitrile molecules to yield the (1Z)-N-[imino(phenyl)methyl]ethanimidate ligand. The coupling of the nitrosyl and the benzylidene is anticipated to occur first, forming an oximate species. The subsequent acetonitrile addition can be envisaged as a heteroene reaction of the oximate and the acetonitrile ligand yielding 3 a and 3 b, which in turn can cyclise and undergo a prototropic shift initiated by an internal attack of the ethaneimidate ligand on the benzonitrile moiety to afford 4 a and 4 b.

The addition of an excess of phenyldiazomethane to chlorobenzene solutions of the cationic dinitrosyl bisphosphine rhenium(-I) complexes [Re(NO)2(PR3)2][BAr(F)4] (R = Cy 1a, R = (i)Pr 1b) gave the corresponding benzylidene complexes [Re{=CH(C6H5)}(NO)2(PR3)2][BAr(F)4] (2a and 2b) in good yields. The treatment of 2b with dioxygen resulted in the oxidation of one of the nitrosyl ligands into the corresponding eta2-nitrito (3b) and nitrato complexes (4b) both in the solid state and in solution. In the case of the tricyclohexylphosphine derivative 2a the analogous conversion was not observed. A mechanism for the reaction of 2b with O2 is proposed which is based on an initial SET to the O2 molecule and subsequent formation of a peroxynitrite complex followed by the formation of a dinuclear mU-N2O4 intermediate. This in turn would undergo fission of the peroxo bond to afford 3b. A related sequence of steps is anticipated for the transformation of 3b to 4b. Furthermore, a similar mechanism seems reasonable for the seemingly topochemical reaction of 2b to 3b and 4b in the solid state. The initial SET to dioxygen and subsequent formation of the peroxynitrite complex is supported by DFT calculations on the trimethylphosphine model complexes [Re=CH{C6H5})(NO)2(PMe3)2]n+ (n = 1 and 2).

Treatment of the complexes [Re(NO)2(PR3)2][BAr(F)4] (R = Cy, 1 a; R = iPr, 1 b) with phenyldiazomethane gave the cationic benzylidene species [Re{CH(C6H5)}(NO)2(PR3)2][BAr(F)4] (2 a and 2 b) in good yields. Upon reaction of 2 a and 2 b with acetonitrile, the consecutive formation of [Re(N[triple bond]CCH3)(N[triple bond]CPh)(NO)(OC(CH3)=NH)(PR3)][BAr(F)4] (3 a and 3 b) and [Re(NCCH3)(OC{CH3}NH{C6H5})(NO)(PR3)2][BAr(F)4] (4 a and 4 b) was observed. The proposed reaction sequence involves the coupling of coordinated NO, carbene and acetonitrile molecules to yield the (1Z)-N-[imino(phenyl)methyl]ethanimidate ligand. The coupling of the nitrosyl and the benzylidene is anticipated to occur first, forming an oximate species. The subsequent acetonitrile addition can be envisaged as a heteroene reaction of the oximate and the acetonitrile ligand yielding 3 a and 3 b, which in turn can cyclise and undergo a prototropic shift initiated by an internal attack of the ethaneimidate ligand on the benzonitrile moiety to afford 4 a and 4 b.

The addition of an excess of phenyldiazomethane to chlorobenzene solutions of the cationic dinitrosyl bisphosphine rhenium(-I) complexes [Re(NO)2(PR3)2][BAr(F)4] (R = Cy 1a, R = (i)Pr 1b) gave the corresponding benzylidene complexes [Re{=CH(C6H5)}(NO)2(PR3)2][BAr(F)4] (2a and 2b) in good yields. The treatment of 2b with dioxygen resulted in the oxidation of one of the nitrosyl ligands into the corresponding eta2-nitrito (3b) and nitrato complexes (4b) both in the solid state and in solution. In the case of the tricyclohexylphosphine derivative 2a the analogous conversion was not observed. A mechanism for the reaction of 2b with O2 is proposed which is based on an initial SET to the O2 molecule and subsequent formation of a peroxynitrite complex followed by the formation of a dinuclear mU-N2O4 intermediate. This in turn would undergo fission of the peroxo bond to afford 3b. A related sequence of steps is anticipated for the transformation of 3b to 4b. Furthermore, a similar mechanism seems reasonable for the seemingly topochemical reaction of 2b to 3b and 4b in the solid state. The initial SET to dioxygen and subsequent formation of the peroxynitrite complex is supported by DFT calculations on the trimethylphosphine model complexes [Re=CH{C6H5})(NO)2(PMe3)2]n+ (n = 1 and 2).

The asymmetric unit of the title compound, C(17)H(13)N(4)(+)center dot BF(4) , contains one half of the benzimidazolium cation and one half of the tetrafluoridoborate anion, with crystallographic mirror planes bisecting the molecules. One F atom of the tetrafluoridoborate is equally disordered about a crystallographic mirror plane. In the crystal, C-H center dot center dot center dot F interactions link the cations and anions into layers parallel to (100). The crystal packing is further stabilized by F center dot center dot center dot pi contacts involving the tetrafluoridoborate anions and the five-membered rings F center dot center dot center dot centroid = 2.811 (2) angstrom].

In the title paramagnetic 19-electron neutral complex, W(BH(4))(C(21)H(24)N(2))(2)(NO)(2)], the W(0) atom is coordinated by two 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) carbene ligands, two NO groups and two H atoms of an eta(2)-tetrahydroborate ligand. Depending on the number of coordination sites (n) assigned to the BH4(-) ligand, the coordination geometry of the W atom may either be described as approximately trigonal-bipyramidal (n = 1) or as very distorted octahedral with the bridging H atoms filling two coordination positions (n = 2). In the latter case, the coplanar NO groups and bridging H atoms (r.m.s. deviation = 0.032 angstrom) form one octahedral plane, with mutually trans-oriented carbene ligands. In the crystal, molecules are connected via C-H center dot center dot center dot O interactions.

The molecular structure of the title compound, WCl(2)(NO)(2)-(C(21)H(24)N(2))(2)]center dot C(4)D(8)O, displays a distorted octahedral arrangement around the W atom with two trans 1,3-bis(2,4,6-trimethylphenyl) imidazol-2-ylidene (IMes) carbene ligands in axial positions. The four equatorial positions are occupied by nitrosyl and chloride ligands, which are trans to each other. The C(carbene)-W-C(carbene) bond angle of 173.44 (18)degrees and the Cl-W-N(nitrosyl) bond angles of 171.34 (11) and 171.32 (13)degrees deviate only slightly from linearity. The distortion comes from the nitrosyl and chloride ligands which are not fully coplanar since the two N atoms deviate from the WCl(2) plane by -0.279 (4) and 0.272 (4) angstrom, respectively. An intermolecular C-H center dot center dot center dot O interaction connects the organometallic molecule and the tetrahydrofuran-d(8) solvent molecule.

Two Zn MOFs, MOF-645 and MOF-646, comprised of polarized 1,3-azulenedicarboxylate were synthesized. The guest free MOF-646 showed strong MOF-H-2 interactions (7.8-6.8 kJ mol(-1)), which revealed the significant impact of internally polarized azulene backbone to stabilized H-2 molecules in the framework.

The title compds., [Mo(C2H4NO2)2(NO)2], (I), and [Mo(C2H6NS)2(NO)2]CH3CN, (II), contain distorted octahedral complexes in which the monoanionic N,S- and N,O-bidentate ligands coordinate the molybdenum centers in different modes. The anionic O atoms of the glycinate ligands in (I) are coordinated trans to the nitrosyl ligands and the amine N atoms are located trans to each other, whereas in (II) the anionic S atoms are coordinated trans to each other and the amine N atoms are located trans to the nitrosyl ligands. Each compd. has a single complete complex in the asym. unit on a general position. Six N-HO contacts with NO distances of less than 3.2 .ANG. are obsd. in (I) between the amine groups and the nitrosyl and carboxylate O atoms. In the 1:1 solvate (II), the acetonitrile mol. forms short N-HN contacts (NN < 3.2 .ANG.) between the solvent N atoms and one of the amine H atoms. In addn., three weak intermol. N-HS interactions (NS > 3.3 .ANG.) contribute to the stabilization of the structure of (II)

In the crystal structure of the title compound, [WCl2(NO)(C6H16P2)2]Cl, the seven-coordinated tungsten(II) center displays a distorted pentagonal-bipyramidal geometry with trans nitrosyl and chloride ligands. The NO and Cl ligands are disordered over two positions; the site occupancy factors are 0.6 and 0.4.

The title binuclear compound, [W2Cl6(NO)2(C10H22P2)3], contains two W atoms which are bridged by a bis(diethylphosphino)ethane (depe) ligand. The seven-coordinated tungsten(II) centres display distorted pentagonal-bipyramidal geometries with trans nitrosyl and chloride ligands. The title molecule lies on a crystallographic inversion centre. The ethane group of the non-bridging depe ligand is positionally disordered, with site-occupancy factors of 0.63 and 0.37. In the crystal structure, the binuclear molecules are linked by weak intermolecular C-H...O and C-H...Cl interactions. In addition, weak intramolecular C-H...Cl interactions are also present.

Re- and Tc-complexes of the oxidation state (+I) offer a useful synthetic pool for the labeling of biomolecules due to their co-ordination properties and stability, which are superior to compounds of the oxidation state (+V). Based on the results for Tc-tricarbonyl complexes it was the topic of this work to develop an access to similar but higher charged compounds, which could be performed by replacing a neutral [CO]-group by a [NO](+)-group. The resulting Re(I)- and Tc(I)-dicarbonyl-nitrosyl complexes, such as [N(CH2CH3)4][ReX3(CO)2(NO)], show a tendency for co-ordination at carboxylic and amine groups of biomolecules (X = Br, Cl). This was shown with picolinic acid (H-pic), a suitable model for amino acids, forming the neutral complex [ReX(pic)(CO)2(NO)]. In a similar fashion conjugation of [188Re(CO)2(NO)](2+)- or [99mTc(CO)2(NO)](2+)-compounds to proteins or antibodies is feasible. This approach opens a way to a potentially new class of radiopharmaceuticals.