Elektrotransfer-katalysierte Substitution in Carbonyl-Komplexen

Tetracyanoethylene (TCNE): The Characteristic Geometries and Vibrational Absorptions of Its Numerous Structures

Tetracyanoethylene (TCNE) undergoes numerous reactions and is reported to exist in many structural motifs. Identification of these forms and motifs can be challenging. Nonetheless, the number of nu(CN) absorptions and their frequencies provide insight with respect to the specific forms and charge on the TCNE fragment. Particularly informative is the average of the fundamental nu(CN) bands, as well as the length of the central C-C bond. This Review discusses the assignment of structure and formal charge for TCNE-containing compounds. Scrutiny of previous assignments reveals some discrepancies which are discussed, and provides a basis for further study of TCNE structure-function relationships. Several multimetal complexes with bridging [TCNE](z) units exhibit mixed valency and extensive delocalization. The scarcity of suitable model compounds, especially those with M(d(pi-pi*)) backbonding to the CN groups, have thwarted the detailed description of these valence ambiguous compounds; thus, new well-characterized polynuclear compounds are needed.

Electrochemical, Spectroscopic, and Structural Evidence for the Mild Hydrolysis of Tetracyanoethylene, TCNE, To Form the 2,3,3-Tricyanoacrylamidate Ligand: Isolation of an Unexpected Quadruply-Bonded Polymeric Material [Mo2(O2CCMe3)3((NC)2CC(CN)CONH)]∞

Under strictly anhydrous conditions, no reaction occurs between Mo(2)(O(2)CCMe(3))(4) and tetracyanoethylene, TCNE, at room temperature, but after addition of 1 equiv of water, a reaction proceeds to form [Mo(2)(O(2)CCMe(3))(3)((NC)(2)CC(CN)CONH)], 1. The compound contains a quadruple-bonded Mo(2) unit and the 2,3,3-tricyanoacrylamidate anion as a ligand (TC3A), a very unusual hydrolyzed form of TCNE. Two different solid-state structures were obtained after crystallization of 1. Crystals obtained from CH(2)Cl(2) consist of a two-dimensional network, and crystals grown from a C(6)H(6) solution form a 1-D chain motif. In both cases, the TC3A ligand acts as a polydentate ligand involving a bidentate OCN bridging unit and two CN groups. The electrochemical and spectroscopic (IR, UV/vis/near-IR, NMR, EPR) properties of 1 support the formulation in solution as a discrete 1:1 complex of the TC3A donor ligand and a Mo(2) unit with no charge transfer. The coordinated TC3A ligand exhibits redox properties similar to those of free TCNE.

Construction of Copper(I) Coordination Polymers of 1,2,4,5-Tetracyanobenzene with Zigzag Sheet and Porous Frameworks

This paper describes two copper(I) supramolecules with the same anion and cation but quite different topologies and properties. The reaction of [Cu(CH(3)CN)(4)]PF(6) and 1,2,4,5-tetracyanobenzene (TCNB) leads to two novel polymeric coordination compounds, [Cu(2)(TCNB)(3)](PF(6))(2)(Me(2)CO)(4)( )()(1) and [Cu(2)(TCNB)(3)](PF(6))(2) (2), depending on the solvents used. The crystal structures have been determined by single-crystal X-ray diffraction. Crystal data are as follows. 1: C(21)H(15)N(6)O(2)CuPF(6), monoclinic, P2(1)/a, a = 11.553(4) Å, b = 16.135(7) Å, c = 15.046(3) Å, beta = 108.08(2) degrees, Z = 4. 2: C(15)H(3)N(6)CuPF(6), orthorhombic, Cmcm, a = 28.282(3) Å, b = 10.337(3) Å, c = 16.285(4) Å, Z = 16. In both polymers, copper(I) ions have similar pseudotetrahedral environments and the four coordination sites are fully occupied by the four bridging ligands, two &mgr;(2)-TCNB and two &mgr;(4)-TCNB groups. Polymer 1, obtained in acetone, revealed a two-dimensional zigzag sheet network between copper(I) ions, whereas 2, synthesized in methylethyl ketone, displayed a three-dimensional porous framework with different functional groups (or atom) in different cavities. The redox, magnetic, and conductive behaviors of both complexes are discussed. It is demonstrated that the two complexes give different physicochemical properties.

New Adducts of Dirhodium(II) Formamidinate Complexes with Polycyano Acceptor Molecules. X-ray Crystal Structure of the Tricyanomethanide Complex Rh(2)(form)(4)[C(CN)(3)] (form = N,N'-Di-p-tolylformamidinate)

The dirhodium(II) formamidinate complexes Rh(2)(form)(2)(O(2)CCF(3))(2)(H(2)O)(2) (I) and Rh(2)(form)(4) (II, form = N,N'-di-p-tolylformamidinate) react with the polycyano acceptor molecules tetracyanoethylene (TCNE), tetracyano-p-quinodimethane (TCNQ), 2,5-dimethyl-N,N'-dicyano-p-quinonediimine (2,5-DMDCNQI), and N,N'-naphthocyano-p-quinonediimine (NCNQI) giving species whose nature is critically dependent on the redox potentials of the two parent complexes. Complex I reacts via axial coordination with negligible charge transfer (CT) from the dimetal unit to the ligand. With TCNE, it gives the labile monoaxial adduct Rh(2)(form)(2)(O(2)CCF(3))(2)(TCNE) (1), which easily loses the cyano ligand restoring the parent complex. TCNQ, 2,5-DMDCNQI, and NCNQI react with I giving polymeric materials of composition {[Rh(2)(form)(2)(O(2)CCF(3))(2)](2)TCNQ)}(n)() (2) and [Rh(2)(form)(2)(O(2)CCF(3))(2)X](n)() (X = 2,5-DMDCNQI (3), NCNQI (4)). The reaction of II with TCNE, TCNQ, and 2,5-DMDCNQI proceeds via a single electron transfer from the dimetal unit to the cyano ligand to form the CT species [Rh(2)(form)(4)X] (X = TCNE (5), TCNQ (6), 2,5-DMDCNQI (7)). Electrochemical and EPR measurements suggest a different extent of coordination between the polycyano fragment and the dirhodium unit, depending upon the polarity of the solvents. Attempts to crystallize complex 5 from acetonitrile unexpectedly led to the formation of the tricyanomethanide complex Rh(2)(form)(4)[C(CN)(3)] (5A), arising from the unprecedented transformation of the tetracyanoethylenide ion into the tricyanomethanide anion. The complex crystallizes in the tetragonal P4/ncc space group with a = 14.169(6) Å, c = 29.20(2) Å, V = 5863(5) Å(3), and Z = 4. The molecule consists of a dirhodium unit symmetrically bridged by four formamidinate ligands and one tricyanomethanide anion N-coordinated at the axial position of Rh(2).