Radu F. Semeniuc

Structurally adaptive multitopic ligands containing tris(pyrazolyl)methane units as supramolecular synthons: manganese carbonyl complexes

Abstract The compounds {p-C6H4[CH2OCH2C(pz)3]2[Mn(CO)3]2}(BF4)2 (1, pz=pyrazolyl ring), {p-C6H4[CH2OCH2C(pz)3]2[Mn(CO)3]2}(OTf)2 (2, OTf−=CF3SO3−), {m-C6H4[CH2OCH2C(pz)3]2[Mn(CO)3]2}(BF4)2 (3) and {1,2,4,5-C6H2[CH2OCH2C(pz)3]4[Mn(CO)3]4}(BF4)4 (4) have been prepared by reaction of the respective ligands with ‘Mn(CO)5+’, prepared ‘in situ’ from the reaction of Mn(CO)5Br and AgBF4 or AgOTf in refluxing acetone. In the structures of all four complexes, the environment around the manganese atom is a slightly distorted octahedron, with the distortion caused by the restricted bite angle of the κ3-bonded tris(pyrazolyl)methane ligand. The structurally adaptive ligands in all four complexes support extended three-dimensional (3D) supramolecular structures. An important organizational feature for the three BF4− complexes is a double π–π and CH⋯π interaction involving the pyrazolyl rings. The double π–π/CH⋯π interaction is intermolecular in 1 and 3 leading to the formation of chains and sheets. In the case of the tetratopic ligand in complex 4, the π–π/CH⋯π interaction is intramolecular between adjacent (ortho) side arms. These supramolecular structures are also supported by weak CH⋯F hydrogen bonds. For 3, classic π–π interactions of the central arene rings are also involved in organizing the 3D network. For 2, the structure is organized solely by CH⋯O hydrogen bonding.

Multitopic third generation tris(pyrazolyl)methane ligands built on alkyne structural scaffolding: first preparation of mixed tris(pyrazolyl)methane/tris(pyrazolyl)borate ligands

A series of new multitopic ligands with rigid linear geometry are formed by joining tris(pyrazolyl)methane and tris(pyrazolyl)borate units with arenyl and alkynyl linkers using Sonogashira and related alkynyl coupling reactions. These ligands are new examples of “third generation” poly(pyrazolyl)borate and poly(pyrazolyl)methane ligands, ligands functionalized at the non-coordinating “back” positions of either the boron or central carbon atoms. The reaction of Na[OCH2C(pz)3] with propargyl bromide yields HC2CH2OCH2C(pz)3 (2) and homocoupling of this alkyne yields [-C2CH2OCH2C(pz)3]2. The reaction of Na[OCH2C(pz)3] with 3,5-(BrCH2)2C6H3I yields 3,5-[(pz)3CCH2OCH2]2C6H3I (4), which can be converted to 3,5-[(pz)3CCH2OCH2]2C6H3(C2H) (6) by reaction with HC2SiMe3 followed by removal of the SiMe3 group. Compounds 4 and 6 can be combined to form {3,3′,5,5′-[(pz)3CCH2OCH2]4(1,1′-C6H3C2C6H3) (7) and 6 homocoupled to form {3,5-[(pz)3CCH2OCH2]2C6H3C2-}2. Compound 6 reacts with p-I2C6H4 to produce 3,3′,5,5′-[(pz)3CCH2OCH2]4[p-(1,1′-C6H3C2)2C6H4], which can also be formed by the reaction of 4 with bis(ethynyl)benzene. The reaction of 2 with Fe[(p-IC6H4)B(pz)3]2 yields the bitopic, metalloligand Fe[(pz)3CCH2OCH2-C2-C6H4B(κ3-N,N′,N″-pz)3]2 (10) and a similar reaction with 6 yields the tetratopic metalloligand Fe[{3,5-[(pz)3CCH2OCH2]2C6H3C2}C6H4B(κ3-N,N′,N″-pz)3]2. The molecular structures of 2, 4, 7, and 10·4CH2Cl2 are reported and their supramolecular structures, organized by a series of CH⋯I and CH–π interactions, are detailed.

Self-assembly of an organometallic silver(I) 1D architecture supported by three different types of bonding interactions

Abstract The new ligand o-C6H4[CH2OCH2C(3-Phpz)3]2 (pz=pyrazolyl ring) reacts with AgBF4 to yield the coordination polymer {o-C6H4[CH2OCH2C(3-Phpz)3]2Ag2(BF4)2}n. The organometallic supramolecular architecture contains two different types of silver(I) cations arranged in bimetallic units forming a 1D coordination polymer. The bimetallic units show three different types of bridging interactions, including a μ-κ1,κ2-tris(3-Ph-pyrazolyl)methane unit, a silver η2-bonded to a phenyl group and π–π stacking interactions.

Supramolecular structure of {C6H2[CH2OCH2C(pz)3]4[Mn(CO)3]4}(BF4)4 based on tetrametallic organometallic building blocks constructed from a multitopic tris(pyrazolyl)methane ligand

The compound {C6H2[CH2OCH2C(pz)3]4[Mn(CO)3]4}(BF4)4 forms a 3D sinusoidal architecture with 16 × 7 A channels organized by π–π stacking and weak C–H⋯F hydrogen bonds.

Directional control of π-stacked building blocks for crystal engineering: the 1,8-naphthalimide synthon

Incorporating the 1,8-naphthalimide group into bis(pyrazolyl)methane ligands triggers the association of their rhenium(i) complexes into directionally ordered dimers in both solution and solid state, as demonstrated by ES+/MS, PGSE-NMR and X-ray diffraction studies.

Silver complexes of 1,1′,3,3′-tetrakis(pyrazol-1-yl)propane: the “quadruple pyrazolyl embrace” as a supramolecular synthon

The reaction between pyrazole and malonaldehyde bis(dimethylacetal) yields the first linked bis(pyrazolyl)methane ligand, CH2[CH(pz)2]2. Reaction of this ligand with Ag(O3SCF3) yields [Ag2{μ-CH2[CH(pz)2]}2](SO3CF3)2 (1). In the solid state 1 contains a dimeric dication in which two ligands sandwich two silver cations forming a bicyclic sixteen-membered ring system. A similar reaction with Ag(NO3) yields a trimetallic complex [Ag3{μ-CH2[CH(pz)2]2}2](NO3)3(CH3CN)2 (2) that crystallizes from acetonitrile as 2·CH3CN. Both 1 and 2 form supramolecular structures dominated by cooperative π–π stacking/CH–π hydrogen bonding interactions that we term the ‘quadruple pyrazolyl embrace.’ A Cambridge Structural Database search showed that this interaction is relatively common for metal complexes of simple poly(pyrazolyl)-methane or -borate ligands and occurs in a quarter of all cases.

Supramolecular structures of {p-C6H4[CH2OCH2C(pz)3]2(AgSbF6)2}∞: formation of argentamacrocycles and argentachains

The coordination polymer {p-C6H4[CH2OCH2C(pz)3]2(AgSbF6)2}∞ crystallizes into two supramolecular structures, one organized into a 3D structure of argentamacrocycles stacked in a tubular network connected by helically oriented organic spacers and the other into argentachains arranged in a 2D sheet structure.