The title N-heterocyclic carbene derivative, C23H30N5 +·Br−·0.25H2O, was synthesized using microwave heating and was characterized by 1H and 13C NMR spectroscopy and a single-crystal X-ray diffraction study. The structure of the title compound are stabilized by a network of intra- and inter­molecular C—H⋯Br hydrogen-bonding inter­actions. The crystal structure is further stabilized by π–π stacking inter­actions between benzene and imidazole fragment rings of parallel benzo[d]imidazole rings, with a separation of 3.486 (3) Å between the centroids of the benzene and imidazole rings. There is also an inter­molecular C—H⋯π inter­action in the crystal structure. The C—N bond lengths for the central benzimidazole ring are shorter than the average single C—N bond, thus showing varying degrees of double-bond character and indicating partial electron delocalization within the C—N—C—N—C fragment. The isopropyl group is disordered over two sites with occupancies of 0.792 (10) and 0.208 (10).

The title complex, [RuCl2(C25H26N2)]·CH2Cl2, is best thought of as containing an octa­hedrally coordinated Ru center with the arene occupying three sites. Two Ru—Cl bonds and one Ru–carbene bond complete the distorted octa­hedron. The carbene portion of the ligand is a benzimidazole ring. This ring is connected to the C6H2(CH3)3 arene group by a CH2 bridge. This leads to a system with very little apparent strain. A dichloro­methane solvent mol­ecule completes the crystal structure. Further stabilization is accomplished via C—H⋯N and C—H⋯Cl interactions.

In the title compound, C25H35N2 +·Cl−·H2O, the imidazolidine ring adopts a twisted conformation, with a pseudo-twofold axis passing through the N—C—N carbon and the opposite C—C bond. The N—C—N fragment of the imidazolidine ring shows some degree of both double- and single-bond character due to partial electron delocalization. One of the tert-butyl groups is disordered over two conformations with occupancies of 0.714 (8) and 0.286 (8). In the crystal, O—H⋯Cl and C—H⋯O hydrogen bonds help to establish the packing.

The asymmetric unit of the title compound, (C13H15N2S2)[RuCl3(C10H14)], contains a 1,3-(2-thienylmeth­yl)-4,5-dihydro­imidazolium cation and a trichlorido(η 6-p-cymene)ruthenate(II) anion. The thio­phene rings of the cation are disordered by an 180° rotation about the thio­phene–CH2 bonds with occupancies of 0.847 (5)/0.153 (5) and 0.700 (5)/0.300 (5), respectively. The Ru atom exhibits a distorted octa­hedral coordination with the benzene ring of the p-cymene ligand formally occupying three sites and three Cl atoms occupying the other three sites. The short C—N bond lengths in the imidazoline ring indicate partial electron delocalization within the N—C—N fragment. Cation and anions are connected through five inter­molecular C—H⋯Cl hydrogen bonds and one C—H⋯π hydrogen bond, forming a three-dimensional hydrogen-bonded network.

A novel N-heterocyclic carbene derivative, C28H33N2O3 +·Br−·H2O, was synthesized and characterized by elemental analysis, 1H and 13C-NMR and IR spectroscopy and a single-crystal X-ray diffraction study. Ions of the title compound are linked by π⋯π stacking inter­actions (face–face separation 3.441 Å) and C—H⋯Br and O—H⋯Br inter­actions. Intra- and intermolecular C—H⋯O inter­actions are also present. The C—N bond lengths for the compound [1.329 (3), 1.325 (3), 1.389 (3) and 1.391 (3) Å] are all shorter than the average single C—N bond length of 1.48 Å, thus showing varying degrees of double-bond character.

A new ruthenium complex, [RuBrCl(C28H32N2)], has been synthesized and characterized by elemental analysis, 1H NMR, 13C NMR, IR-spectroscopy and a single-crystal X-ray diffraction study. The Ru atom in this complex is best described as having a considerably distorted octa­hedral coordination environment with the arene occupying three coordination sites. Two further coordination sites are occupied by chloride and bromide ligands, while the sixth site is occupied by the carbene. The carbene portion of the ligand is a benzimidazole ring. This ring is connected to the C6H4C(CH3)3 arene by a CH2 bridge. This leads to a system with very little apparent strain. The two halogen atoms are disordered between Br and Cl. Two partial Cl atoms share the same sites as two partial Br atoms so that the title compound effectively has one Cl and one Br atom. C—H⋯X (X = Cl, Br) hydrogen bonds help to stabilize the crystal structure.

The asymmetric unit of the title compound, (C14H17N2S2)[Ru(C10H14)Cl3], contains a 1,3-bis­(thio­phen-2-ylmeth­yl)-3,4,5,6-tetra­hydro­pyrimidinium cation and a trichlorido(η6-p-cymene)ruthenate(II) anion. The Ru atom exhibits a distorted octa­hedral coordination with the benzene ring of the p-cymene ligand formally occupying three sites and three chloride atoms occupying the other three sites. The N—C bond lengths of the N—C—N unit of the pyrimidinium cation are shorter than the average single C—N bond length of 1.48 Å, thus showing double-bond character, indicating a partial electron delocalization within the N—C—N fragment. The pyrimidine ring has an envelope conformation. Four inter­molecular C—H⋯Cl hydrogen bonds generate a three-dimensional hydrogen-bonded framework.

The title N-heterocyclic carbene derivative, C23H33N4 +·Cl−, has been synthesized and characterized by elemental analysis, 1H and 13C NMR, IR spectroscopy and a single-crystal X-ray diffraction study. Ions of the title compound are linked by three C—H⋯Cl inter­actions. The seven-membered 1,3-diazepane ring has a form inter­mediate between twist-chair and twist-boat.

In the title salt, C26H29N2 +·Br−, which may serve as a precursor for N-heterocyclic carbenes, the imidazolidine ring adopts a twist conformation with a pseudo-twofold axis passing through the N—C—N carbon and the opposite C—C bond. The N—C—N bond angle [113.0 (4)°] and C—N bond lengths [1.313 (6) and 1.305 (6) Å] confirm the existence of strong resonance in this part of the mol­ecule. In the crystal, a C—H⋯Br inter­action is present. The dihedral angle between the biphenyl rings is 64.3 (2)° and the phenyl rings make angles of 76.6 (3) and 18.5 (3)° with the plane of the imidazolidine ring.