Crystal structures of 3/4-pyridyl-based thiosemicarbazones and related Cu and Ni coordination compounds

In this investigation, the crystal structures of the thio-ligands 3-formylpyridine 4-phenylthiosemicarbazone (C13H12N4S, 1) and 4-benzoylpyridine 4-ethylthiosemicarbazone (C15H16N4S, 2), and of two new coordination compounds, chlorido(3-formylpyridine 4-phenylthiosemicarbazone-κS)bis(triphenylphosphane-κP)copper(I) acetonitrile monosolvate, [CuCl(C13H12N4S)(C18H15P)2]·CH3CN, 3, and bis(3-formylpyridine 4-ethylthiosemicarbazonato-κ2 N 1,S)nickel(II), [Ni(C9H11N4S)2], 4, are reported. In complex 3, the thio-ligand coordinates in a neutral form to the Cu atom through its S-donor atom, and in complex 4, the anionic thio-ligand chelates to the Ni atom through N- and S-donor atoms. The geometry of complex 3 is distorted tetrahedral [bond angles 99.70 (5)–123.23 (5)°], with the P—Cu—P bond angle being the largest, while that of complex 4 is square planar, with trans-S—Ni—S and N—Ni—N bond angles of 180°.

Synthesis and Coordination of Bicyclic Phosphorus-Nitrogen Ligands

<p>This thesis describes the synthesis and coordination chemistry of bicyclic phosphorus-nitrogen (PN) ligands containing the rigid and preorganised bicyclo[3.3.1]nonan-9-one framework. The PN ligands were prepared via the Mannich condensation reaction of four different phosphorinanone classes with amines and aldehydes. The phosphorinanone compounds, 2,6-dimethyl-3,5-diphenyl-4-phenyl-4- phosphacyclohexanone (isomers 50 and 51), 3,5-diphenyl-4-phenyl-4- phosphacyclohexanone (44, 45) and 4-phenyl-4-phosphacyclohexanone (42) were prepared by literature methods, whereas the isomers of 4-t-butyl-2,6- di(carbomethoxy) - 3,5 - bis(p - dimethylaminophenyl) - 4 - phosphacyclohexanone (53, 54) were synthesised by the reaction of ButPH2 with 2,4-di(carbomethoxy)- 1,5 - bis(p - dimethylaminophenyl)penta - 1,4 - dien - 3 - one (38). The Mannich reactions of phosphorinanones 50 and 51 were not successful, whereas the reactions of 44, 45 and 42 produced unidentifiable products. The reaction of phosphorinanone 53 with methylamine and formaldehyde produced the bicyclic PN compound 7-t-butyl-1,5-di(carbomethoxy)-6,8-bis(p-dimethylaminophenyl)- 3 - methyl - 3 - aza - 7 - phosphabicyclo[3.3.1]nonan - 9 - one (65). The identical Mannich reaction of phosphorinanone 54 also yielded 65, as well as the PN compound 4-t-butyl-6-carbomethoxy-5-(p-dimethylaminophenyl)- 2-methyl-2-aza-4-phosphacyclohexanone (66) and the E/Z isomers of 3-(p-dimethylaminophenyl)methyl-2-propenoate (67). The bicyclic PN ligand 65 adopts a chair-chair conformation in solution and the solid state as confirmed by X-ray crystallography. The coordination chemistry of this ligand was comprehensively explored with rhodium, palladium and platinum, and a wide range of complexes were synthesised including [ML2(65)] (M = Pd, Pt; L = Cl, Me), [ML(65)] (M = Rh, Pd, Pt; L = C2H4, cod, dba, norb) (cod = cycloocta-1,5-diene, dba = trans,trans- dibenzylideneacetone, norb = norborn-2-ene), [Pd(n3 -C3H5)(65)]X (X = Cl, SbF6) and [PtL(65)]CH(SO2CF3)2 (L = 1-o,4-5-n-C8H13, 1-3-n-C8H13). Cycloplatination at the ortho-position of the 6,8-dimethylaminophenyl sub- stituents was an interesting feature of the coordination chemistry of PN ligand 65. Ortho-metallation at both dimethylaminophenyl groups led to the formation of complex [Pt(C2H4)(65-2H)] (76), whereas metallation of only one aryl group produced the complex [Pt(C8H13)(65-H)] (87). Further reaction of complex 76 yielded the trans- and cis-hydroxo-bridged dimers [Pt2(u-OH)2(65-H)2] (98, 101). The nitrogen donor atom is not coordinated to the platinum metal centres in the cyclometallated PN complexes. Protonation of [Pt(C2H4)(65)] (75) with CH2(SO2CF3)2 produced the hydride complex [PtH{CH(SO2CF3)2}(65)] (92) and the agostic ethyl complex [Pt(C2H5)(65)]CH(SO2CF3)2 (93). Similarly, protonation of [Pt(norb)(65)] (74) with CHPh(SO2CF3)2 gave the norbornyl agostic complex [Pt(C7H11)(65)]CPh(SO2CF3)2 (94) as confirmed by X-ray crystallography. In addition, hydrated analogues of some of the coordination complexes of PN ligand 65 mentioned previously were also observed. In such complexes, the central carbonyl group at position 9 was hydrated to form a geminal diol. The hydrated complexes exhibited similar chemical characteristics to their ketone counterparts. The 15N NMR chemical shifts of the nitrogen donor atom in PN ligand 65 and its various metal complexes were obtained from inversely-detected 1H- 15N HMBC experiments. The NMR data showed no explicit relationship between the coordination mode of the nitrogen group and the 15N chemical shift.</p>

Synthesis and Coordination of Bicyclic Phosphorus-Nitrogen Ligands

<p>This thesis describes the synthesis and coordination chemistry of bicyclic phosphorus-nitrogen (PN) ligands containing the rigid and preorganised bicyclo[3.3.1]nonan-9-one framework. The PN ligands were prepared via the Mannich condensation reaction of four different phosphorinanone classes with amines and aldehydes. The phosphorinanone compounds, 2,6-dimethyl-3,5-diphenyl-4-phenyl-4- phosphacyclohexanone (isomers 50 and 51), 3,5-diphenyl-4-phenyl-4- phosphacyclohexanone (44, 45) and 4-phenyl-4-phosphacyclohexanone (42) were prepared by literature methods, whereas the isomers of 4-t-butyl-2,6- di(carbomethoxy) - 3,5 - bis(p - dimethylaminophenyl) - 4 - phosphacyclohexanone (53, 54) were synthesised by the reaction of ButPH2 with 2,4-di(carbomethoxy)- 1,5 - bis(p - dimethylaminophenyl)penta - 1,4 - dien - 3 - one (38). The Mannich reactions of phosphorinanones 50 and 51 were not successful, whereas the reactions of 44, 45 and 42 produced unidentifiable products. The reaction of phosphorinanone 53 with methylamine and formaldehyde produced the bicyclic PN compound 7-t-butyl-1,5-di(carbomethoxy)-6,8-bis(p-dimethylaminophenyl)- 3 - methyl - 3 - aza - 7 - phosphabicyclo[3.3.1]nonan - 9 - one (65). The identical Mannich reaction of phosphorinanone 54 also yielded 65, as well as the PN compound 4-t-butyl-6-carbomethoxy-5-(p-dimethylaminophenyl)- 2-methyl-2-aza-4-phosphacyclohexanone (66) and the E/Z isomers of 3-(p-dimethylaminophenyl)methyl-2-propenoate (67). The bicyclic PN ligand 65 adopts a chair-chair conformation in solution and the solid state as confirmed by X-ray crystallography. The coordination chemistry of this ligand was comprehensively explored with rhodium, palladium and platinum, and a wide range of complexes were synthesised including [ML2(65)] (M = Pd, Pt; L = Cl, Me), [ML(65)] (M = Rh, Pd, Pt; L = C2H4, cod, dba, norb) (cod = cycloocta-1,5-diene, dba = trans,trans- dibenzylideneacetone, norb = norborn-2-ene), [Pd(n3 -C3H5)(65)]X (X = Cl, SbF6) and [PtL(65)]CH(SO2CF3)2 (L = 1-o,4-5-n-C8H13, 1-3-n-C8H13). Cycloplatination at the ortho-position of the 6,8-dimethylaminophenyl sub- stituents was an interesting feature of the coordination chemistry of PN ligand 65. Ortho-metallation at both dimethylaminophenyl groups led to the formation of complex [Pt(C2H4)(65-2H)] (76), whereas metallation of only one aryl group produced the complex [Pt(C8H13)(65-H)] (87). Further reaction of complex 76 yielded the trans- and cis-hydroxo-bridged dimers [Pt2(u-OH)2(65-H)2] (98, 101). The nitrogen donor atom is not coordinated to the platinum metal centres in the cyclometallated PN complexes. Protonation of [Pt(C2H4)(65)] (75) with CH2(SO2CF3)2 produced the hydride complex [PtH{CH(SO2CF3)2}(65)] (92) and the agostic ethyl complex [Pt(C2H5)(65)]CH(SO2CF3)2 (93). Similarly, protonation of [Pt(norb)(65)] (74) with CHPh(SO2CF3)2 gave the norbornyl agostic complex [Pt(C7H11)(65)]CPh(SO2CF3)2 (94) as confirmed by X-ray crystallography. In addition, hydrated analogues of some of the coordination complexes of PN ligand 65 mentioned previously were also observed. In such complexes, the central carbonyl group at position 9 was hydrated to form a geminal diol. The hydrated complexes exhibited similar chemical characteristics to their ketone counterparts. The 15N NMR chemical shifts of the nitrogen donor atom in PN ligand 65 and its various metal complexes were obtained from inversely-detected 1H- 15N HMBC experiments. The NMR data showed no explicit relationship between the coordination mode of the nitrogen group and the 15N chemical shift.</p>

Rollover Cyclometalation as a Valuable Tool for Regioselective C–H Bond Activation and Functionalization

Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reaction occurs when a chelated heterocyclic ligand loses its bidentate coordination mode and undergoes an internal rotation, after which a remote C–H bond is regioselectively activated, affording an uncommon cyclometalated complex, called “rollover cyclometalated complex”. The key of the process is the internal rotation of the ligand, which occurs before the C−H bond activation and releases from coordination a donor atom. The new “rollover” ligand has peculiar properties, being a ligand with multiple personalities, no more a spectator in the reactivity of the complex. The main reason of this peculiarity is the presence of an uncoordinated donor atom (the one initially involved in the chelation), able to promote a series of reactions not available for classic cyclometalated complexes. The rollover reaction is highly regioselective, because the activated C–H bond is usually in a symmetric position with respect to the donor atom which detaches from the metal stating the rollover process. Due to this novel behavior, a series of potential applications have appeared in the literature, in fields such as catalysis, organic synthesis, and advanced materials.