Philip J. Bailey

The coordination chemistry of guanidines and guanidinates

Abstract Species containing the Y-shaped CN3 unit have recently attracted increasing attention as electronically and sterically flexible ligands. Neutral guanidines [(R2N)2CNR], guanidinates(−1) [(RN)2CNR2]− and guanidinates(2) [(RN)2CNR]2− are capable of exhibiting a variety of coordination modes and a range of donor properties leading to compatibility with a remarkably wide range of metal ions from all parts of the periodic table. The coordination chemistry of these species is reviewed up to July 2000, and aspects of their electronic structures and metal-ligand bonding characteristics discussed.

Carbide forming and cluster build-up reactions in ruthenium carbonyl cluster chemistry

Abstract The reinvestigation of an early synthesis of hexaruthenium carbido clusters has lead to the isolation of a number of new clusters which have been fully characterised by spectroscopic and crystallographic techniques. The thermolysis of Ru 3 (CO) 12 in the presence of mesitylene (1,3,5-trimethylbenzene) at moderate temperatures yields two new clusters, [Ru 6 (μ 4 -η 2 -CO) 2 (CO) 13 (η 6 -C 6 H 3 Me 3 )] (I) and [HRu 6 (μ 4 -η 2 -CO)(CO) 13 (μ 2 -η 7 -C 6 H 3 Me 2 CH 2 )] (II), the structures and reactivity of which indicate the origin and mechanism of formation of the carbido-carbon in the hexaruthenium carbido clusters [Ru 6 C(CO) 14 (η 6 -C 6 H 3 Me 3 )] (III) and [Ru 6 C(CO) 17 ] (IV). A further product of the reaction is the decaruthenium carbido cluster dianion [Ru 10 C(CO) 24 ] 2− (V) which has the tetracapped octahedral geometry. The monohydrido-cluster anion [HRu 10 C(CO) 24 ] − (VI) may be synthesised quantitatively from V by protonation. The nature of the hydrido-ligand in VI has been investigated in the solid state by NMR spectroscopy and it has been found to be fluxional, its location being temperature dependent. The decanuclear dianion V has been found to react with mercury salts to yield the 21 metal atom cluster dianion [Ru 18 Hg 3 C 2 (CO) 42 ] 2− (VII) which consists of two tricapped octahedral nonaruthenium “subclusters” fused by a bi-facecapping (Hg 3 ) 2+ unit.

Exploiting outer-sphere interactions to enhance metal recovery by solvent extraction

Interactions, particularly hydrogen bonds, between ligands in the outer coordination spheres of metal complexes have a major effect on their stabilities in the hydrocarbon solvents used in commercial solvent extraction and it is now possible to use these interactions to tune the strength and selectivity of extractants.

Trismethimazolylhydroborate (Tm) complexes of ruthenium and manganese

Abstract A number of new complexes of the tris(methimazolyl)hydroborate (Tm) ligand have been synthesised: [(Tm)RuCl(DMSO) 2 ] ( 1 ), [(Tm)Ru( p -cymene)]Cl ( 2 ), [(Tm)RuCp] ( 3 ) and [(Tm)Mn(CO) 3 ] ( 4 ). Complexes 2 and 4 have been characterised structurally by X-ray crystallography and a partial crystallographic analysis was obtained for 1 . The Tm ligand is found to coordinate as a tripod ligand through its sulphur donors in all complexes except 3 , for which there is evidence of bidentate coordination and formation of a 16-electron species.

Guanidine anions as chelating ligands; syntheses and crystal structures of [Rh(η-C5Me5){η2-(NPh)2CNHPh}Cl] and [Ru(η-MeC6H4Pri-p)-{η2-(NPh)2CNHPh}Cl]

Treatment of the chloro-bridged dimers [{Rh(η-C5Me5)Cl2}2] and [{Ru(η-MeC6H4Pri-p)Cl2}2] with 1,2,3-triphenylguanidine in toluene solution led to the formation of [Rh(η-C5Me5){η2-(NPh)2CNHPh}Cl]1 and [Ru(η-MeC6H4Pri-p){η2-(NPh)2CNHPh}Cl]2 respectively. These represent the first examples of complexes containing guanidine anions as chelating ligands. Crystal structure analyses of both complexes have been performed.

The synthesis, characterization and molecular structures of two mixed metal octahedral carbido clusters, Ru5RhC(CO)14(η5-C5Me5) and Ru5RhC(CO)9(η5-C5Me5)(η5-C5H5)2

Abstract Ionic coupling between the dianionic ruthenium cluster [Ru 5 C(CO 14 ] 2− and the dicationic rhodium species [Rh(C 5 Me 5 )MeCN) 3 ] 2+ in refluxing CH 2 Cl 2 yields the hexanuclear mixed metal carbido cluster Ru 5 RhC(CO) 14 (η 5 -C 5 Me 5 ) ( 1 ). Activation of ( 1 ) towards reaction with C 5 H 6 or C 6 H 8 by trimethylamine- N -oxide (Me 3 NO) results in the formation of Ru 5 RhC (CO) 9 (η 5 -C 5 Me 5 )(η 5 C 5 H 5 ) 2 ( 2 ) and Ru 5 RhC(CO) 11 (η 5 -C 5 Me 5 (μ 3 -η 2 :η 2 :η 2 -C 6 H 6 ) 3 respectively. Complexes 1 and 2 have been structurally characterized by X-ray diffraction.

The synthesis, structural characterisation and variable temperature 1H NMR study of the bis-toluene hexaruthenium carbidocarbonyl cluster [Ru6C(CO)11(η6C6H5Me)(μ3-η2: η2: η2-C6H5Me)]

Abstract The synthesis, chemical characterisation and single crystal X-ray structural study of the bis-toluene hexaruthenium carbidocarbonyl cluster [Ru 6 C(CO) 11 (η 6 C 6 H 5 Me)(μ 3 -η 2 : η 2 : η 2 -C 6 H 5 Me)] is reported. A variable temperature 1 H n.m.r. study reveals that in solution the complex exists in two isomeric forms, one of them, that observed in the solid state and the other the trans -[Ru 6 C(CO) 11 ](η 6 -C 6 H 5 Me) 2 ] isomer. Interchange of the toluene ligand between the μ 3 -η 2 : η 2 : η 2 and η 6 co-ordination mode if confirmed by deuterum labelling experiments involving C 6 D 5 CD 3 .

Reactions of the hexaruthenium cluster anions [Ru6C(CO)16]2− and [Ru6(CO)18]2− with Au2{Ph2PCH2PPh2}Cl2: crystal and molecular structures of Ru6C(CO)16Au2{Ph2PCH2PPh2} and Ru5(CO)15Au2{Ph2PCH2PPh2}

Abstract The reaction of the carbido dianion [Ru 6 C(CO) 16 ] 2− with Au 2 {Ph 2 PCH 2 PPh 2 }Cl 2 , in dichloromethane, in the presence of TIPF 6 , affords the neutral cluster Ru 6 C(CO) 16 Au 2 {Ph 2 PCH 2 PPh 2 } ( 1 ) in 90% yield. An X-ray analysis of 1 shows that the octahedral ruthenium core has remained intact, and that the two Au atoms of the chelating gold phosphine bridge two adjacent edges of one of the triangular faces of the Ru 6 octahedron. In marked contrast, the reaction of the non-carbido dianion [Ru 6 (CO) 18 ] 2− with Au 2 {Ph 2 PCH 2 PPh 2 }Cl 2 under similar reaction conditions leads to the breakdown of the octahedral ruthenium core and the formation of Ru 5 (CO) 15 Au 2 {Ph 2 PCH 2 PPh 2 } ( 2 ) in ca . 50% yield. The X-ray analysis of 2 shows that the ruthenium atoms adopt a trigonal bipyramidal framework with the Au atoms of the Au 2 {Ph 2 PCH 2 PPh 2 } ligand μ 3 - capping adjacent faces of the trigonal bipyramid in a manner not previously observed for mixed ruthenium-gold clusters.

The synthesis, molecular structure and interconversion of two novel benzene-coordinated pentaruthenium–carbido cluster isomers [Ru5C(CO)12(µ3 : η2 : η2 : η2-C6H6)] and [Ru5C(CO)12(η6-C6H6)]

Two isomers of a benzene-coordinated pentaruthenium–carbido cluster, [Ru5C(CO)12(µ3 : η2 : η2:η2-C6H6)]1 and [Ru5C(CO)12(η6-C6H6)]2 have been synthesised from [Ru5C(CO)15]3 and structurally characterised by single crystal X-ray diffraction; 1 is irreversibly converted to 2 on mild thermolysis.

The first decaruthenium hydrido cluster: synthesis and crystal structure of [N(PPh3)2]2[Ru10C(CO)24]·C6H14 and [N(PPh3)2][HRu10C(CO)24]

Abstract X-ray structural studies of new thermolysis products from the reaction of Ru 3 (CO) 12 in heptane in the presence of 1,3,5-trimethylbenzene (mesitylene) confirm that they are the decaruthenium carbido-cluster dianion [Ru 10 C(CO) 24 ] 2− (I) and the hydrido decaruthenium carbido-cluster monoanion [HRu 10 C(CO) 24 ] − (II). Both anions have the giant tetrahedron Ru 10 metal framework, and the monohydride provides the first example of a hydrido ligand in a tetrahedral Ru 4 cavity.