Hester E. Oosthuizen

Metal Isocyanide Complexes

Publisher Summary This chapter discusses metal–isocyanide chemistry. In the interim, reviews have appeared on specific aspects of isocyanide chemistry. The generally accepted valence bond and molecular orbital (MO) approach to the bonding of metal isocyanides has been well described in Treichels review, and has been used to rationalize variations in infrared (IR) stretching frequencies between bonded and nonbonded isocyanides and the better π-acceptor qualities of aryl versus alkyl isocyanide groups. A number of new synthetic routes to isocyanide complexes of chromium, molybdenum, and tungsten have been investigated. A number of attempts have been made over the years to develop reproducible synthetic routes to six- and seven-coordinate isocyanide complexes of molybdenum and tungsten. A number of routes have been employed for the synthesis of metal–isocyanide complexes by generating the isocyanide ligand on the metal atom. A number of monomeric complexes have been prepared, which may be considered as substitution products of the [Co(CNR) 5 ] + and [M(CNR) 4 ] + cations. Electrochemical investigations have been reported on a range of homoleptic and mixed carbonyl–isocyanide complexes, in attempts to rationalize substituent effects on the isocyanide with the electronic structure of the metal. Insertion reactions of isonitriles into metal–alkyl or metal–aryl bonds are now well established, occurring with metal–alkyl or –aryl groups from group IVA to IB and, recently, with uranium and thorium carbon bonds.

The preparation and some reactions of chloro(η4-cycloocta-1,5-diene)(η5-cyclopentadienyl)ruthenium(II): A versatile, new synthetic precursor for cyclopentadienylruthenium(II) chemistry

Abstract Facile substitution of the cyclooctadiene and/or chloro ligands in [(η 5 -C 5 H 5 )Ru(C 8 H 12 Cl] (C 8 H 12 = cycloocta-1,5-diene) under mild reaction conditions provides high yield synthetic routes to a range of new neutral and cationic cyclopentadienylruthenium(II) complexes.

Cationic ruthenium and osmium systems: V. Cationic osmium(II) hydrazine and hydrazone complexes derived from the polymer [OsCl2(COD)]x (COD = cyclo-octa-1,5-diene; x > 2). The crystal structure of [Os(COD(CNBut)2(NH2H:CMe2)2][BPh4]2·(acetone)2

Abstract The polymer [OsCl 2 (COD)] x ( 1 ; COD = cycloocta-1,5-diene; x > 2) and the appropriate hydrazine have been used to prepare the salts [OsCl(COD)(N 2 H 4 ) 3 ]BPh 4 ( 2 ), [Os(COD)(N 2 H 4 ) 4 ][BPh 4 ] 2 ( 3 ) and [OsCl(COD)(NH 2 NMe 2 ) 3 ]PF 6 ( 4 ). Treatment of 3 with t-butyl isocyanide produced mer -[Os(CNBu t ) 3 (N 2 H 4 ) 3 ][BPh 4 ] 2 ( 5 ) and trans -[Os(CNBu t ) 4 (N 2 H 4 ) 2 ][BPh 4 ] 2 ( 6 ) from refluxing ethanol and the hydrazone complex [Os(COD)(CNBu t ) 2 (NH 2 N:CMe 2 ) 2 ][BPh 4 ] 2 ( 7 ) from refluxing acetone. Reactions of 3 and L {L = CNxylyl, P(OMe) 3 , and P(OMe) 3 Ph; xylyl = 2,6-dimethylphenyl} in acetone gave trans -[Os(NH 2 N:CMe 2 ) 2 L 4 ][BPh 4 ] 2 ( 8 ). The crystal structure of [Os(COD)(CNBu t ) 2 (NH 2 N:CMe 2 ) 2 ][BPh 4 ] 2 ·(Acetone) 2 ( 7 ) has been determined from three-dimensional X-ray counter data and refined to a final R (on F ) of 0.090 based on 3014 reflections. The compound crystallizes in the monoclinic space group C 2/ c with four formula units in a cell of dimensions a 24.60(2), b 13.31(1), c 24.12(2) A and β 111.51(2)°. The cation has a crystallographically imposed C 2 symmetry, with octahedral coordination of the osmium atom, assuming that the COD ligand occupies two adjacent coordination sites. Coordination of the mutually trans hydrazone ligands to the osmium atom is through the amino-N atoms rather than through the less basic, more sterically hindered, imino-N atoms. relevant bond distances are: Os-N 2.19(2) (mean), Os-C(COD) 2.19(2) and 2.29(2), and Os-C(isocyanide) 1.93(2) (mean) A.

Formation of a homoleptic unbridged metal–metal bonded isocyanide dimer of ruthenium(I) by metal–carbon bond cleavage in [Ru(1–2,5-η-C8H13)(CN-xylyl)4]PF6: the X-ray structure determination of [Ru2(CN-xylyl)10][BPh4]2

Refluxing [Ru(1–2,5-η-C8H13)(CN-xylyl)4]PF6 in [2H6]acetone gives C8H13D and [Ru2(CN-xylyl)10][PF6]2; an X-ray structure determination of [Ru2(CN-xylyl)10][BPh4]2 shows the cation to be an unbridged, metal–metal bonded dimer of ruthenium(I) containing eclipsed 2,6-dimethylphenyl isocyanide ligands.

The X-ray structural characterization and solution dynamics of bis[(μ-2,6-dimethylphenylisocyanide)-(cyclopentadienyl)(2,6-dimethylphenylisocyanide)iron(I)]

Abstract The X-ray structure of trans-[{Fe(η5-C5H5)(CNC6H3Me2-2,6)2}2] (1a) and the solution dynamics of both cis- and trans-[{Fe(η5-C5H5)(CNC6H3Me2-2,6)2}2] have been studied. The trans-isomer of 1a crystallizes in the space group P21/n with a 14.588(4), b 8.811(2) and c 14.847(4) A, β 92.08(2)°. The molecule lies across a crystallographic centre of inversion with a trans arrangement of cyclopentadienyl ligands and a strictly planar bridging Fe2C2 ring. The FeFe bond lenght is 2.518(1) A and the bridging isocyanide ligands are symmetrically bonded to iron with a mean FeC(bridging) bond lenght of 1.928(3) A. Solution 1H NMR spectra of 1a show the presence of both cis- and trans-isomers, and a 500 MHz 1H NMR study at low temperature reveals two distinct exchange processes; the lower energy one results in the coalescence of the signals for the inequivalent methyl groups on the bridging isocyanide ligands of the cis-isomer, whereas the higher energy process brings about coalescence of the methyl signals for the bridging and terminal isocyanide ligands of the trans-isomer. At elevated temperatures all the methyl signals coalesce.

Hydrogen transfer processes in the formation of cationic η5 -dienyl complexes of ruthenium(II): X-ray structure of [Ru(1-5-η-cyclooctadienyl)(PMe2Ph)3][PF6]

Abstract The cations [Ru(1—3:5—6-η-C 8 H 11 )(η 6 -1,3,5-cyclooctatriene)] + ( 2 ) and [RuH(COD)L 3 ] + ( 5 ) (COD = cycloocta-1,5-diene, L = PMe 2 Ph, AsMePh 2 ) are convenient precursors to a range of η 5 -dienyl complexes of ruthenium(II); evidence for hydrogen transfer processes is presented.

The polymer [OsCl2 (cod)]x as a route to hydrazine- and hydrazone-osmium(II) complexes; The crystal structure of [Os(cod)(CNBut)2(NH2NCMe2)2] (BPh4)2·(acetone)2

Abstract The salts, [OsCl(cod)(NH2NR2)3]X (R = H, X = BPh4; R = Me, X = PF6) and [Os(cod)(NH2NH2)4](BPh4)2, formed from [OsCl2(cod)]x and hydrazines, can be converted into a range of hydrazine- and hydrazone-osmium(II) complexes with isocyanides and tertiary phosphorus ligands. The crystal structure of [Os(cod)(CNBut)2(NH2NCMe2)2](BPh4)2·(acetone)2 has been elucidated.

Formation of the η5-bicyclo[5.1.0]octadienyl ligand by reaction of cyclooctatetraene with a ruthenium(II) hydride complex: Molecular structure of [Ru(2–6-η-bicyclo[5.1.0]octadienyl)(PMe2Ph)3][PF6]

Abstract [Ru(2–6-η-bicyclo[5.1.0]octadienyl)(PMe 2 Ph) 3 ][PF 6 ], formed from the reaction of cyclooctatetraene with [RuH(COD)(PMe 2 Ph) 3 ][PF 6 ] (COD = cycloocta-1,5-diene), has been characterised spectroscopically from 1 J (CH) coupling constants and an X-ray structural analysis; the bicyclic ligand contains an elongated bridging CC bond (1.63 A).