Daniel F. Chodosh

Distortions in trihapto-allyls induced by electronic asymmetry: A comparison of the structures of (η5-C5H5)Mo(CO)2(η3-C3H5) and (η5-C5H5)Mo(NO(I)(η3-C3H5)

Abstract The electronic asymmetry induced by replacing two carbonyls by a nitrosyl and iodide ligand causes severe distortion in the allyl moiety. The allyl group in the nitrosyl complex is bound in a sigma-pi mode rather than the symmetrical mode found in the dicarbonyl. This change in ground state structure alters the exo—endo conformer interconversion mechanism from a rotation of the allyl in the dicarbonyl to a sigma-pi interconversion in the nitrosyl iodide.

A tri-coordinate hydrogen ligand in a trinuclear iridium cluster

Abstract The novel complex [{IrH 2 ,(PCy 3 )(C 5 H 5 N)} 3 (μ 3 -H)] [PF 6 ] 2 has been characterized by X-ray crystallography, IR and 1 H NMR spectroscopy. It contains a tricoordinate hydrogen ligand within a triangle of iridium atoms.

Syntheses and Reactivity of Organohletallic Cohlpounds Containing Ihlinoacyl Ligands. Reactions of Hletal Carbonyl Anions with Ihlidoyl Halides

Abstract Metal carbonyl anions readily react with imidoyl halides through nucleophilic displacement of the halide atom to produce complexes containing η1-iminoacyl ligands. However, weakly nucleophilic anions, such as tetracarbonylcobaltate, induce a head-to-tail coupling reaction of two imidoyl groupings via the incorporation of two anions. This has been established by an X-ray crystallographic analysis of the compound CO2(CO)5(P(CH3)2C6H5)[(C6H5)CN(C6H5)]2. The bis-imidoyl ligand chelates one cobalt atom while one of the carbon atoms bridges the two mutually bonded cobalt atoms. Photolytic decarbonylation of the complexes containing η1-iminoacyl ligands may proceed by either of three processes. When the substituent on the nitrogen atom is an alkyl group, either a migration with formation of an isocyanide ligand or formation of an η2-iminoacyl ligand can occur. When the substituent is an aryl group, ortho-metallation of the N-aryl ring occurs. This has been demonstrated by an X-ray crystallographic analysis of the compound (C5H5)Fe-(CO)[C(C6H5)N(H)p-CH3C6H3)] which contains a phenyl-N-p-tolylaminocarbene ligand in which the p-tolyl ring is bonded to the iron atom in an ortho position.

Syntheses of organometallic compounds containing iminoacyl ligands. Reactions of metal carbonyl anions with imidoyl halides

Abstract Reactions of metal carbonyl anions with imidoyl halides provide a convenient route for the preparation of organometallic complexes containing both η 1 - and η 2 -iminoacyl ligands. With poorer nucleophiles such as tetracarbonyl cobaltate anion, coupling of imidoyl groupings becomes important. This is illustrated by the molecules Co 2 (CO) 5 (P(CH 3 ) 2 C 6 H 5 ){(C 6 H 5 )CN(C 6 H 5 )} 2 which has been crystallographically analyzed.

Iridium Compounds in Homogeneous Hydrogenation

Recently, we reported the new complexes [Ir(cod) LL’]PF6 la (\( \mathop{1}\limits_{\sim } \), L = Pi-Pr3, \( \mathop{a}\limits_{\sim } \); PCy3, b. L’ = pyridine, cod = 1, 5-cyclooctadiene.), which appear to be the most active homogeneous hydrogenation catalysts yet described2. They readily reduce even tri-and tetra-substituted olefins, such as 1-methylcyclohexene or 2, 3-dimethyl-2-butene, at rates (0°, H2: 62 cmHg) of ca.4000 catalytic cycles per hour. Less hindered olefins, such as cyclohexene and 3, 3-dimethyl-1-butene are reduced somewhat more rapidly**: 4500 and 8300 cycles h-1, respectively 2. For comparison, the rates (cycles h-1) of reduction of 2, 3-dimethyl-2-butene and cyclohexene by RhCl (PPh3)3 (1:1 benzene-ethanol, 0°) are <0.1 and 70, and by RuHCl (PPh3)3 are <0.1 and 7, respectively lb, 3. While less active, the related and previously described 4a complexes [Ir (cod) L2]PF6 (\( \mathop{2}\limits_{\sim } \), L = PMePh2, \( \mathop{2}\limits_{\sim } \); PPh3, b) share many of the characteristics of the catalysts \( \mathop{1}\limits_{\sim } \), including a high activity for the reduction of polysubstituted olefins (for \( \mathop{2}\limits_{\sim } \mathop{a}\limits_{\sim } \) at 0°, rates: 2, 3-dimethyl-2-butene, 50; cyclohexene, 3800). The active catalysts are formed after (cod) has been lost from the metal coordination sphere by reduction to cyclooctane (coa).2

Isonitrile derivatives of dimanganese decacarbonyl : I. Evidence for metal—metal ligand exchange

The compound heptacarbonyltrimethylisonitriledimanganese has been prepared and investigated by variable temperature PMR spectroscopy. It has been shown that the isonitrile ligands are rapidly exchanged between the two metal atoms at approximately 100°C. Comparison of these results with those of the complex [(η5-C5H5)Fe(CO)(CNCH3)]2 shows that the activation barriers are very similar and suggests that geometrical variations may not be very important factors in determining the facility by which bridge-terminal coordination rearrangements occur.

Intermediates in insertion rearrangements: A π-bonded iminoacyl —Metal Complex

Abstract The complex, (η 5 -C 5 H 5 )Mo(CO) 2 (CH 3 CNC 6 H 5 ), has been synthesized. It crystallizes in the space group P 2 1 / c ; a 7.789(4), b 6.810(3), c 26.754(15) A, β 91.91°, Z  4. An X-ray crystal structure analyses shows the presence of a π-bonded iminoacyl group. Pertinent internuclear separations are Moz.sbnd;N  2.108(5), MoN  2.142(4) and CN  1.232(6) A. The product is believed to be formed by isocyanideinsertion into a molybdenum—methyl bond with incorporation of the nitrogen atom into the coordination sphere of the molybdenum atom. It is suggested that similar π-bonded species may be important intermediates in the mechanisms of carbonyl insertion rearrangements.