William K. Glass

The general use of i.r. spectral criteria in discussions of the bonding and structure of metal dithiocarbamates

Abstract Normal coordinate analyses of a series of chromium (III) dithiocarbamates are reported. Variation of the alkyl substituent is shown to produce both kinematic and electronic effects on the thioureide band at ca . 1550 cm −1 and to effect profoundly the degree of mixing of the asymmetric N-alkyl and symmetric C S modes in the 1000 cm −1 region. Vibrational analyses are also reported on model monodentate and unsymmetrical bidentate dithiocarbamate complexes. The Ugo—Bonati distinguishing monodentate and bidentate bonding by the number of observed bands in the 1000 cm −1 region is shown to be valid, provided comparison is made between complexes containing the same alkyl group, but unsymmetrical bidentate bonding is shown to produce similar splitting effects to those of the monodentate case although smaller in magnitude and consequently it is suggested that only if the splitting in the 1000 cm −1 region is greater than 20 cm −1 should monodentate bonding be assumed.

Conformational behaviour of hydroxamic acids: ab initio and structural studies

The conformational behaviour of a series of monohydroxamic acids, p-RC6H4CONR′OH (R = Me, R′= H, Me; R = MeO, R′= H, Me; R = NO2, R′= H), and a series of dihydroxamic acids, (CH2)n(CONR′OH)2(n= 3–8, 10, R′= H and n= 7, R′= Me), in methanol, DMSO and chloroform and in the solid state has been examined using IR and NMR spectroscopy. X-Ray crystal structure determinations of p-MeC6H4CONMeOH and the monohydrate of glutarodihydroxamic acid (n= 3) together with ab initio molecular orbital calculations for several hydrated and unhydrated hydroxamic acids have been performed. Hydrogen bonding effects are shown to be important in both the solid state and solution. The cis(Z) conformation of the hydroxamate group(s)(CONHOH) is preferentially stabilized by hydrogen bonding with water molecules.

Transition metal complexes of monohydroxamic acids

Complexes of monohydroxamic acids and Fe(III), Co(II), Ni(II) and Cu(II) are shown to involve chelation via the oxygen atoms of the donor ligand. Spectral and magnetic properties of the complexes of Fe(III), Co(II), and Ni(II) indicate octahedral coordination with the latter two metal ions forming polymeric species. The monohydroxamic acid complexes show slightly larger 10Dq values than the corresponding aquo and acetylacetonato complexes. Cu(II) forms a square planar complex probably with a dxy ground state.

The infrared and Raman spectra of chromium (III) oxide

The chromium—oxygen stretching and deformation modes in Cr2O3 have been assigned on the basis of an octahedrally co-ordinated chromium ion. Force constants have been calculated using a simple Urey—Bradley field. Comments are made on the applicability of the Urey—Bradley field in Oh system calculations using Raman data obtained from solid-state studies.

The infrared spectra of monohydroxamic acid complexes of copper, iron and nickel

A normal coordinate treatment of Cu(MAHA)2, Fe(MAHA)2 and Ni(MAHA)2, (MAHA = N-methylhydroxamic acid) has been carried out, using a 1:1 metal-ligand model and a Urey-Bradley force field. The methyl group was treated as a point mass. Very satisfactory agreements of observed and calculated inplane infrared frequencies were obtained for copper(II) and iron(III); the metal-oxygen bonds are equivalent, having force constants of ca. 1.08 mdyn/ A. Delocalization does occur over the chelate system resulting in significant double bond character of the CN bond, and to a lesser extent of the NO bond.

Metal complexes of glutamic acid-γ-hydroxamic acid (Glu-γ-ha)(N-Hydroxyglutamine) in aqueous solution

Stability constants and assumptions concerning the bonding mode are summarized for the complexes formed in aqueous solution in nickel(II)–, copper(II)–, zinc(II)– and iron(III)–L-glutamic acid-γ-hydroxamic acid (Glu-γ-ha) systems and nickel(II)–, copper(II)– and zinc(II)–acetohydroxamic acid-α-alanine ternary systems as models. Mononuclear species have been found with bidentate co-ordination of the HA–(monoprotonated) and tridentate co-ordination of the A2–(deprotonated) form of Glu-γ-ha under the conditions employed. Co-ordination of the hydroxamate and carboxylate oxygens is proposed in the case of iron(III). Complexes with different bonding modes existing in equilibria are formed with nickel(II) and copper(II), while preference for co-ordination via hydroxamate oxygens and amino-N is found with zinc(II).

Reactions of some Group 15 ligands with [(η5-indenyl)Fe(CO)3]BF4

Abstract [(η 5 -Indenyl)Fe(CO) 3 ]BF 4 ( I ) undergoes facile monocarbonyl substitution at room temperature in acetone by monophosphines, monophosphites and MPh 3 (M =1cr; As, Sb, Bi) ligands (L) to form [(η 5 -Indenyl)Fe(CO) 2 L]BF 4 . Ditertiary phosphines, PPh 2 (CH 2 ) n PPh 2 ( n = 1, 2, 4, 6, 8) and both the arsines, AsPh 2 (CH 2 ) 2 AsPh 2 and AsMe 2 (CH 2 ) 5 AsMe 2 react similarly to form monosubstituted complexes e.g. [(η 5 -Indenyl)Fe(CO) 2 (η 1 - PPh 2 (CH 2 ) n PPh 2 )]BF 4 and dimeric complexes, e.g. [{(η 5 -Indenyl) Fe(CO) 2 } 2 -μ-PPh 2 (CH 2 ) n PPh 2 )] [BF 4 ] 2 Prolonged refluxing of I with these ligands gives the chelates, e.g. [(η 5 -Indenyl)Fe(CO)(η 2 - PPh 2 (CH 2 ) n PPh 2 )]BF 4 . The enhanced reactivity of the [(η 5 -Indenyl)Fe(CO) 3 ] + cation over that of [(η 5 ,-C 5 H 5 )Fe(CO) 3 ] + in solvents such as acetone may be attributed to the “indenyl” effect, i.e. ring slippage from η 5 to η 3 . However, no evidence was obtained for intermediates such as [(η 3 -C 9 H 7 )Fe(CO) 3 (acetone)] + , and so the effect must operate solely in the transition state of the reaction.

Monohydroxamic acid complexes of iron(II and III), cobalt(II and III), copper(II) and zinc(II)

Abstract Iron(II) and Cobalt(III) complexes of monohydroxamic acids (aceto-, propiono- and steareo-) are reported for the first time. Spectral and magnetic properties indicate octahedral coordination via the oxygen atoms of the deprotonated hydroxamic acid ligand. Both series are relatively unstable, the former undergoing rapid oxidation to Fe(III) and the latter reduction to Co(II) with concomitant oxidation of the ligand to acetate. Complexes of Fe(III), Co(II), Cu(II) and Zn(II) are also reported.

Some mononuclear π-cyclopentadienyltungsten dicarbonyl dithiocarbamates

Abstract Mononuclear tungsten dithiocarbamate complexes π-C 5 H 5 W(CO) 2 S 2 CN(CH 3 ) 2 , π-C 5 H 5 W(CO) 2 )S 2 CN(C 2 H 5 ) 2 , and π-C 5 H 5 W(CO) 2 S 2 CNC 5 H 10 (NC 5 H 10 = piperidinyl) have been prepared. 1 H NMR ultraviolet spectra and IR carbonyl stretching spectra are discussed. The dithiocarbamate ligand is bidentate in these diamagnetic complexes, in which tungsten obeys the Effective Atomic Number rule.

Novel coordination of a hydroxamic acid: Crystal structures of bis(glycinohydroxamoto)nickel(II) and tris(glycinohydroxamoto)cobalt(III)

Abstract The structures of two glycinohydroxamoto (GHA) complexes of Ni(II) and Co(III) have been determined by single-crystal X-ray diffraction methods. The crystals of Ni(GHA) 2 are monoclinic with a = 5.360(1), b = 7.315(4), c = 10.194(4) A, β = 96.57(3)∘, Z = 2, and space group P 2 1 / c . The crystals of Co(GHA) 3 • 1 2 H 2 O are monoclinic with a = 22.467(19), b = 8.041(4), c = 13.700(11) A, β = 116.01(7)∘, Z = 8, and space group C 2/ c . The values of the final residuals R for Ni(GHA) 2 and Co(GHA) 3 • 1 2 H 2 O are 0.0275 and 0.032, respectvely. The molecular structures of Ni(GHA) 2 and Co(GHA) 3 consist of a square planar and an octahedral coordination, respectively, with the glycinohydroxamato (NH 2 CH 2 CONOH − ) ligands coordinating to the metal ion via the N (amino) and the N (NOH − ). These two complexes are the first well-established cases of coordination of the NHO − group of a hydroxamic acid to a transition metal via the nitrogen atom.