The main part of this thesis is concerned with the study of the reactions of fluorocyclophosphonitriles, (NPF₂)₃₋₅, with methyllithium, which exhibit a new orientation pattern, and which appear to involve inductive interactions of the substituent (the CH₃ group) with a homomorphic π-system. Nuclear magnetic resonance spectroscopy has been the principal tool for deducing the structures of the isomers isolated by gas liquid chromatography from reactions of the fluorocyclophosphonitriles with methyl-lithium. ⁵JCH₃F and ⁴JFF have been observed for the first time in phosphonitrilic derivatives. Although the assignments of the frequencies in the infrared spectra of the methylfluoro- and methylcyclophosphonitriles are inadequate for a complete vibrational analysis, the pattern of frequencies found for trans-1,5-N₄P₄F₆Me₂, shows that it is not centro-symmetrical and neither is the derivative 1,1,5,5-N₄P₄F₄Me₄. In the crystal the latter compound has a saddle shape, and it is likely that the flexibility is caused by the interconversion of the tub to saddle forms, which can take place by bond torsional movements only, without angular deformation. The most important aspect of the work is the fresh evidence which is provided on the nature and extent of delocalisation within effect of the substituents is seen in the significant alternation of bond lengths in 1, l-N₄P₄F₆Me₂. Since the molecular framework is nearly planar, the conditions for the application of simple Huckel theory are satisfied, and the effect of a π-inductive perturbation at P has therefore been estimated through the calculation of bond-atom polarisabilities πr₅,t = [formula omitted] for a delocalised π-system based on an 8-membered ring. The close correspondence in pattern of the observed deviations in the individual bond lengths from the mean and the bond-atom polarisabilities seems very direct evidence for electronic delocalisation in phosphonitrilic molecules, and suggests that simple Huckel methods can provide a useful guide to their chemistry. The predominantly geminal substitution observed in the reaction of (NPF₂)₄ with LiMe has been well explained by an inductive effect of the methyl substituent on the π-system of the phosphonitrilic ring. The atom-atom polarisabilities for the three ring systems investigated have been calculated using simple Huckel theory, which show that, from this cause alone, a second nucleophilic substitution should take place principally at P₁, as found. Also the atom-atom polarisabilities explain the observed geminal and antipodal substitution, an orientation pattern which has not been recognised previously. This is the first case in which cyclic delocalisation has been shown to have a decisive effect on phosphonitrilic chemistry. / Science, Faculty of / Chemistry, Department of / Graduate

The solvolysis of methyltin(IV) chlorine compounds of the general type (CH₃)nSnCl₄₋n with n ranging from 0 to 4, is studied in aqueous and anhydrous hydrogen fluoride under a variety of conditions. The studies in anhydrous HF have resulted in the synthesis of the new compounds methyltin(IV) trifluoride, dimethyltin(IV) chloride fluoride and methyltin(IV) dichloride fluoride. Methyltin(IV) chloro difluoride could not be synthesized in this way. A special monel reflux reactor was utilized for these reactions. Attempts to solvolyze vinyl- and phenyltin compounds with anhydrous HF did not yield pure products. In these cases, the evidence indicates that cleavage of the Sn-Cl and Sn-C bonds occurs in an unpredictable manner. A convenient method for the preparation of SnCl₂F₂ is found in the solvolysis of SnCl₄ with anhydrous HF. Interaction of this compound with either S₂O₆F₂ or C1OSO₂F results in the formation of SnF₂(SO₃F)₂. Attempts to find alternative synthetic routes to SnF₂(SO₃F)₂ were unsuccessful. Structural proposals for these compounds are based on infrared, Raman and ¹¹⁹Sn Mössbauer spectra. All the new compounds are found to be polymeric via fluorine or fluorosulphate bridges, resulting in penta- or hexacoordination around tin. Dialkyltin(IV) difluorides are easily obtained when the corresponding chlorides are solvolyzed in aqueous hydrogen fluoride. Dimethyltin, diethyltin, dipropyltin, dibutyltin and dioctyltin difluorides are prepared in this way. However, divinyltin(IV) difluoride and diphenyltin(IV) difluoride cannot be made via this route. Also, CH₃SnF₃ and the methyltin(IV) chloride fluorides cannot be synthesized from solvolysis reactions involving aqueous HF. / Science, Faculty of / Chemistry, Department of / Graduate

Single crystal X-ray diffraction methods have been used to determine the structures of four cyclic phosphonitriles: 1,1,5,5-tetrafluoro-3,3,7,7-tetramethylcyclotetra- phosphonitrile, N(4)P(4)F(4)Me(4) ; 1,1,3,3,5,5-hexafluoro-7,7-dimethyl- cyclotetraphosphonitrile, N(4)P(4)F(4)Me(2); hexaphenoxycyclotriphosphonitrile, [NP(OPh)2](3) and dodeca(dimethylamino)-cyclohexaphosphonitrilechlorocopper (II) dichlorocuprate (I), [formula omitted]. Intensity measurements were made on a Datex automated General Electric diffractometer using a scintillation counter; Cu-K [symbol omitted], radiation being used for the first three structure determinations and Mo-K [symbol omitted] radiation for the fourth. The structure of N(4)P(4)F(4)Me(4) has been determined by Patterson and Fourier methods and refined by full-matrix least-squares. The molecule is situated on a C(2) axis, and the phosphonitrilic ring has the 'saddle' conformation. Different electronegativities of the substituent groups result in two distinct P-N bond lengths, 1.53 and 1.59 Å explicable in terms of π -bonding theories. Patterson, Fourier, and full-matrix least-squares methods have been used to determine the structure of N(4)P(4)F(6)Me(2). This molecule is also situated on a C(2) axis and has the 'saddle' conformation, but tends strongly towards planarity. The most interesting features of the ring are four distinct P-N bond lengths (1.584, 1.470, 1.532, and 1.487 Å), and large valency angles (145°) at nitrogen, which are explicable in terms of π -bonding theories. The structure of [NP(CPh)2]3 was determined from Patterson and Fourier syntheses, and refinement of positional and thermal parameters of the atoms by block-diagonal least-squares. The phosphonitrilic ring is slightly non-planar, with two nitrogen atoms displaced by 0.15 Å in opposite directions from the plane of the other four (3P and 1N) atoms. The conformations of the phenoxy groups are different at the three phosphorus atoms, and there are small deviations among chemically-equivalent angles; these differences are probably a result of intra- and intermolecular steric effects. There are no differences among chemically equivalent bond lengths, the mean distances being P-N 1.575(2), P-O 1.582(2), 0-C 1.406(3) Å. The structure of [formula omitted] was determined by Patterson, Fourier, and full-matrix least-squares methods. The structure is ionic with the cation and anion each situated on a C(2) axis. The cation consists of a Cu(II) bonded to four nitrogens of the phosphonitrilic ring (N-Cu 2.07 Å) and a chlorine (Cℓ-Cu 2.28 Å) in a distorted square pyramid. The Cu(I)Cℓ2¯ anion is linear with a Cu-Cℓ bond length of 2.11 Å. There are two distinct P-N bond lengths in the phosphonitrilic ring, 1.62 and 1.55 Å, explicable by π -bonding theory. The overall shape of the structure is determined primarily by steric effects and the distortion of the phosphonitrilic ring caused by the bonding to copper. / Science, Faculty of / Chemistry, Department of / Graduate

The previously known complexes, RU₂H₄Cl₂(PR₃)₄, have now been correctly reformulated as the η²-H₂ species (η²-H₂)(PR₃)₂Ru(μ-Cl)₂(μ-H)RuH(PR₃)₂ (R = Ph, p-tol), 1a and 1b, and it is confirmed that in solution they are dimeric and undergo no ligand dissociation. Also, a new analogue of complexes of type 1 is reported: the complex (η²-H₂)(isoPFA)Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂,4, is formed from the reaction of RuCl₂(PPh₃)(isoPFA), 3b, with H₂ in methanol/benzene, and a crystal structure of 4 shows the η²-H₂ ligand; isoPFA and PPFA (see below) are ferrocene based, chelating P-N ligands, with the structures: [Chemical compound diagram omitted] R = Pri and Ph for isoPFA and PPFA, respectively. Complexes 1a, 1b and 4 all react with 1-hexene to give hexane; the main ruthenium phosphine product in the case of 1 is the corresponding RuHCl(PR₃)₃ complex, while 4 reacts to give a complex mixture of ruthenium phosphine complexes, including 3b. The amount of hexane formed from the reaction of 4 with hexene is quantified as 2 mol/mol 4. The hydrogenation of 1-hexene catalyzed by 1a is re-interpreted as occurring via the mechanism: (η²-H₂)(PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ + hexene K₁→(PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ + hexane (1) (PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ + H₂ K₂⇆(η²-H₂)(PPh₃)₂Ru(μ-Cl)₂(μ-H)RuH(PPh₃)₂ (2) Reactions of RuCl₂(PPh₃)(PPFA), 3a, and RuCl₂(PPh₃)(isoPFA), 3b, with H₂ have been further studied, in connection with earlier mechanistic studies on hydrogenation of organic substrates catalyzed by complex 3a. The complex 3a reacts with 2-8 atm H₂ in n-butanol to give ruthenium phosphine products including 1a. The complex 3b reacts with H₂ in methanol/benzene to give 4, as mentioned above, as well as a number of unidentified hydrides; in DMA, the reaction of 3b with H₂ gives 1a, 4, RuHCl(PPh₃)(isoPFA) (7), RuHCl(PPh₃)₃ and other unidentified ruthenium phosphine complexes. The product H₂NMe₂+Cl⁻ was also isolated from the methanol/benzene reaction mixture, and this product provides evidence that the amine functionality of the P-N ligands is involved in the promotion of the heterolytic cleavage of dihydrogen to give a proton and a hydride (H₂→ H⁺ + H⁻). Kinetic studies on the hydrogenation of 1-hexene catalyzed by 3a, and by 3b in the present work, are now interpreted according to the mechanism [Chemical compound diagram omitted] Reactions involving 3b and methanol have also been studied, and 3b is also active for the transfer hydrogenation (from methanol) of ketones and activated olefins. The reaction of 3b with methanol in the absence of base is proposed to occur with the stoichiometry: RuCl₂(PPh₃)(isoPFA) + 2MeOH→ H₂NMe₂⁺Cl⁻ + H₂ + 3b RuHCl(CO)(PPh₃)(isoPOF), 5 (5) where the ligand isoPOF is formed from isoPFA by replacement of the NMe₂ group on isoPFA by a methoxo group; reaction 6 could occur via the following steps: RuCl₂(PPh₃)(isoPFA) + MeOH→ RuHCl(CO)(PPh₃)(isoPFA), 6 3b + H₂ + HCl (6) RuHCl(CO)(PPh₃)(isoPFA) + MeOH→ RuHCl(CO)(PPh₃)(isoPOF), 5 + HNMe₂ (7) HCl + HNMe₂ H₂NMe₂⁺Cl⁻ (8) A mechanism for reaction 7 is presented and invokes reversible attack by MeOH with replacement of Cl⁻, followed by reversible deprotonation of coordinated MeOH to give successively methoxo, formaldehyde and formyl intermediates, and finally the hydrido-carbonyl, 6. The reaction of 3b with methanol in the presence of KOH is proposed to occur according to the stoichiometry: RuCl₂(PPh₃)(isoPFA) + KOH + CH₃OH→ RuHCl(CO)(PPh₃)(isoPFA) + KCI + H₂ + H₂O (9) and two pathways have been identified, one base-independent, identical to that proposed for reaction 7, and one showing a second-order dependence on KOH. The latter pathway invokes initial reversible attack on RuCl₂(PPh₃)(isoPFA), 3b, by MeO⁻, replacing Cl⁻ to give RuCl(OMe)(PPh₃)(isoPFA), and subsequent reversible replacement of PPh₃ by OH⁻, followed by concerted loss of OH⁻ and hydride transfer from coordinated OMe⁻ to give a hydrido-formaldehyde complex RuHCl(η²-CH₂O)(isoPFA). A subsequently formed formyl intermediate reacts via intramolecular hydride transfer from the formyl to the metal, H₂ loss, and phosphine coordination to give the hydrido-carbonyl 6. / Science, Faculty of / Chemistry, Department of / Graduate

This thesis describes a study of the low temperature specific heat of LiⅹNbS₂, where x is between 0 and 1. Samples were prepared by intercalating lithium into niobium disulfide in electrochemical cells. Structural data obtained by x-ray diffraction are presented. These, together with electrochemical measurements, show that staged phases exist for some values of x. The electronic specific heat of LiⅹNbS₂, is consistent with complete charge transfer from the intercalated lithium to the bands of the NbS2 host. The lattice specific heat also shows large changes as a function of x. A discussion of the data in terms of continuum elasticity theory suggests that intercalation produces large changes in the shear elastic constant C₄₄ . A brief discussion of superconductivity in LiⅹNbS₂, is also included. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An understanding of the electrochemical properties of organometallic nitrosyl compounds provides a good understanding of their chemistry and a more rational way to approach synthetic investigations. Cyclic voltammetry studies of [(ƞ)⁵-C₅H₅)Cr(NO)₂]₂ in CH₂Cl₂ and CH₃CN reveal that the dimer undergoes a single two-electron oxidation to form [(ƞ⁵⁻C₅H₅)Cr(NO)₂]⁺ which is reduced to [(ƞ⁵-C₅H₅)Cr(NO)₂]• (or [(ƞ⁵-C₅H₅)Cr(NO)₂(CH₃CN)]• in the presence of CH₃CN) in a subsequent reduction step. The radical couples to form [(ƞ⁵-C₅H₅)Cr(NO)₂]₂ or decomposes. The dimer also is reversibly reduced in a one-electron step in CH₂Cl₂ and quasi-reversibly in CH₃CN. These inferences are supported by cyclic voltammograms of (ƞ)⁵-CH₅)Cr(NO)₂BF₄ and [(ƞ⁵-C₅H₅)Cr(NO)₂(CH₃CN)]PF₆. In contrast, the isoelectronic dimer [(ƞ⁵-C₅H₅)Fe(CO)₂]₂ oxidizes in two one-electron steps (the first of which is reversible and negative of the oxidation of [(ƞ⁵-C₅H₅)Cr(NO)₂]₂) and reduces to form [(ƞ⁵-C₅H₅)Fe(CO)₂]⁻. The differing oxidation behaviours of these dimers suggest that their reactions with HBF₄•OMe₂ [(ƞ⁵-C₅H₅)Cr(NO)₂]₂ cleaves into [(ƞ⁵-C₅H₅)Cr(NO)₂]⁺ and [ƞ⁵-C₅H₅)Fe(CO)₂]₂ forms [ {(ƞ⁵-C₅H₅)Fe(CO)₂}₂H]⁺) do not occur by initial electron transfer. The new radical anion complex [(ƞ⁵-C₅H₅)Fe(ƞ⁶-C₆Me₆)] [ {(ƞ₅-C₅H₅)Cr(NO)₂}₂] can be isolated by reaction of the neutral dimer with (ƞ⁵-C₅H₅)Fe(ƞ⁶-C₆Me₆) in Et₂0. Its spectroscopic properties are consistent with derealization of the extra electron onto the NO ligands, particularly the bridging nitrosyl groups. These observations provide a better understanding of the reactivity of [(ƞ⁵-C₅H₅)Cr(NO)₂]₂ with- nucleophiles. A comparative electrochemical study of the oxidations of [(ƞ⁵-C₅H₅)M(NO)₂R (M = Cr, R = CH₃; M = Mo, W, R = CH₃, C₂H₅),(ƞ⁵-C₅H₅)Fe(CO)₂CH₃ and (ƞ⁵-C₅H₅)M(CO) ₃R (M = Cr, R = CH₃; M = Mo, W, R = CH₃, C₂H₅) in CH₂Cl₂ reveals that the dinitrosyl complexes are harder to oxidize than their related carbonyl compounds. Electrophilic cleavage reactions of M-R bonds in these complexes, which proceed differently for the nitrosyl and carbonyl complexes are proposed to involve different mechanisms, with the nitrosyl-alkyl complexes reacting with electrophiles by direct attack at the metal-alkyl bonds, rather than by prior oxidation. Interestingly, (ƞ⁵-C₅H₅)Cr(NO) ₂CH₃ reacts with NOPF₆ to form the NO-insertion product [(ƞ⁵-C₅H₅)Cr(NO)₂(CH₂NOH)]PF₆ which has been structurally and spectroscopically characterized. The reactions of (ƞ⁵-C₅H₅)M(NO)₂CH₃ (M = Mo, W) with electrophiles and oxidants result in cleavage of the M-CH₃ bonds. The complexes (ƞ⁵-C₅H₅)M(NO)₂Y (M = Cr, Y = CH₃; M = Mo, Y = CH₃, C₂H₅, Cl; M = W, Y = CH₃, C₂H₅, H, Cl), [(ƞ⁵-C₅H₅)M(NO)₂L] BF₄ (M = Mo, L = PPh₃; M = W, L = PPh₃, P(OMe)₃, ƞ²-C₈H₁₄) and W(NO)₂Cl₂L₂ (L = P(OMe)₃, PMePh₂) exhibit quite reversible, one-electron reductions in CH₂Cl₂ and the new radical complexes [(ƞ⁵-C₅H₅) ₂Co] [(ƞ⁵-C₅H₅)M(NO)₂Y] (M = Mo, Y = CH₃, C₂H₅, Cl; M = W, Y = CH₃, H, Cl) are isolable by reactions of (ƞ⁵-C₅H₅)₂Co with the neutral precursor. Spectroscopic characterization of these and an X-ray crystallogrpahic analysis of [(ƞ⁵-C₅H₅)₂Co] [(ƞ⁵-C₅H₅)Mo(NO)₂C₂H₅] suggest that the anions possess monomeric, "three-legged piano stool" geometries with delocalization of the extra electron onto the NO ligands. In light of these observations the chemistry of (ƞ⁵-C₅H₅)M(N0)₂Y complexes becomes more understandable. / Science, Faculty of / Chemistry, Department of / Graduate

The etching of indium phosphide and indium by H atoms and methyl radicals has been studied in a discharge flow system at temperatures between 25 and 300°C. The results indicate that the hydrogen atoms react with InP to produce In metal globules and PH₃(g) at temperatures greater than 160°C. Methyl radicals were not found to react with InP. However these radicals were found to react with indium metal and the globules that are produced in the reaction of hydrogen atoms with InP. Reactions were conducted by alternately etching with H atoms and then with CH₃ radicals. Rate constants for these reactions were determined at 300°C and these values were found to be consistent with the continuous etch rates observed for a mixture of H atoms and CH₃ radicals. The etched surfaces were studied by SEM, XPS and surface profilometry and their properties found to be consistent with the proposed mechanism for the reaction. / Science, Faculty of / Chemistry, Department of / Graduate

The compounds tris(N-ռ-propyl-3-hydroxy-2-methyl-4-pyridinonato) aluminum(III), -gallium(III), and -indium(III) and tris(N-ռ-butyl-3-hydroxy-2-methyl-4-pyridinonato)aluminum(III), -gallium(III), and -indium(III) were synthesized. All six compounds were prepared via the metal template effect. They were characterized by IR, FAB-MS, ¹H NMR, ²⁷Al NMR, and elemental analysis. Three of the six complexes were studied by single-crystal X-ray diffraction. They formed trihydrates, unlike their N-methyl and N-ethyl analogues, which formed dodecahydrates. The ռ-butyl complex Al(C₁₀H₁₄N0₂)₃‧3H₂0 (1) and ռ-propyl complexes Al(C₉H₁₂N0₂)₃‧3H₂0 [2], and Ga(C₉H₁₂N0₂)₃‧3H₂0 {3} were basically isostructural, crystallizing in the space group P3 with the following crystal parameters for 1, [2], and {3}: α= 15.885 (1) ([15.328 (1)], {15.367 (2)}) Å, c = 7.280 (8) ([7.2321 (2)], {7.256 (2)}) Å, Z = 2. The data were refined by using 1280 ([1377], {1802}) reflections with I>3σ(I) to R and Rա values of 0.047 ([0.057], {0.055)) and 0.061 ([0.077], {0.081}), respectively. The complexes exist as the rigidly fac geometries with infinite chains of hydrogen bonds parallel to the c axis. / Science, Faculty of / Chemistry, Department of / Graduate

Complexes of dodeca(dimethylamino)cyclohexaphosphonitrile with, divalent first series transition metal ions manganese through zinc have been studied. Previous X-ray work has established that N₆P₆ (NME₂)₁₂ forrns five-coordinate complexes with transition metal chlorides in which the phosphonitrile donates to the metal through four ring nitrogen atoms and the metal atom is close to the centre of the phosphonitrilic ring. In the present work, the complexes with metal nitrates have been shown to have the formulae (M(N₆P₆ (NMe₂)₁₂)N0₃+)N0₃~, with M = Mn,Co,Ni,Cu, and Zn, on the basis of conductivity measurements and the electronic spectra of the Co, Ni, and Cu complexes. Magnetic susceptibility measurements indicate that the nitrate complexes with M = Mn,Co, and Ni are high spin complexes. For the copper nitrate complex the above formulation is probably correct in the solid state, but in solution coordination evidently depends on the solvent. The electronic spectra are best interpreted in terms of D₃[sub h] symmetry about the metal, and the crystal field parameters derived from published energy level diagrams are similar to corresponding values derived for five-coordinate complexes formed with N (CH₂CH₂N(CH₃)₂)₃ • a saturated tetradentate amine ligand. Infrared spectra of N₆P₆(NMe₂)₁₂ and its complexes are also discussed. In order to investigate changes in -the ligand geometry-occurring when other phosphonitrilic derivatives coordinate to transition metals or interact with other acceptor groups the crystal structures of (N₄P₄Me₉⁺)(Cr(CO)₅I⁻), ((NPMe₂)₅H₂²⁺)(CuCl₄²⁻)•H20, and (N₄P₄ (NMe₂)₈-W(CO)₄ have been determined. For all three structures intensity data were collected on a diffractometer and the positional and thermal parameters were refined by full-matrix least-squares methods. In (N₄P₄ (NPME⁺)(Cr(CO)₅l⁻) a ring nitrogen atom is bonded to a methyl group, and the N₄P₄ ring has an unusual 'distorted tub' conformation, most likely a result of steric requirements The P-N bond lengths are not equal around the ring, and the observed pattern of bond length variation agrees qualitatively with the pattern predicted by a simple Hiickel M.O. calculation The geometry of the Cr(CO)^I~ ion closely approaches the expected C4v symmetry. In ((NMe₂)₅ H₂²⁺)( CuCl₄²⁻)•H20 the 10-membered phosphonitrilic ring is protonated at two sites, and the P-N bond lengths show a variation which is explained in terms of perturbation of a homomorphic ring π-system. The conformation of the N₅P₅, ring is influenced primarily by hydrogen 2-bondmg considerations. The CuCl₄ ion has a distorted tetrahedral geometry. In N₄P₄(NMe₂)₈-W(CO)₄ the phosphonitrile acts as a bi-dentate ϭ-ligand, coordination occurring through a ring nitrogen atom and an exocyclic nitrogen atom on an adjacent phosphorus atom. The observed variation in the ring P-N bond lengths is understood in terms of perturbations of the ring π systems at two sites. The conformation of the phospho-nitrilic ring is different from that in N₄P₄(NMe₂)₈, the ring being formed from two nearly planar segments making an angle of 48°. The coordination geometry about W is distorted octahedral, the NWN angle being 65.4°. / Science, Faculty of / Chemistry, Department of / Graduate

The reaction of chromocene with nitrogen monoxide in a variety of organic solvents leads to the formation of CpCr(NO)₂ (n¹-C₅H₅) as the major product, as well as CpCr(NO)₂ (NO₂) and [CpCr(NO)₂]₂ as minor products. Their formation in these conversions can be rationalized in terms of the reactive intermediate CpCr(NO) ₂. The reaction of photochemically generated molybdenocene with nitrogen monoxide to produce CpMo (NO) ₂ (n¹-C₅H₅) is also described. Sodium dihydridobis(2-methoxyethoxy)aluminate, I, undergoes metathetical reactions in benzene with a variety of nitrosyl halide complexes. Thus treatment of CpCr(NO) ₂X (X = NO₃, NO₂, I, n¹-C₅H₅, or BF₄), CpMn(CO) (NO)I, CpCo(NO)I, and [CpMo(NO) I₂] ₂ with I in 1:1 stoichiometries affords the respective dimeric compounds [CpCr (NO) ₂]₂, [CpMn (CO) (NO) ] ₂, [CpCo(NO)] ₂ and [CpMo (NO) I] ₂ . These latter conversions probably proceed via thermally unstable hydrido complexes. The chromium dimer also results from the reaction [CpCr(NO)₂ (CO)]PF₆ with the aluminum reagent and reacts further with I to produce in low yields a mixture of Cp₂Cr₂ (NO) (NH₂), Cp₂Cr₂ (NO) ₂ (NH₂)₂, and Cp₂Cr₂ (NO) ₂~ (NH₂)(OH). In a similar manner, Fe(NO) ₃Cl is converted by I to Fe₂ (NO) ₄ (NH₂)₂. Reduction of [CpCr(NO) ₂]₂ with BH₃ and with LiEt₃BH produces the same three bimetallic products as when I serves as the reducing agent, and in comparably low yields. However, with LiEt₃BH as reductant the complexes CpCr(NO) ₂Et and Cp₂Cr₂ (NO) ₃ (EtNBEt₂) are also formed, reflecting unprecedented modes of reactivity of the hydridoborate. An x-ray crystallographic analysis of the new Cp₂Cr₂ (NO) ₃ (EtNBEt₂) complex has been performed. The most chemically interesting feature of the molecular structure is the novel EtNBEt₂ ligand which is coordinated via N in a symmetrical fashion to the two Cr atoms. The coordination environment around N is that of a distorted tetrahedron, but the N-B distance of 1.459(5) & suggests some degree of multiple bonding between these two atoms. Such an inference is consistent with the stability of the complex and its spectroscopic properties. The preparation and characterization of several organometallic hydridonitrosyl complexes, i.e. CpMo(NO)₂H and [Cp₂M₁M₂ (NO) ⁴H] ⁺X⁻ (M₁ = M₂ = Mo, W; M₁ = Mo, M₂ = W: X = BF₄ and/or PF₆) are described. The monometallic hydride is prepared by reduction of CpMo(NO)₂Cl with I, while the homonuclear bimetallic cations are formed upon reaction of CpM(NO)₂H (M = Mo, W) with 0.5 equivalents of a hydride abstraction agent such as Ph₃C⁺X⁻ or C₇H₇BF₄ in CH₂Cl₂. The heteronuclear cation can be prepared by the reaction of CpMo(NO)₂Cl with AgBF₄ to produce CpMo(NO)₂ ⁺BF₄⁻, which may then be reacted with CpW(NO)₂H to yield the cation. Attempts to deprotonate these cations with a variety of bases result in cleavage of the metal-metal bond to yield the hydride and a monometallic cation of the type CpM(NO)₂(L)⁺ (where L is the base used). The failure of the attempted deprotonations led to an examination of the Lewis base properties of CpW(NO)₂H and of the Lewis acid properties of CpW(N0)₂⁺. Specifically, the interaction of CpW(NO)₂H with a variety of soft (i.e. Cr(CO)₅, W(CO)₅, (MeCp)Mn(CO)₂, HgCl₂, and CdCl₂), borderline (i.e. ZnCl₂), and hard (i.e. H+, AlCl₃, and BEt₃) Lewis acids is observed spectroscopically. The observed Lewis base characteristics of CpW(NO) ₂H are discussed in light of these results, and when combined with the Lewis acid properties of CpW(NO)₂+, it is possible to rationalize the failure to prepare the dimers [CpM(NO)₂]₂ (M = Mo, W) via the desired route. / Science, Faculty of / Chemistry, Department of / Graduate