Doherty, Simon; (1991) Aspects of the transition metal coordination chemistry of phenylphosphine. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis describes the synthesis and reactions of phosphido complexes of both the early and late transition-metals. The thermal reaction of dodecacarbonyltriruthenium with phenylphosphine (and its cyclohexyl analogue) was investigated and new trinuclear clusters with combinations of terminal phosphine, bridging phosphido and μ3-phosphinidene ligands were isolated. These have been characterised by n.m.r. methods and the single-crystal structures of [Ru3 (μ-H)2(μ3-PPh)(PPhH2)(CO)8] and [Ru3(μ-H)(μ-PPhH)3(CO)7] have been deduced. The pyrolysis of [Ru3(m-PPh)2(CO)9] was investigated and was found to yield new hexanuclear clusters of which the fluxional trigonal prismatic structures [Ru6(μ3-H)2(μ3-PPh)2(μ4-PPh)2(CO)12] and [Ru6(μ3-PPh)2(μ4-PPh)2(CO)12] have been crystallographically determined. Their metal frameworks were found to have interesting features and are compared with the known structure [Ru6(μ3-PPh)2(μ4-PPh)3(CO)12]. We have synthesised the terminal phosphine complexes [IrCl2(PMe2Ph)3(PHR1R2)][ClO4] (R1 = R2 = H, R1 = H R2 = Ph, R1 = R2 = Ph) and these were found to deprotonate readily in the presence of base to afford the corresponding neutral phosphido complexes. Reactions of these phosphido complexes with both organic and metallic electrophiles was investigated and the crystal structure of [{IrCl2(PMe2Ph)3(PH2)}2Au][ClO4] was determined. Investigating the origin of the broad n.m.r. spectrum of [IrCl2(PMe2Ph)4][ClO4] (formed from the reaction of the phosphido complex [IrCl2(PMe2Ph)3(PPhMe)] with MeI) afforded evidence for at least three isomers in solution at low-temperature. The low temperature 31P-{1H} n.m.r. spectrum and its 31P-31P DQCOSY spectrum recorded at -75 °C have been analyzed in terms of these conformational isomers. Further investigations of the tetrakis-phosphine complexes [IrCl2(PMe3)3(PMe2Ph)][ClO4] and [IrCl2(PMe3)3(PMePh2)][ClO4] also showed the presence of rotational isomers. A controlled synthesis of the cluster [Os3(μ-H)(μ-PPhMe)(CO)10] is reported and the reactions of the anionic phosphinidene cluster [Os3(μ-H)(μ-PPh)(CO)10] with electrophiles are included. Reaction of the anion with methyliodide gave [Os3(μ-H)(μ- PPhMe)(CO)10] characterised crystallographically and found to contain an endo phenyl group indicating inversion of stereochemistry at phosphorus. The crystal structure of [{Os3(μ3-PPh)(CO)10}2Hg] is described. Reaction of the anionic phosphido complex [Mo(CO)5(PPhH)] with the metal electrophiles [PtCl2(dppe)] and [PtCl2(Pet3)2] was seen to be simple nucleophilic substitution at the platinum(II) centres. A single major product isolated from the reaction of the [Mo(CO)5(PPhH)]- with [PtCl2(dppe)] was isolated. The single-crystal X- ray structure of this compound revealed it to be [Pt(μ-PPhH)2{Mo(CO)5}2(dppe)]. 31P{1H) n.m.r. studies of this complex confirmed the existence of two diastereoisomers and these have been separated using preparative HPLC techniques. We have also shown that these complexes exist as several rotameric isomers in solution giving rise to broad n.m.r. signals in the 31P{1H} n.m.r. spectrum. The synthesis of [Pt(μ-PPhH)2{Mo(CO)5)2(PPh2C2H2PPh2)] and [Pt(μ-PPh)2{Mo(CO)4}(dppe)] reinforced the above proposal regarding rotamers in solution and these compounds are observed to occur in both possible diastereoisomeric forms. Three products have been identified from the reaction of [Mo(CO)5(PPhH)]- with [PtCl2(PEt3)2] and extensive 31P{1H} n.m.r. investigations carried out. The single-crystal X-ray structures of the two products [Pt(μ- PPhH){Mo(CO)5}Cl(PEt3)2] and trans-[Pt(μ-PPhH)2{Mo(CO)5}2(PEt3)2] have been determined. Variable-temperature 31P{1H} n.m.r. studies have shown the former complex to exist in three rotameric forms in solution and these are rapidly exchanging at room temperature. The trinuclear complex [Pt(μ-PPhH)2{Mo(CO)5)2}(PEt3)2] was identified in both cis and trans forms, the former isomer was identified by n.m.r. methods whilst the single-crystal X-ray structure of the trans isomer was determined. The 31P{1H} n.m.r. spectrum of trans-[Pt(μ-PPhH)2{Mo(CO)5}2(PEt3)2] revealed the existence of two diastereiosomeric forms.

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