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Pyrazolyl ligands in mixed metal complexes

University of British Columbia

The anions LMo(CO)₃⁻ (L = MeGapz₃ or MeGa(3,5-Me₂pz)₃) have been isolated as the Na⁺, Et₄N⁺ or HAsPh₃⁺ salts and the solution structures of the Na⁺ salts in THF have been defined by analysis of the v[sub CO] ir spectra. Ion-pair interaction of the LMo(CO)₃⁻ anion with Na⁺cation in THF solution is apparent from the spectroscopic evidence obtained. The MeGapz₃Mo(CO)₃ ⁻anion reacted with HCl or EtBr to give the seven-coordinate [MeGapz₃]-Mo(CO)₃R (R = H or Et) complexes. However, with Mel or PhCOCl complexes of the type [MeGapz₃]Mo(CO)₂(n₂-COR) (R = Me or Ph) were obtained. The reactions of the LMo(CO)₃⁻ ions (L = MeGapz₃ HBpz₃ or Me₂Gapz(0-CH₂CH₂NMe₂)) with a variety of transition metal halide species have yielded complexes with transition metal-transition metal bonds. The X-ray crystal structures of two such complexes [MeGapz₃]Mo(CO)₃Cu(PPh₃) and [MeGapz₃]Mo-(CO)₃Rh(PPh₃)₂ have been determined. The former complex provides a rare example of a 3:3:1, or capped octahedral structure, with a short (mean) Mo-Cu distance of 2.513(9)Å. The latter compound displays one terminal and two bridging CO ligands and a Mo-Rh distance of 2.6066(5)Å. Transition metal-group 14 (Si, Ge or Sn) element bonded complexes of the type [MeGapz₃]Mo(CO) ₃M'Y (Y = Me₃ or Ph₃, M' = Ge or Sn; Y = Me₃, M' = Si; Y = Me₂Cl, M' = Sn) have been prepared from the reaction of the MeGapz₃Mo(CO)₃anion with the appropriate organo-group 14 chloride. In all the complexes, direct Mo-M' (M' = Si, Ge or Sn) single bonds are featured. The [MeGapz₃]Mo(CO) ₃SnMe₂Cl complex shows an interesting solution behaviour in which a transition from a 3:4, or piano stool structure, to a 3:3:1, or capped octahedral arrangement, is thought to occur. The 3:3:1 structure has been demonstrated in the solid state for the [MeGapz₃]Mo(CO)₃SnPh₃ compound by means of a crystal structure determination. The 'Mo-SnPh₃' and the 'Mo-Cu' compounds discussed in this work are the first examples of such complexes incorporating either the MeGapz₃⁻, HBpz₃⁻ or C₅H₅⁻ ligands in which the 3:3:1 arrangement has been demonstrated unequivocally. The novel tridentate unsymmetric ligands Me₂GapzO(C₅H₃N)CH₂NMe₂⁻ (L[sub a]⁻) and Me₂GapzO(C₉H₆N)⁻ (L[sub q]⁻) have been prepared and numerous transition metal compounds containing these ligands synthesized. The compounds L[sub a] M(CO)₃(M = Mn or Re) are the first examples of transition metal carbonyl complexes in which both the fac and mer arrangements of the unsymmetric ligand about the central metal have been found to co-exist in solution. The square planar rhodium(I) complex, L[sub q]Rh(CO) has been shown to add Mel oxidatively, followed by facile methyl migration reaction to produce the five-coordinate Rh(III) acetyl derivative, L[sub q]Rh(COMe)I. In contrast, the reaction of L[sub a]Rh(CO) with Mel, led to the six-coordinate Rh(III) oxidative addition product, L[sub a]Rh(Me)(I)CO.

Text

2010-08-07

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http://hdl.handle.net/2429/27178

Chemistry

University of British Columbia

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