Donor-acceptor complexes incorporating ferrocenes: spectroelectrochemical characterisation, quadratic hyperpolarisabilities and the effects of oxidising and reducing agents

Royal Society of Chemistry
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Journal Article
Journal of the Chemical Society - Dalton Transactions, 2001, 20 pp. 3025 - 3038
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The donor-acceptor complexes [Fe(C5H5){C5H4QNHM(NO)(TpMe,Me)X}] {TpMe,Me= tris(3,5-dimethylpyrazolyl)borate; Q = nothing, M = Mo, X = Cl, Br, I; M = W, X = Cl; Q = C6H4, M = Mo, X = Cl, Br, I; M = W, X = Cl; Q = CHCHC6H4 or NNC6H4, M = Mo, X = Cl), which contain 16-valence electron metal nitrosyl centres, [Fe(C5H5){C5H4QpyMo(NO)(TpMe,Me)Cl}] (py = 4-pyridyl; Q = CHCH, CHCHCO, NCH and C6H4CHCH), [Fe(C5Me4H){C5H4CHCHpyMo(NO)(TpMe,Me)Cl}] and [Fe(C5Me4H)(C5Me4QpyZ)] {Q = CHCH or CHN, Z = Mo(NO)(TpMe,Me)Cl or W(CO)5; Q2,4-CHCH(C4H2S)CHCH, Z = W(CO)5 or Me+I}, some of which contain 17-valence electron molybdenum nitrosyl centres, and [Fe(C5Me4H){C5Me4CHCH(C4H2S)CHCHpy}], have been characterised electrochemically, by their electronic spectra, and spectroelectrochemically. Hyper-Rayleigh scattering was used to determine the first hyperpolarisability, , the data showing that (a) is dependent on the metal in the acceptor fragment, (b) increased when Cl or Br was replaced by I and (c) increased when the number of methyl groups on the cyclopentadienyl rings increased. The -values for comparable complexes containing {Mo(NO)(TpMe,Me)Cl} and {W(CO)5} moieties were similar. Chemical oxidation of the ferrocenyl or chemical reduction of the molybdenum nitrosyl acceptor fragments in selected complexes caused a reduction of between 25% and 100% in the NLO response. X-Ray structural studies of [Fe(C5H5){C5H4NHMo(NO)(TpMe,Me)Cl}] (P) and [Fe(C5Me4H){C5Me4CHCHpyMo(NO)(TpMe,Me)Cl}] (P) are reported.
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