The reduction of high oxidation state metal complexes in the presence of molecular nitrogen is one of the most common methods to synthesize a dinitrogen complex. However, the presence of strong reducing agents combined with the poor binding ability of N2 can lead to unanticipated outcomes. For example, the reduction of [NPN]ZrCl2(THF) (where NPN = PhP(CH2SiMe2NPh)2) with KC8 under N2 leads to the formation of the side-on bridged dinuclear dinitrogen complex ([NPN]Zr(THF))2(mu-eta2:eta2-N2) with an N-N bond distance of 1.503(3) A; however, reduction of the corresponding titanium precursor, [NPN]TiCl2, under N2 does not generate a dinitrogen complex, rather the bis(phosphinimide) derivative, ([N(PN)N]Ti)2, is isolated in which the added N2 is incorporated between the titanium and phosphine centers. Performing the reaction under 15N2 results in the 15N label being incorporated in the phosphinimide unit. A suggested mechanism for this process involves an initially formed dinitrogen complex being over reduced to generate a species with bridging nitrides that undergoes nucleophilic attack by the coordinated phosphine ligands and formation of the P=N bond of the phosphinimide.

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Reduction of titanocene difluoride (Cp2TiF2) with 1.5 equiv of potassium in toluene at 60−100 °C affords the dinuclear η5:η5-fulvalene complex [(η5-C5H5)Ti(μ-F)]2(μ-η5:η5-C10H8) (2). 2 was also obtained via reaction of Me3SnF with the corresponding chloride and hydride compounds [(η5-C5H5)Ti(μ-X)]2(μ-η5:η5-C10H8) (X = Cl, H). 2 has been characterized by mass spectrometry, IR spectroscopy, and chemical analyses. The molecular structure of 2, as determined by the X-ray crystal structural analyses, reveals a Ti2F2 fragment symmetrically folded along the Ti−Ti direction and assuming a butterfly configuration with a dihedral angle of 27.6(2)°. A dihedral angle of 15.3(3)° is observed between the two C5H4 rings of the folded fulvalene ligand.

The reaction of the dilithiodiamidophosphine ligand precursor PhP(CH2SiMe2NPh)2Li2(THF)2([NPN]Li2(THF)2) with LnCl3(THF)3 (Ln = Y, Sm, Ho, Yb, Lu; THF = tetrahydrofuran) in refluxing toluene generates the mononuclear complexes [NPN]LnCl(THF) in good yield. The molecular structures have been shown to be five-coordinate in the solid state and in solution. Attempts to prepare alkyl derivatives have only met with partial success; the reaction of MeMgCl with [NPN]YCl(THF) generates the partially characterized mixed-metal derivative [NPN]YMe2MgCl. The reaction with LiAlH4 results in complete ligand exchange and the formation of the tetranuclear lithium aluminum hydride derivative {[NPN]AlH2Li(THF)}2. Reduction of the lutetium derivative with KC8 and naphthalene generated the dinuclear naphthalene-bridged species {[NPN]Lu}2(µ-η4:η4-C10H8) wherein each Lu centre engages in η4-coordination to opposite sides of the arene moiety. X-ray crystallography was used to characterize the four complexes.Key words: lanthanides, yttrium, mixed-donor ligands, aluminum, lithium, naphthalene.

Trapped as molecular solids, the transition metal fluorides ZnF(2) and MeZnF-the latter isolated for the first time-exist as adducts in [(Cp*TiF(3))(8)(ZnF(2))(3)] (1) and [(Cp*TiF(3))(4)(MeZnF)(2)] (2), respectively. Compounds 1 and 2 were obtained in reactions of [Cp*TiF(3)] (Cp*=C(5)Me(5)) with ZnMe(2) and Me(3)SnF in various molar ratios. The single-crystal structure of 1 is shown here; the unlabeled circles are F atoms.