Tris(acetonitrile-κN){2,6-bis[(diphenylphosphanyl)amino]-4-ethoxy-1,3,5-triazine-κ3 P,N 1,P′}iron(II) bis(tetrafluoridoborate) acetonitrile disolvate

In the title compound, [Fe(CH3CN)3(C29H27N5OP2)](BF4)2·2CH3CN, the FeII ion is octahedrally coordinated by a meridionally chelating tridentate pincer-type PNP ligand derived from 2,6-diamino-4-ethoxy-1,3,5-triazine and by three acetonitrile molecules. The four Fe—N bond lengths range from 1.9142 (12) to 1.9579 (11) Å, while the Fe—P bonds are 2.2452 (4) and 2.2506 (4) Å [P—Fe—P = 165.523 (14)°], consistent with FeII in a low-spin state. Unlike related Fe PNP complexes based on 2,6-diaminopyridine, the BF4 anions are not hydrogen bonded to the two NH groups of the pincer ligand but show instead anion–π interactions with the triazine ring and acetonitrile molecules in addition to ten C—H⋯F interactions. Most remarkable among these is an anion–π(triazine) interaction with a short distance of 2.788 (2) Å between one F and the centroid of the π-acidic triazine ring. The corresponding shortest distance between this F atom and a triazine carbon atom is 2.750 (2) Å. The two NH groups of the pincer ligand donate N—H⋯N hydrogen bonds to the triazine N atom of a neighbouring complex and to an uncoordinated acetonitrile molecule. This last molecule is in a side-on head-to-tail association with the second uncoordinated acetonitrile at C⋯N distances of 3.467 (2) and 3.569 (2) Å. In contrast to several related compounds with diaminopyridine- instead of diaminotriazine-based PNP ligands, the title crystal structure is remarkably well ordered. This suggests that the diaminotriazine moiety exerts notable crystal structure stabilizing effects.

In the title compound, [Fe(CH 3 CN) 3 (C 29 H 27 N 5 OP 2 )](BF 4 ) 2 Á-2CH 3 CN, the Fe II ion is octahedrally coordinated by a meridionally chelating tridentate pincer-type PNP ligand derived from 2,6-diamino-4-ethoxy-1,3,5-triazine and by three acetonitrile molecules. The four Fe-N bond lengths range from 1.9142 (12) to 1.9579 (11) Å , while the Fe-P bonds are 2.2452 (4) and 2.2506 (4) Å [P-Fe-P = 165.523 (14) ], consistent with Fe II in a low-spin state. Unlike related Fe PNP complexes based on 2,6-diaminopyridine, the BF 4 anions are not hydrogen bonded to the two NH groups of the pincer ligand but show instead anion-interactions with the triazine ring and acetonitrile molecules in addition to ten C-HÁ Á ÁF interactions. Most remarkable among these is an anion-(triazine) interaction with a short distance of 2.788 (2) Å between one F and the centroid of the -acidic triazine ring. The corresponding shortest distance between this F atom and a triazine carbon atom is 2.750 (2) Å . The two NH groups of the pincer ligand donate N-HÁ Á ÁN hydrogen bonds to the triazine N atom of a neighbouring complex and to an uncoordinated acetonitrile molecule. This last molecule is in a side-on head-to-tail association with the second uncoordinated acetonitrile at CÁ Á ÁN distances of 3.467 (2) and 3.569 (2) Å . In contrast to several related compounds with diaminopyridine-instead of diaminotriazine-based PNP ligands, the title crystal structure is remarkably well ordered. This suggests that the diaminotriazine moiety exerts notable crystal structure stabilizing effects.
In the title compound, (I), iron is in a distorted octahedral coordination by the PNP ligand and three acetonitrile molecules providing a P 2 N 4 set of donor atoms ( Fig. 1) with bond lengths to Fe1 listed in Table 1  Whereas the above mentioned related Fe PNP compounds are all plagued by orientation disorder of their BF 4 counter anions, the title compound (I) is well ordered with respect to BF 4 and the two noncoordinating acetonitrile solvent molecules as well. This is interesting because the BF 4 anions normally form N-H···F hydrogen bonds with the distinctly acidic NH groups of the PNP ligands (Benito-Garagorri et al., 2006), while in (I) they do not. As outlined in Fig. 2 Fig. 2, this CH 3 CN molecule is in close head-to-tail association with the second noncoordinating CH 3 CN molecule, N9···C38 = 3.569 (2) Å, C36···N10 = 3.467 (2) Å, helping to fix that molecule in the crystal lattice. The two BF 4 anions in turn are engaged in C-H···F and anion-π interactions. There are ten C-H···F interactions with C···F distances in the range 3.144 (2) to 3.464 (2) Å (cf. Table 2) of which a part is shown in  , 2008). The three shortest distances of F7 to ring atoms are N1 3.012 (2), C1 2.750 (2), N2 2.915 (2) Å. Compared with literature data this is among the shortest F-π-interactions reported so far (Gamez et al., 2007;Mooibroek et al., 2008;Manzano et al., 2008, Quinonero et al., 2010Lu et al., 2009). For instance, Mooibroek et al.
(2008) report in their exhaustive CSD date base analysis a mean value of D = 3.060±0.184 Å for eight crystal structures with BF 4 anions and 1,3,5-triazines, and a corresponding value of D = 3.076±0.185 Å for 26 cystal structures with PF 6 anions.
A packing diagram of the structure is presented in Fig. 3. It gives only the N-H···N hydrogen bonds showing that they link two Fe PNP complexes and two noncoordinating CH 3 CN molecules into a centrosymmetric dimer. The C-H···F and anion-π interactions link all constituents in a three-dimensional supramolecular fashion. π-π stacking between arene rings is lacking in (I).

Experimental
The title compound, (I), was synthesized by a three-step procedure. 2,6-Diamino-4-ethoxy-1,3,5-triazine: 2,6-Diamino-4chloro-1,3,5-triazine (3.0 g, 20.6 mmol, Sigma-Aldrich) was suspended in 40 ml of EtOH and treated with KOH (   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.