N,N,N′,N′,N′′-Pentamethyl-N′′-[3-(trimethylazaniumyl)propyl]guanidinium bis(tetraphenylborate)

In the crystal structure of the title salt, C12H30N4 2+·2C24H20B−, the C—N bond lengths in the central CN3 unit of the guanidinium ion are 1.3388 (17), 1.3390 (16) and 1.3540 (17) Å, indicating partial double-bond character in each. The central C atom is bonded to the three N atoms in a nearly ideal trigonal-planar geometry and the positive charge is delocalized in the CN3 plane. The bonds between the N atoms and the terminal C-methyl groups of the guanidinium moiety, all have values close to a typical single bond [1.4630 (16)–1.4697 (17) Å]. C—H⋯π interactions are present between the guanidinium H atoms and the phenyl C atoms of one tetraphenylborate ion. The phenyl rings form a kind of aromatic pocket, in which the guanidinium ion is embedded.

In the crystal structure of the title salt, C 12 H 30 N 4 2+ Á2C 24 H 20 B À , the C-N bond lengths in the central CN 3 unit of the guanidinium ion are 1.3388 (17), 1.3390 (16) and 1.3540 (17) Å , indicating partial double-bond character in each. The central C atom is bonded to the three N atoms in a nearly ideal trigonal-planar geometry and the positive charge is delocalized in the CN 3 plane. The bonds between the N atoms and the terminal C-methyl groups of the guanidinium moiety, all have values close to a typical single bond [1.4630 (16)-1.4697 (17) Å ]. C-HÁ Á Á interactions are present between the guanidinium H atoms and the phenyl C atoms of one tetraphenylborate ion. The phenyl rings form a kind of aromatic pocket, in which the guanidinium ion is embedded.  Table 1 Hydrogen-bond geometry (Å , ).

Refinement
The hydrogen atoms of the methyl groups were allowed to rotate with a fixed angle around the C-N bond to best fit the experimental electron density, with U(H) set to 1.5 U eq (C) and d(C-H) = 0.98 Å. The remaining H atoms were placed in calculated positions with d(C-H) = 0.99 Å (H atoms in CH 2 groups) and (C-H) = 0.95 Å (H atoms in aromatic rings).
They were included in the refinement in the riding model approximation, with U(H) set to 1.2 U eq (C).

Figure 1
The structure of the title compound with displacement ellipsoids at the 50% probability level. All hydrogen atoms were omitted for the sake of clarity.  C-H···π interactions (brown dashed lines) between the hydrogen atoms of the guanidinium ion and the phenyl carbon atoms of one tetraphenylborate ion.

N,N,N′,N′,N′′-Pentamethyl-N′′-[3-(trimethylazaniumyl)propyl]guanidinium bis(tetraphenylborate)
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 R-factors(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.