Bis{μ-[(diphenylphosphoryl)methyl](phenyl)bis(1H-pyrazol-1-yl)boranuido}dilithium

The title compound, [Li2(C25H23BN4OP)2], features a centrosymmetric dimeric complex. The four-memberered Li2O2 ring is exactly planar due to symmetry. The Li atom is four-coordinated by two O atoms and by two N atoms of two different pyrazole rings. The dihedral angle between two pyrazole rings bonded to the same B atom is 45.66 (9)°. The B—N—N—Li—N—N metalla ring adopts a boat conformation. The crystal packing is stabilized by van der Waals interactions only.

The title compound, [Li 2 (C 25 H 23 BN 4 OP) 2 ], features a centrosymmetric dimeric complex. The four-memberered Li 2 O 2 ring is exactly planar due to symmetry. The Li atom is fourcoordinated by two O atoms and by two N atoms of two different pyrazole rings. The dihedral angle between two pyrazole rings bonded to the same B atom is 45.66 (9) . The B-N-N-Li-N-N metalla ring adopts a boat conformation. The crystal packing is stabilized by van der Waals interactions only.
Supporting information for this paper is available from the IUCr electronic archives (Reference: SJ5403).

Comment
One way to alter the donor/acceptor properties of scorpionate ligands over a wider range is to replace the pyrazolyl rings by phosphorus-containing groups (Trofimenko, 1993;Trofimenko, 1999;Bieller et al., 2006). Similar to parent scorpionates these ligands provide a monoanionic, tridentate, face-capping coordination mode, but they differ from parent scorpionates with regard to the softness of their donor sets. Recently we have investigated the syntheses of the hybrid scorpionates Li(tmeda)[PhBpz 2 (CH 2 PPh 2 )] (I) and Li(tmeda) 2 [PhB(CH 2 PPh 2 ) 3 ] (II) (Müller et al., 2014a). The lithium scorpionates I and II, however, are air-sensitive. The heteroscorpionates I and II react with oxygen from the air to give the corresponding oxo-heteroscorpionates as shown in the scheme (Fig. 1). After storing solutions of I and II under ambient conditions (in the presence of oxygen from the air) crystals of the oxo-heteroscorpionates III and IV could be isolated (Müller et al., 2014b).
The title compound features a centrosymmetric dimeric complex (Fig. 2). The four-memberered Li 2 O 2 ring is exactly planar due to the symmetry. Each Li centre is four-coordinated by two oxygen atoms and two nitrogen atoms of two different pyrazol rings. The dihedral angle between two pyrazol rings bonded to the same boron atom is 45.66 (9)°. The B -N-N-Li-N-N ring adopts a boat conformation. The crystal packing is stabilized only by van der Waals interactions (Fig. 3).

Experimental
Single crystals of the oxo-scorpionate III were grown from a thf solution of I in the presence of air oxygen at r.t.

Figure 2
Perspective view of the title compound with displacement ellipsoids drawn at the 50% probability level. Hydrogen atoms omitted for clarity.  Packing diagram of the title compound with view onto the bc plane. Hydrogen atoms omitted for clarity.

Bis{µ-[(diphenylphosphoryl)methyl](phenyl)bis(1H-pyrazol-1-yl)boranuido}dilithium
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.