4-[(tert-Butyldiphenylsilyloxy)methyl]pyridazin-3(2H)-one

In the title compound, C21H24N2O2Si, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether group are placed toward opposite sides and the tert-butyl and pyridazinone moieties are anti-oriented across the Si—O bond [torsion angle = −168.44 (19)°]. In the crystal, molecules are assembled into inversion dimers through co-operative N—H⋯O hydrogen bonds between the NH groups and O atoms of the pyridazinone rings of neighbouring molecules. The dimers are linked by π–π interactions involving adjacent pyridazinone rings [centroid–centroid distance = 3.8095 (19) Å], generating ladder-like chains along the b-axis direction. The chains are further linked into a two-dimensional network parallel to the ab plane through weak C—H⋯π interactions.

In the title compound, C 21 H 24 N 2 O 2 Si, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether group are placed toward opposite sides and the tert-butyl and pyridazinone moieties are anti-oriented across the Si-O bond [torsion angle = À168. 44 (19) ]. In the crystal, molecules are assembled into inversion dimers through co-operative N-HÁ Á ÁO hydrogen bonds between the NH groups and O atoms of the pyridazinone rings of neighbouring molecules. The dimers are linked byinteractions involving adjacent pyridazinone rings [centroid-centroid distance = 3.8095 (19) Å ], generating ladder-like chains along the b-axis direction. The chains are further linked into a two-dimensional network parallel to the ab plane through weak C-HÁ Á Á interactions.   Table 1 Hydrogen-bond geometry (Å , ).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. All H-atoms were positioned and refined using a riding model with d(C-H)= 0.93 Å, U iso = 1.2U eq (C) for aromatic C-H groups,d(C-H)= 0.97 Å, U iso = 1.2U eq (C) for CH 2 group and d(C-H)= 0.96 Å, U iso = 1.5U eq (C) for CH 3 group; except for the hydrogen atoms of the NH group which were located from a Fourier-difference map and refined isotropically

Results and discussion
The compound I, an isomer of the 5-(tert-butyldiphenylsilyloxymethyl)pyridazin-3(2H)-one (Costas-Lago et al., 2013), was prepared in order to develop new pyridazinone analogues C4-substituted as antiplatelet agents. In the titled compound, the carbonyl group of the heterocyclic ring and the oxygen atom of the silyl ether group are placed toward opposite sides, this contrasts with the geometry found in the C5-substituted regioisomer and could explain the nearly flat disposition of the sequence C4-C1′-O1′-Si, with a torsion angle of -174.30 (15)°. The pyridazinone ring forms dihedral angles of 89.10 (8)° and 77.53 (7)°, respectively, with the C2′-C7′ and C8′-C13′ benzene rings, while the dihedral angle between both benzene rings is 48.41 (10)°.
The geometry of titled compound lets the assembly of molecules in supramolecular organizations based on hydrogen bonding, π-π and CH···π interactions. The cooperative N-H···O hydrogen bonds between the NH group of one pyridazinone ring and the oxygen atom of an adjacent ring form supramolecular dimers ( symmetry code iii: 2 -x, -2 -y, -z]. In this case the pyridazinone ring arrangement prevents the three-dimensional growth observed in the C5-substituted regioisomer (Costas-Lago et al., 2013).

Figure 3
View of the ladder chain along crystallographic b axis generated by π-π interactions.

Figure 4
View of the two-dimensional organization generated by CH···π interactions (H atoms, no-involved in supramolecular structure, have been omitted to clarify). 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.