[3-(Iodoacetamido)propyl]triphenylphosphonium tetraphenylborate

The title compound, C23H24INOP+·C24H20B−, was prepared by treatment of 3-aminopropyl triphenylphosphonium bromide hydrogen bromide with p-nitrophenyl iodoacetate at 203 K. The asymmetric unit contains a single cation and anion, which are linked in the crystal by intermolecular N—H⋯π and inversion-related R 2 2(14) C—H⋯O interactions, which combine to form chains of cations and anions along the c axis.

The title compound, C 23 H 24 INOP + ÁC 24 H 20 B À , was prepared by treatment of 3-aminopropyl triphenylphosphonium bromide hydrogen bromide with p-nitrophenyl iodoacetate at 203 K. The asymmetric unit contains a single cation and anion, which are linked in the crystal by intermolecular N-HÁ Á Á and inversion-related R 2 2 (14) C-HÁ Á ÁO interactions, which combine to form chains of cations and anions along the c axis.
Cg is the centroid of the C61-C66 ring.

Comment
One aspect of our research into mitochondrially targeted bio-active agents (Murphy and Smith, 2007) involves synthesis of a series of targeted iodoacetamides from aminoalkyl-triphenylphosphonium salts (Porteous et al., 2010). The use of iodoacetamides in labelling of cysteine residues in proteins and peptides is well established (Ying et al., 2007) allowing attachment of key markers such as fluorescein (Baty et al., 2002) or biotin (Kim et al., 2000). Given the widespread use of the iodoacetamide functionality it is surprising that there appears to be no structural data available for non-aryl iodoacetamides.
The title compound crystallizes with one cation and anion in the asymmetric unit (  et al., 1995). The combination of these two types of interactions form chains of cations and anions as viewed along the c axis.

Experimental
The title compound was prepared from 3-aminopropyl triphenylphosphonium bromide hydrogen bromide (prepared using methods similar to McAllister et al., 1980) using a modified literature procedure (Trujillo et al., 1991). Triethylamine (0.43 mmol) was added to a dichloromethane solution (20 mL) of 3-aminopropyl triphenylphosphonium bromide hydrogen bromide (0.43 mmol), the solution cooled to -70°C and solid p-nitrophenyl iodoacetate (0.43 mmol) added in one portion. The solution was stirred at -70°C for 20 minutes and the solvent removed under vacuum. The solid residue was dissolved in acetone (5 mL), excess sodium tetraphenylborate (1 mmol) added and the solution stirred for 2 h at room temperature. Solvent was removed under vacuum, the compound redissolved in dichloromethane (2 mL) and precipitated by addition to diethylther (20 mL). Crystals were prepared by vapour diffusion of diethylether into an ethanolic solution of the compound at room temperature.
supplementary materials sup-2 Refinement All H-atoms were positioned geometrically and refined using a riding model with d(C-H) = 0.93 Å, U iso =1.2U eq (C) for aromatic and 0.97 Å, U iso = 1.2U eq (C) for CH 2 and 0.86 Å, U iso = 1.2U eq (N) for the NH atom. Fig. 1. View of the two ions in the asymmetric unit showing the atom-labelling scheme. Ellipsoids are drawn at the 50% probability level with H atoms represented by circles of arbitrary size.    (11) 0.0015 (9) −0.0019 (10) 0.0008 (9)