Attaching high charge density metal ions to surfaces and biomolecules. Reaction chemistry of hypodentate cobalt diamine complexesThis paper is dedicated to Professor David Cole-Hamilton on the occasion of his retirement and for his outstanding contribution to transition metal catalysis.Electronic supplementary information (ESI) available: EDX analysis of PEAA bead grafted with [Co(NH3)5NH2CH2(CH2)4CH2NH3]4+. See DOI: 10.1039/c3dt51758f

Hypodentate diamine cobalt( iii ) pentammine complexes [Co(NH 3 ) 5 (NH 2 (CH 2 ) n NH 3 )](ClO 4 ) 4 ( 8 : a : n = 3; b : n = 4; c : n = 6; d : n = 8) have been synthesized via the reaction of [Co(NH 3 ) 5 (OTf)](OTf) 2 (TfOH = CF 3 SO 3 H) with the corresponding diamines. The analogous t -boc protected diamine complexes [Co(NH 3 ) 5 (NH 2 (CH 2 ) n NH t -boc)](ClO 4 ) 3 ( 7a-d ) were prepared in 4-26% yield. Low yields for the formation of 7a-d are due to competing side reactions which also gave [Co(NH 3 ) 6 ] 3+ . Complexes 7a-d were deprotected using trifluoroacetic acid to give the corresponding hypodentate diamine complexes [Co(NH 3 ) 5 (NH 2 (CH 2 ) n NH 3 )](CF 3 CO 2 ) 0.5 (ClO 4 ) 3.5 ( 9a-d ). HBTU coupling of 8c with N -( t -boc)- l -phenylalanine gave an amino acid functionalized cobalt pentammine complex [Co(NH 3 ) 5 (NH 2 (CH 2 ) 6 NH t -boc)- l -phenylalanine)](ClO 4 ) 3 ( 10 ). All new complexes were characterized using UV-vis and 1 H NMR spectroscopy, and elemental analysis. Grafting of 8c onto 2.4 mm poly(ethylene- co -acrylic acid) (PEAA) beads was achieved via amide coupling. Complex 8c was coupled to thioctic acid via amide coupling and the resulting cobalt disulfide complex [Co(NH 3 ) 5 ( N -(6-aminohexyl)-5-(1,2-dithiolan-3-yl)pentanamide)](ClO 4 ) 3 ( 11 ) was attached to 10 nm Au nanoparticles. The amount of cobalt loading onto PEAA beads and Au nanoparticles was determined using ICP-MS and EDX. A series of hypodentate diamine complexes of cobalt( iii ) pentammine [Co(NH 3 ) 5 (NH 2 (CH 2 ) n NH 3 )](ClO 4 ) 4 ( 8 : a : n = 3; b : n = 4; c : n = 6; d : n = 8) have been prepared, coupled to an amino acid and grafted onto 2.4 mm poly(ethylene- co -acrylic acid) beads.