SYNTHESIS, STRUCTURE, AND FLASH-PHOTOLYSIS KINETIC-STUDIES OF BORYLATED BIS(DIOXIMATO)IRON(II) CARBONYL-COMPLEXES

The synthesis and characterization of various borylated bis(dimethylgl yoximato)iron complexes, Fe(DMGBR(2))(2-) LL' (BR(2) = BH2, BF2, BPh(2 ), or BBN (9-borabicyclo[3.3.1]nonane) and axial ligands L or L' pyrid ine, 1-methylimidazole, CO, butylamine, nitriles, NH3, etc.) are descr ibed. Carbonyl complexes crystallize in the C-2 nu conformation with b oth axial boron groups on the CO binding face. The bis(butylamine) com plexes all show a C-2h conformation. mash photolysis studies of the ca rbonyl complexes and ligand substitution kinetics of other derivatives probe the linkage between the conformational dynamics of the macrocyc le and the ligational. dynamics of the iron complex. On-rate effects p roduced by groups which block access to the iron are compared with tho se for hemoproteins and superstructured hemes. Off-rate constants are largely unrelated to bond lengths or pi-bonding/charge transfer effect s. The off-rates reflect the true coordinate bond energy while structu ral and spectroscopic data only measure local phenomena. Electrochemic al studies of Fe(DMGBR(2))(2)(PY)(2) complexes and the nitrile complex es Fe(DMGBPh(2))(2)(PY)(RCN), RCN = 2,3-dichloro-5,6-dicyano-1,4-benzo quinone (DDQ) and tetracyanoethylene (TCNE), are described. Crystal da ta: Fe(DMGBF(2))(2)(PY)(CO). CH2Cl2, orthorhombic space group P2(1)2(1 )2(1), alpha = 12.436(3) Angstrom, b = 13.246(2) Angstrom, c = 14.158( 3) Angstrom, Z = 4; Fe(DMGBPh(2))(2)(PY)(CO). CH2Cl2, orthorhombic spa ce group Pbcn, alpha = 14.943(3) Angstrom, b = 15.890(3) Angstrom, c = 16.211(3) Angstrom, Z = 4; Fe(DMGBBN)(2-)(PY)(CO), monoclinic space g roup P2(1)/n, alpha = 11.611(2) Angstrom, b = 19.512(3) Angstrom, c = 14.907(2) Angstrom, beta = 108.53(2)degrees, Z = 4; Fe(DMGBF(2))(2)(Bu NH(2))(2), hexagonal space group R ($) over bar 3, alpha = 27.874(4) A ngstrom, c = 8.443(2) Angstrom, Z = 9; Fe(DMGBPh(2))(2)(BuNH(2))(2), m onoclinic space group P2(1)/n, alpha = 13.928(3) Angstrom, b = 9.845(2 ) Angstrom, c 15.288(3) Angstrom,beta = 105.86(3)degrees, Z = 2; Fe(DM GBBN)(2)(BuNH(2))(2), monoclinic space group Cc, alpha = 9.029(4) Angs trom, b = 19.303(9) Angstrom, c= 20.562(10) Angstrom, beta = 92.790(1) degrees, Z = 4.