Janet Braddock-Wilking
Dr.
Braddock-Wilking received her B.A. degree from the University
of Missouri-St. Louis and her Ph.D. from Washington University.
She joined the UM-St. Louis faculty in 1993 following postdoctoral
fellowships at Harvard University and Mallinckrodt Medical, Inc. Between 1993 and 2004 she was Research assistant and then Research Associate Professor and Manager of the NMR Facility. In 2004 she was appinted to a tenure track position.
wilkingj@umsl.edu
Office: N306
Phone: (314) 516-6436
Fax: (314) 516-5342
Research Interests
Dr. Braddock-Wilking’s research focuses on the synthesis, characterization, and reactivity of compounds containing heavier Group 14 elements (E = Si, Ge, Sn). Of particular interest is the formation of new complexes containing El-transition metal bonds. There are a variety of synthetic methods known for the formation of complexes containing E-M bonds but by far the most common and versatile approach involves the formal insertion of the metal center into an E-H bond. In an oxidative-addition pathway this reaction can proceed to full addition of the E-H bond at M or may be arrested at an earlier stage to give a nonclassical (M…H…E) interaction. This reaction is known for nearly all of the transition metal elements with hydrosilanes containing a variety of substituents. However, the related chemistry involving Ge-H and Sn-H bonds is largely unexplored. The Si-H bond activation by a metal center has been extended to catalytic processes such as hydrosilylation and dehydrocoupling.
Our previous results have shown that constrained cyclic secondary hydrosilanes (R2SiH2) such as silafluorene (C12H8SiH2) show enhanced reactivity compared to the acyclic analog (Ph2SiH2) upon reaction with (Ph3P)2Pt(η2-C2H4). Three major products were produced from the reaction including a mononuclear, unsymmetrical dinuclear, and an unexpected trinuclear complex. The nature of the Group 14 element center also has an effect on the type of products that are generated. However, the type of platinum-phosphine precursor used has a dramatic influence on the structural motif formed. An array of different products have been produced the reactions of Pt(0) and Pt(II) phosphine precursors with secondary hydrosilanes, germanes, and stannanes as shown in Figure 1 below.
Group 14 containing metalloles are known to exhibit unusual electronic properties and have potential application as components for electronic devices such as OLEDs and as chemical sensors. We are currently investigating the preparation of siloles, germoles, and stannoles that contain either H, alkyl or aryl groups at the Group 14 center and a variety of π-conjugated organic groups at the ring carbons that can potentially coordinate to a transition-metal moiety through a terminal phosphorus unit (eq. 1).
Selected Publications
“Sila- and Germaplatinacycles produced from a Stepwise E-E Bond Forming Reaction”, J. Braddock-Wilking, T. Bandrowsky, N. Praingam, N. P. Rath, Organometallics 2009, 28, 4098.
"Preparation of 1,1-disubstituted silacyclopentadienes " J. Braddock-Wilking, Y. Zhang, J. Y. Corey and N. P. Rath, J. Organomet. Chem. 2008, 693, 1233
"Activation of Group 14 El-H Bonds at Platinum(0)", C. P. White, J. Braddock-Wilking, J. Y. Corey, H. Xu, E. Redekop, S. Sedinkin, and N. P. Rath, Organometallics, 2007, 26, 1996
"Si-H Bond Activation by (Ph3P)2Pt(η2-C2H4) in Dihydrosilicon Tricycles that also contain O and N Heteroatoms," J. Braddock-Wilking, J. Y. Corey, L. M. French, E. Choi, V. J. Speedie, M. F. Rutherford, S. Yao, H. Xu, and N. P. Rath,Organometallics, 2006, 25, 3974.
"Spectroscopic and Reactivity Studies of Pt-Si Monomers and Dimers," J. Braddock-Wilking, J. Y. Corey, C. White, H. Xu, and N. P. Rath, Organometallics, 2006, 25, 2859.
"Reaction of Diphenylgermane with (Ph3P)2Pt(h2-C2H4): Generation of Mono- and Dinuclear Complexes Containing Pt-Ge Bonds. X-ray Crystal Structure Determination of [(Ph3P)Pt(m-h2-H-GePh2)]2," J. Braddock-Wilking, J. Y. Corey, K. A. Trankler, H Xu, L. M. French, N. Praingam, C. White, and N. P. Rath Organometallics, 2005, 24, 4113.
"Reaction of Silafluorenes with (Ph3P)2Pt(h2-C2H4): Generation and Characterization of Pt-Si Monomers, Dimers and Trimers," J. Braddock-Wilking, J. Y. Corey, K. A. Trankler, K. M. Dill, L. M. French, N. P. Rath, Organometallics, 2004, 23, 4576.
" Formation and X-ray Crystal Structure Determination of a Novel Triplatinum Cluster, ([(Ph3P)Pt(m-SiC12H8)]3 from Reaction of Silafluorene with (Ph3P)2Pt(h2-C2H4)," J. Braddock-Wilking, J. Y. Corey, K. Dill, N. P. Rath, Organometallics, 2002, 21, 5467.
"Reactivity
of {(Ph3P)Pt[m-h2-H-SiH(Ar)]}2 (Ar =
2-isopropyl-6-methylphenyl) with Phosphines. X-ray Crystal
Structure of trans-{(dppe)Pt[m-SiH(Ar)]}2," J. Braddock-Wilking,
Y. Levchinsky, N. P. Rath, Inorg. Chim.
Acta, 2002, 330, 82.
"Synthesis,
Characterization, and X-ray Structural Analysis of Diplatinum
Complexes Containing Bridging m-SiHAr
Ligands, {(PhnMe3-nP)2Pt[m-SiHAr]}2 [n = 0-2; Ar = 2-isopropyl-6-methyl(phenyl)]," J.
Braddock-Wilking, Y. Levchinsky, N. P. Rath, Organometallics, 2001, 20,
474.
"13C NMR spectroscopy of amorphous hydrogenated carbon. Further evidence of inhomogeneity". J. Braddock-Wilking, S-H. Lin and B. J. Feldman, Solid State Communications 2001, 119, 19.
"Synthesis and characterization of m,m '-M(B5H8)2 (M = Cd, Hg and Zn): a reassignment of the NMR spectra for 2,3-m -metalloderivatives of pentaborane(9)". H. Fang, J. Bould, J. Braddock-Wilking and L. Barton, Journal of Organometallic Chemistry 2000, 614-615, 223.
" Synthesis and Characterization of Diplatinum Complexes Containing Bridging m-h2-H-SiHAr ligands. X-ray Structure Determination of {(Ph3P)Pt[m-h2-H-SiHAr]}2 (Ar = 2,4,6-(CF3)3C6H2 and C6Ph5," J. Braddock-Wilking, Y. Levchinsky, N. P. Rath, Organometallics, 2000, 19, 5500.
"Synthesis and Characterization of a Symmetrical Diplatinum Complex Containing Bridging m-h2-H-SiHAr ligands (Ar = 2-isopropyl-6-methylphenyl). X-ray structure of {(Ph3P)Pt[m-h2-H-SiHAr]}2," J. Braddock-Wilking, Y. Levchinsky, N. P. Rath, Organometallics, 1999, 18, 2583.
Reactions of Hydrosilanes with Transition-Metal Complexes: Formation of Stable Transition-Metal Silyl Compounds". J. Y. Corey and J. Braddock-Wilking, Chemical Reviews 1999, 99, 175