X-ray structural studies of selected group VIII metal complexes

by Marsden, Karen

Abstract (Summary)
This thesis describes the single crystal x-ray analyses of six novel organometallic osmium complexes and three complexes of the tridentate dentate ligand 1,6-bis(diphenylphosphino)-trans-hex-3-ene with the transition metals iridium, rhodium and ruthenium. The complexes of carbon monosulphide and carbon monotelluride with osmium, OsCl2(CO)(CS)(PPh3)2 and OsCl2(CO)(CTe)(PPh3)2, exhibit linear thio- and telluro-coordination similar to that of the carbonyl. The -CS and -CTe ligands exert strong trans-bond weakening influences. In the dihapto-thioacyl complex of osmium, Os(?1-o2CCF3)[C(S)-(p-tolyl)](CO)(PPh3)2, the bidentate thioacyl is coordinated to the osmium through the carbon and sulphur atoms. This bonding involves a considerable degree of ?-interaction between the C, S and Os atoms, concomitant with a lengthening of the C-S bond. The dichlorocarbene complex, OsCl2(CO)(CCl2)(PPh3)2 is disordered in the crystalline state. Consequently, while the presence of the dichlorocarbene is verified, no unambiguous conclusions can be drawn from the associated geometry. In the carbyne complex of osmium, Os(C-p-tolyl)Cl(CO)(PPh3)2, the osmium is in a trigonal bipyramidal environment with an approximately linear arrangement of the Os-C-R group. The Os-Ccarbyne bond is short (corresponding to a bond order of ca. 3), confirming the formation of the C-p-tolyl group as a carbyne. The formaldehyde ligand in the osmium complex, Os(?2-CH2O)(CO)2(PPh3)2, is bonded to the osmium centre via both the carbon and oxygen atoms. The C-O bond of the formaldehyde lengthens considerably upon coordination, resulting in a bond order apparently less than 1. Also present in the crystal structure are molecules of water which are hydrogen bonded into pairs (O…O separation 2.56 Å). The (H2O)2 units do not hydrogen bond to any other atoms, but rather occupy hydrophobic interstices in the structure. The three complexes of 1,6-bis(diphenylphosphino)-trans-hex-3-ene, (BDPH), IrIIICl3(BDPH), RhIIICl3(BDPH), and RuIICl2(CO)(BDPH) are isomorphous. The ruthenium complex is, however, disordered in the crystalline state. In each of the three structures the olefin of the BDPH moiety is only weakly bound to the metal, leaving the C-C double bond virtually unchanged from that of the free ligand. The olefin exerts a stronger trans-bond weakening influence than do the chlorine ligands in these complexes.
Bibliographical Information:


School:The University of Auckland / Te Whare Wananga o Tamaki Makaurau

School Location:New Zealand

Source Type:Master's Thesis

Keywords:fields of research 250000 chemical sciences


Date of Publication:01/01/1981

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