The Influence of Steric Pressure on the Structure of Homodimetallic Rhodium(I) and Iridium(I) Complexes Containing a Bis(bidentate) Phosphane Ligand

Autor: Markus Fessler, Peter Brüggeller, Holger Kopacka, Sylvia Eller, Georg Czermak, Alexander Dumfort, Karl-Hans Ongania, Christian Bachmann, Rene Gutmann
Rok vydání: 2007
Předmět:
Zdroj: European Journal of Inorganic Chemistry. 2007:3227-3239
ISSN: 1099-0682
1434-1948
DOI: 10.1002/ejic.200601210
Popis: Fifteen novel homodimetallic Rh I and Ir I complexes containing the bis(bidentate) phosphane ligand cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphanyl)cyclobutane (dppcb) were prepared and characterized by NMR spectroscopy ( 1 H, 13 C{ 1 H}, 31 P{ 1 H}), mass spectrometry, IR spectroscopy, elemental analyses and melting points. Furthermore, the solid-state structures of seven of these new compounds were fully determined by single-crystal X-ray diffraction analyses to study the influence of steric pressure. The precursor complex [Rh 2 (η4-cod)2(dppcb)]X2 (1), X- = BF 4 -, PF 6 -, SbF 6 -, completely characterized by its X-ray structure, smoothly reacts with mono- or bidentate ligands containing phosphorus or nitrogen donor atoms. Thus, monophosphanes and monophosphites produce compounds of the structure type [Rh2L4(dppcb)](SbF 6 )2 [L = PMe 2 Ph, 2; PMePh 2 , 3; P(OMe) 3 , 5; P(OPh) 3 , 6]. The X-ray structures of 3 and 6 show that PMePh 2 and P(OPh) 3 are capable of compensating steric interactions. The treatment of 1 with diphosphanes leads to the structure type [Rh 2 L 2 (dppcb)](SbF 6 ) 2 [L = bis(diphosphanyl)-methane, dppm, 7; bis(diphenylphosphanyl)amine, dppam, 8; 1,2-bis(diphenylphosphanyl)ethane, dppe, 9; cis-1,2-bis(diphenylphosphanyl)ethene, cis-dppen, 10]. The X-ray structures of 8, 9 and 10 clearly indicate the onset of steric pressure as a consequence of mechanical coupling, which results in two different coordination moieties for homodimetallic species 9 and 10. Under steric pressure, the quadrant effects of dppcb and dppe become comparable to Rh 1 complexes. The use of mono- or bidentate ligands containing nitrogen donor atoms leads to the compounds [Rh 2 (PYridine) 4 -(dppcb)](SbF 6 ) 2 (11), [Rh2(2,2'-bipyridine)2(dppcb)](SbF 6 )2 (12) and [Rh2(1,10-phenanthroline)2(dppcb)](SbF 6 )2 (13). The crystal structures of 1 and the novel complex [Ir 2 (η 4 -cod) 2 -(dppcb)]X 2 (14), X - = BF 4 -, SbF 6 - , are isomorphous. However, it was only possible to produce restricted examples of derivatives of 14 owing to the reluctance of 14 to release cod. Thus, monophosphanes lead to the five-coordinate species [Ir 2 (η 4 -cod)2(PMe2Ph)2(dppcb)](BF4)2 (15), whereas the four-coordinate compound [Ir2(PMePh2)4(dppcb)](BF4)2 (16) is formed by using the sterically more demanding ligand PMePh 2 instead of PMe 2 Ph.
Databáze: OpenAIRE
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