Heat of reaction of (norbornadiene) molybdenum tetracarbonyl with monodentate and bidentate ligands. Solution thermochemical study of ligand substitution in the complexes cis-L2Mo(CO)4

Shakti L. Mukerjee, Steven P. Nolan, Carl D. Hoff, Ramon Lopez de la Vega

Research output: Contribution to journalArticle

57 Scopus citations

Abstract

The enthalpy of reaction of (NBD)Mo(CO)4 (NBD = norbornadiene) with a number of monodentate and bidentate ligands forming cis-L2Mo(CO)4 has been measured at 30°C in THF solution. The heats of reaction span a range of 33 kcal/mol. The order of stability for monodentate ligands is PCl3 < As(C6H5)3 < py < P(C6H5)3 < AsEt3 < P(OC6H5)3 < P(C6H5)2(CH3) < CO < P(C6H5)(CH3)2 < P(OCH3)3 < P(n-Bu)3 < (C6H11)NC < PEt3 < PMe3. The series of chelating bidentate phosphines R2P-(CH2)nPR2 (n = 1-4, R = C6H5; n = 1, 2, R = CH3) and several related ligands were investigated. The chelating ring systems in the metallacycles show strain energies of about 8 kcal/mol for four-membered rings. The mixed ligand (C6H5)2PCH2CH2-As(C 6H5)2 shows a heat of binding midway between the heats of binding of (C6H5)2PCH2CH2P(C 6H5)2 and (C6H5)2AsCH2C-H2As(C 6H5)2, implying group additivity in this system. The complex (phen)Mo(CO)4 is some 5 kcal/mol more stable than (bpy)Mo(CO)4, presumably due to conformational effects in the free ligand. The ligand 1,5-cyclooctadiene forms a complex 2 kcal/mol less stable than that of norbornadiene. The influences of steric and electronic factors in determining the Mo-L bond strength are discussed.

Original languageEnglish (US)
Pages (from-to)81-85
Number of pages5
JournalInorganic Chemistry
Volume27
Issue number1
DOIs
StatePublished - Jan 1 1988

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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