Tertiary phosphine adducts of manganese(II) dialkyls. Part 2. Synthesis, properties, and structures of monomeric complexes

Christopher G. Howard, Gregory S. Girolami, Geoffrey Wilkinson, Mark Thornton-Pett, Michael B. Hursthouse

Research output: Contribution to journalArticlepeer-review

Abstract

Monomeric tetrahedral manganese dialkyl tertiary phosphine complexes of stoicheiometry MnR2(PR′3)2 have been identified in solutions by electron spin resonance spectra and the alkyl complex Mn(CH2CMe2Ph)2(PMe3)2 isolated and structurally characterised by X-ray crystallography. The molecule has a severely distorted tetrahedral geometry with P-Mn-P and C-Mn-C angles of 96.2 and 137.9° respectively, which reflect the relative sizes of the two kinds of ligand. The Mn-C and Mn-P distances are 2.149(6) and 2.633(4) Å respectively. Use of the chelating phosphine, 1,2-bis(dimethylphosphino)ethane (dmpe), has allowed the isolation of the tetrahedral monomers MnR2(dmpe) (R = CH2SiMe3, CH2CMe3, and CH2Ph). The chelate dialkyl o-xylylene, o-(CH2)2C6H4, gives an octahedral complex Mn[o-(CH2)2C6H4](dmpe)2 whose structure has also been determined by X-ray diffraction. In this molecule, all metal-ligand bond lengths are shorter than the corresponding bonds in Mn(CH2CMe2Ph)2(PMe3)2. This is consistent with a significant reduction in the MnII radius on adoption of the low-spin state observed. The Mn-C distances are 2.110(5) and 2.1 04(6) Å, while the Mn-P distances of 2.230(3) (trans to P) and 2.298(3) Å (trans to C) reflect the different trans-influence abilities of alkyls and phosphines. The X-band e.s.r. spectra of the monomeric complexes have been studied in detail and are discussed in terms of distorted tetrahedral high-spin MnII and octahedral low-spin MnII species.

Original languageEnglish (US)
Pages (from-to)2631-2637
Number of pages7
JournalJournal of the Chemical Society, Dalton Transactions
Issue number12
DOIs
StatePublished - 1983
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)

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