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 language||English (US)|
|Number of pages||7|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|State||Published - 1983|
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