Extending the Lindqvist Family to Late 3d Transition Metals: A Rational Entry to CoW 5 Hexametalate Chemistry

• Published in: European journal of inorganic chemistry 2009-12, Vol.2009 (34), p.5240-5246
• Main Authors: Errington, R. John, Harle, Gavin, Clegg, William, Harrington, Ross W.
• Format: Article
• Language: English
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200900640

The dimeric CoW 5 Lindqvist‐type anion [{CoW 5 O 18 H} 2 ] 6– ( 1 ) has been obtained as a tetrabutylammonium (TBA) salt by addition of either [Co(MeCN) 4 (H 2 O) 2 ] 2+ or CoCl 2 to a “virtual” W 5 O 18 6– precursor generated by non‐aqueous hydrolysis of a mixture of (TBA) 2 WO 4 and WO(OMe) 4 . Analysis of the X‐ray crystal structure of (TBA) 7 1 (BF 4 ) by using the Bond Valence Sum (BVS) method reveals that cobalt is present as Co II and that two protons are associated with CoOW bridging oxygen atoms, one of which is located in a hydrogen bond between the two CoW 5 O 18 units, whereas the other is disordered between an adjacent oxygen atom and its symmetry‐related site on the other CoW 5 O 18 unit. Treatment with pyridine cleaves dimer 1 to give [(py)CoW 5 O 18 H] 3– ( 2 ), and the single protonated CoOW site was identified by BVS analysis of an X‐ray crystal structure. Due to the higher anionic charge of [CoW 5 O 18 ] 4– , bands due to terminal ν W=O in the FTIR spectra of 1 and 2 are shifted to lower wavenumbers (933 and 935 cm –1 , respectively) compared to those of [W 6 O 19 ] 2– (974 cm –1 ) and group 4 derivatives [(X)MW 5 O 18 ] 3– (945–955 cm –1 ), despite protonation of the oxometalate framework. Peaks due to CoW 5 oxometalates dominate the electrospray ionisation mass spectra of (TBA) 7 1 (BF 4 ) and (TBA) 3 2 , the most intense being assigned to {CoW 5 O 17 } 2– , which is formally derived from [CoW 5 O 18 H] 3– by protonation and loss of H 2 O.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)