Syntheses, properties and Mossbauer studies of cyanamide and cyanoguanidine complexes of iron(II).: Crystal structures of trans-[FeH(NCNH2)(Ph2PCH2CH2PPh2)2][BF4] and trans-[Fe (NCNEt2)2(Et2PCH2CH2PEt2)2][BF4]2

The complexes trans-[FeH(NCR)(dppe)(2)][BF4] (1) (R=NH2 NMe2, NEt2 or NC(NH2)(2); dppe=Et2PCH2CH2PPh2) and trans-[FeL(NCR)(depe)(2)]Y-n (R = NH2, NMe2, NEt2 or NC(NH2)(2); depe = Et2PCH2CH2PEt2; Y = BF4 or BPh4; (2), L = Br, n = 1; (3), L = NCR, n = 2) have been prepared by treatment of trans-[FeHCl(dppe),] (in THF and in the presence of Tl[BF4]) or trans-[FeBr2(depe)(2)] (in MeOH and in the presence of [NBu4][BF4] or Na[BPh4]), respectively, with the appropriate cyanamide. NMR and Mossbauer spectral, as well as FAB mass spectrometric data are reported. Mossbauer partial isomer shift (PIS) and partial quadrupole splitting (PQS) parameters have been estimated for the cyanamide and dppe ligands and rationalised, with the overall IS and QS, in terms of pi- and sigma-electronic effects, the cyanamides behaving as more effective sigma-donors and weaker pi-acceptors than organonitriles. FAB MS fragmentation patterns are also proposed. The crystal structures of 1 (R = NH,) and 3 (R = NEt2,, Y = BF,) are reported. (C) 1999 Elsevier Science S.A. All rights reserved.