Synthesis and reactivity of bis(diphenylphosphino)amine-bridged heterobimetallic iron-platinum mu-isonitrile and mu-aminocarbyne complexes

Reaction of [(OC)(3)Fe(mu-CO)(mu-dppa) Pt(PPh3)] (1) (dppa = bis(diphenylphosphino) amine) with various isonitriles in a 1:1 or 1:2 ratio yields the isonitrile-bridged compounds [(OC)(3)Fe(mu-CN-R)(mu-dppa) Pt(PPh3)] (2) and [(OC)(2)(RNC)Fe(mu-CN-R)(m-dppa)Pt(PPh3)] (3), respectively. However, addition of tert-butylisonitrile to 1 affords the carbonyl-bridged complex [(OC)(2)(tert-BuNC)Fe(mu-CO)(m-dppa)Pt(PPh3)] (2g). Upon treatment of [(OC)(3)Fe(mu-CN-o-anisyl)(mu-dppa)Pt(PPh3)] (2b) with SO2, the mu-CNR ligand is chased from its bridging position to give the sulfur dioxide-bridged compound [(OC)(2)(o-anisylNC) Fe(mu-SO2)(mu-dppa)Pt(PPh3)] (4). These compounds are converted to the mu-aminocarbyne salts [(OC)(2)(L)Fe{mu-CN(R)R'}(mu-dppa)Pt(PPh3)](+) (5 R' = Me, Et) by N-alkylation using [Me3O][BF4] or ethyl triflate as electrophiles. In function of the sterical crowding exerted by m-aminocarbyne groups, two stereoisomers can be formed. Upon addition of P(OMe)(3) or tert-BuNC to 5, no carbonyl substitution occurs. Instead the Pt-bound PPh3 ligand is replaced by L' in a regioselective manner to give [(OC)(2)(L)Fe{mu-CN(Me) R}(mu-dppa) Pt(L')][BF4] (5e, 5f, 5g). Deprotonation of the NeH function of the bis(diphenylphosphino) amine ligand of salts 5 by KSi(OMe)(3) or KH produces the zwitterionic compounds [(OC)(2)(L)Fe{mu-CN(R)R'}(mu-Ph2PNPPh2) Pt(PPh3)] (6). The latter react with various organic and inorganic electrophiles to produce the N-alkylated or metallated aminocarbyne complexes [(OC)(2)(L)Fe{mu-CN(R)R'}{mu-Ph2PN(E)PPh2}Pt(PPh3)](+) (7: E = Me, 8: E = AuPPh3, CuAsPh3, CuPPh3, HgMe). The molecular structures of 2c, 3b, 5b, 8a and 8b have been determined by X-ray diffraction studies. (C) 2014 Elsevier B. V. All rights reserved.