Protonation of isonitriles ligating molybdenum(0) and tungsten(0) at nitrogen giving complexes of carbyne and carbene ligands

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Abstract
Treatment of the complexes trans-[M(CNR)2(dppe)2](1 : M = Mo or W; R = Me, But, or 4-MeC6H4; dppe = Ph2PCH2CH2PPh2) with mineral acids causes protonation at one or both nitrogen atoms to give the compounds trans-[M(CNHR)(CNR)(dppe)2]X (2: M = Mo, R = Me, X = BF4, HSO4, or SFO3; M = W, R = Me, X = BF4, HSO4, SFO3, or H2PO4; R = But, X = BF4, HSO4, or SFO3) and trans-[M(CNHR)2(dppe)2]X2(3: M = Mo, R = Me, X = BF4; M = W, R = Me, X = BF4, HSO4, SFO3, or SCIO3; R = 4-MeC6H4, X = BF4). Deuterioanalogues have been prepared. Treatment of trans-[W(CNMe)2(dppe)2] with Al2Et6 in benzene gives an unstable adduct trans-[W{CN(AlEt3)Me}2(dppe)2]. With HX (X = BF4 or HSO4), cis-[Mo(CO)2(dppe)2] gives, under dinitrogen, trans-[M(CO)2(dppe)2]X. Spectroscopic (i.r. and n.m.r.) data for these compounds are discussed in terms of their structure.