Synthesis and Structure of a Dimeric Iminophosphorane Stabilized Zinc Carbene: (ZnCR2)2

Single deprotonation of the bis­(iminophosphorano)­methane ligand (PhNPPh2)2CH2 (5-H2) with 1 equiv of p-tBu-benzylpotassium followed by reaction with zinc­(II) chloride led to the formation of the homoleptic complex ((PhNPPh2)2CH)2Zn, (5-H)2Zn. Deprotonation of 5-H2 with 2 equiv of p-tBu-benzylpotassium gave known potassium compound (5-K2)2 which reacted further with zinc­(II) chloride to the dimeric carbene complex [(PhNPPh2)2CZn]2 ((5-Zn)2). Crystal structures of (5-H)2Zn and (5-Zn)2 are compared to those of closely related Ca and Mg compounds. To analyze the charge distribution of these zinc complexes, density functional theory calculations on simple model systems were employed. Although the Zn–C bond in (5-Zn)2 is highly ionic (81%) it is significantly more covalent than that in a similar dimeric Ca carbene complex (91% ionic).