Experimental and Theoretical Studies of Carbodiphosphorane−CX₂ Adducts with Unusual Bonding Situations: Preparation, Crystal Structures, and Bonding Analyses of S₂CC(PPh₃)₂, O₂CC(PPh₃)₂, and [(CO)₄MS₂CC(PPh₃)₂] (M = Cr, Mo, W)^†

We report about the first X-ray structure analyses of the CS2 and CO2 adducts with carbodiphosphorane C(PPh3)2 and the synthesis and X-ray structure analysis of group 6 carbonyl complexes with compound S2CC(PPh3)2 as a ligand [(CO)4MS2CC(PPh3)2] (M = Cr, Mo, W). The nature of the carbon−carbon bonding in X2CC(PPh3)2 and in the model compounds X2CC(PH3)2 and the metal−ligand bonding in [(CO)4MoS2CC(PH3)2] have been analyzed with charge and energy decomposition methods using DFT calculations. Carbodiphosphoranes C(PR3)2 are double electron pair donors having σ- and π-carbon lone-pair orbitals as the two highest occupied MOs.