Reaction of the terminal electrophilic phosphinidene complexes [Cp*M(CO)3{PN(i-Pr)2}][AlCl4] (3,
M = Mo; 4, M = W) with PEt3 results in replacement of a metal carbonyl by the phosphine. The reactions
occur via initial nucleophilic attack by the phosphine at the phosphinidene phosphorus, followed by
carbonyl loss and migration of the phosphine to the metal. Reactions of 3 and 4 with bis(dimethylphosphino)methane (dmpm) lead to [Cp*M(CO)2{P(N(i-Pr)2)P(Me2)CH2P(Me2)-κ2
P
1,P
4}][AlCl4]
(9, M = Mo; 10, M = W), in which one end of the diphosphine coordinates to phosphorus and the other
end coordinates to the metal. The reactions proceed by initial nucleophilic attack by one end of the
diphosphine at phosphorus, followed by carbonyl loss and coordination of the other end of the ligand to
the metal. Compound 3 (M = Mo) reacts with bis(dimethylphosphino)ethane (dmpe) to give the analogous
product [Cp*Mo(CO)2{P(N(i-Pr)2)P(Me2)CH2CH2P(Me2)-κ2
P
1,P
5}][AlCl4] (12), in which the two ends
of the dmpe ligand coordinate to phosphorus and molybdenum, respectively. Reaction of compound 4
(M = W) with dmpe leads to two products, [Cp*W(CO)2{P(N(i-Pr)2)P(Me2)CH2CH2P(Me2)-κ2
P
1,P
5}][AlCl4] (13) and [{Cp*W(CO)2(PN(i-Pr)2)}2(μ-dmpe)][AlCl4]2 (14). Compound 13 is analogous to 12.
In compound 14, the two ends of the diphosphine ligand displace carbonyl ligands from two molecules
of 4, resulting in a novel bis-phosphinidene structure in which the diphosphine ligand bridges two metal
centers, each of which retains a terminal phosphinidene ligand. Loss of an additional carbonyl ligand
from 12, followed by migration of one end of the phosphine from phosphorus to the metal, results in
re-formation of a terminal phosphinidene ligand, leading to [Cp*Mo(CO)(PN(i-Pr)2)(dmpe-κ2
P)][AlCl4]
(17). The structural characterization of the phosphine adducts and carbonyl substitution products of the
terminal phosphinidene complexes 3 and 4 has provided valuable insights into metal−phosphinidene
bonding in these compounds.